JP2006333011A - Transmission loss redducing method and apparatus, transmission loss compensator and system for wavelength division multiplex system passive optical network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frequency division multiplex system passive optical network system utilizing optical signals wavelength-locked to incoherent light which suppresses the optical loss to minimum and improves transmission quality and a transmission distance. <P>SOLUTION: A central base station comprises a 2×N optical multiplexer/demultiplexer 610, first and second 1×2 space type optical switches 614, 615, and a 4-terminal optical route setting unit 613. A first optical cable 616 for connection in a normal state, and a second optical cable 617 for detouring at recovery from troubles are provided between the central base station and a remote branch node, and the remote branch node comprises a 2×N optical multiplexer/demultiplexer 618. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wavelength division multiplexing passive optical network. In particular, a wavelength division multiplexing passive optical network using a wavelength division multiplexing optical communication light source that outputs an optical signal wavelength-locked to incoherent light minimizes optical loss and improves transmission quality and transmission distance. Related to technology.

  The wavelength division multiplexing passive optical network includes a central base station, a plurality of optical subscribers, and an optical distribution network that connects the central base station to each optical subscriber. The optical distribution network is composed of a remote branch node having no power supply and comprising light receiving elements such as a wavelength division multiplexer / demultiplexer and an optical divider, and an optical cable. A wavelength division multiplexed optical signal is transmitted between the central base station and the remote branch node through a single optical cable, and a specific wavelength is assigned to the optical subscriber by the remote branch node.

  In the case of a wavelength division multiplexing passive optical network, a plurality of light sources having different wavelengths are required to assign one or more wavelengths to subscribers. Moreover, a means for recovering when a failure occurs in the optical transmission line between the central base station and the remote branch node is required.

  FIG. 1 is a diagram illustrating a conventional wavelength division multiplexing passive optical network, and FIG. 2 is a diagram illustrating a conventional wavelength division multiplexing passive optical network having a failure recovery function.

  FIG. 1 shows a low-cost light source that outputs an optical signal wavelength-locked to injected incoherent light and a wavelength-division-multiplexing passive optical network as described in “A low-cost WDM source with an ASE”. Injected Fabry-Perot semiconductor laser ”and“ Wavelength Division Multiplexing Passive Optical Network ”of Patent Document 1 by Tsugan Wook, Yi Fan, Wu Taiyuan.

  Figure 2 shows the proposed method for disaster recovery presented in "ITU-T G.983.1 Broadband optical access systems based on passive optical networks", which is a standard proposed by the International Telecommunication Union. It is the Example applied to.

  A light source that outputs an optical signal that is wavelength-locked to the injected incoherent light is an incoherent and wide line-width spontaneous emission light source, Fabry-Perot laser diode, optical multiplexer / demultiplexer, and optical modulation function Means a light source that always outputs a wavelength division multiplexed optical signal that matches the multiplexed / demultiplexed wavelength of the optical multiplexer / demultiplexer.

Referring to FIG. 1, incoherent light from the B-band spontaneous emission light source 112 is transmitted as a downward signal from the central base station to the optical subscriber by the 2 × 2 3db optical splitter 113, 1 × N optical multiplexer / demultiplexer 110, and the A band and B A wavelength-locked optical signal that is injected into an optical transmitter 101-103 having a Fabry-Perot laser diode of a central base station through an optical multiplexer / demultiplexer 107-109 that multiplexes / demultiplexes the band is output. , An optical signal wavelength-locked in the B band is transmitted to the optical receivers 122-124 of the optical subscribers. As an upward signal from the optical subscriber to the central base station, the incoherent light from the A-band spontaneous emission light source 111 multiplexes the 2 × 2 3db optical splitter 113, the optical cable 114, the remote branch node 115, and the A and B bands. A wavelength-locked optical signal injected into an optical transmitter 119-121 having a Fabry-Perot laser diode of an optical subscriber is output through an optical multiplexer / demultiplexer 116-118 that performs demultiplexing, and wavelength-locked within the A band. The transmitted optical signal is transmitted to the optical receivers 104-106 of the central base station.
Korean Patent No. 10-2002-0003318 Specification Hyun Deok Kim, Seung-Goo Kang, Chang-Hee Lee, “IEEE Photonic Technology Letters, vol.12, no.8” , P.1067-1069

  As described above, in the case of a light source that outputs an optical signal that is wavelength-locked to the injected incoherent light, the wavelength locking phenomenon is more efficiently performed as the intensity of the incoherent light injected into the optical transmitter increases. Is called. Therefore, the incoherent light from the A-band spontaneous emission light source 111 and the B-band spontaneous emission light source 112 needs to be transmitted to the optical transmitters 101-103 and 119-121 as much as possible.

