JP4429271B2 - Optical signal branch circuit and optical communication network - Google Patents

Abstract

By using the wavelength multiplexing technique and a wavelength router, a sophisticated network structure such as full mesh is built on a ring-shaped optical fiber network and the problem of isolation shortage generated can be solved. By using a wavelength router having two sets of optical add/drop multiplexers, each consisting of (N-1) sets of a pair of add means and drop means, a communication route of full mesh is built between N nodes.

Description

The present invention relates to a wavelength router and an optical add / drop multiplexer (OADM) used for optical fiber communication. The present invention also relates to an optical signal branch circuit and an optical fiber communication network used for optical fiber communication. In particular, the ring-shaped optical fiber communications networks and passive optical signal branching circuit and the time division multiple access is provided an optical fiber passive optical fiber communication network is a combination of an (TDM) (PON: P assive O ptical Fiber N etwork) About.

  FIG. 44 shows a conventional optical add / drop multiplexer. FIG. 44A shows an optical add / drop multiplexer using an optical fiber grating (FBG) 601 and an optical circulator 602. The optical signal incident from the port 603 is reflected by the optical fiber grating (FBG) 601 only at the wavelength λi, and the reflected optical signal of λi is guided to the add / drop port 605 by the optical circulator 602. Light having a wavelength other than λi is guided to the port 604.

  FIG. 44B shows an optical add / drop multiplexer using dielectric thin film filter type three-port devices 611 and 612. Among the optical signals incident from the port 613, the optical signal of λi is guided to the drop port 615 by the dielectric thin film filter type three port device 611. The optical signal having the wavelength λi from the add port 616 is guided to the port 614 by the dielectric thin film filter type three port device 612.

FIG. 45A shows the structure of a dielectric thin film filter type three-port device 620 . Light from the incident port (optical fiber) 621 passes through a collimator 624 and a dielectric thin film filter 625, and light having a wavelength λi is guided to a transmission port (optical fiber) 623 through a collimator 626. Light other than the wavelength λi is reflected by the dielectric thin film filter 625, passes through the collimator 624 again, and is guided to the reflection port (optical fiber) 622.

  In this specification, the distinction between the incident port, the transmission port, and the reflection port will be made using symbols as shown in FIG. A characteristic of this symbol is that the line indicating the reflection port extends into the box.

Further, the conventional passive optical fiber communication network is shown in Figure 46: shows the (PON P assive O ptical Fiber N etwork). An optical signal from the base station 1210 is branched by a passive tree splitter (tree coupler) 1200 and sent to a large number of client station groups 1213 via an optical fiber group 1201. In addition, optical signals from the client station group 1213 to the base station 1210 are transmitted by time division multiple access (TDM). The branching ratio of the tree-type splitter 1200 is often selected to be about 32.

  Most conventional optical add / drop multiplexers add / drop a single wavelength. However, with the advancement of optical fiber communication networks, there is an increasing need to construct a more complicated network structure using wavelength multiplexing. In order to meet such needs, a design technique for wavelength arrangement of the optical add / drop multiplexer is required. Further, depending on conditions, a high isolation characteristic may be required for the optical add / drop multiplexer. An object of the present invention is to solve these problems and to realize a flexible network configuration with practically sufficient physical characteristics.

  In the conventional passive communication network, since the optical fiber branches into 32 after being branched by the tree-type splitter 1200, a very large number of optical fibers must be installed. There was a problem. In addition, there is a problem that the tree-type splitter 1200 has a very complicated configuration when more branches than 32 branches are made.

  In order to solve the above problems, the wavelength router of the present invention, for example, includes a first input port, a first optical add / drop multiplexer, a first output port, a second input port, a second, In the wavelength router having the second output port, the first add-drop multiplexer has (N−1) sets of add means drop means pairs for a predetermined number N of nodes. And the second optical add / drop multiplexer includes N-1) sets of add means drop means pairs. By using a wavelength router having this configuration, a redundant communication path having a full mesh structure can be realized by wavelength multiplexing on a dual ring optical fiber communication network having two optical fibers.

Details of the means and operation of the present invention will be described in more detail through the description of the following examples. The above-mentioned and other aspects of the present invention are described in the claims, and will be described in detail with reference to the following examples.
In order to solve the above problems, the present invention realizes an increase in the number of branches by applying an optical add / drop multiplexer (OADM) using a wavelength multiplexing technique to an optical signal branch circuit unit. Details of the means and operation of the present invention will be described in more detail through the description of the following examples.

According to the present invention, various network topologies including a full mesh can be flexibly constructed using wavelength multiplexing on a ring-shaped optical fiber communication network. In addition, problems such as insufficient isolation that occur at that time can be solved. Further, according to the present invention, passive optical fiber communication network: it is possible to reduce the optical fiber usage in (PON P assive O ptical Fiber N etwork). In addition, a redundant optical communication network can be realized.

  Examples of the present invention will be described below.

A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an internal configuration of the wavelength router 20 according to the first embodiment of the present invention. FIG. 2 shows a configuration of a double ring optical communication network constructed by using four wavelength routers 21 to 24 having the wavelength router 20 as a basic form. FIG. 3 shows a state of routing of the optical signal having the wavelength λ 1 between the wavelength router 21 and the wavelength router 22. FIG. 4 is a diagram showing a wavelength routing path realized by this embodiment.

As shown in FIG. 1, the wavelength router 20 includes dielectric thin film filter type three-port devices 1 to 12, and has a so-called optical add / drop filter structure. When the wavelength router 20 is used on the optical communication network shown in FIG. 2, the basic configuration is the same for each node (station) of the optical communication network, but the wavelength of each dielectric thin film filter type three-port device is different. Wavelength routers 21, 22, 23, and 24 are used. FIG. 1 shows the state of add / drop of optical signals of respective wavelengths in the case of the wavelength router 21.

The wavelength router 21 will be described. The dielectric thin film filter type three-port device 1 takes out light of wavelength λ1 input from the optical fiber 25a and outputs it to the local port group 30 (corresponding to 31 in FIG. 2). The dielectric thin film filter type three-port device 2 guides the light of wavelength λ1 input from the local port group 30 (corresponding to 31 in FIG. 2) to the optical fiber 25b. The dielectric thin film filter type three-port device 3 takes out light of wavelength λ2 input from the optical fiber 25a and outputs it to the local port group 30 (corresponding to 31 in FIG. 2). The dielectric thin film filter type three-port device 4 guides the light of wavelength λ2 input from the local port group 30 (corresponding to 31 in FIG. 2) to the optical fiber 25b. The dielectric thin film filter type three-port device 5 takes out light of wavelength λ3 input from the optical fiber 25a and outputs it to the local port group 30 (corresponding to 31 in FIG. 2). The dielectric thin film filter type three-port device 6 guides the light of wavelength λ3 inputted from the local port group 30 (corresponding to 31 in FIG. 2) to the optical fiber 25b. The dielectric thin film filter type three-port device 8 takes out light of wavelength λ1 input from the optical fiber 26a and outputs it to the local port group 30 (corresponding to 31 in FIG. 2). The dielectric thin film filter type three-port device 7 guides the light of wavelength λ1 input from the local port group 30 (corresponding to 31 in FIG. 2) to the optical fiber 26b. The dielectric thin film filter type three-port device 10 takes out light of wavelength λ2 input from the optical fiber 26a and outputs it to the local port group 30 (corresponding to 31 in FIG. 2). The dielectric thin film filter type three-port device 9 guides light of wavelength λ2 input from the local port group 30 (corresponding to 31 in FIG. 2) to the optical fiber 26b. The dielectric thin film filter type three-port device 12 takes out the light of wavelength λ3 inputted from the optical fiber 26a and outputs it to the local port group 30 (corresponding to 31 in FIG. 2). The dielectric thin film filter type three-port device 11 guides the light of wavelength λ3 input from the local port group 30 (corresponding to 31 in FIG. 2) to the optical fiber 26b.

  The other wavelength routers 22 to 24 operate in the same manner as the wavelength router 21, but the handled wavelengths are different. The wavelength router 22 operates by replacing λ2 of the wavelength router 21 with λ4 and λ3 with λ5. The wavelength router 23 operates by replacing λ1 of the wavelength router 21 with λ2, λ2 of the wavelength router 21 with λ5, and λ3 with λ6. The wavelength router 24 operates by replacing λ1 of the wavelength router 21 with λ3, λ2 of the wavelength router 21 with λ5, and λ3 with λ6.

  FIG. 2 is a diagram showing the configuration of a double ring optical communication network comprising wavelength routers 21 to 24 and outer peripheral side optical fibers 25 to inner peripheral side optical fibers 26. Optical signals with wavelengths λ1 to λ6 are transmitted clockwise on the outer peripheral side optical fiber 25, and optical signals with wavelengths λ1 to λ6 are transmitted counterclockwise on the inner peripheral side optical fiber 26. In the wavelength router 21, optical signals having wavelengths λ1, λ2, and λ3 are added and dropped, and optical signals having wavelengths λ4, λ5, and λ6 are bypassed. In the wavelength router 22, optical signals having wavelengths λ1, λ4, and λ5 are added and dropped, and optical signals having wavelengths λ2, λ3, and λ6 are bypassed. In the wavelength router 23, optical signals having wavelengths λ2, λ4, and λ6 are added and dropped, and optical signals having wavelengths λ1, λ3, and λ5 are bypassed. In the wavelength router 24, optical signals having wavelengths λ3, λ5, and λ6 are added and dropped, and optical signals having wavelengths λ1, λ2, and λ4 are bypassed.

  The wavelength routers 21, 22, 23, and 24 are provided with local-side ports 31, 32, 33, and 34, respectively, and these ports include a switch (or router) 41 having a tree-like architecture, 42, 43, and 44 are connected correspondingly. These switches (or routers) 41, 42, 43 and 44 are equipped with a detachable optical transceiver 45. The detachable optical transceiver 45 includes an optical transceiver called GBIC or SFP, for example. These optical transceivers are designed to output an optical signal having a wavelength corresponding to CWDM (low density wavelength multiplexing) or DWDM (high density wavelength multiplexing). Since the optical transceiver 45 can individually output different wavelengths, the optical transceiver 45 is switched (or switched) so that the wavelength corresponds to each dielectric thin film filter type three-port device in the wavelength router. Router) 41, 42, 43, and 44. In this embodiment, a detachable optical transceiver is used, but a wavelength conversion mechanism is interposed between the wavelength routers 21, 22, 23 and 24 corresponding to the switches (or routers) 41, 42, 43 and 44. You may let them.

  Specific wavelengths of each optical signal are values such as λ1: 1490 nm, λ 2: 1510 nm, λ 3: 1530 nm, λ 4: 1550 nm, λ 5: 1570 nm, λ 6: 1590 nm from the CWDM wavelengths determined by the ITU, for example. Can be selected. Of course, this wavelength can be selected from any other combination of wavelengths, for example, six waves from the C-band 100 GHz grid from the DWDM wavelength band defined by the ITU.

  In FIG. 3, the optical signals of the two wavelengths λ1 from the local side port 31 of the wavelength router 21 are propagated on the outer side optical fiber 25 in the clockwise direction by one system (λ1a) to reach the wavelength router 22. One system (λ1c) propagates counterclockwise on the inner circumference optical fiber 26, bypasses the wavelength routers 24 and 23 in order, reaches the wavelength router 22 and is output to the local port 32 together. On the other hand, two optical signals of wavelength λ1 from the local side port 32 of the wavelength router 22 propagate counterclockwise on the inner peripheral optical fiber 26 in one system (λ1b) and reach the wavelength router 21. The system (λd) propagates on the outer optical fiber 25, bypasses the wavelength routers 23 and 24 in order, reaches the wavelength router 21 and is output to the local port 31 together. That is, between the wavelength router 21 and the wavelength router 22, two clockwise and counterclockwise full-duplex signal paths are formed by the optical signal having the wavelength λ1. For this reason, even if an optical fiber is cut at any one place in the double ring optical fiber communication network shown in FIG. 3, either the clockwise or the counterclockwise system survives, and the reliability of the communication network is increased. Can be improved.

