JP2016066935A - Node device and node device control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a signal unnecessary in a terminal station from being intercepted by the terminal station, without great change in the power of an optical signal transmitted from a node to the terminal station.SOLUTION: A node device comprises: a first optical unit which outputs a first optical signal addressed to a second terminal station and received from a first terminal station and a second optical signal addressed to a third terminal station and received from the first terminal station, the second optical signal having a wavelength band different from that of the first optical signal; and a second optical unit which receives the first and second optical signals outputted from the first optical unit, distributes at least one of the polarized wave and the phase of the first optical signal to make a fourth optical signal, allows the second optical signal to pass as it is, combines the second and fourth optical signals, and transmits the result to the third terminal station.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a node device and a node device control method, and more particularly to a node device having a function of branching an optical signal between trunk stations to a branch station and a node device control method.

  In recent years, in an undersea communication system using submarine cables, an OADM (optical add-drop multiplexing) system and a ROADM (reconfigurable OADM) having a function of separating and combining optical signals in units of wavelength (ie, frequency) System introduction is progressing.

  FIG. 6 is a block diagram showing a general configuration of a submarine communication system 900 in which an OADM system or a ROADM system (hereinafter referred to as “OADM / ROADM system”) is introduced. The node 910 has an OADM / ROADM function.

  Sub-bands 1 to 3 indicate wavelength bands of optical signals. The destination of the optical signal transmitted from the trunk station 51 and whose wavelength band is subband 1 is the trunk station 52, and the destination of the optical signal whose wavelength band is subband 2 is the branch station 53. In the following, “an optical signal whose wavelength band is subband 1 (or 2, 3)” will be referred to as an “optical signal of subband 1 (or 2, 3)”.

  The node 910 transmits the subband 2 optical signal among the optical signals 13 received from the trunk station 51 to the branch station 53. Further, the node 910 splits the optical signal of subband 1 from the optical signal 13 received from the trunk station 51 into two branches, and transmits them to the trunk station 52 and the branch station 53, respectively. Further, the node 910 removes the dummy signal from the optical signal 15 received from the branch station 53. The node 910 combines the subband 3 optical signal received from the branch station 53 and the subband 1 optical signal received from the trunk station 51, and transmits the combined optical signal 14 to the trunk station 52. Further, an optical submarine repeater (not shown) is installed in the middle of the submarine cable between the node 910 and the trunk stations 51 and 52 and the branch station 53.

  In FIG. 6, since the optical signal addressed to the branch station 53 is only the subband 2 optical signal, the subband 1 optical signal addressed to the trunk station 52 does not need to be transmitted to the branch station 53. However, by transmitting the optical signal of subband 1 also to the branch station 53, it is possible to prevent the input power to the optical submarine repeater installed between the node 910 and the branch station 53 from being greatly reduced. As a result, the optical submarine repeater can be operated within a predetermined rated range common to the submarine communication system 900 without greatly reducing the input power. For the same reason, the dummy signal 5 is transmitted from the branch station 53 in addition to the optical signal of the subband 3.

  FIG. 7 is a diagram illustrating the wavelength bands of the optical signals 13 to 15 transmitted and received at the node 910. In FIG. 7, the wavelength band of the optical signal 13 is divided into two wavelength bands, an optical signal 1 of subband 1 and an optical signal 2 of subband 2. The wavelength band of the optical signal 14 is divided into two wavelength bands: an optical signal 1 in subband 1 and an optical signal 3 in subband 3. Further, the wavelength band of the optical signal 15 is divided into two wavelength bands of the dummy signal and the optical signal 3 of the subband 3. The wavelength band of subband 1 and the wavelength band of the dummy signal match. The wavelength band of subband 2 also matches the wavelength band of subband 3. Furthermore, the wavelength band of subband 1 and the wavelength band of subband 2 do not overlap. Each of the optical signals 13 to 15 has a channel capable of transmitting at least one carrier (optical carrier wave). Each of the subbands 1 to 3 also has a channel capable of transmitting at least one carrier. Each carrier is wavelength-multiplexed and transmitted as optical signals 13-15.

  FIG. 8 is a diagram showing a more detailed configuration of the submarine communication system 900 shown in FIG. The submarine communication system 900 includes trunk stations 51 and 52, a branch station 53, and a node 910. The trunk stations 51 and 52 and the branch station 53 transmit and receive the optical signals 1 to 3 illustrated in FIG. The node 910 includes couplers 6 and 12 and wavelength filters 7 and 8. The trunk stations 51 and 52 and the branch station 53 and the node 910 are connected by a submarine cable including an optical submarine repeater 54. In FIG. 8, optical signals 1 and 2 transmitted from the trunk station 51 correspond to the optical signal 13 in FIG. Similarly, the optical signals 1 and 3 received by the trunk station 52 correspond to the optical signal 14 in FIG. The optical signal 3 and the dummy signal 5 transmitted from the branch station 53 correspond to the optical signal 15 in FIG.