  In the case of the wavelength division multiplexing passive optical network as described above, the 2 × 2 optical splitter 113 is used to inject incoherent light. The 2 × 2 optical splitter 113 divides the optical signal 50 to 50 with respect to the A band and the B band. Therefore, when incoherent light from the A-band spontaneous emission light source 111 is transmitted to the optical cable 114 through the 2 × 2 optical splitter 113, a 3 dB optical loss occurs, and the incoherent light from the B-band spontaneous emission light source 112 is also 1 × N optical multiplexer / When transmitted to the demultiplexer 110, an optical loss of 3 db occurs. Further, since the 2 × 2 optical splitter 113 is located on the optical transmission line, unnecessary optical loss is caused for the upward signal and the downward signal.

  When a failure occurs in the optical cable between the central base station and the remote branch node, communication of all optical subscribers is interrupted, so a failure recovery function is essential. Referring to FIG. 2, in addition to the 1 × N optical multiplexer / demultiplexer 201, the A-band spontaneous emission light source 202, the B-band spontaneous emission light source 203, and the 2 × 2 optical splitter 204, a 1 × 2 spatial light switch 205 is installed at the central base station. An optical splitter 208 is installed in the remote branch node 209, and when a failure occurs in the first optical cable 206, communication is possible by detouring to the second optical cable 207. In the case of the method described above, the use of the optical splitter 208 in the remote branch node 209 adds an additional 3 db of optical loss.

  As described above, in the wavelength division multiplexing passive optical network, it is necessary to minimize the loss that occurs when incoherent light is injected. In addition, the optical loss that occurs before the signal transmitted by the optical transmitter reaches the optical receiver greatly affects the transmission quality or expandability. Therefore, the optical loss is minimized or compensated for. A method is needed.

  The present invention has been devised to solve the above-described problems of the prior art, and is a wavelength division multiplexing passive method using a wavelength division multiplexing optical communication light source that outputs an optical signal wavelength-locked to incoherent light. It aims at minimizing optical loss by an optical network and improving transmission quality and transmission distance.

  As a technical idea for achieving the above-described object of the present invention, the present invention improves the wavelength locking phenomenon of the wavelength division multiplexing optical communication light source by increasing the injection amount of incoherent light. The present invention also provides a method for reducing optical transmission line loss and compensating for optical transmission line loss. In addition, the present invention provides a failure recovery method using a four-terminal optical path setter without any additional loss.

  A method for reducing transmission loss of a wavelength division multiplexing passive optical network according to the present invention is provided with an A-band optical signal including a plurality of optical wavelengths and a B-band optical signal including a plurality of optical wavelengths. In the transmission loss reduction method of the wavelength division multiplexing passive optical network having the A-band optical signal input to the first terminal of the four-terminal optical path setter is output to the third terminal and input to the third terminal The A-band optical signal is output to the fourth terminal, the B-band optical signal input to the second terminal of the four-terminal optical path setter is output to the fourth terminal, and the B-band light input to the fourth terminal. The signal is output to the third terminal.

  A transmission loss reduction apparatus for a wavelength division multiplexing passive optical network according to the present invention is provided with an A-band optical signal including a plurality of optical wavelengths and a B-band optical signal including a plurality of optical wavelengths. In the transmission loss reducing apparatus of the wavelength division multiplexing passive optical network having the first optical multiplexer / demultiplexer, the 4-terminal optical path setter multiplexes / demultiplexes the A-band optical signal and the B-band optical signal. And a second optical multiplexer / demultiplexer, an A-band optical circulator operating in the A band and having three terminals, and a B-band optical circulator operating in the B band and having three terminals.