FIG. 4 shows a wavelength routing path formed by the double ring optical fiber communication network of the present embodiment shown in FIG. The double ring optical fiber communication network of the present embodiment forms a full mesh and redundant wavelength routing path indicated by 50 in FIG. 4 between the switches (or routers) 41, 42, 43 and 44. For example, the wavelength routing path 51 is a full-duplex wavelength routing path composed of a set of optical signals having the wavelengths λ1a and λ1b shown in FIG. The wavelength routing path 52 is a full-duplex wavelength routing path composed of a set of optical signals having the wavelengths λ1c and λ1d shown in FIG.

The wavelength routing path 50 has a wavelength λ1 between the switches 41 and 42, a wavelength λ2 between the switches 41 and 43, a wavelength λ3 between the switches 41 and 44, and a wavelength λ4 between the switches 42 and 43. FIG. 4 shows that the switch 42 and the switch 44 are connected at a wavelength λ5, and the switch 43 and the switch 44 are connected at a wavelength λ6.

  There are six paths between the four switches, but each path corresponds to a respective wavelength. Moreover, each route is provided with a clockwise and counterclockwise redundant route. The full-mesh communication path is a path with high communication efficiency, and each path is made redundant, and has the advantage that one path is secured even in the event of a physical optical fiber cut or the like.

  In addition, as shown in FIG. 2, each wavelength router optically bypasses optical signals other than those wavelength routers that add and drop, so there is no need for the switches 41 to 44 to process these bypassed optical signals. The processing capacity of the switch has been reduced. In other words, each node (wavelength router) adds and drops only three waves, and the other three waves are bypassed, so that the hardware scale of the switch can be halved compared with the case where all of them are electrically processed. .

A second embodiment of the present invention will be described with reference to FIGS. In the first embodiment, a double ring is constructed using two optical fibers. However, in this embodiment, a duplex ring is constructed by performing bidirectional transmission at different wavelengths on a single optical fiber. . FIG. 5 shows an internal configuration of the wavelength router 70 according to the second embodiment of the present invention. FIG. 6 shows a configuration of a double ring optical communication network constructed using three wavelength routers 71 to 73 having the wavelength router 70 as a basic form. FIG. 7 is a diagram showing a wavelength routing path realized by this embodiment.

As shown in FIG. 5, the wavelength router 70 includes dielectric thin film filter type three-port devices 61 to 68, and has a so-called optical add / drop filter structure. When the wavelength router 70 is used on the optical communication network shown in FIG. 2, the basic configuration is the same for each node (station) of the optical communication network, but the wavelength of each dielectric thin film filter type three-port device is different. Wavelength routers 71, 72, and 73 are used. FIG. 5 shows an add / drop state of the optical signal of each wavelength in the case of the wavelength router 71.

  The wavelength router 71 will be described. The dielectric thin film filter type three-port device 71 outputs an optical signal having a wavelength λ1 from the local port side to the optical fiber 75a side. The dielectric thin film filter type three-port device 62 takes out light of wavelength λ2 input from the optical fiber 75a and outputs it to the local side. A pair of full-duplex optical signal transmission lines is formed by optical signals of wavelengths λ1 and λ2.

  The dielectric thin film filter type three-port device 63 outputs light of wavelength λ1 from the local port side to the optical fiber 75b side. The dielectric thin film filter type three-port device 64 outputs the light of wavelength λ2 input from the optical fiber 75b to the local port side. The dielectric thin film filter type three-port device 65 outputs light of wavelength λ3 from the local port side to the optical fiber 75a side. The dielectric thin film filter type three-port device 66 outputs light of wavelength λ4 from the optical fiber 75a side to the local port side. The thin film three-port device 67 outputs the light of wavelength λ3 from the local port side to the optical fiber 75b side. The thin film three-port device 68 outputs light having a wavelength λ4 from the optical fire 75b side to the local port side.

  The other wavelength routers 72 and 73 operate in the same manner as the wavelength router 71, but the wavelengths handled are different as shown in FIG.

  FIG. 6 is a diagram showing a configuration of a ring-shaped optical communication network composed of wavelength routers 71 to 73 and an optical fiber 75. Switches (or routers) 81, 82, and 83 having a tree-like architecture are connected to the wavelength routers 71, 72, and 73, respectively. A detachable optical transceiver 85 is attached to the switches 81, 82, and 83. The detachable optical transceiver 85 includes, for example, an optical transceiver called GBIC or SFP. These optical transceivers are designed to output an optical signal having a wavelength corresponding to CWDM (low density wavelength multiplexing) or DWDM (high density wavelength multiplexing).

  As shown in FIG. 6, the wavelength router 71 sends optical signals λ1a and λ1b of two wavelengths λ1 to the wavelength router 72. Further, the wavelength router 72 sends optical signals λ2a and λ2b of two wavelengths λ2 to the wavelength router 71. The wavelength λ1a and the wavelength λ2a form one full-duplex communication path, and the wavelength λ1b and the wavelength λ2b form another full-duplex communication path. As a result, two redundant communication paths (clockwise and counterclockwise) are formed.

FIG. 7 shows a wavelength routing path formed by the ring-shaped optical fiber communication network of this embodiment shown in FIG. The ring-shaped optical fiber communication network of this embodiment forms a full mesh and redundant wavelength routing path indicated by 90 in FIG. 8 between the switches 81, 82, and 83.

FIG. 8 shows an internal configuration of the wavelength router 100 according to the third embodiment of the present invention. In this embodiment, high-density wavelength division multiplexing (DWDM) is used and an optical fiber amplifier is provided inside. The wavelength router 100 according to this embodiment includes optical add / drop multiplexers (OADM) 101 and 102 and erbium-doped fiber optical amplifiers (EDFA) 103 and 104.

  Dielectric thin film filter type three-port devices (not shown) are incorporated in the optical add / drop multiplexers (OADM) 101 and 102, and a predetermined wavelength can be added (added) or taken out (dropped). .

  The optical signal from the optical fiber 107a is first amplified by an erbium-doped fiber optical amplifier (EDFA) 103, and then a predetermined optical signal is added / dropped by an optical add / drop multiplexer (OADM) 101, and then to the optical fiber 107b. Is output. Similarly, an optical signal from the optical fiber 108a is first amplified by an erbium-doped fiber optical amplifier (EDFA) 104, and then a predetermined optical signal is added / dropped by an optical add / drop multiplexer (OADM) 102. To 108b.

  The local port groups 105 and 106 are connected to a switch (not shown). Optical signals connected to other wavelength routers are input to and output from the local port group 105 counterclockwise. An optical signal extracted (dropped) from the optical signals input from the optical fiber 107 a is sent to the local port group 105. An optical signal group input from the switch side (not shown) to the local port group 105 is added (added) to the optical signal transmitted to the optical fiber 108b side. An optical signal group connected to other wavelength routers in the counterclockwise direction is input to and output from the local port group 106. The optical signal extracted (dropped) from the optical signals input from the optical fiber 108 a is sent to the local port group 106. The optical signal group input from the switch side (not shown) to the local port group 106 is added (added) to the optical signal transmitted to the optical fiber 107b side.

  FIG. 9 shows the configuration of a double ring optical communication network formed using the wavelength router of this embodiment. This double ring optical communication network includes wavelength routers 111 to 118, an outer peripheral side optical fiber 121, and an inner peripheral side optical fiber 122. The optical signal is transmitted clockwise in the outer peripheral optical fiber 121, and the optical signal is transmitted counterclockwise in the inner peripheral optical fiber 122. In this embodiment, 28 types of optical signals of λ1 to λ28 are used, and 28 redundant full-duplex communication paths are formed in a full mesh between the wavelength routers 111 to 118.

  In total, 28 types of wavelengths are used, but in each node (wavelength router), only 7 wavelengths specific to each node are added and dropped, and the remaining 21 wavelengths are bypassed. That is, the hardware scale of the switch and router connected to the wavelength router is 25% compared to the case where all of them are electrically processed.

Here, the number of wavelengths and wavelength arrangement necessary for forming a full mesh communication path between a plurality of nodes will be described. In the case of N stations, a route from N nodes to the remaining N-1 nodes is required. However, since the number of routes is also counted twice in the partner node, N routes are eventually obtained. In order to form a full mesh communication path between nodes, M paths given by the following equations are required.

  These M paths can be realized with M wavelengths if two optical fibers are used as shown in FIG. 2 and FIG. 9, and can be realized by using one optical fiber as shown in FIG. If the communication path is formed by changing the downstream wavelength, 2M wavelengths are required.

When two optical fibers are used as shown in FIGS. 2 and 9 and there are 8 nodes, 28 wavelengths are required from equation (1). When the wavelength arrangement at this time is expressed in matrix, it is expressed by equation (2).

  Λ1 is a vector having eight elements, and its elements λ1 to λ7 indicate wavelengths that form a communication path from the node 1 to another node. The element φ of Λ1 is a “wavelength” indicating a communication path from the node 1 to the node 1, but since this does not actually need to be provided, a concept φ representing an empty set is inserted. If the communication path between the node 1 and the node 2 is formed with the wavelength λ1, the wavelength λ1 is always included in the vector indicating the communication path from the node 2 to another node, and the fact that the element of Λ2 is [ λ1, φ, λ8, λ9, λ10, λ11, λ12, λ13]. That is, the matrix of the equation (2) is a transposed matrix. In an optical communication network formed by using two optical fibers as shown in FIGS. 2 and 9, the wavelength used as the communication path from node 2 to node 1 is the communication path from node 1 to node 2. This is because it must match the wavelength used. Note that forming a communication path from node 1 to node 2 at wavelength λ1 means that the wavelength of the optical signal transmitted from node 1 is λ1, and that the optical signal of λ1 is received by node 2. ing.

In order to form a communication path with the minimum number of wavelengths with a full mesh between N nodes using the communication network shown in FIG. 2 or FIG. 9, it is necessary to provide the wavelength arrangement shown in the equations (3) to (4). is there.

  Although the empty set is included in the above (3), it is not necessary to mount the wavelength represented by the empty set, so the wavelength to be mounted is a wavelength at which a full mesh is provided between N nodes. The router may be mounted with N-1 wavelengths. Since different wavelengths are mounted on each node, N types of optical add / drop multiplexers corresponding to Λ1 to ΛN are mounted.

  In addition, in order to provide a redundant path in a ring network, it is necessary to perform clockwise transmission and reception and counterclockwise transmission and reception for each wavelength. Therefore, it is necessary to provide two sets of add means and drop means for each wavelength. Eventually, optical add / drop multiplexer 2 (N-1) sets of add means drop means pairs corresponding to the full mesh connection between N nodes are provided. (N-1) add means drop means pairs are provided for clockwise rotation and another (N-1) add means drop means pairs are provided for counterclockwise use. The add means and drop means may specifically be a dielectric thin film filter or a fiber Bragg grating filter.

  In the above-described wavelength arrangement, for example, the upper right half of the non-diagonal component of the matrix of equation (3) can be arbitrarily determined, but the lower left side is uniquely located corresponding to the upper right half. This is effective for reducing the number of wavelengths to be used, but has the disadvantage that the degree of freedom of wavelength arrangement is reduced. Therefore, as another embodiment, the network may be configured without matching the wavelength of the communication path from the node 1 to the node 2 with the wavelength of the communication path from the node 2 to the node 1. In this case, the number of wavelengths to be used is doubled, but there is an advantage that the wavelength arrangement becomes free.

  As shown in FIG. 6, when a communication path is formed by changing the wavelength between upstream and downstream using a single optical fiber, the wavelength arrangement as shown in equation (3) can be taken, for example, between nodes. To form a full mesh, 56 different wavelengths are required. Generally speaking, in the communication network of FIG. 6, a full mesh is formed by providing 2M wavelengths between N nodes. Here, M is a value represented by the equation (1).

The wavelength arrangement when the wavelength of the communication path from the node 1 to the node 2 and the wavelength of the communication path from the node 2 to the node 1 are not matched is given by the following expression.

  The wavelength arrangement washed by equations (5) and (6) can also be used when bidirectional transmission is realized by changing the upstream and downstream wavelengths with a single optical fiber.

  In some embodiments, wavelengths are arranged in the optical add / drop multiplexer so that a full mesh communication path can be realized, and some of the communication paths are not used. Since the full mesh has all possible paths between N nodes, a star topology can be realized by not using a part of the full mesh path.