  The trunk station 51 transmits the optical signal 1 of subband 1 and the optical signal 2 of subband 2. In the coupler 6 of the node 910, the optical signals 1 and 2 are branched into two. One of the two branched optical signals is transmitted to the branch station 53. The other of the two optical signals branched in the coupler 6 passes through the wavelength filter 7 and the coupler 12 and is transmitted to the trunk station 52. The wavelength filter 7 transmits an optical signal in the subband 1 wavelength band and blocks an optical signal in the subband 2 wavelength band.

  As described above, in order to operate the optical submarine repeater 54 installed in the transmission path from the node 910 to the branch station 53 within the rated range, the optical signal 2 and the optical signal 2 are transmitted from the node 910 to the branch station 53. Signal 1 is also transmitted. As a result, the branch station 53 receives the target optical signal 2 while receiving the optical signal 1 transmitted to the trunk station 52.

  In connection with the present invention, Patent Document 1 discloses that an unnecessary optical signal is received by a terminal device by blocking an unnecessary optical signal in units of subbands using a blocking filter arranged in a transmission line. Techniques for preventing this are described. Patent Document 2 describes an OADM device using an optical filter.

Japanese Patent Laying-Open No. 2011-082751 (paragraphs [0020]-[0021], FIG. 1) JP-T-2012-527189 (paragraph [0021]-[0024], FIG. 2)

  In the submarine communication system 900 shown in FIG. 8, in order to operate the optical submarine repeater 54 installed between the node 910 and the branch station 53 within the rated range, the subband 1 that is not originally required is used. The optical signal 1 is transmitted to the branch station 53. That is, the branch station 53 can receive the optical signal 1 of the subband 1 destined for the trunk station 52. For this reason, there is a possibility that the security of the optical signal of the subband 1 in the branch station 53 is not sufficiently ensured.

  Patent Document 1 describes a configuration in which an optical signal in a wavelength band (S band or L band) that is not required by a branch station is removed using an optical filter. However, in the configuration described in Patent Document 1, since all the optical signals in the S band or L band wavelength band are removed by the optical filter, the power of the optical signal addressed to the branch station is greatly reduced. As a result, the input power to the optical submarine repeater that amplifies the optical signal addressed to the branch station is reduced, and the operating condition of the optical submarine repeater may be out of rating. For this reason, the technique described in Patent Document 1 has a problem that the operating condition of the optical submarine repeater may be out of the rating due to the fluctuation of the input power to the optical submarine repeater. Further, Patent Document 2 does not describe means for solving the problem that there is a possibility that the security of an optical signal that is not addressed to a branch station may not be sufficiently secured.

(Object of invention)
The present invention relates to a node device and a control of the node device for preventing a signal not required in the terminal station from being intercepted in the terminal station without greatly changing the power of the optical signal transmitted from the node to the terminal station. It aims to provide a method.

  The node device according to the present invention includes a first optical signal destined for the second terminal station received from the first terminal station and a third optical terminal addressed to the third terminal station received from the first terminal station. A first optical unit that outputs a second optical signal having a wavelength band different from that of the first optical signal, and the first and second optical signals output from the first optical unit, A third end is obtained by perturbing at least one of the polarization and the phase of the optical signal to obtain the fourth optical signal and passing the second optical signal as it is to combine the second and fourth optical signals. A second optical unit for transmitting to the station.

  In the node device control method according to the present invention, the first optical signal destined for the second terminal station received from the first terminal station and the first optical signal received from the first terminal station have the wavelength A second optical signal destined for a third terminal station having a different band, and a disturbance is applied to at least one of the polarization and phase of the output first optical signal to form a fourth optical signal. The second and fourth optical signals are combined and transmitted to the third terminal station.

  INDUSTRIAL APPLICABILITY The node device and the node device control method of the present invention can prevent a terminal station from intercepting a signal that is not required by the terminal station without greatly reducing the power of the optical signal transmitted from the node to the terminal station. .

It is a block diagram which shows the structure of the submarine communication system of the 1st Embodiment of this invention. It is a figure which shows the relationship of each wavelength band of a subband and a dummy signal. It is a block diagram which shows the structure of a polarization | polarized-light rotator. It is a block diagram which shows the structure of the submarine communication system of the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the submarine communication system of the 3rd Embodiment of this invention. It is a block diagram which shows the general structure of the submarine communication system in which the OADM / ROADM system was introduced. It is a figure which shows the wavelength band of the optical signal transmitted / received by a node. It is a figure which shows the detailed structure of a general submarine communication system.