  In the transmission loss reducing apparatus for a wavelength division multiplexing passive optical network according to the present invention, the first terminal of the 4-terminal optical path setter is the first terminal of the A-band optical circulator, and the 4-terminal optical path setter The second terminal is the first terminal of the B-band optical circulator, the third terminal of the 4-terminal optical path setting device is the first terminal of the first optical multiplexer / demultiplexer, and the 4-terminal optical path setting device. The fourth terminal of the second optical multiplexer / demultiplexer is the first terminal of the second optical multiplexer / demultiplexer, and the second terminal of the A-band optical circulator is connected to the second terminal of the first optical multiplexer / demultiplexer. The third terminal of the circulator is connected to the second terminal of the second optical multiplexer / demultiplexer, and the second terminal of the B-band optical circulator is connected to the second terminal. Is connected to the third terminal of the multiplexer / demultiplexer, third terminal of the B band optical circulator is characterized in that it is connected to the third terminal of said first optical multiplexer / demultiplexer.

  A transmission loss compensator for a wavelength division multiplexing passive optical network according to the present invention is provided with an A-band optical signal including a plurality of optical wavelengths and a B-band optical signal including a plurality of optical wavelengths. In the transmission loss compensator of the wavelength division multiplexing passive optical network having the first optical multiplexer / demultiplexer and the second optical, the 4-terminal optical path setter multiplexes / demultiplexes the A band and the B band. A multiplexer / demultiplexer, an A-band optical circulator operating in the A band and having three terminals, a B-band optical circulator operating in the B band and having three terminals, an A-band optical amplifier operating in the A band; And a B-band optical amplifier operating in a band.

  In the transmission loss compensator for a wavelength division multiplexing passive optical network according to the present invention, the first terminal of the 4-terminal optical path setter is the first terminal of the A-band optical circulator, The second terminal is the first terminal of the B-band optical circulator, the third terminal of the 4-terminal optical path setting device is the first terminal of the first optical multiplexer / demultiplexer, and the 4-terminal optical path setting device. The fourth terminal of the second optical multiplexer / demultiplexer is the first terminal of the second optical multiplexer / demultiplexer, and the second terminal of the A-band optical circulator is connected to the second terminal of the first optical multiplexer / demultiplexer. The third terminal of the circulator is connected to the input terminal of the A-band optical amplifier, and the output terminal of the A-band optical amplifier is the second optical multiplexer / demultiplexer. The second terminal of the B-band optical circulator is connected to the third terminal of the second optical multiplexer / demultiplexer, and the third terminal of the B-band optical circulator is connected to the B-band optical amplifier. It is connected to an input terminal, and the output of the B-band optical amplifier is connected to the third terminal of the first optical multiplexer / demultiplexer.

  In the transmission loss compensation apparatus for a wavelength division multiplexing passive optical network according to the present invention, the A-band optical amplifier and the B-band optical amplifier are rare-earth doped optical fiber amplifiers, rare-earth doped optical waveguide amplifiers, semiconductor optical amplifiers, and optical nonlinear optical fibers. Any one of the optical fiber amplifiers using the characteristics is selected and used.

  A wavelength division multiplexing passive optical network system according to the present invention has a failure recovery function between a central base station and a remote branch node, and uses a wavelength signal that is wavelength-locked to injected incoherent light. In a divisional multiplexing passive optical network system, a central base station is equipped with a 2xN optical multiplexer / demultiplexer, a first 1x2 spatial optical switch, a second 1x2 spatial optical switch, and a four-terminal optical path setter, and is remote from the central base station A first optical cable for normal connection and a second optical cable for detouring at the time of failure recovery are provided between the branch nodes and a 2 × N optical multiplexer / demultiplexer is provided at the remote branch node.

  In the wavelength division multiplexing passive optical network system according to the present invention, the first 1 × 2 spatial optical switch of the central base station is connected to one terminal and the four terminals of two terminals of the 2 × N optical multiplexer / demultiplexer of the central base station. An optical path setter is connected, and the second 1 × 2 spatial optical switch of the central base station connects the first optical cable or one end of the second optical cable and the four-terminal optical path setter. To do.

  The wavelength division multiplexing passive optical network system according to the present invention is characterized in that the 2 × N optical multiplexer / demultiplexer uses an optical element utilizing integrated optical technology, micro-optical technology, and optical fiber technology.