  In FIG. 8, there is also a mode in which the optical signal for clockwise rotation and the optical signal for counterclockwise wavelength multiplexing are further realized by a single optical fiber. For example, a C-band (1530-1560 nm) optical amplifier is used for the erbium-doped fiber optical amplifier 103, an L-band (1565-1605 nm) optical amplifier is used for the erbium-doped fiber optical amplifier 10L, and clockwise and counterclockwise signals are obtained. In this embodiment, multiplexing is performed on one optical fiber by a wavelength multiplexer (not shown). The input port 107a of the erbium-doped fiber optical amplifier 103 and the output port 108b of the optical add-drop multiplexer 102 are multiplexed by a wavelength multiplexer (not shown). Similarly, the input port 108a of the erbium-doped fiber optical amplifier 104 and the optical add-drop multiplexer are multiplexed. What is necessary is just to multiplex the output port 107b of the kusa 101 with the wavelength multiplexer which is not illustrated.

  The same C-band erbium-doped fiber optical amplifier may be used to divide the C-band into a short wavelength side and a long wavelength side.

  In the above embodiment, an optical add / drop multiplexer is realized by a dielectric thin film filter type three-port device. However, this can be achieved by combining other means such as a fiber Bragg grating filter (FBG) and an optical circulator. An add-drop multiplexer can also be realized.

  Further, the optical amplifier is not limited to the erbium-doped fiber optical amplifier, but other rare-earth doped fiber optical amplifier, Raman optical amplifier, semiconductor laser optical amplifier, rare-earth doped planar waveguide optical amplifier, or the like may be used.

  FIG. 10 shows the internal structure of the wavelength router according to the fourth embodiment of the present invention. This embodiment is a modification of the wavelength router of FIG. FIG. 10A shows the case of the third embodiment, and an erbium-doped optical fiber amplifier 103 is arranged in front of an optical add / drop multiplexer (OADM) 101 as a preamplifier.

  In FIG. 10B, an erbium-doped optical fiber amplifier 105 is arranged at the subsequent stage of the optical add / drop multiplexer (OADM) 101 as a boost amplifier. In FIG. 10C, the erbium-doped optical fiber amplifier 103 is arranged as a preamplifier and the erbium-doped optical fiber amplifier 105 is arranged as a boost amplifier.

  10A, 10B, and 10C can operate, but FIGS. 10A to 10C are preferable in consideration of the isolation characteristics of the optical add-drop multiplexer (OADM) 101. FIG. From the viewpoint of long-distance transmission characteristics, FIG. 10C in which a preamplifier and a booster amplifier are arranged is most desirable. On the other hand, FIGS. 10A to 10B are desirable from the viewpoint of cost.

  The relationship between the isolation characteristics of the optical add-drop multiplexer (OADM) 101 and the arrangement of the erbium-doped optical fiber amplifier will be described with reference to FIG. Dielectric thin film filter type three-port devices 131 and 132 are provided inside the optical add / drop multiplexer (OADM) 101. The optical signal 133 from the port 136 side is added by the dielectric thin film filter type three port device 131, and the optical signal 134 is dropped by the dielectric thin film filter type three port device 131. As shown in FIG. 10B, when there is no erbium-doped optical fiber amplifier in all stages of the optical add-drop multiplexer (OADM) 101, the optical signal 134 may be attenuated by long-distance transmission. On the other hand, the added optical signal 133 is strong. For example, the optical signal 134 may be attenuated to about −25 dBm. On the other hand, the optical signal 133 is about 0 dBm. As a result, the amount of light 135 from which the optical signal 133 leaks from the dielectric thin film filter type three-port device 132 to the port 137 side cannot be ignored.

  The ratio at which the dielectric thin film filter type three-port device does not leak light signals of other wavelengths is called isolation 138, and this value is usually about 25 to 30 dB. Here, the isolation of 25 dB means that the amount of leaked light is attenuated to −25 dB. In the case of isolation, the minus is usually omitted.

  Therefore, although the received optical signal 134 dropped to the port 137 is −25 dBm, the leakage light quantity 135 reaches −30 dB, and the difference is only 5 dB. Usually, it is said that the difference between the signal component (in this case, the reception signal 134) and the amount of leakage light 135 in the case of a noise signal is at least 20 dB, preferably 25 dB, so that the reception signal 134 is correctly received. (See FIG. 11 (b)).

  In addition, when a signal attenuated by passing through many stages of optical add / drop multiplexers from a distant node, a strong signal from a close node may cause crosstalk.

  As shown in FIG. 10A, when the erbium-doped optical fiber amplifier 103 is arranged in all stages of the optical add / drop multiplexer (OADM) 101, the dropped received optical signal is also amplified to a value close to 0 dBm. The problem of a decrease in the signal-to-noise ratio as described above does not occur. Therefore, from this point of view, the configuration as shown in FIG. 10A or 10C is desirable. That is, if the configuration as shown in FIG. 10A or 10C is used, an optical add / drop multiplexer (OADM) having an isolation value of about 25 to 30 dB can be used. There is no need to use an enhanced optical add drop multiplexer (OADM).

  FIG. 12 shows a case where the gain control mechanism of the erbium doped fiber optical amplifier 103 is further attached to the present embodiment. A part of the optical signal dropped from the port 141 of the optical add / drop multiplexer (OADM) 101 is taken out by the optical fiber coupler 142 and inputted to the port 143 of the erbium doped fiber optical amplifier 103. The erbium-doped fiber optical amplifier 103 operates so as to change the gain according to the input optical signal of the port 143 and keep the optical signal intensity from the port 143 substantially constant.

  The branching ratio of the optical fiber coupler 142 is preferably selected so that the branching to the port 143 side is about 1/10 to 1/100. A normal optical signal may be used as the optical signal from the port 141, but it is particularly preferable to use a monitor channel (or supervisor channel) optical signal for network monitoring.

  In FIG. 12, a light quantity detection mechanism is provided in the erbium-doped fiber optical amplifier 103. However, a received light quantity detection mechanism is provided in the optical transceiver to be connected to the optical add / drop multiplexer (OADM) 101, and the detection result thereof. May be sent to the erbium-doped fiber optical amplifier 103 in the form of an electrical signal to perform gain control. This method is advantageous in that the optical transceiver has a complicated structure, but the light loss is small.

  FIG. 14 shows a wavelength router (optical add / drop multiplexer) according to the fifth embodiment of the present invention. A significant feature is the use of a duplicate dielectric thin film filter type three-port device described below.

By sharing the collimator and the filter, substantially two dielectric thin film filter type three-port devices can be formed. FIG. 13 is a diagram showing the structure of such a duplicate dielectric thin film filter type three-port device 150 . The incident port 151, the reflection port 152, and the transmission port 153 form one dielectric thin film filter type three-port device, and the incident port 161, the reflection port 162, and the transmission port 163 form another dielectric three-port device. Forming. The collimator lenses 154 and 156 and the dielectric thin film filter 155 are shared. Since the dielectric thin film filter is shared, the transmission wavelengths of the two dielectric thin film filter type three-port devices formed as described above are the same.

The wavelength router 20 shown in FIG. 1 uses many dielectric thin film filter type three-port devices having the same wavelength. For example, the dielectric thin film filter type three-port devices 1, 2, 7, and 8 have a wavelength of λ1. Therefore, the number of dielectric thin film filters and collimator lenses to be actually used is reduced by using a duplicate dielectric thin film filter type three port device 150 as shown in FIG. 13 for these dielectric thin film filter type three port devices. As a result, cost can be reduced.

The problem of isolation as described in FIG. 11 also occurs in the wavelength router (optical add / drop multiplexer) shown in FIG. In order to solve such a lack of isolation, a dielectric thin film filter type three-port device may be provided twice at a port where an optical signal is dropped as shown in FIG. FIG. 14 shows a configuration in which such a double filter configuration is provided in the drop port of the wavelength router 70 of FIG. Assuming that the isolation of the filter stage is 25 dB, the isolation is doubled to 50 dB when two stages of filters are stacked. Therefore, the lack of isolation can be resolved.

  In FIG. 14, the dielectric thin film filter type three port devices 62a and 62b can be constituted by the duplicate type dielectric thin film filter type three port device shown in FIG. In this way, the number of dielectric thin film filters and collimator lenses that are actually used can be reduced to reduce the cost. Similarly, the dielectric thin film filter type three-port devices 64a and 64b, the dielectric thin film filter type three port devices 66a and 66b, and the dielectric thin film filter type three port devices 68a and 68b are respectively used as duplicate type dielectric thin film filter type three port devices. Can be configured. Furthermore, the dielectric thin film filter type three-port devices 61 and 63 and the dielectric thin film filter type three port devices 65 and 67 can also be replaced with a duplicate type dielectric thin film filter type three port device.

FIG. 15A shows a double-pass type dielectric thin film filter three-port device 180 . This is because the light from the incident port 181 is guided to the dielectric thin film filter 185 through the collimator 184, the reflected light is guided to the reflection port 182 and the transmitted light is reflected by the mirror 186, and then passes through the dielectric thin film filter 185 again. In this method, the light is transmitted and guided through the collimator 184 to the transmission port 183. Since the transmitted light passes through the dielectric thin film filter twice (double pass), the isolation is doubled. Further, only one collimator lens is required, and the incident port, the reflection port, and the transmission port are all provided on the same side with respect to the dielectric thin film filter 185.

FIG. 15B further shows a double-pass type dielectric thin film filter three-port device 190 having a duplicate structure according to a sixth embodiment of the present invention. The incident port 181, the reflection port 182, and the transmission port 183 form one double pass type dielectric thin film filter three-port device, and the incident port 191, the reflection port 192, and the transmission port 193 form another single double pass type dielectric thin film filter three. A port device is formed. Since these two double-pass type dielectric thin film filter three-port devices share the collimating lens 184, the dielectric thin film filter 185, and the mirror 186, the number of parts can be reduced and the cost can be reduced.

  By using the double pass type dielectric thin film filter / filter three-port device as a port for dropping an optical signal of the optical add / drop multiplexer, the problem of insufficient isolation as shown in FIG. 11 can be solved.

  In addition, a double-pass type dielectric thin film filter three-port device having a duplicate structure can replace, for example, the dielectric thin film filter three-port devices 62 and 64 shown in FIG. Optical add / drop multiplexers often have a structure that uses multiple dielectric thin film filter three-port devices of the same wavelength to add and drop optical signals of the same wavelength, so duplicate dielectric thin film filter three-port devices By using, the number of parts can be reduced and the cost can be reduced.

FIG. 16 shows an embodiment 200 in which the wavelength router (optical add / drop multiplexer) 170 of FIG. 14 is mounted in a box. Since it is necessary to use a port using a two-stage filter as a drop port, misuse of the drop port and the add port must be prevented. Therefore, in this embodiment, a drawing 201 showing a wavelength routing path is provided on the upper surface of the box, and symbols indicating wavelength and transmission / reception distinction, clockwise and counterclockwise distinction are provided on each port (receptacle) 210 to 219 on the front face 202 of the box. The feature is that it is displayed. The symbols on the front face 202 of the box represent wavelengths as λ1, λ2, λ3, and λ4, transmit as Tx, receive as Rx, clockwise as Right, counterclockwise as Left, and common port as C.

  Receptacle 210 is a counterclockwise common port, receptacle 211 is a counterclockwise wavelength λ1 transmission port, receptacle 212 is a counterclockwise wavelength λ2 reception port, receptacle 213 is a counterclockwise wavelength λ3 transmission port, and receptacle 214 is counterclockwise The receiving port of the wavelength λ4. In addition, the receptacle 215 is a transmission port having a clockwise wavelength λ1, the receptacle 216 is a reception port having a clockwise wavelength λ2, the receptacle 217 is a transmission port having a clockwise wavelength λ3, and the receptacle 218 is a reception port having a clockwise wavelength λ4. The receptacle 219 is a clockwise common port.

FIG. 17 shows another embodiment 220 in which the wavelength router (optical add / drop multiplexer) 170 of FIG. 14 is mounted in a box. Another drawing 221 showing the wavelength routing path is provided on the top surface of the box. This drawing shows how the own station (Station-1) and other stations (Station-2, Station-3) are routed. From the viewpoint of the user, the logical connection form may be more important than how each station (node) is physically connected. The embodiment of FIG. 17 is useful in such a case. It is a display method.

  The symbols on the front face 222 of the box represent wavelengths as λ1, λ2, λ3, and λ4, Tx for transmission, Rx for reception, Right for right, Left for left, and C for common port. Moreover, the display of Station-2 and Station-3 has shown the other party of the communication path | route.