(Outline of the embodiment)
In the following embodiments, in an undersea communication system composed of a terminal station (referred to as a trunk station and a branch station) and a node, among the optical signals transmitted from the node to the terminal station, light unnecessary for the terminal station is used. The signal changes to a state where the terminal station cannot receive the signal at the node. Hereinafter, changing the optical signal to a state in which the terminal station cannot receive is referred to as “invalidation”.

  In each embodiment, an example in which an optical signal transmitted to a branch station is invalidated will be described. The optical signal is invalidated by a polarization rotator. The polarization rotator is equipped with a polarization beam splitter, a polarization rotation plate (for example, a λ / 2 wavelength plate), and a coupler. To do. The branch station cannot demodulate the disabled optical signal. Further, since the optical signal is invalidated only by the disturbance of the phase and the polarization, the power of the optical signal addressed to the branch station does not decrease. Thus, the security of information included in the optical signal is ensured by invalidating the optical signal that is not required in the branch station.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a submarine communication system 100 according to the first embodiment of the present invention. The submarine communication system 100 is a submarine cable communication system in which trunk stations 51 and 52 and a branch station 53 are connected to a node 110. The trunk stations 51 and 52 and the branch station 53 and the node 110 are connected by a submarine optical cable. An optical submarine repeater 54 is installed in each submarine optical cable. The quantity and installation interval of the optical submarine repeaters 54 are determined by the installation conditions of the submarine communication system 100.

  In the submarine communication system 100, polarization multiplexing coherent transmission is used. That is, in the submarine communication system 100, the optical signal is phase-modulated, and two independent pieces of phase-modulated information are multiplexed and transmitted with mutually orthogonal polarizations. Thus, in polarization multiplexing coherent transmission, information is transmitted by the phase and polarization of an optical signal.

  The node 110 includes a coupler 6, WSS (Wavelength Selectable Switch) modules 16 and 17, a polarization rotator 10, and a coupler (CPL) 11. The coupler 6 is a 1: 1 directional coupler. The WSS modules 16 and 17 perform a predetermined separation and combination operation on the input WDM signal and output it. As the coupler 11, a multiplexer capable of wavelength-multiplexing an optical signal 4 of a subband 1 ′ and an optical signal 2 of a subband 2 described later is used. Alternatively, a directional coupler may be used as the coupler 11.

  The trunk station 51 wavelength-multiplexes the optical signal 1 of the subband 1 and the optical signal 2 of the subband 2 and transmits them to the node 110. The destination of the optical signal 1 is the trunk station 52, and the destination of the optical signal 2 is the branch station 53. The branch station 53 transmits the optical signal 3 of the subband 3 and the dummy signal 5 to the node 110. The destination of the optical signal 3 is the trunk station 52. The dummy signal 5 is a signal having no information to be transmitted.

  FIG. 2 shows the relationship between the wavelength bands of the optical signals 1 to 3 of the subbands 1 to 3 and the dummy signal 5. The subband 1 and the dummy signal 5 have the same wavelength band, and the subband 2 and the subband 3 have the same wavelength band. Furthermore, the wavelength band of subband 1 and the wavelength band of subband 2 do not overlap. From the trunk station 51 to the node 110, the optical signal 1 of the subband 1 and the optical signal 2 of the subband 2 are wavelength-multiplexed and transmitted. From the node 110 to the trunk station 52, the optical signal 1 of the subband 1 and the optical signal 3 of the subband 3 are wavelength-multiplexed and transmitted. From the branch station 53 to the node 110, the dummy signal 5 and the subband 3 optical signal are wavelength-multiplexed and transmitted.

  As shown in FIG. 1, the optical signal 1 and the optical signal 2 transmitted from the trunk station 51 are branched in the coupler 6 into the direction of the trunk station 52 and the direction of the branch station 53. The optical signals 1 and 2 branched in the direction of the branch station 53 are input to the WSS module 16. The WSS module 16 separates the optical signal 1 and the optical signal 2 and outputs them from different ports.

  Here, the destination of the optical signal 1 is the trunk station 52, and the optical signal 1 is not required in the branch station 53. For this reason, the optical signal 1 output from the WSS module 16 is invalidated by the polarization rotator 10 so that the optical signal 1 cannot be received by the branch station 53.

  The optical signal 1 output from the WSS module 16 is input to the polarization rotator 10. The polarization rotator 10 invalidates the optical signal 1 by perturbing the phase and polarization of the optical signal 1. The invalidated optical signal 1 is output from the polarization rotator 10 as an optical signal 4. The optical signal 4 is combined with the optical signal 2 output from the WSS module 16 by the coupler 11 and transmitted to the branch station 53. Details of the process for disturbing the phase and polarization of the optical signal 1 in the polarization rotator 10 will be described later.

  On the other hand, the optical signals 1 and 2 branched from the coupler 6 toward the trunk station 52 are input to the WSS module 17. The WSS module 17 blocks the subband 2 optical signal 2 received from the trunk station 51 and passes the subband 1 optical signal 1.