  The wavelength division multiplexing passive optical network system according to the present invention is characterized in that an arrayed waveguide grating wavelength division multiplexer / demultiplexer is used as the 2 × N optical multiplexer / demultiplexer.

  The wavelength division multiplexing passive optical network system according to the present invention switches the connection between the first 1x2 spatial optical switch and the second 1x2 spatial optical switch when a failure occurs in the optical network, and The optical path is controlled so that the input terminal settings of the central base station and the remote branch node with the 2 × N optical multiplexer / demultiplexer are changed by synchronization.

  The wavelength division multiplexing passive optical network system according to the present invention is characterized in that the wavelength is automatically assigned by the wavelength change of the injected incoherent light when the failure is recovered in the optical network.

  According to the present invention, the optical loss of a wavelength division multiplexing passive optical network using a light source that outputs an optical signal that is wavelength-locked to the injected incoherent light can be reduced, and the optical loss is compensated. can do. The four-terminal optical path setter according to the present invention can be realized at low cost by using a conventional optical element. Further, the wavelength division multiplexing passive optical network having the failure recovery function according to the present invention can be realized without additional optical loss.

  According to the present invention, the optical loss in the wavelength division multiplexing passive optical network is an important factor that limits the transmission distance and the number of subscribers that can be accommodated. The economics of the wavelength division multiplexing passive optical network can be improved by increasing the transmission distance and the number of subscribers by reducing and compensating the optical loss.

Hereinafter, the present invention will be described in detail with reference to the drawings showing the configuration and operation of the embodiment.
FIG. 3 is a diagram showing operating characteristics of the four-terminal optical path setting device according to the present invention.

  The A-band optical signal input to the first terminal of the four-terminal optical path setter according to the present invention is output to the third terminal. The A-band optical signal input to the third terminal of the four-terminal optical path setter is output to the fourth terminal. The B-band optical signal input to the second terminal of the four-terminal optical path setter is output to the fourth terminal. The B-band optical signal input to the fourth terminal of the four-terminal optical path setting device is output to the third terminal.

  As shown in FIG. 3, the 4-terminal optical path setter of the present invention is replaced with the 2 × 2 optical splitter 113 of FIG. 1 to reduce optical loss.

  The four-terminal optical path setting device of the present invention is realized by using a single optical element using a micro-Optics technique or an integrated-Optics technique or an existing optical element.

  FIG. 4 is a diagram showing an embodiment of a four-terminal optical path setting device according to the present invention. Referring to FIG. 4, the four-terminal optical path setter operates in a first band, a first optical multiplexer / demultiplexer 401 and a second optical multiplexer / demultiplexer 402 that multiplex / demultiplex A band and B band. And an A-band optical circulator 403 having three terminals and a B-band optical circulator 404 having three terminals that operate in the B band.

  The A-band optical signal input to the first terminal of the four-terminal optical path setter according to the present invention passes through the A-band optical circulator 403 and the second optical multiplexer / demultiplexer 402 and is output to the third terminal.

  The A-band optical signal input to the third terminal of the four-terminal optical path setter passes through the second optical multiplexer / demultiplexer 402, the A-band optical circulator 403, and the first optical multiplexer / demultiplexer 401 to the fourth terminal. Is output.

  The B-band optical signal input to the second terminal of the four-terminal optical path setter passes through the B-band optical circulator 404 and the first optical multiplexer / demultiplexer 401 and is output to the fourth terminal.

  The B-band optical signal input to the fourth terminal of the four-terminal optical path setter passes through the first optical multiplexer / demultiplexer 401, the B-band optical circulator 404, and the second optical multiplexer / demultiplexer 402, and the third terminal. Is output.

  Preferably, the first optical multiplexer / demultiplexer 401, the second optical multiplexer / demultiplexer 402, the A-band optical circulator 403, and the B-band optical circulator 404 presented from the embodiment of the four-terminal optical path setter of the present invention are respectively used. Considering that there are three terminals, the first optical multiplexer / demultiplexer 401 and the second optical multiplexer / demultiplexer 402 output the A-band optical signal input to the first terminal to the second terminal and output the second terminal The A-band optical signal input to is output to the first terminal. The B-band optical signal input to the first terminal is output to the third terminal, and the B-band optical signal input to the third terminal is output to the first terminal.