  Connection of each receptacle provided on the box front surface 222 is different from that in FIG. Receptacle 230 is a counterclockwise common port, receptacle 231 is counterclockwise a transmission port of wavelength λ1 toward Station-2, receptacle 232 is counterclockwise and a reception port of wavelength λ2 received from Station-2, and receptacle 233 is clockwise and Station -2 is a transmission port having a wavelength λ1 and a receptacle 234 is a reception port having a wavelength λ2 received from Station-2 in a clockwise direction. In addition, the receptacle 235 is a transmission port of wavelength λ3 that goes counterclockwise toward the station-3, the receptacle 236 is a reception port of wavelength λ4 that receives counterclockwise from the station-3, and the receptacle 237 is a wavelength that goes clockwise to the station-3 The transmission port of λ3, the receptacle 238 is a reception port of wavelength λ4 received from the clockwise Station-3, and the receptacle 239 is a clockwise common port.

Figure 18 shows the case of mounting the wavelength router (OADM) 170 of FIG. 14 as a patch cord 240. The patch cord 240 main body upper surface 241 shows signal paths between the stations (shown as S1, S2, and S3). An optical connector 242 is provided at the tip of the optical fiber cord 244 coming out from the patch cord, and a tag 243 is provided near the optical connector 242. Each tag indicates the wavelength, role, communication path, etc. of each optical connector. Has been.

  The configuration of the seventh embodiment is useful not only for the optical add / drop multiplexer. FIG. 19 shows an optical fiber communication network in which bidirectional transmission is realized on a single optical fiber 270 by changing the upstream wavelength and downstream wavelength.

In FIG. 19, the wavelength multiplexer 250 includes dielectric thin film filter type three-port devices 251 to 254. The wavelength multiplexer 260 includes dielectric thin film filter type three-port devices 261 to 264.

An optical signal with a wavelength λ1 for transmission is added to the port 255 of the wavelength multiplexer 250 , and an optical signal with a wavelength λ2 for transmission is added to the port 256, respectively. The optical signals multiplexed by the dielectric thin film filter type three port devices 251 and 252 are sent to the common port 259, the optical fiber 270, and the common port 269 of the wavelength multiplexer 260 . The multiplexed optical signals are separated by the dielectric thin film filter type three-port devices 261 and 262 in the wavelength multiplexer 260 into optical signals of the original wavelengths λ1 and λ2, respectively, and output to the ports 265 and 266, respectively. Is done.

An optical signal with a wavelength λ3 for transmission is added to the port 267 of the wavelength multiplexer 260 , and an optical signal with a wavelength λ4 for transmission is added to the port 268, respectively. The optical signals multiplexed by the dielectric thin film filter type three port devices 263 and 264 are sent to the common port 269, the optical fiber 270, and the common port 259 of the wavelength multiplexer 250 . The multiplexed optical signals are separated by the dielectric thin film filter type three-port devices 253 and 254 in the wavelength multiplexer 250 into optical signals of the original wavelengths λ3 and λ4, respectively, and output to the ports 257 and 258, respectively. Is done.

  These wavelength multiplexers 250 to 260 can be regarded as wavelength routers having the simplest function. This is because wavelength routing is performed although it is point-to-point.

  In the wavelength multiplexer 250, it is meaningful to dispose the dielectric thin film filter type three port devices 251 to 252 for transmission at positions close to the common port 259. This will be described with reference to FIG.

In FIG. 20, a port 281 is an incident port, a port 282 is a reflection port, and a port 283 is a transmission port. A dielectric thin film filter type three-port device 280 is constituted by these ports, the collimator 284, the dielectric thin film filter 285, and the collimator 285. Here, in the dielectric thin film filter type three-port device 280 , it is known that when a transmission optical signal is incident from the transmission port 283 side, almost no crosstalk occurs on the reflection port 282 side. This is because the component that becomes the crosstalk of the light incident from the transmission port 283 side is reflected to the direction 287 side and hardly propagates to the direction 288 side coupled to the reflection port 282.

  The configuration of FIG. 19 is effective even when there is an optical connector or the like in the immediate vicinity of the incident port 281 and a large reflection (so-called −13 dB reflection caused by Fresnel reflection at the air-glass interface) occurs. It is known that most of the Fresnel reflected light from the vicinity of the incident port 281 is guided to the transmission port 283, and the amount of light reflected toward the direction 288 is attenuated to -15 dB to -20 dB with respect to the incident light. This attenuation amount is added to the isolation of the dielectric thin film filter type three-port devices 253, 254, 261, or 262 on the receiving side. Therefore, effective isolation of about 40 dB to 50 dB in total can be realized, and the problem of crosstalk can be eliminated.

  Utilizing the above properties, in the wavelength multiplexer 250, the dielectric thin film filter type three-port devices 251 to 252 for transmission are arranged at positions close to the common port 259. As a result, it is possible to realize bidirectional transmission using different wavelengths for upstream and downstream on one optical fiber without causing the problem of insufficient isolation as described with reference to FIG. In FIG. 19, a two-channel full-duplex communication path is realized using four wavelengths, but a one-channel full-duplex communication path is realized using two wavelengths, or four wavelengths are used. A channel full-duplex communication path can also be realized. In either case, it is necessary to dispose the dielectric thin film filter type three-port device for transmission closer to the common port than the dielectric thin film filter type three-port device for reception.

FIG. 21 shows an example in which the wavelength router (wavelength multiplexer) according to the eighth embodiment of the present invention is mounted in the boxes 290 and 300 . In this embodiment, if the transmission port and the reception port are not distinguished to prevent misuse, an isolation problem may occur. Therefore, drawings 291 and 301 showing wavelength routing paths are provided on the upper surfaces of the boxes 290 and 300 , respectively. The wavelength routing paths shown in FIGS. 291 and 301 are different from the connection of the actual dielectric thin film filter type three-port device shown in FIG. 19, but are easy to understand from the user.

Ports (receptacles) 255 to 258 on the front surface 292 of the box 290 correspond to the ports shown in FIG. The box front 292 shows transmission as Tx, reception as Rx, and channels (full-duplex communication paths) as CH1 and CH2, respectively. The wavelengths are expressed as λ1, λ2, λ3, and λ4. The common port is represented as common port C.

Each port (receptacle) 265 to 268 on the front surface 302 of the box 300 corresponds to the port shown in FIG. The box front 292 shows transmission as Tx, reception as Rx, and channels (full-duplex communication paths) as CH1 and CH2, respectively. The wavelengths are expressed as λ1, λ2, λ3, and λ4. The common port is represented as common port C.

  In this embodiment, the case where the wavelength multiplexer is mounted on the box is shown, but it may be mounted as a patch cord.

FIG. 22 shows a wavelength router (optical add / drop multiplexer) 310 according to the ninth embodiment of the present invention. By devising a method and wavelength arrangement to compensate for the lack of isolation by arranging the dielectric thin film filter type three-port devices 321, 322, 327 and 328 for transmission shown in the eighth embodiment at positions close to the output port The wavelength routers 311 to 313 are realized without using a double filter or a double path structure. The dielectric thin film filter type three-port devices 323, 324, 235, and 326 are used for reception. Reference numeral 315 indicates an optical fiber, and reference numerals 331 to 338 indicate an drop port.

  The wavelength router 311 uses wavelengths λ1, λ2, λ4, and λ5. The wavelength router 312 uses wavelengths λ1, λ2, λ7, and λ8. The wavelength router 313 uses wavelengths λ4, λ5, λ7, and λ8.

  Eight wavelengths preferably used in low density wavelength multiplexing (CWDM), λ1 = 1470 nm, λ2 = 1490 nm, λ3 = 1515 nm, λ4 = 1530 nm, λ5 = 1550 nm, λ6 = 1570 nm, λ7 = 1590 nm, λ8 = 1610 nm, λ1 Λ2, λ4, λ5, and λ7 and λ8 are selected from three pairs of wavelengths. The paired wavelengths are used as the transmitting wavelength and the receiving wavelength, respectively, and the technique shown in the eighth embodiment is used for the wavelength filter, so that the lack of isolation between the paired wavelengths is first compensated. Furthermore, the lack of isolation is further compensated by leaving one wavelength between the paired wavelengths.

  If the wavelength is used continuously, for example, the problem of the crosstalk 340 as shown in FIG. 23 occurs. In FIG. 23, the optical signal of wavelength λ2 is dropped in the wavelength router 311 and the light of wavelength 3 is bypassed. Here, it is assumed that the optical signal of wavelength λ2 is from a distant node and is greatly attenuated. For example, the optical intensity is −30 dBm. On the other hand, it is assumed that the optical signal having the wavelength λ3 is from an adjacent node and is hardly attenuated and has an intensity of 0 dBm. Since isolation between the wavelengths λ2 and λ3 is only about 30 dB in the case of a single-stage filter, the crosstalk from the wavelength λ3 and the optical signal intensity at the wavelength λ2 are almost equal and cannot be received properly.

  A dielectric thin film filter type three-port device for low-density wavelength multiplexing has isolation of about 25 to 30 dB for adjacent wavelengths, but isolation of about 50 to 60 dB for non-adjacent wavelengths. Therefore, if the wavelength λ3 is not used as in the present embodiment, the wavelengths bypassing the wavelength router 311 are all non-adjacent wavelengths, and thus the above-described problem does not occur.

  The wavelength router of FIG. 22 can be used to configure a full mesh communication path on a ring-shaped optical fiber communication network as shown in FIGS. Further, when combined with the wavelength router shown in FIG. 24, a star-type communication path can be configured on a ring-shaped optical fiber communication network.

FIG. 24 shows a wavelength router 350 for forming a star communication path. The dielectric thin film filter type three-port devices 361 and 364 for transmission are arranged on the outside, and the dielectric thin film filter type three port devices 362 and 363 for reception are arranged on the inner side. Reference numeral 355 indicates an optical fiber, and reference numerals 365 to 368 indicate add-drop ports.

  The wavelength router 351 uses wavelengths λ1 and λ2. The wavelength router 352 uses wavelengths λ4 and λ5. The wavelength router 353 uses wavelengths λ7 and λ8. The wavelength router 354 uses wavelengths λ7 and λ8, but the wavelength router 353, the transmission wavelength and the reception wavelength are opposite.

  FIG. 25 shows an optical communication network formed by wavelength routers 311, 351, 352, 353, and 354. The wavelength routers 311, 351, 352, 353, and 354 are connected by a single optical fiber 361. The wavelength routers 351 and 352 are connected in a star shape with the wavelength router 311 as the center. Redundant full-duplex communication paths 362 and 363 are formed between the wavelength router 311 and the wavelength routers 351 and 352, respectively. On the other hand, a point-to-point full-duplex communication path 364 is formed between the wavelength routers 353 and 354. The network composed of the wavelength routers 311, 351, and 352 and the network composed of the wavelength routers 353 and 354 are logically independent.

  FIG. 26 shows a wavelength router (wavelength multiplexer) according to the tenth embodiment of the present invention. This embodiment is a wavelength multiplexer for performing bidirectional transmission using different wavelengths in one optical fiber. The present embodiment is an application of the method of using the CWDM wavelength shown in the ninth embodiment.

  The dielectric thin film filter type three-port device 370 transmits a wavelength λ6 (1570 nm). The dielectric thin film filter type three-port device 380 transmits the wavelength λ4 (1530 nm). A transmission optical signal having a wavelength of λ4 is input to the reflection port 372 of the dielectric thin film filter type three-port device 370. In addition, a transmission optical signal having a wavelength λ4 is input to the reflection port 382 of the dielectric thin film filter type three-port device 370. The optical signal having the wavelength λ 6 that has propagated through the optical fiber 378 is guided to the transmission port 373 through the incident port 371 of the dielectric thin film filter type three-port device 370. The optical signal having the wavelength λ 4 propagating through the optical fiber 378 is guided to the transmission port 383 through the incident port 381 of the dielectric thin film filter type three-port device 380.