  The branch station 53 transmits the optical signal 3 of the subband 3 and the dummy signal 5 to the node 110. The optical signal 3 is a signal transmitted from the branch station 53 and destined for the trunk station 52. The wavelength band of the optical signal 3 is the same as that of the optical signal 2. The dummy signal 5 is used to increase the total power of the optical signal from the branch station 53 to the node 110 and operate the optical submarine repeater 54 on the transmission line within the rated range. The dummy signal 5 is an optical signal in the subband 1 wavelength band.

  The optical signal 3 and the dummy signal 5 transmitted from the branch station 53 are input to the WSS module 17. The WSS module 17 blocks the wavelength band of the dummy signal 5, wavelength-multiplexes the optical signal 1 received from the trunk station 51 and the optical signal 3 received from the branch station 53, and transmits the multiplexed signal to the trunk station 52. Since the wavelength band of the optical signal 1 is subband 1 and the wavelength band of the optical signal 3 is subband 3, the wavelength bands of the optical signal 1 and the optical signal 3 do not overlap. The trunk station 52 receives the optical signal 1 and the optical signal 3 transmitted by the WSS module 17.

  Next, an optical signal transmitted from the node 110 to the branch station 53 will be described. In the polarization rotator 10, the optical signal 1 is disturbed in phase and polarization to become an optical signal 4. The optical signal 4 is a signal obtained by combining the original optical signal 1 with the optical signal 1 having a different carrier phase and polarization. By disturbing the phase and polarization of the optical signal 1, noise is superimposed on the phase and polarization of the optical signal 1. When the polarization rotator 10 gives disturbance to the polarization and phase, the phase and polarization of the carrier included in the optical signal 1 change, and the optical signal 1 and the optical signal 4 that cannot be received by the branch station 53 Become.

  FIG. 3 is a block diagram showing a configuration of the polarization rotator 10. The polarization rotator 10 includes a PBS 10A, a half-wave plate (λ / 2 wavelength plate) 10B, and a coupler 10C. The PBS 10A is a polarization beam splitter that separates incident light into an optical signal 1A and an optical signal 1C whose polarizations are orthogonal to each other. The optical signal 1A is input to the half-wave plate 10B. The half-wave plate 10B rotates the polarization plane of the input optical signal 1A by a predetermined angle and outputs it as an optical signal 1B. For example, the half-wave plate 10B rotates the polarization of the optical signal 1A by 90 degrees. Furthermore, the phase of the optical signal 1A changes by passing through the half-wave plate 10B. The coupler 10C is, for example, a directional coupler, and combines the optical signal 1B output from the half-wave plate 10B and the optical signal 1C output from the PBS 10A, and outputs the optical signal 4.

  The polarization angle and phase of the optical signal 1B input to the coupler 10C become different from the polarization angle and phase of the optical signal 1C due to the passage through the half-wave plate 10B. Therefore, the optical signal 1B and the optical signal 1C are combined in the coupler 10C, so that the optical signal 4 includes two optical signals derived from the optical signal 1 having different polarization angles and phases. In other words, the optical signal 4 is obtained by adding a noise component to the polarization and phase of the optical signal 1. That is, the optical signal 4 is a signal in which the polarization and phase are disturbed with respect to the optical signal 1.

  Since the polarization rotator 10 only disturbs the polarization and phase of the optical signal 1, the frequency band of the optical signal 4 is the same as the frequency band of the optical signal 1.

  In polarization multiplexing coherent transmission, information is transmitted in the optical signal by polarization and phase. However, since the polarization rotator 10 perturbs the polarization and phase of the optical signal 1 and outputs it as the optical signal 4 in the above procedure, the branch station 53 accurately detects the polarization and phase of the optical signal 4. Difficult to do. As a result, the reception error rate of the optical signal 4 received by the branch station 53 increases, and the optical signal 4 is difficult to receive or cannot be received at the branch station 53.

  As described above, the polarization rotator 10 invalidates the optical signal 1 by outputting a disturbance to the polarization and phase of the optical signal 1 and outputs it as the optical signal 4. On the other hand, since the optical signal 2 in the subband 2 does not pass through the polarization rotator 10, the optical signal 2 is not invalidated. Further, since the optical signal 2 and the optical signal 4 have different wavelength bands, the branch station 53 can easily extract only the optical signal 2. Therefore, the branch station 53 can demodulate the optical signal 2 without being affected by the disturbance of the optical signal 4.

  As described above, since the branch station 53 cannot receive the optical signal 4, the submarine communication system 100 according to the present embodiment is an optical signal that is not required in the branch station 53 among the optical signals branched from the trunk station 51 to the branch station 53. Interception of signal 1 can be made difficult.