  In the A-band optical circulator 403, the A-band optical signal input to the first terminal is output to the second terminal, and the A-band optical signal input to the second terminal is output to the third terminal. In the B-band optical circulator 404, the B-band optical signal input to the first terminal is output to the second terminal, and the B-band optical signal input to the second terminal is output to the third terminal.

  At this time, the first terminal of the 4-terminal optical path setter is the first terminal of the A-band circulator 403, and the second terminal of the 4-terminal optical path setter is the first terminal of the B-band optical circulator 404. The third terminal of the 4-terminal optical path setter is the first terminal of the first optical multiplexer / demultiplexer 401, and the fourth terminal of the 4-terminal optical path setter is the first terminal of the second optical multiplexer / demultiplexer 402. Terminal.

  The second terminal of the A-band optical circulator 403 is connected to the second terminal of the first optical multiplexer / demultiplexer 401, and the third terminal of the A-band optical circulator 403 is connected to the second terminal of the second optical multiplexer / demultiplexer 402. Is done. The second terminal of the B-band optical circulator 404 is connected to the third terminal of the second optical multiplexer / demultiplexer 402, and the third terminal of the B-band optical circulator 404 is connected to the third terminal of the first optical multiplexer / demultiplexer 401. Is done.

  Since the four-terminal optical path setter according to the present invention has no theoretical optical loss except for the additional loss caused by the manufacturing process of the individual optical elements, it is possible to eliminate the theoretical 3 db optical loss due to the 2 × 2 optical splitter 113. it can.

  Therefore, when the 4-terminal optical path setter according to the present invention and the 2 × 2 optical splitter 113 described above are replaced, the injection rate of the spontaneous emission light source can be improved by 3 db. Further, the optical loss of 3 db can be reduced for the upward signal and the downward signal, respectively.

  FIG. 5 is a diagram showing an embodiment of a four-terminal optical path setting device according to the present invention. Referring to FIG. 5, the 4-terminal optical path setter operates in the A band, the first optical multiplexer / demultiplexer 501 and the second optical multiplexer / demultiplexer 502 that multiplex / demultiplex A band and B band. And an A-band optical circulator 503 having three terminals, a B-band optical circulator 504 operating in the B-band, an A-band optical amplifier 505, and a B-band optical amplifier 506.

  The 4-terminal optical path setter for compensating for optical loss according to the present invention in FIG. 5 is replaced with the 2 × 2 optical splitter 113 described above.

  The A-band upward signal is input to the third terminal of the 4-terminal optical path setter according to the present invention, and the second optical multiplexer / demultiplexer 502, the A-band optical circulator 503, the A-band optical amplifier 505, and the first optical multiplexer / demultiplexer. The signal passes through the multiplexer 501 and is output to the fourth terminal. As the A-band optical amplifier 505, a rare-earth doped optical fiber amplifier, a rare-earth doped optical waveguide amplifier, a semiconductor optical amplifier, and an optical fiber amplifier using optical nonlinearity of an optical fiber are used. The A-band optical amplifier 505 compensates for the optical loss of the upward signal.

  The downward signal of the B band is input to the fourth terminal of the four-terminal optical path setter according to the present invention, and the first optical multiplexer / demultiplexer 501, the B band optical circulator 504, the B band optical amplifier 506, and the second optical multiplexer / demultiplexer. The signal passes through the multiplexer 502 and is output to the third terminal. As the B-band optical amplifier 506, a rare-earth doped optical fiber amplifier, a rare-earth doped optical waveguide amplifier, a semiconductor optical amplifier, and an optical fiber amplifier using optical nonlinearity of an optical fiber are used. The B-band optical amplifier 506 compensates for the optical loss of the downward signal.

  By compensating for the optical loss of the upward signal and the downward signal, optical subscribers can be accommodated, and the transmission distance between the central base station and the optical subscribers can be increased.

  Preferably, the first optical multiplexer / demultiplexer 501, the second optical multiplexer / demultiplexer 502, the A-band optical circulator 503, and the B-band optical circulator 504 provided in the embodiment of the four-terminal optical path setter according to the present invention are three. In consideration of being a terminal, the first optical multiplexer / demultiplexer 501 and the second optical multiplexer / demultiplexer 502 output the A-band optical signal input to the first terminal to the second terminal and output to the second terminal The input A-band optical signal is output to the first terminal. The B-band optical signal input to the first terminal is output to the third terminal, and the B-band optical signal input to the third terminal is output to the first terminal.