  In the dielectric thin film filter type three-port device 370, as shown in FIG. 20, the optical signal incident on the reflection port hardly leaks to the transmission port 373 due to the positional relationship of the optical system. However, when there is a reflection point 374 in the vicinity of the incident port 371, the transmission light signal 376 reflected at the reflection point 374 has an isolation of 25 dB or more for adjacent wavelengths and 50 dB or more for non-adjacent wavelengths. can get. The amount of reflection at the reflection point 374 may reach 4% (-13 dB) of the Fresnel reflection at the glass-air interface. If the optical signal input to the reflection port 372 is an optical signal of 0 dBm, the crosstalk reaches a maximum of −38 dBm in the case of an adjacent wavelength. On the other hand, the optical signal transmitted from the dielectric and other filter type three-port device 380 may attenuate to -35 dBm while propagating through the optical fiber 378. In this case, the S / N ratio (signal-to-noise ratio) is only 3 dB, and it cannot be received properly.

  However, in this embodiment, the transmission wavelength and the reception wavelength are set to λ4 = 1530 nm and λ6 = 1570 nm which are non-adjacent wavelengths of the CWDM wavelength, so that the dielectric thin film filter type three-port devices 370 to 380 can take isolation of 50 dB or more. become. Then, an S / N ratio of 28 dB or more can be obtained, and conditions for good reception, an S / N ratio of 20 dB or more (preferably 25 dB or more) can be realized.

  According to the present embodiment, since one dielectric thin film filter type three-port device is used for realizing bidirectional transmission with one optical fiber using two wavelengths, there is an effect of cost reduction. Further, since non-adjacent wavelengths are used, sufficient isolation can be obtained. It should be noted that the wavelength used is not limited to the CWDM wavelength and is not limited to λ4 = 1530 nm and λ6 = 1570 nm.

  FIG. 27 shows an example in which this embodiment is applied to the case of four wavelengths. The wavelength multiplexer 390 includes dielectric thin film filter type three-port devices 391, 392, and 393. The wavelength multiplexer 400 includes dielectric thin film filter type three-port devices 401, 402, and 403. In addition, λ3 = 1510 nm, λ4 = 1530 nm, λ6 = 1570 nm, and λ7 = 1590 nm are selected from the CWDM wavelengths defined by ITU-T.

  The wavelength multiplexer 390 has four ports 395 to 398. The optical signal of wavelength λ4 input from the port 398 is multiplexed with the optical signal of wavelength λ3 input from the port 397 by the dielectric thin film filter type three port device 393, and the dielectric thin film filter type three port devices 392 and 391 are connected. Then, it is output to the port 399 and reaches the port 409 of the wavelength multiplexer 400 through the optical fiber 410. The optical signals of wavelengths λ6 and λ7 from the port 409 of the wavelength multiplexer 400 reach the port 399 of the wavelength multiplexer 390 through the optical fiber 410, and then dielectric thin film filter type three-port devices 391 and 392. To the ports 395 and 396, respectively.

  The wavelength multiplexer 400 includes four ports 405 to 408. The optical signal of wavelength λ6 input from the port 408 is multiplexed with the optical signal of wavelength λ7 input from the port 407 by the dielectric thin film filter type three port device 403, and the dielectric thin film filter type three port devices 402 and 401 are connected. Then, it is output to the port 409 and reaches the port 399 of the wavelength multiplexer 390 through the optical fiber 410. The optical signals of wavelengths λ4 and λ3 from the port 409 of the wavelength multiplexer 390 reach the port 409 of the wavelength multiplexer 400 via the optical fiber 410, and then the dielectric thin film filter type three port devices 401 and 402. To the ports 405 and 406, respectively.

  According to the configuration shown in FIG. 27, a four-wavelength wavelength multiplexing multiplexer for bidirectional transmission can be realized by using three dielectric thin film filter type three-port devices. Therefore, cost reduction can be performed. In addition, since an interval of one wavelength is placed between the transmission wavelength group and the reception wavelength group, sufficient isolation can be obtained.

FIG. 28 shows a wavelength multiplexer 420 according to the eleventh embodiment of the present invention. This wavelength multiplexer 420 is a wavelength multiplexer for performing bidirectional transmission by changing the wavelength between upstream and downstream with a single optical fiber. As described in the ninth and tenth embodiments, since high isolation is obtained at non-adjacent wavelengths in CWDM, the problem of isolation during bidirectional transmission can be solved using this.

  In this embodiment, in the wavelength multiplexer 421, the transmission wavelength is selected as λ1 = 1470 nm, λ2 = 1490 nm, λ3 = 1515 nm, and λ4 = 1530 nm, and the reception wavelengths are λ5 = 1550 nm, λ6 = 1570 nm, λ7 = 1590 nm, and λ8 = 1610 nm was selected. In addition, in the wavelength multiplexer 422 used as a pair with the wavelength multiplexer 421, the transmission wavelength is selected as λ5 = 1550 nm, λ6 = 1570 nm, λ7 = 1590 nm, and λ8 = 1610 nm, and the reception wavelength is λ1 = 1470 nm. Λ2 = 1490 nm, λ3 = 1515 nm, and λ4 = 1530 nm.

  The wavelength multiplexer 421 includes seven dielectric thin film filter type three-port devices 431 to 437. Ports 441 to 444 are reception local ports corresponding to the wavelengths λ1 to λ4, and ports 445 to 448 are transmission local ports corresponding to the wavelengths λ5 to λ8. Port 449 is a transmission / reception remote port.

  In the wavelength multiplexer 421, in particular, a double-pass dielectric thin film filter type three-port device 434 is used as the dielectric thin film filter type three-port device 434 having a wavelength λ4 = 1530 nm. The double-pass type dielectric thin film filter type three-port device has a structure as shown in FIG. 15A, and has high isolation with respect to adjacent wavelengths. This is because, in the case of wavelength λ4, an optical signal of λ5, which is an adjacent wavelength, is used. If reflection occurs in the vicinity of the transmission / reception remote port 449, there may be a problem of insufficient isolation. This is because it is necessary to provide particularly high adjacent wavelength isolation. For other wavelengths, a normal dielectric thin film filter type three-port device is used because there is no fear that the adjacent wavelength is reflected and returned. The wavelength multiplexer 422 used in a pair with the wavelength multiplexer 421 uses a double-pass dielectric thin film filter type three-port device as a dielectric thin film filter type three port device having a wavelength of λ5.

  Note that a simple two-stage filter is used instead of the double-pass type dielectric thin film filter type three-port device, or a two-stage filter using the duplicate type dielectric thin film filter type three-port device shown in FIG. Also good. When a continuous transmission wavelength group and a continuous reception wavelength group are provided at the CWDM wavelength, it is only necessary to provide a dielectric thin film filter type three-port device having a high adjacent wavelength isolation only at the reception port of the wavelength serving as the boundary. .

  FIG. 29 shows an embodiment in which the wavelength multiplexer is implemented as a patch cord. The dielectric thin film filter type three-port device is connected by fusing an optical fiber, but the fuser requires an optical fiber of a certain length. Therefore, a dielectric thin film filter type three-port device group is usually provided in a rectangular box, and optical fibers are wired in an arc shape. On the other hand, in this embodiment, the dielectric thin film filter type three port device groups 431, 433, 435, and 437 are mounted on the housing 451, and the dielectric thin film filter type three port device groups 432, 434, and 436 are mounted. It is mounted on a housing 453, and the two housings are connected by a cord 452. FIG. 29A is a diagram corresponding to the circuit diagram of the wavelength multiplexer shown in FIG. 28, and FIG. 29B is a diagram showing a state of actual mounting. The housing 451 is provided with a hook 454, and the housing 453 is provided with a hook 455. These hooks are devices that are hooked and held by an optical connector or an appropriate mounting bracket on a front panel of a device such as a router or a switch.

  The patch cord type wavelength multiplexer shown in FIG. 29 (b) has an advantage that it can be flexibly attached to a front panel of a router, a switch or the like because it has a form in which two housings are connected by a cord. Moreover, there is an advantage that it is small compared with the case where it is mounted in a rectangular box as in the prior art.

  If a two-stage filter or a duplicate type dielectric thin film filter type three-port device is used instead of the double-pass type dielectric thin film filter type three port device 434, wiring of a loop-shaped optical fiber in the housing 453 is required. Increases the size of the housing. Therefore, when the wavelength multiplexer of FIG. 28 is mounted as a patch cord, it is desirable to employ a double-pass type dielectric thin film filter type three-port device.

  Note that a wavelength router such as a wavelength multiplexer or an optical add / drop multiplexer may be mounted on the housing by dividing the dielectric thin film filter type three-port device group into two groups as shown in FIG. 29, and the housings may be connected with a cord. Needless to say. That is, the configuration of FIG. 29 is not limited to the circuit configuration of FIG.

  A wavelength router and an optical communication network according to a twelfth embodiment of the present invention will be described with reference to FIGS. As described with reference to FIG. 25 in the ninth embodiment, when the wavelength router of the present invention is used, a plurality of logical network topologies can be formed on a ring-shaped optical fiber network. In this embodiment, a flexible network structure is formed by using dense wavelength division multiplexing (DWDM) which can use a larger number of wavelengths.

  In FIG. 30A, wavelength routers 461 to 468 are connected in a double ring shape by two optical fibers 471 and 472. In the third embodiment, the structure is similar to the network described with reference to FIGS. 9 and 8. The difference from the third embodiment is that a full mesh network is not formed between all wavelength routers. First, a full mesh network is formed between the wavelength routers 461, 464, 465, and 468 using wavelengths λ1 to λ6. A first star network (star 1) is formed between the wavelength routers 462 and 463 with the wavelength router 461 as the center, using the wavelengths λ7 and λ8. Further, a second star network (star 2) is formed between the wavelength routers 466 and 467 with the wavelength router 468 as the center, using the wavelengths λ9 and λ10. Such a wavelength arrangement is shown in FIG.

  In the star topology, an optical add / drop multiplexer that can add / drop the number of wavelengths of the number of slave stations N is arranged in the wavelength router that is the center (master station), and the wavelength router of the slave station is one that identifies the slave station. An optical add / drop multiplexer that adds / drops only the wavelength is arranged. Therefore, a star topology master station accommodating up to N slave stations includes an N wavelength optical add / drop multiplexer. However, when bidirectional transmission is performed with a single optical fiber changing the upstream and downstream wavelengths, 2N wavelengths are required.

  FIG. 31 shows an internal structure of the wavelength router 461 as an example. An optical signal from the input port 492a is amplified by an erbium-doped fiber optical amplifier 491a, and then passes through a first optical add / drop multiplexer (OADM) 481a and a second optical add / drop multiplexer (OADM) 482a, and an output port 493a. Sent. The first optical add / drop multiplexer (OADM) 481a has a wavelength arrangement that forms a full mesh using wavelengths λ1 to λ6. On the other hand, the second optical add / drop multiplexer (OADM) 482a has a wavelength arrangement that forms the star 1 using the wavelengths λ7 and λ8.

  In order to form a plurality of network topologies on the ring-shaped optical fiber topology as shown in FIG. 30, optical add / drop multiplexers having an appropriate wavelength arrangement may be vertically connected as necessary.

  Note that the erbium-doped fiber optical amplifier 491b and the optical add / drop multiplexers 481b and 482b perform optical amplification and add / drop similar to the above on the optical signal from the port 492b.

  FIG. 32 shows a wavelength router according to a modification of this embodiment. In this figure, only a functional part that amplifies an optical signal from the left side of FIG. 32, that is, optically add-drops and sends it to the right side, is shown. Actually, the wavelength router is provided with an optical amplifier and an optical add / drop multiplexer (not shown) in order to amplify and add / drop an optical signal from the right side in FIG.

  In FIG. 32A, the first optical add / drop multiplexer 483 is connected to the subsequent stage of the erbium-doped fiber optical amplifier 491c. This optical add / drop multiplexer 483 has the same structure as that of the optical add / drop multiplexer 101 shown in FIG. 8, and a full mesh network between eight nodes (wavelength routers) using wavelengths λ1 to λ28. Is forming. A second optical add / drop multiplexer 484 is connected to the subsequent stage of the optical add / drop multiplexer 483.

  The second optical add / drop multiplexer 484 has a structure as shown in FIG. This is an optical add-drop multiplexer composed of two arrayed waveguide diffraction gratings 485a and 485b. The two arrayed waveguide gratings 485a and 485b can multiplex and demultiplex 16 wavelengths from λ29 to λ44. Wavelengths that are not added are short-circuited between the corresponding ports of the two arrayed waveguide diffraction gratings 485a and 485b by an optical fiber, and the wavelengths that are added and dropped are drawn out to the outside.