  Further, the polarization rotator 10 performs only a process for disturbing the polarization and phase of the input optical signal 1 and does not significantly attenuate the power of the optical signal 1. Therefore, for example, compared with a configuration in which the entire optical signal 1 of the subband 1 is blocked by the optical filter, the power of the optical signal transmitted from the node 110 to the branch station 53 due to the blocking of the optical signal 1 is greatly reduced. Does not occur. For this reason, the input / output power of the optical submarine repeater 54 installed on the transmission path from the node 110 to the branch station 53 is not significantly reduced. As a result, the submarine communication system 100 according to the present embodiment can ensure the security of unnecessary optical signals in the branch station while rated operation of the branch-side optical submarine repeater.

  Note that the polarization rotation direction, rotation amount, and phase change amount given to the optical signal 1A in the polarization rotator 10 may be arbitrarily determined so that the demodulation of the optical signal 4 in the branch station 53 becomes difficult. . In addition, the rotation direction, the rotation amount, and the phase change amount of the polarization applied to the optical signal 1A may be determined so that the reception error rate of the optical signal 4 in the branch station 53 is a predetermined value or more.

  As described above, the submarine communication system 100 according to the first embodiment can transmit only the target optical signal to the branch station while ensuring the security of the optical signal that is not required in the branch station. The reason is that it becomes difficult to intercept the optical signal that is not required at the branch station because disturbance is given to the polarization and phase of the optical signal that is not required at the branch station. Further, since the total power of the optical signal 2 and the optical signal 4 from the node 110 to the branch station 53 is not reduced by the disturbance of the polarization and the phase, the optical submarine repeater to the branch station is operated within the rated range. Can do.

  That is, the submarine communication system 100 of the first embodiment can prevent a terminal station from intercepting a signal that is not required by the terminal station without greatly reducing the power of the optical signal transmitted from the node to the terminal station. .

  Furthermore, the submarine communication system 100 according to the first embodiment can configure a node with a small number of parts by using the WSS module. Further, the setting of the filtering wavelength of the WSS module can be changed even after the operation of the node. Therefore, the submarine communication system 100 of the first embodiment can realize a submarine communication system that is small in size and easy to maintain.

(First modification of the first embodiment)
PBS may be used as the coupler 10 </ b> C used in the polarization rotator 10. By using PBS as the coupler 10C and combining the optical signal 1B and the optical signal 1C as optical signals whose polarizations are orthogonal to each other, the power reduction of the optical signal 4 output from the coupler 10C can be further reduced. As a result, a reduction in input power to the optical submarine repeater 54 can be further suppressed.

(Second modification of the first embodiment)
In the first embodiment, the optical signal 1 is disturbed by the polarization rotator 10 in both polarization and phase. However, if the optical signal 4 cannot be demodulated in the branch station 53, the polarization rotator 10 may give the optical signal 1 a disturbance of only the polarization or the phase.

(Second Embodiment)
FIG. 4 is a block diagram illustrating a configuration of the submarine communication system 200 according to the second embodiment of this invention. In the subsequent drawings, the same reference numerals are given to the same elements as those described in the above-mentioned drawings, and a duplicate description is omitted. The submarine communication system 200 includes trunk stations 51 and 52, a branch station 53, and a node 210. The trunk stations 51 and 52 and the branch station 53 and the node 210 are connected by a submarine optical cable. Compared with the node 110 described in FIG. 1, the node 210 is different in that it does not include the WSS modules 16 and 17, and includes the wavelength filters 7 and 8 and the three-port wavelength filter 9 and the coupler 12.

  The wavelength filter 7 transmits an optical signal in the subband 1 wavelength band and blocks an optical signal in the subband 2 wavelength band. The wavelength filter 8 transmits the optical signal in the subband 2 wavelength band and blocks the optical signal in the subband 1 wavelength band. The 3-port wavelength filter 9 separates an optical signal obtained by wavelength-multiplexing the optical signals of the subband 1 and the subband 2 into the optical signal 1 of the subband 1 and the optical signal 2 of the subband 2.

  At the node 210, the optical signals 1 and 2 that are branched by the coupler 6 and directed toward the branch station 53 are separated into the subband 1 optical signal 1 and the subband 2 optical signal 2 by the three-port wavelength filter 9. The The polarization and the phase of the optical signal 1 are disturbed by the polarization rotator 10 as in the first embodiment. That is, the polarization and phase of the optical signal 1 are disturbed by the polarization rotator 10 and output from the polarization rotator 10 as the optical signal 4. The coupler 11 combines the optical signal 4 and the optical signal 2 and transmits the combined optical signal to the branch station 53. The optical signals 2 and 4 output from the coupler 11 reach the branch station 53 through the submarine cable including the optical submarine repeater 54. Similar to the first embodiment, a coupler or a directional coupler capable of wavelength multiplexing the optical signal 4 of the subband 1 ′ and the optical signal 2 of the subband 2 is used as the coupler 11.