  In the A-band optical circulator 503, the A-band optical signal input to the first terminal is output to the second terminal, and the A-band optical signal input to the second terminal is output to the third terminal. In the B-band optical circulator 504, the B-band optical signal input to the first terminal is output to the second terminal, and the B-band optical signal input to the second terminal is output to the third terminal.

  At this time, the first terminal of the 4-terminal optical path setter is the first terminal of the A-band optical circulator 503, and the second terminal of the 4-terminal optical path setter is the first terminal of the B-band optical circulator 504. . The third terminal of the 4-terminal optical path setter is the first terminal of the first optical multiplexer / demultiplexer 501, and the fourth terminal of the 4-terminal optical path setter is the first terminal of the second optical multiplexer / demultiplexer 502. Terminal.

  The second terminal of the A-band optical circulator 503 is connected to the second terminal of the first optical multiplexer / demultiplexer 501, and the third terminal of the A-band optical circulator 503 is connected to the input terminal of the A-band optical amplifier 505. The output terminal of the optical amplifier 505 is connected to the second terminal of the second optical multiplexer / demultiplexer 502.

  The second terminal of the B-band optical circulator 504 is connected to the third terminal of the second optical multiplexer / demultiplexer 502, and the third terminal of the B-band optical circulator 504 is connected to the input terminal of the B-band optical amplifier 506. The output of the optical amplifier 506 is connected to the third terminal of the first optical multiplexer / demultiplexer 501.

  FIG. 6 is a diagram illustrating a wavelength division multiplexing passive optical network having a failure recovery function according to the present invention. Referring to FIG. 6, the wavelength division multiplexing passive optical network includes a 2 × N optical multiplexer / demultiplexer 610 and 618, a first 1 × 2 spatial optical switch 614, a second 1 × 2 spatial optical switch 615, and a second optical cable 617 during detouring. And wavelength-locked optical signals are used.

  That is, the central base station includes a 2 × N optical multiplexer / demultiplexer 610, a first 1 × 2 spatial optical switch 614, a second 1 × 2 spatial optical switch 615, and a four-terminal optical path setting device 613, and the central base station, the remote branching node, The first optical cable 616 for normal connection and the second optical cable 617 for detouring at the time of failure recovery are provided, and the 2 × N optical multiplexer / demultiplexer 618 is provided at the remote branch node.

  At this time, the first 1 × 2 spatial optical switch 614 of the central base station connects one terminal of the two terminals of the 2 × N optical multiplexer / demultiplexer 610 of the central base station to the four-terminal optical path setting device 613, and the second 1 × 2 The spatial optical switch 615 connects one end of the first optical cable 616 or the second optical cable 617 and the 4-terminal optical path setting device 613.

  The 2 × N optical multiplexer / demultiplexer 610, 618 uses optical elements utilizing integrated optical technology, micro-optical technology, and optical fiber technology. In general, an arrayed-waveguide grating multiplexer (AWG) is used. The operating characteristics of AWG are H. Described in “Transmission characteristics of arrayed-waveguide NxN wavelength multiplexer” published by H. Takahashi et al., “IEEE Photonic Technology Letters, vol.13, p. 447-455” Yes.

  The wavelength division multiplexing passive optical network having the failure recovery function shown in FIG. 6 can reduce the optical loss of 3 db since the 1 × 2 optical splitter can be removed from the remote branch node.