  In place of the arrayed waveguide diffraction grating, a wavelength multiplexer formed by multiplex longitudinal connection of dielectric thin film three-port devices or a wavelength multiplexer formed by multiplex longitudinal connection of fiber Bragg grating filters may be used. good. The point is that wavelength multiplexers (multiplexers, demultiplexers) should be face-to-face.

  Since the configuration shown in FIGS. 32A and 32B is employed, the wavelength arrangement as shown in FIG. 32C can be realized. That is, a full-mesh network can be constructed using the wavelengths λ1 to λ28, and additional communication paths can be arbitrarily provided using the wavelengths λ29 to λ44.

  Various communication paths are realized by wavelength multiplexing on a ring-shaped optical fiber network by arbitrarily connecting full-mesh optical add-drop multiplexer, star optical add-drop multiplexer, free optical add-drop multiplexer, etc. be able to.

  In FIG. 30 (b) and FIG. 32 (c), continuous wavelength arrangement is shown as the wavelength used for each topology form (full mesh, star, free, etc.). However, this wavelength arrangement need not be continuous. Each topology form can be realized by a set having a required number of wavelengths as elements, and each wavelength does not have to be physically continuous.

  Further, there is no limit to the number of topologies such as full meshes and stars, and it is possible to provide two or more full meshes.

  FIG. 33 shows a wavelength router according to the thirteenth embodiment of the present invention. The full-mesh type and star type wavelength routers (optical add-drop multiplexers) described so far can be realized by vertically connecting the basic components shown in FIG.

FIG. 33A shows a basic component 500 of an optical add / drop multiplexer for a network configured using two optical fibers. The basic component 500 includes four dielectric thin film filter type three-port devices 501 to 504. The four dielectric thin film filter type three-port devices 501 to 504 each include a dielectric thin film filter having a wavelength of λi.

The reflection port of the dielectric thin film filter type three port device 501 is connected to the reflection port of the dielectric thin film filter type three port device 502. The reflection port of the dielectric thin film filter type three port device 504 is connected to the reflection port of the dielectric thin film filter type three port device 503. The incident port of the dielectric thin film filter type three port device 501 is one of the input ports of this basic element, and the incident port of the dielectric thin film filter type three port device 504 is another one of the input ports of this basic element 500 . The incident port of the dielectric thin film filter type three-port device 502 and the incident port of the dielectric thin film filter type three port device 503 are output ports of the basic element 500 , respectively. The transmission ports of the dielectric thin film filter type three-port devices 501 to 504 are add-drop ports.

FIG. 33B shows a basic component 510 of an optical add / drop multiplexer applied to a ring-shaped optical fiber communication network of a type in which two optical transmissions are performed using different wavelengths in upstream and downstream using a single optical fiber. Indicates. The basic component 510 is composed of four dielectric thin film filter type three-port devices 501 to 504. The dielectric thin film filter type three-port devices 511 and 513 include a dielectric thin film filter having a wavelength λi, and the dielectric thin film filter type three port devices 512 and 514 include a dielectric thin film filter having a wavelength λj.

The reflection port of the dielectric thin film filter type three port device 511 is connected to the incident port of the dielectric thin film filter type three port device 512. The reflection port of the dielectric thin film filter type three port device 512 is connected to the reflection port of the dielectric thin film filter type three port device 513. The incident port of the dielectric thin film filter type three port device 513 is connected to the reflection port of the dielectric thin film filter type three port device 514. The incident port of the dielectric thin film filter type three-port device 511 is one of the input / output ports of the basic element 510 , and the incident port of the dielectric thin film filter type three-port device 514 is one of the input / output ports of the basic element. Become. The transmission ports of the dielectric thin film filter type three-port devices 511 to 514 are add-drop ports.

When two sets of basic components 500 are used, a point-to-point redundant communication path can be realized on a double ring optical fiber communication network using two optical fibers. Point-to-point can be compared to a “line”, and by combining these lines, any topology can be constructed, whether full mesh or star.

When two sets of basic components 510 are used, a point-to-point redundant communication path can be realized on a ring-shaped optical fiber communication network using one optical fiber. Point-to-point can be compared to a “line”, and by combining these lines, any topology can be constructed, whether full mesh or star.

33. An optical circuit equivalent to the basic elements 500 to 510 in FIG. 33 is a free space optical system, a free space optical system using a structure in which a dielectric thin film filter is mounted on a glass block, and a planar optical waveguide made of glass, plastic, or the like. Needless to say, the present invention includes these implementation examples.

  FIG. 34 shows an optical communication network according to the fourteenth embodiment of the present invention. A base station 1002 and optical signal branch circuit units 1001 a to 1001 d are connected in series by an optical fiber 1004. Client station groups 1003a to 1003d are connected to the optical signal branch circuit units 1001a to 1001d, respectively.

  FIG. 35 shows the internal structure of the optical signal branch circuit unit 1001. The optical signal branch circuit unit 1001 includes dielectric thin film filter type three-port devices 1011 and 1012, a CWDM optical transceiver 1013 having a transmission wavelength of CWDM (low density wavelength division multiplexing), and a transmission wavelength of 1.5 μm. The optical transceiver 1014 includes a WDM (wavelength multiplexing) optical fiber coupler 1015, and a 32-branch tree coupler 1016. A port 1017 is a port on the side different from the base station, and a port 1018 is a port connected to the optical signal branch circuit unit in the next stage. The port group 1021 is a port connected to the client station group.

  Dielectric thin film filter type three-port devices 1011 and 1012 have the same internal structure as that shown in FIG. 45A and are represented by simplified symbols as shown in FIG.

FIG. 36 is a diagram showing a wavelength multiplexing apparatus 1040 provided in the base station 1002. It comprises local optical transceivers 1041a to 1041d, remote CWDM (low density wavelength division multiplexing) optical transceivers 1042a to 1042d, and a wavelength multiplexer 43. A PON switch (not shown) is connected to the left side of the local optical transceivers 1041a to 1041d. CH1 to CH4 indicate PON channels.

  The optical signals of CH1 to CH4 from a PON switch not shown are converted into electrical signals by local optical transceivers 1041a to 1041d, and then determined by ITU-T by remote CWDM (low density wavelength division multiplexing) optical transceivers 1042a to 1042d. The wavelength is converted into wavelengths of λ1, λ3, λ5, and λ7 selected from the CWDM wavelengths, wavelength-multiplexed by the wavelength multiplexer 43, and then to the optical signal branch circuit units 1001a to 1001d through the optical fiber 1004. Sent. Here, R of the optical transceiver is an optical signal reception port, T is an optical signal transmission port, Rx is an electrical signal output port corresponding to the optical signal reception signal, and Tx is an electrical signal corresponding to the optical signal transmission signal. Input port.

  Also, optical signals having wavelengths λ2, λ4, λ6, and λ8 are sent from the optical signal branch circuit units 1001a to 1001d through the optical fiber 1004, respectively. These wavelengths λ2, λ4, λ6, and λ8 are also selected from CWDM wavelengths determined by ITU-T.

  In ITU-T, CWDM wavelengths are determined every 20 nm from 1270 nm to 1610 nm. Of the CWDM wavelengths defined by ITU-T, 8 wavelengths from 1470 nm to 1610 nm are particularly often used. In this embodiment, λ1 = 1470 nm, λ2 = 1490 nm, λ3 = 1510 nm, λ4 = 1530 nm, λ5 = 1550 nm, λ6 = 1570 nm, λ7 = 1590 nm, and λ8 = 1610 nm are used.

  The optical signal sent through the optical fiber 1004 is dropped by an optical signal branch circuit unit 1001 as shown in FIG. For example, the optical signal branch circuit unit 1001a drops the optical signal having the wavelength λ1 by the dielectric thin film filter type three-port device 1011. On the other hand, an optical signal having a wavelength λ2 is added by the dielectric thin film filter type three-port device 1012 and sent to the base station 1002 side. A CWDM (low density wavelength multiplexing) optical transceiver 1013 in the optical signal branch circuit unit 1001a transmits an optical signal of λ2. A CWDM (low density wavelength division multiplexing) optical transceiver 1013 and a 1.5 μm optical transceiver 1014 are combined back to back. An optical signal received by a CWDM (Low Density Wavelength Multiplexing) optical transceiver 1013 is converted into an electrical signal, sent to a 1.5 μm optical transceiver 1014 and converted to a wavelength of 1.5 μm, and a WDM optical fiber coupler / tree coupler 1016. And sent to the client station group 1003a.

  The optical signal branching unit 1001b drops the optical signal having the wavelength λ3 and adds the optical signal having the wavelength λ4. The optical signal branching unit 1001c drops the optical signal having the wavelength λ5 and adds the optical signal having the wavelength λ7. The optical signal branching unit 1001d drops the optical signal having the wavelength λ7 and adds the optical signal having the wavelength λ8.

  An optical signal having a wavelength of 1.3 μm from the client station group 1003a is sent to the reception port (R) of the 1.5 μm optical transceiver 1014 through the tree coupler 1016 and the WDM coupler 1015. This optical signal having a wavelength of 1.3 μm is converted into an electrical signal by a 1.5 μm optical transceiver 1014, and then converted to an optical signal having a wavelength λ1 by a CWDM (low density wavelength division multiplexing) optical transceiver 1013. The data is sent to the base station 1002 via the port device 1012.

  Since it is configured as described above, in this embodiment, it is possible to transmit and receive 4-channel TDM signals using a single optical fiber. Each channel can accommodate up to 32 client stations, so a total of 128 client stations can be accommodated. Therefore, it is effective in reducing the optical fiber installation cost.

FIG. 37 shows an optical signal branching circuit 5 according to Embodiment 15 of the present invention. The optical signal branch circuit unit 5 includes dielectric thin film filter type three-port devices 1011 and 1012, a CWDM (low density wavelength multiplexing) optical transceiver 1013, a WDM (wavelength multiplexing) optical fiber coupler 1015, and a tree coupler 1016 having 32 branches. . A port 1017 is a port on the side different from the base station, and a port 1018 is a port connected to the optical signal branch circuit unit in the next stage. The port group 1021 is a port connected to the client station group.

The difference between the optical signal branch circuit unit 5 and the optical signal branch circuit unit 1001 is that the optical signal branch circuit unit 1050 does not include the 1.5 μm optical transceiver 1014, and only the CWDM (low density wavelength division multiplexing) optical transceiver 1013 has a tree. The wavelength conversion of the upstream optical signal from the coupler 1016 to the base station (1.3 μm → CWDM wavelength) is performed. An optical signal having a wavelength of 1.3 μm input to the optical signal input port (R) of the CWDM (low density wavelength division multiplexing) optical transceiver 1013, where the Tx terminal and the Rx terminal of the CWDM (low density wavelength division multiplexing) optical transceiver 1013 are short-circuited. Is converted to an optical signal λj having a CWDM wavelength and sent to a base station via a dielectric thin film filter type three-port device 1012.

  Also, the optical signal of CWDM wavelength λi sent from the base station is sent to the tree coupler 1016 via the dielectric thin film filter type three-port device 1011 and the WDM optical fiber coupler 1015. In general, a photodiode used to receive an optical signal has sensitivity in a wide wavelength range over the entire CWDM wavelength range (1270 to 1610 nm). Therefore, even if configured as described above, there is a problem in reception on the client station side. Does not occur.

  This embodiment is mainly characterized in that the cost is reduced by omitting the 1.5 μm optical transceiver 1014 using this feature of the photodiode. A clock recovery retiming circuit (not shown) may be provided between the Rx terminal and the Tx terminal of the CWDM (low density wavelength division multiplexing) optical transceiver 1013. By providing the clock recovery retiming circuit, it is possible to correct the distortion of the optical signal. Further, in place of the WDM optical fiber coupler 1015, other wavelength multiplexing means such as a dielectric other thin film filter type three-port device may be used.

  According to the configuration of the present embodiment, the 1.5 μm optical transceiver can be omitted from the optical signal branching unit as compared with the case of the fourteenth embodiment, and the cost can be reduced.

A sixteenth embodiment of the present invention will be described with reference to FIGS. FIG. 38 shows the internal structure of the optical signal branch circuit units 1050a , 1050b , 1050c , and 1050d and an optical communication network including these optical signal branch circuit units. FIG. 39 shows a wavelength multiplexing apparatus provided in the base station.