  On the other hand, in the optical signals 1 and 2 transmitted in the direction of the trunk station 52 branched by the coupler 6, the optical signal 2 of the subband 2 is removed by the wavelength filter 7 and only the optical signal 1 of the subband 1 is the coupler. 12 is input.

  The branch station 53 transmits the optical signal 3 and the dummy signal 5 destined for the trunk station 52 to the node 210. The dummy optical signal 5 received from the branch station 53 is blocked by the wavelength filter 8 connected to the coupler 12, and only the optical signal 3 is input to the coupler 12. The coupler 12 combines the optical signal 1 and the optical signal 3 and outputs them to the trunk station 52. A directional coupler is used as the coupler 12. Alternatively, a coupler capable of wavelength multiplexing the optical signal 1 of the subband 1 and the optical signal 3 of the subband 3 is used as the coupler 12.

  As described above, the submarine communication system 200 according to the second embodiment disturbs the polarization and the phase of the optical signal 1 that is not required in the branch station, similarly to the submarine communication system 100 according to the first embodiment. Invalidate by. As a result, the submarine communication system 200 according to the second embodiment prevents the branch station from intercepting a signal that is not required by the branch station without greatly reducing the power of the optical signal transmitted from the node to the branch station. it can.

  Furthermore, the submarine communication system 200 according to the second embodiment does not require a relatively expensive WSS module, although the number of parts constituting the node 201 is increased as compared with the first embodiment. For this reason, the submarine communication system 200 of the second embodiment has an effect that the cost of the node 210 is reduced.

(Third embodiment)
FIG. 5 is a block diagram showing the configuration of the submarine communication system 300 according to the third embodiment of the present invention. The submarine communication system 300 includes trunk stations 51 and 52, a branch station 53, and a node 310. The trunk stations 51 and 52 and the branch station 53 and the node 310 are connected by a submarine optical cable. Compared with the node 210 described in FIG. 4, the node 310 is different in that it does not include the three-port wavelength filter 9 and includes the coupler 18 and the two wavelength filters 8.

  At the node 310, one of the optical signals 1 and 2 branched by the coupler 6 toward the branch station 53 is transmitted only by the optical signal 2 of the subband 2 through the wavelength filter 8, and the optical signal of the subband 1 is transmitted. 1 is blocked.

  On the other hand, the optical signal 2 of the other optical signal branched by the coupler 6 is blocked by the wavelength filter 7 and only the optical signal 1 is input to the coupler 18. The coupler 18 branches the optical signal 1 into two branches. One of the optical signals 1 branched by the coupler 18 is subjected to polarization and phase disturbance by the polarization rotator 10 as in the first and second embodiments, and is output as the optical signal 4. The other of the optical signals 1 branched by the coupler 18 is input to the coupler 12.

  The coupler 11 combines the optical signal 2 that has passed through the coupler 6 and the wavelength filter 8 and the optical signal 4 output from the polarization rotator 10, and transmits the combined signal to the branch station 53. The optical signal 2 and the optical signal 4 transmitted from the coupler 11 are transmitted through the submarine cable including the optical submarine repeater 54 and reach the branch station 53.

  The branch station 53 receives the optical signal 2 and the optical signal 4 transmitted from the node 310. The branch station 53 transmits the dummy signal 5 and the optical signal 3 destined for the trunk station 52 to the node 310. The dummy signal 5 is removed at the node 310 by the wavelength filter 8 connected to the coupler 12, and only the optical signal 3 is input to the coupler 12. The coupler 12 combines the optical signal 1 output from the coupler 18 and the optical signal 3 output from the wavelength filter 8 and transmits the combined signal to the trunk station 52. As in the first and second embodiments, the coupler 11 can be a directional coupler or a multiplexer. In addition, as in the second embodiment, a directional coupler or a multiplexer can be used for the coupler 12 as well.

  Similarly to the submarine communication systems 100 and 200 of the first and second embodiments, the submarine communication system 300 of the third embodiment also uses a polarization rotator 10 to change the polarization and phase of an optical signal that is not required in the branch station. It is invalidated by giving a disturbance using. Therefore, the submarine communication system 300 according to the third embodiment also prevents the branch station from intercepting a signal that is not required by the branch station without greatly reducing the power of the optical signal transmitted from the node to the branch station. it can.

  Further, since the submarine communication system 300 of the third embodiment does not use the WSS module as in the submarine communication system 200 of the second embodiment, there is an effect that the cost of the node 310 is reduced.

(Minimum configuration of the embodiment)
The effect of the submarine communication system 100 of the first embodiment is also brought about by the following node device including a part of the configuration of the node 110 of FIG. That is, the node device includes a first optical unit and a second optical unit.

  The first optical unit (coupler 6 in FIG. 1) outputs a first signal (optical signal 1) and a second signal (optical signal 2). The first signal is a signal received from the first terminal station (trunk station 51) and destined for the second terminal station (trunk station 52). The second signal is a signal having a wavelength band different from that of the first optical signal received from the first terminal station and destined for the third terminal station (branch station 53).