  Referring to FIG. 6, the operation and effect of the apparatus according to the present invention will be described below. If the first optical cable 616 fails on the optical network using the first optical cable 616, the first 1 × 2 spatial optical switch 614 of the central base station is connected to another terminal of the 2 × N optical multiplexer / demultiplexer 610, At the same time, the second 1 × 2 spatial light switch 615 is connected to the second optical cable 617. Thereafter, as a downward signal from the central base station to the optical subscriber, incoherent light from the B-band spontaneous emission light source 612 is converted into a four-port optical path setter 613, a first 1 × 2 spatial light switch 614, and a 2 × N optical multiplexer / demultiplexer. 610 and an optical multiplexer / demultiplexer 607-609 that multiplexes / demultiplexes the A band and B band, and is injected into an optical transmitter 601-603 having a Fabry-Perot laser diode of a central base station and wavelength-locked. The optical signal is output, and the optical signal wavelength-locked in the B band is transmitted to the optical receiver 625-627 of the optical subscriber. As an upward signal from the optical subscriber to the central base station, incoherent light from the A-band spontaneous emission light source 611 is converted into a 4-terminal optical path setter 613, a second 1 × 2 spatial light switch 615, a second optical cable 617, and a 2 × N optical multiplexer. / Demultiplexer 618 and optical multiplexer / demultiplexer 619-621 that multiplexes / demultiplexes the A band and the B band, and is injected into an optical transmitter 622-624 having an optical subscriber Fabry-Perot laser diode. The locked optical signal is output, and the optical signal wavelength-locked within the A band is transmitted to the optical receivers 604 to 606 of the central base station.

  When the connection terminal of the 2 × N optical multiplexer / demultiplexer 610, 618 is changed, since the pass wavelength characteristic between the input end and the output end of the 2 × N optical multiplexer / demultiplexer 610, 618 changes, the optical transmission of the central base station It is necessary to newly set the output wavelengths of the optical transmitters 601-603 and the optical transmitters 622-624 of the optical subscribers. However, since the light source of the optical transmitter of the present invention uses the wavelength locking phenomenon caused by the injected incoherent light, the wavelength is synchronized even if the connection terminals of the 2 × N optical multiplexer / demultiplexers 610 and 618 are changed. Has the advantage of being automatically assigned.

  While the invention has been described in terms of preferred embodiments, such embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art to which the present invention pertains that various changes, modifications or adjustments can be made to the above-described embodiments without departing from the spirit of the present invention. Therefore, the protection scope of the present invention should be limited only to the appended claims, and should be construed to include all the various modifications or adjustments.

It is the figure which showed the conventional wavelength division multiplexing passive optical network. It is the figure which showed the wavelength division multiplexing system passive optical network which has the conventional failure recovery function. It is the figure which showed the operating characteristic of the 4 terminal optical path setting device by this invention. It is the figure which showed the Example of the 4 terminal optical path setting device by this invention. It is the figure which showed the Example of the 4 terminal optical path setting device by this invention. 1 is a diagram illustrating a wavelength division multiplexing passive optical network having a failure recovery function according to the present invention. FIG.

Explanation of symbols

401, 501 First optical multiplexer / demultiplexer 402, 502 Second optical multiplexer / demultiplexer 403, 503 A-band optical circulator
404, 504 B-band optical circulator 505 A-band optical amplifier 506 B-band optical amplifier 610, 618 2xN optical multiplexer / demultiplexer 613 4-terminal optical path setter 614 1st 1x2 spatial optical switch 615 2nd 1x2 spatial optical switch 616 First optical cable 617 Second optical cable

Claims (12)