  In the present embodiment, four wavelengths are used for the downlink signal and one wavelength is used for the uplink signal, and an asymmetric transmission capacity is realized between the uplink and the downlink. Further, the optical signal branch circuit is constituted by a complete passive circuit.

  In FIG. 38, reference numbers 1051a, 1051b, and 1051c are dielectric thin film filter type three-port devices having wavelengths λ1, λ2, and λ3 as transmission wavelengths, respectively, and reference numbers 1052a, 1052b, and 1052c transmit wavelengths λ1, λ2, and λ3, respectively. Dielectric thin film filter type three-port devices having wavelengths, reference numbers 1053a to 1053c and 1054a to 1054c are dielectric thin film filter type three port devices having a transmission wavelength of λ0, and reference numbers 1055a, 1055b and 1055c are branching ratios of 3: 1, 2: 1, 1: 1 optical fiber couplers, and reference numerals 1056a to 1056d are 8-branch tree couplers.

  Among the downstream optical signals from the base station, the optical signal of wavelength λ1 is dropped by the dielectric thin film filter type three-port device 1051a in the optical signal branch circuit unit 1050a, and passes through the dielectric thin film filter type three port device 1052a. The data is branched by the tree coupler 1056a and sent to a client station group (not shown).

  Among the downstream optical signals from the base station, the optical signal of wavelength λ2 is dropped by the dielectric thin film filter type three port device 1051b in the optical signal branch circuit unit 1050b, and passes through the dielectric thin film filter type three port device 1052b. The data is branched by the tree coupler 1056b and sent to a client station group (not shown).

  Among the downstream optical signals from the base station, the optical signal of wavelength λ3 is dropped by the dielectric thin film filter type three port device 5cb in the optical signal branch circuit unit 1050c, and passes through the dielectric thin film filter type three port device 1052c. The data is branched by the tree coupler 1056c and sent to a client station group (not shown).

  Of the downstream optical signals from the base station, the optical signal of wavelength λ4 is branched by the tree coupler 1056d in the optical signal branch circuit unit 1050d and sent to a client station group (not shown).

  On the other hand, an optical signal having an upstream wavelength λ0d from a client station group (not shown) connected to the optical signal branch circuit unit 1050d passes through the tree coupler 1056d in the optical signal branch circuit unit 1050d, and then enters the optical signal branch circuit unit 1050c. The dielectric thin film filter type three-port device 1054c is dropped and sent to the optical fiber coupler 1055c. An upstream optical signal of wavelength λ0c from a client station group (not shown) connected to the optical signal branch circuit unit 1050c passes through the tree coupler 1056c and the reflection port of the dielectric thin film filter type three-port device 1052c to the optical fiber coupler 1055c. Sent. The upstream signal of the optical signal branch circuit unit 1050d and the upstream signal of the optical signal branch circuit unit 1050c are merged by the optical fiber coupler 1055c. The joined upstream signal is sent to the base station side by the dielectric thin film filter type three port device 1053c.

  The combined signal of the upstream signals of the optical signal branch circuit units 1050d and 1050c is dropped by the dielectric thin film filter type three-port device 1054b in the optical signal branch circuit unit 1050b and sent to the optical fiber coupler 1055b. An optical signal having an upstream wavelength λ0b from a client station group (not shown) connected to the optical signal branch circuit unit 1050b passes through the tree coupler 1056b and the reflection port of the dielectric thin film filter type three-port device 1052b to the optical fiber coupler 1055b. Sent. The upstream signals of the optical signal branch circuit units 1050d and 1050c and the upstream signal of the optical signal branch circuit unit 1050b are merged by the optical fiber coupler 1055b. The joined upstream signal is sent to the base station side by the dielectric thin film filter type three port device 1053b.

  The combined signals of the upstream signals of the optical signal branch circuit units 1050d, 1050c, and 1050b are dropped by the dielectric thin film filter type three-port device 1054a in the optical signal branch circuit unit 1050a and sent to the optical fiber coupler 1055a. An optical signal having an upstream wavelength λ0a from a client station group (not shown) connected to the optical signal branch circuit unit 1050a passes through the reflection port of the tree coupler 1056a and the dielectric thin film filter type three-port device 1052c, and the optical fiber coupler 1055a. Sent to. The upstream signals of the optical signal branch circuit units 1050d, 1050c, and 1050b and the upstream signal of the optical signal branch circuit unit 1050a are merged by the optical fiber coupler 1055a. The joined upstream signal is sent to the base station side by the dielectric thin film filter type three port device 1053a.

  The wavelength λ0 is a wavelength in the range of about 1310 nm ± 40 nm. This is because the client station uses a Fabry-Perot laser that is inexpensive but has low wavelength accuracy. The wavelengths λ0a to λ0d are only distinguished for explaining the flow of the optical signal, and the wavelengths are included in the range of about 1310 nm ± 40 nm.

  Since the optical communication network of FIG. 38 operates as described above, the downstream signals of wavelengths λ1 to λ4 are branched into 8 branches and sent to client stations, and optical signals of wavelength λ0 from a maximum of 32 client stations are combined into one. It is merged and sent to the base station.

  FIG. 39 shows the structure of a wavelength multiplexing apparatus incorporated on the base station side. CWDM optical transceivers 1057a to 1057d and a wavelength multiplexer 1058 are included. In the CWDM optical transceivers 1057a to 1057d, the Rx terminal and the Tx terminal are short-circuited, and wavelength conversion is realized by one optical transceiver. Downlink signals from CH1 to CH4 and uplink signals from CH0 are multiplexed by the wavelength multiplexer 1058.

  According to this embodiment, since the optical signal branch circuit is entirely composed of passive components, it is not necessary to supply power to the optical signal branch circuit and the reliability is high. Further, since four waves are used for the downstream signal and one wave for the upstream signal, the downstream bandwidth can be widened. For example, if the transmission speed is 100 Mbps per wave, 100 Mbps is shared by 32 stations in the uplink, and 100 Mbps is shared by 8 stations in the downlink. In general, since a downlink signal from a base station is often required to have a wide band, such an arrangement of transmission capacity has a great economic effect.

  FIG. 40 shows an internal structure of the optical signal branch circuit units 1060a to 1060d according to the seventeenth embodiment of the present invention and an optical communication network including these optical signal branch circuit units.

  In FIG. 40, reference numbers 1061a, 1061b, and 1061c are dielectric thin film filter type three-port devices that transmit wavelengths λ1, λ2, and λ3, respectively, and reference numbers 1062a, 1062b, and 1062c transmit wavelengths λ1, λ2, and λ3, respectively. Dielectric thin film filter type three-port device having a wavelength, reference numerals 1063a to 1063b, 1064a and 1064c are dielectric thin film filter type three-port devices having a transmission wavelength of λ0, and reference numeral 1063c is a dielectric having a transmission wavelength of λ5 Thin film filter type three-port devices, reference numerals 1065a and 1065c are 1: 1 optical fiber couplers, reference numerals 1066a to 1066d are eight-branch tree couplers, and reference numeral 1067 is a CWDM optical transceiver.

  The optical signal branch circuit unit 1060a has the same configuration as that of the optical signal branch circuit unit 1050a according to the sixteenth embodiment, and only the point that the branch ratio of the optical fiber coupler 1065a is 1: 1 is the same as the optical signal branch circuit unit 1050a. Different. The optical signal branch circuit unit 1060d has the same structure as the optical signal branch circuit unit 1050d of the sixteenth embodiment. The optical signal branch circuit units 1060b and 1060c have a structure different from that of the sixteenth embodiment.

  In the optical signal branch circuit unit 1060c, the upstream signals of the optical signal branch circuits 1060d and 1060c are joined to the optical fiber coupler 1065c by the same mechanism as in the sixteenth embodiment. The combined optical signal is converted into an optical signal of wavelength λ5 by the CWDM transceiver 1067, and then sent to the base station side through the dielectric thin film filter type three-port device 1063c. In this way, the main difference from the sixteenth embodiment is that only the upstream signals of the optical signal branch circuit units 1060d and 1060c are merged, wavelength-converted, and sent to the base station.

  In the optical signal branch circuit unit 1060b, the upstream signal of the wavelength λ0b from the tree coupler 1066b is sent to the base station side through the reflection port of the dielectric thin film filter type three port device 1062b and the dielectric thin film filter type three port device 1063b. In the optical signal branch circuit unit 1060a, the optical signal having the wavelength λ0b sent from the optical signal branch circuit unit 1060b is dropped by the dielectric thin film filter type three-port device 1064a and then sent to the optical fiber coupler 1065a. Further, the upstream signal of wavelength λ0a from the tree coupler 1066a is sent to the optical fiber coupler 1065a through the reflection port of the dielectric thin film filter type three port device 1062a. In the optical fiber coupler 1065a, the optical signals of λ0b and λ0a are merged, added by the dielectric thin film filter type three-port device 1063a, and sent to the base station side.

  Since the optical communication network of the present embodiment is configured as described above, the downstream optical signal is transmitted to the client station side after eight optical signals having four wavelengths of λ1 to λ4 are branched. In addition, the upstream signals of 16 stations for each of the two wavelengths λ0 and λ5 are combined and sent to the base station.

  According to the present embodiment, there is an effect that the number of wavelengths allocated to the downlink and the uplink can be arbitrarily changed.

  The optical signal branch circuit unit and the optical communication network according to the eighteenth embodiment of the present invention will be described with reference to FIGS. 41 and 42. FIG. FIG. 41 is a diagram showing the configuration of the optical communication network of the present embodiment. FIG. 42 is a diagram showing the internal structure of the optical signal branch circuit unit 1071 of this embodiment.

  In FIG. 41, reference numerals 1071a, 1071b, 1071c, and 1071d are optical signal branch circuit units of the present embodiment, and reference numeral 1072 is a base station. The base station 1072 and the optical signal branch circuit units 1071a to 1071d are connected in a ring shape by an optical fiber 1074. Further, client station groups 1073a to 1073d are connected to the optical signal branch circuit units 1071a to 1071d, respectively.

  42, reference numerals 1081 and 1083 are dielectric thin film filter type three-port devices having a transmission wavelength λi, and reference numbers 1082 and 1084 are dielectric thin film filter type three port devices having a transmission wavelength λj. Reference numeral 1086 is a CWDM optical transceiver having a transmission wavelength λj, reference numeral 1087 is a crosspoint switch and control unit, reference numerals 1088 and 1089 are optical transceivers having a transmission wavelength of 1.5 μm, and reference numerals 1090 and 1091 are WDM optical signals. These are fiber couplers, and reference numerals 1092 and 1093 are 32-branch tree couplers. Reference numeral 1096 is an input / output port for a counterclockwise transmission path, reference numeral 1097 is an input / output port for a clockwise transmission path, and reference numerals 1094 and 1095 are input / output ports to a client station group.

  41 and 42, a communication path is formed in two directions, clockwise and counterclockwise, from the base station 1072 to the optical signal branch circuit unit 1071 using two wavelengths λi and λj. be able to. Therefore, not only can the communication capacity be doubled with the same number of wavelengths compared to the case of the embodiment 14 or the like, but also when one part of the ring-shaped fiber is cut off, it is either clockwise or counterclockwise. This path has an advantage that a redundant communication network can be realized.

  In FIG. 42, the optical signal of wavelength λi from the input / output port 1096 for the clockwise transmission path is dropped by the dielectric thin film filter type three port device 1081 and sent to the reception port (R) of the CWDM optical transceiver 1085. . The optical signal of wavelength λi converted into an electrical signal is normally sent from the Rx terminal of the CWDM optical transceiver 1085 to the optical transceiver 1088 via the crosspoint switch and control unit 1087. Then, the wavelength is converted to a wavelength of 1.5 μm and sent to the input / output port 1094 to the client station group via the WDM optical fiber coupler 1090 and the tree coupler 1092.

  Conversely, an optical signal having a wavelength of 1.3 μm sent from the client station group to the input / output port 1094 passes through the tree coupler 1092, the WDM optical fiber coupler 1090, the optical transceiver 1088, the crosspoint switch and the control unit 1087, and is usually Is sent to the CWDM optical transceiver 1085 and converted into an optical signal of wavelength λj. The optical signal having the wavelength λj is added by the dielectric thin film filter type three-port device 1082 and sent to the input / output port 1096 for the clockwise transmission path.