  The first and second optical signals output from the first optical unit are input to the second optical unit (WSS module 16, polarization rotator 10 and coupler 11), and the first optical signal is shifted. Disturbance is applied to at least one of the wave and the phase to form a fourth optical signal (optical signal 4). The second optical unit passes the second optical signal as it is, combines the second and fourth optical signals, and transmits the combined signal to the third terminal station.

  The node device having such a configuration makes it difficult to intercept the first optical signal at the third terminal station by disturbing at least one of the polarization and the phase of the first optical signal. Therefore, in the above node device, as in the node device of the first embodiment, a signal that is not required in the branch station does not significantly reduce the power of the optical signal transmitted from the node device to the branch station. Can be intercepted.

  Furthermore, the first optical unit described above includes the coupler 6 of the node 210 described with reference to FIG. 4, and the second optical unit described above further includes the three-port wavelength of the node 210 described with reference to FIG. The filter 9, the polarization rotator 10, and the coupler 11 may be included.

  Alternatively, the first optical unit described above includes the coupler 6, the wavelength filter 7, and the coupler 18 of the node 310 described in FIG. 5, and the second optical unit further includes the node described in FIG. 310 may include the wavelength filter 8, the polarization rotator 10, and the coupler 11 connected between the coupler 6 and the coupler 11.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  For example, in each embodiment, the submarine communication system has been described as an example. However, the configuration of each embodiment can be applied to a land communication system. Further, the invalidation of the optical signal by the polarization rotator may be performed not only on the optical signal transmitted to the branch station but also on the optical signal transmitted to the trunk station as necessary.

  In addition, although embodiment of this invention can be described also as the following additional remarks, it is not limited to these.

(Appendix 1)
A first optical signal destined for the second terminal station received from the first terminal station; and a first optical signal destined for the third terminal station received from the first terminal station; Is a first optical unit that outputs a second optical signal having a different wavelength band; and
The first and second optical signals output from the first optical unit are input, and at least one of the polarization and phase of the first optical signal is disturbed to form a fourth optical signal. A second optical unit that passes the second optical signal as it is, combines the second and fourth optical signals, and transmits the second optical signal to the third terminal station;
A node device comprising:

(Appendix 2)
The node device according to appendix 1, wherein the amount of the disturbance is determined such that the fourth optical signal cannot be received by the third terminal station.

(Appendix 3)
The node device according to appendix 1 or 2, wherein the amount of disturbance is determined based on an error rate of the fourth optical signal in the third terminal station.

(Appendix 4)
The second optical unit includes a WSS (wavelength selective switch) module that outputs the first optical signal and the second optical signal output from the first optical unit from different ports, and the WSS module. A polarization rotator that generates the fourth optical signal by applying the disturbance to at least one of the polarization and phase of the first optical signal output from the first optical signal, and the second and fourth optical signals And a second coupler that transmits to the third terminal station.

(Appendix 5)
The second optical unit includes a three-port wavelength filter that separates the first and second optical signals output from the first optical unit into the first optical signal and the second optical signal; A polarization rotator that applies the disturbance to at least one of the polarization and phase of the first optical signal separated by the three-port wavelength filter and outputs it as the fourth optical signal; and the three-port wavelength filter And a second coupler that combines the second optical signal and the fourth optical signal separated in step (b) to transmit to the third terminal station. Node device.

(Appendix 6)
The first optical unit includes a first coupler that bifurcates and outputs the first and second optical signals received from the first terminal station, and light that is bifurcated by the first coupler. A first wavelength filter that removes the second optical signal from one of the signals and outputs the first optical signal; and the first optical signal output from the first wavelength filter is bifurcated. And a third coupler that outputs
The second optical unit includes a second wavelength filter that removes the first optical signal from the other of the optical signals branched into two by the first coupler and outputs the second optical signal; A polarization rotator that applies the disturbance to at least one of the polarization and phase of one of the optical signals output from the third coupler and outputs the resultant as the fourth optical signal; the fourth optical signal; A fourth coupler for combining the second optical signal output from the second wavelength filter and transmitting the second optical signal to the third terminal station;
A node device according to any one of appendices 1 to 3.

(Appendix 7)
The polarization rotator is
A polarization beam splitter for polarization-separating the input first optical signal;
A polarization rotation plate for applying a phase change and a polarization rotation to one of the first optical signals subjected to the polarization separation;
A fifth coupler that combines the other of the polarization-separated first optical signals and the first optical signal that has passed through the half-wave plate to output the fourth optical signal;
A node device according to any one of appendices 4 to 6, comprising:

(Appendix 8)
The node device according to appendix 7, wherein the polarization rotation plate is a half-wave plate.