  In FIG. 42, the optical signal of wavelength λi from the input / output port 1097 for the counterclockwise transmission path is dropped by the dielectric thin film filter type three-port device 1083 and sent to the reception port (R) of the CWDM optical transceiver 1086. . The optical signal of wavelength λi converted into an electrical signal is normally sent from the Rx terminal of the CWDM optical transceiver 1086 to the optical transceiver 1089 via the crosspoint switch and control unit 1087. Then, the wavelength is converted to a wavelength of 1.5 μm and sent to the input / output port 1095 to the client station group via the WDM optical fiber coupler 1091 and the tree coupler 1093.

  On the other hand, an optical signal having a wavelength of 1.3 μm sent from the client station group to the input / output port 1095 passes through the tree coupler 1093, the WDM optical fiber coupler 1091, the optical transceiver 1089, the crosspoint switch and the control unit 1087. Is sent to the CWDM optical transceiver 1086 and converted into an optical signal of wavelength λj. The optical signal having the wavelength λj is added by the dielectric thin film filter type three-port device 1084 and sent to the input / output port 1097 for the clockwise transmission path.

  When the ring-shaped optical fiber 1074 of FIG. 41 is cut somewhere and any of the non-clockwise left-handed optical communication paths is blocked, the cross-point switch and control unit 1087 Operate to connect 1088 and 1089 in parallel. The interruption of the communication path can be detected by a link signal detection mechanism (not shown) from the CWDM optical transceivers 1085 to 1086. 41, two systems corresponding to the wavelength multiplexing apparatus 1040 shown in FIG. 36 are provided in the base station 1072.

  In the optical signal branch circuit unit of FIG. 42, the dielectric thin film filter type three-port devices 1081 and 1083 can also be configured by one duplicate type dielectric filter type three-port device. In addition, the dielectric thin film filter type three-port devices 1082 and 1084 can be configured by one duplicate type dielectric filter type three-port device.

  The duplicate type dielectric filter type three-port device has been described in the fifth embodiment with reference to FIG.

  By using the duplex dielectric thin film filter type three-port device in the optical signal branch circuit unit of this embodiment, there is an advantage that the number of parts can be reduced and the cost can be reduced.

  An optical communication network according to the twentieth embodiment of the present invention will be described with reference to FIG. In FIG. 43, an optical signal from the base station side communication device 1501 passes through a 2 × 2 optical switch 1502, passes through an optical fiber (normal path) 1505 or an optical fiber (backup path) 1504, and passes through a 2 × n splitter 1508. Connected to station 9. Usually, about 32 client stations are connected to one splitter 1508. Therefore, normally, n = 32, but n can take any integer of 2 or more. A monitoring device (OTDR) device 1503 is connected to the 2 × 2 optical switch 1502, and monitoring light (OTDR light) is cut between the optical fiber (normal path) 1505 and the 2 × n branch splitter 1508. In the filter 1507, a monitoring light (OTDR light) cut filter 1506 is provided between the optical fiber (backup path) 1504 and the 2 × n branch splitter 1508, respectively.

  The base station side communication device 1501 is a device called OLT (Optical Line Terminal) in PON (Passive Optical Network), and a client station 1509 is provided with a device called ONU (Optical Network Unit) in PON. In the PON, a signal from the base station side communication device (OLT) 1501 is distributed to a large number (about 32 stations) of client stations (ONU) 1509 by a 2 × n splitter splitter 1508. Also, signals from the client station (ONU) 1509 are collected by a 2 × n-branch splitter 1508 and sent to a base station side communication device (OLT) 1501.

  In this embodiment shown in FIG. 43, a so-called protection mechanism is realized by the 2 × 2 optical switch 1502. If disconnection or the like occurs in the optical fiber (normal path) 1505, the signal transmission path can be switched to the optical fiber (backup path) 1504 by the 2 × 2 optical switch 1502. Since the monitoring device (OTDR) device 1503 is connected to the optical fiber (normal path) 1505, the disconnection point of the optical fiber can be checked by OTDR (Optical Time Domain Reflectometry). Since the monitoring light (OTDR light) is cut by the monitoring light (OTDR light) cut filters 1506 to 1507, the monitoring light (OTDR light) is sent to the client station 1509 side through the 2 × n splitter 1508. In addition, it is possible to detect an optical fiber breakage point while operating the PON.

  Note that the monitoring device (OTDR) device 1503 is not essential for protection. This is because even if the monitoring device (OTDR) device 1503 is omitted by using a 1 × 2 optical switch, switching to the backup route can be performed when the normal route is disconnected. Further, protection can be realized by switching with an electrical switch instead of switching with an optical switch. Two optical transceivers are prepared in the base station side communication device (OLT) 1501, each transceiver is connected to the normal path and the backup path, and the path is switched when an abnormality occurs.

  According to the present embodiment, an optical fiber (normal path) 1505 and an optical fiber (backup path) 1504 are provided between the base station side communication device (OLT) 1501 and the 2 × n branch splitter 1508 in the PON. Switching from the normal path to the backup path (protection) can be performed when an abnormality such as disconnection of the optical fiber occurs. Further, by providing a monitoring device (OTDR) device 1503 at one end of the 2 × 2 optical switch, there is an effect that it is possible to detect a disconnection point of a path where an abnormality has occurred without stopping the operation of the PON. .

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

It is a figure which shows the internal structure of the wavelength router of Example 1 of this invention. It is a figure which shows the double ring-shaped optical communication network of Example 1 of this invention. It is a figure which shows the wavelength routing between the wavelength router 21 and the wavelength router 22. FIG. It is a figure which shows the wavelength routing path in Example 1 of this invention. It is a figure which shows the internal structure of the wavelength router of Example 2 of this invention. It is a figure which shows the ring-shaped optical communication network of Example 2 of this invention. It is a figure which shows the wavelength routing path in Example 2 of this invention. It is a figure which shows the internal structure of the wavelength router of Example 3 of this invention. It is a figure which shows the double ring-shaped optical communication network of Example 3 of this invention. It is a figure which shows the internal structure of the wavelength router of Example 4 of this invention. It is a figure which shows the problem of insufficient isolation of an optical add drop multiplexer. It is a figure which shows the gain control mechanism of the optical amplifier in Example 4 of this invention. It is a figure which shows the structure of a duplicate dielectric material thin film filter type | mold three port device. It is a figure which shows the wavelength router of Example 5 of this invention. It is a figure which shows the duplicate type | mold double pass type dielectric thin film filter three port device which is Example 6 of this invention. It is a figure which shows the wavelength router mounted in the box of Example 7 of this invention. It is a figure which shows the wavelength router mounted in another box. It is a figure which shows the wavelength router mounted as a patch cord. It is a figure which shows a bidirectional | two-way transmission optical fiber communication network. It is a figure which shows the relationship between the transmitted light and reflected light in a dielectric material thin film filter type | mold three port device. FIG. 10 is a diagram illustrating a wavelength router (wavelength multiplexer) mounted in a box according to an eighth embodiment. It is a figure which shows the wavelength router (optical add drop multiplexer) of Example 9 of this invention. 6 is a diagram illustrating a problem of crosstalk in the wavelength router 311. FIG. It is a figure which shows the wavelength router for star type | mold communication path formation. 1 is a diagram illustrating an optical communication network formed by wavelength routers 311, 351, 352, 353, and 354. It is a figure which shows the wavelength router (wavelength multiplexer) of Example 10 of this invention. It is a figure which shows the wavelength router (wavelength multiplexer) of 4 wavelengths of Example 10 of this invention. It is a figure which shows the wavelength router (wavelength multiplexer) of Example 11 of this invention. It is a figure which shows the Example which mounted the wavelength multiplexer of Example 11 of this invention as a patch cord. It is a figure which shows the optical communication network of Example 12 of this invention. It is a figure which shows the internal structure of the wavelength router of Example 12 of this invention. It is a figure which shows the modification of the wavelength router of Example 12 of this invention. It is a figure which shows the wavelength router of Example 13 of this invention. It is a figure which shows the optical communication network of Example 14 of this invention. 2 is a diagram showing an internal structure of an optical signal branch circuit unit 1001. FIG. It is a figure which shows the wavelength multiplexing apparatus 1040 provided in the base station 1002. FIG. It is a figure which shows the internal structure of the optical signal branch circuit of Example 15 of this invention. It is a figure which shows the optical signal branch circuit and optical communication network of Example 16 of this invention. It is a figure which shows the structure of the wavelength multiplexing apparatus integrated in a base station in Example 16 of this invention. It is a figure which shows the optical signal branch circuit unit and optical communication network of Example 17 of this invention. It is a figure which shows the structure of the optical communication network of Example 18 of this invention. It is a figure which shows the internal structure of the optical signal branch circuit unit 1071 of the Example of this invention. It is a figure explaining the optical communication network of Example 19 of this invention. It is a figure which shows the conventional optical add drop multiplexer. It is a figure which shows the structure of the conventional dielectric material thin film filter type | mold three port device 620. FIG. It is a figure which shows the conventional passive optical fiber communication network (PON).

Explanation of symbols

1-12: Dielectric thin film filter type three-port device 20, 21-24 ... Wavelength router 25 ... Outer optical fiber 26 ... Inner optical fibers 25a, 25b, 26a, 26b ... Optical fibers 30, 31-34 ... Local Port group 41-44 ... Switch or router 45 ... Removable optical transceiver 50, 51, 52 ... Wavelength routing path

Claims (4)

The first input port, a first output port, a second input port, the second output port and the wavelength router having a plurality of optical add unit Optical Drop unit pair,
The first input port and the first output port are provided for counterclockwise signals;
The second input port and the second output port are provided for clockwise signals;
The wavelength of the optical add means and the optical drop means forming the pair constituting each of the optical add means and the optical drop means pair is the same,
And to predetermined number of nodes N, (N-1) pieces of the add unit first set of optical add unit Optical Drop means pair group having a drop unit pair, and (N-1) pieces of the add A second set of optical add means optical drop means pairs with means drop means pairs is provided;
The first set of optical add means and optical drop means pairs are provided for the counterclockwise signal,
The second set of optical add means and optical drop means pairs are provided for the clockwise signal,
The wavelength of each of the (N-1) optical add means optical drop means pairs other than the wavelength represented by the empty set from the wavelength arrangement given by the row vector Λi represented by the following equation :
A wavelength router, wherein the off-diagonal components of the upper right half of the matrix in the following formula are different from each other .

First input-output port, the second input-output port and a wavelength router having a plurality of optical add unit Optical Drop unit pair,
The first input / output port and the second input / output port are for a clockwise signal coming from the left-hand path, and for a counter-clockwise signal going to the left-hand path, and for a counter-clockwise signal coming from the right-hand path, and Shared for the clockwise signal going to the right path above,
The wavelengths of the optical add means and the optical drop means forming a pair constituting each of the optical add means optical drop means pairs are different from each other,
And to predetermined number of nodes N, (N-1) pieces of the add unit first set of optical add unit Optical Drop means pair group having a drop unit pair, and (N-1) pieces of the add A second set of optical add means optical drop means pairs with means drop means pairs is provided;
The first set of light add means light drop means pair group is provided for the left path,
The second set of light add means light drop means pair group is provided for the right path,
As a wavelength of the optical add means belonging to the first set of optical add means optical drop means pair group, other than the wavelength represented by the empty set from the wavelength arrangement given by the row vector Λi shown by the following formula ,
The wavelength of the optical drop means corresponding to the optical add means in the first set of optical add means optical drop means pair group is given by the row vector Λ′i (i = 1 to N) of the transposed matrix of the following equation Implement other than the wavelength represented by the empty set from the wavelength arrangement,
As a wavelength of the optical add means belonging to the second set of optical add means optical drop means pair group, other than the wavelength represented by the empty set from among the wavelength arrangement given by the row vector Λi shown by the following formula ,
The wavelength of the optical drop means corresponding to the optical add means in the second set of optical add means optical drop means pairs is given by the row vector Λ′i (i = 1 to N) of the transposed matrix of the following matrix. Implement other than the wavelength represented by the empty set from the wavelength arrangement,
A wavelength router characterized in that the non-diagonal components of the matrix are different from each other in the following equation .

In an optical communication network in which a plurality of nodes are connected by two ring optical fibers,
An optical communication network, wherein at least one of the nodes comprises the wavelength router according to claim 1 . In an optical communication network in which a plurality of nodes are connected by a single ring optical fiber,
An optical communication network, wherein at least one of the nodes comprises the wavelength router according to claim 2 .

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