(Appendix 9)
The node device according to appendix 7 or 8, wherein the disturbance is given by the phase change and the polarization rotation.

(Appendix 10)
A second optical signal received from the third terminal station and destined for the second terminal station is combined with the first optical signal output from the first optical unit to combine the second optical signal. The node device according to any one of appendices 1 to 9, comprising a third optical unit that transmits to a terminal station.

(Appendix 11)
The node device according to attachment 10, wherein the third optical unit includes a WSS module.

(Appendix 12)
A communication system in which first to third terminal stations are connected to a node device according to any one of appendices 1 to 11 via a transmission line.

(Appendix 13)
A third terminal station having a wavelength band different from that of the first optical signal received from the first terminal station and destined for the second terminal station and the first optical signal received from the first terminal station A second optical signal destined for
Disturbing at least one of the polarization and phase of the output first optical signal to form a fourth optical signal;
Combining the second and fourth optical signals and transmitting to the third terminal,
Node device control method.

100, 200, 300, 900 Submarine communication system 110, 210, 310, 910 Node 1, 1A, 1B, 1C, 2, 3, 4, 13, 14, 15 Optical signal 5 Dummy signal 6, 11, 12, 18 Coupler 7, 8 Wavelength filter 9 3-port wavelength filter 10 Polarization rotator 10A PBS
10B Half wave plate 10C Coupler 16, 17 WSS module 51, 52 Trunk station 53 Branch station 54 Optical submarine repeater

Claims (10)

A first optical signal destined for the second terminal station received from the first terminal station; and a first optical signal destined for the third terminal station received from the first terminal station; Is a first optical unit that outputs a second optical signal having a different wavelength band; and
The first and second optical signals output from the first optical unit are input, and at least one of the polarization and phase of the first optical signal is disturbed to form a fourth optical signal. A second optical unit that passes the second optical signal as it is, combines the second and fourth optical signals, and transmits the second optical signal to the third terminal station;
A node device comprising:   The node device according to claim 1, wherein the amount of disturbance is determined such that the fourth optical signal cannot be received by the third terminal station.   The node device according to claim 1 or 2, wherein the amount of disturbance is determined based on an error rate of the fourth optical signal in the third terminal station.   The second optical unit includes a WSS (wavelength selective switch) module that outputs the first optical signal and the second optical signal output from the first optical unit from different ports, and the WSS module. A polarization rotator that generates the fourth optical signal by applying the disturbance to at least one of the polarization and phase of the first optical signal output from the first optical signal, and the second and fourth optical signals The node device according to claim 1, further comprising: a second coupler that transmits to the third terminal station.   The second optical unit includes a three-port wavelength filter that separates the first and second optical signals output from the first optical unit into the first optical signal and the second optical signal; A polarization rotator that applies the disturbance to at least one of the polarization and phase of the first optical signal separated by the three-port wavelength filter and outputs it as the fourth optical signal; and the three-port wavelength filter And a second coupler for combining the second optical signal and the fourth optical signal separated in step (b) and transmitting the combined signal to the third terminal station. Node equipment. The first optical unit includes a first coupler that bifurcates and outputs the first and second optical signals received from the first terminal station, and light that is bifurcated by the first coupler. A first wavelength filter that removes the second optical signal from one of the signals and outputs the first optical signal; and the first optical signal output from the first wavelength filter is bifurcated. And a third coupler that outputs
The second optical unit includes a second wavelength filter that removes the first optical signal from the other of the optical signals branched into two by the first coupler and outputs the second optical signal; A polarization rotator that applies the disturbance to at least one of the polarization and phase of one of the optical signals output from the third coupler and outputs the resultant as the fourth optical signal; the fourth optical signal; A fourth coupler for combining the second optical signal output from the second wavelength filter and transmitting the second optical signal to the third terminal station;
The node device according to claim 1, further comprising: The polarization rotator is
A polarization beam splitter for polarization-separating the input first optical signal;
A polarization rotation plate for applying a phase change and a polarization rotation to one of the first optical signals subjected to the polarization separation;
A fifth coupler that combines the other of the polarization-separated first optical signals and the first optical signal that has passed through the half-wave plate to output the fourth optical signal;
The node device according to claim 4, comprising:   The node device according to claim 7, wherein the polarization rotation plate is a half-wave plate.   A second optical signal received from the third terminal station and destined for the second terminal station is combined with the first optical signal output from the first optical unit to combine the second optical signal. The node device according to claim 1, comprising a third optical unit that transmits to a terminal station. A third terminal station having a wavelength band different from that of the first optical signal received from the first terminal station and destined for the second terminal station and the first optical signal received from the first terminal station A second optical signal destined for
Disturbing at least one of the polarization and phase of the output first optical signal to form a fourth optical signal;
Combining the second and fourth optical signals and transmitting to the third terminal,
Node device control method.

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