In a method for reducing transmission loss of a wavelength division multiplexing passive optical network, which is provided with an A-band optical signal including a plurality of optical wavelengths and a B-band optical signal including a plurality of optical wavelengths, and having a four-terminal optical path setter,
The A-band optical signal input to the first terminal of the 4-terminal optical path setter is output to the third terminal, and the A-band optical signal input to the third terminal is output to the fourth terminal.
The B-band optical signal input to the second terminal of the four-terminal optical path setter is output to the fourth terminal, and the B-band optical signal input to the fourth terminal is output to the third terminal. A method for reducing transmission loss in a wavelength division multiplexing passive optical network. In a transmission loss reduction apparatus for a wavelength division multiplexing passive optical network, which is provided with an A-band optical signal including a plurality of optical wavelengths and a B-band optical signal including a plurality of optical wavelengths, and having a four-terminal optical path setter,
The 4-terminal optical path setting device is:
A first optical multiplexer / demultiplexer and a second optical multiplexer / demultiplexer for multiplexing / demultiplexing an A-band optical signal and a B-band optical signal;
An A-band optical circulator that operates in the A-band and has three terminals;
A transmission loss reduction apparatus for a wavelength division multiplexing passive optical network, characterized by comprising a B-band optical circulator having three terminals and operating in the B-band. The first terminal of the 4-terminal optical path setter is the first terminal of the A-band optical circulator, and the second terminal of the 4-terminal optical path setter is the first terminal of the B-band optical circulator,
The third terminal of the 4-terminal optical path setter is the first terminal of the first optical multiplexer / demultiplexer, and the fourth terminal of the 4-terminal optical path setter is the first terminal of the second optical multiplexer / demultiplexer. Terminal
The second terminal of the A-band optical circulator is connected to the second terminal of the first optical multiplexer / demultiplexer, and the third terminal of the A-band optical circulator is connected to the second terminal of the second optical multiplexer / demultiplexer. And
The second terminal of the B-band optical circulator is connected to the third terminal of the second optical multiplexer / demultiplexer, and the third terminal of the B-band optical circulator is connected to the third terminal of the first optical multiplexer / demultiplexer. The transmission loss reducing apparatus for a wavelength division multiplexing passive optical network according to claim 2, wherein: In a transmission loss compensation apparatus for a wavelength division multiplexing passive optical network, which is provided with an A-band optical signal including a plurality of optical wavelengths and a B-band optical signal including a plurality of optical wavelengths, and having a four-terminal optical path setter.
The 4-terminal optical path setting device is:
A first optical multiplexer / demultiplexer and a second optical multiplexer / demultiplexer that multiplex / demultiplex A band and B band;
An A-band optical circulator that operates in the A-band and has three terminals;
A B-band optical circulator that operates in the B-band and has three terminals;
An A-band optical amplifier operating in the A-band;
A transmission loss compensation apparatus for a wavelength division multiplexing passive optical network, comprising: a B-band optical amplifier operating in a B-band. The first terminal of the 4-terminal optical path setter is the first terminal of the A-band optical circulator, and the second terminal of the 4-terminal optical path setter is the first terminal of the B-band optical circulator,
The third terminal of the 4-terminal optical path setter is the first terminal of the first optical multiplexer / demultiplexer, and the fourth terminal of the 4-terminal optical path setter is the first terminal of the second optical multiplexer / demultiplexer. Terminal
The second terminal of the A-band optical circulator is connected to the second terminal of the first optical multiplexer / demultiplexer, the third terminal of the A-band optical circulator is connected to the input terminal of the A-band optical amplifier, and the A The output terminal of the band optical amplifier is connected to the second terminal of the second optical multiplexer / demultiplexer,
The second terminal of the B-band optical circulator is connected to the third terminal of the second optical multiplexer / demultiplexer, the third terminal of the B-band optical circulator is connected to the input terminal of the B-band optical amplifier, and the B 5. The transmission loss compensation apparatus for a wavelength division multiplexing passive optical network according to claim 4, wherein the output of the band optical amplifier is connected to the third terminal of the first optical multiplexer / demultiplexer.   The A-band optical amplifier and the B-band optical amplifier are selected from a rare earth-doped optical fiber amplifier, a rare-earth doped optical waveguide amplifier, a semiconductor optical amplifier, and an optical fiber amplifier using optical nonlinearity of an optical fiber. 5. The transmission loss compensation apparatus for a wavelength division multiplexing passive optical network according to claim 4, In the wavelength division multiplexing passive optical network system having a failure recovery function between the central base station and the remote branch node and using the optical signal wavelength-locked to the injected incoherent light,
The central base station comprises a 2xN optical multiplexer / demultiplexer, a first 1x2 spatial optical switch, a second 1x2 spatial optical switch, and a four-terminal optical path setter,
A first optical cable for normal connection and a second optical cable for detouring at the time of fault recovery between the central base station and the remote branch node;
2. A wavelength division multiplexing passive optical network system comprising a 2 × N optical multiplexer / demultiplexer at a remote branch node. The first 1 × 2 spatial optical switch of the central base station connects one terminal of two terminals of the 2 × N optical multiplexer / demultiplexer of the central base station and the four-terminal optical path setting device,
The wavelength division division according to claim 7, wherein the second 1x2 spatial optical switch of the central base station connects one end of the first optical cable or the second optical cable and the four-terminal optical path setting device. Multiplex passive optical network system.   The wavelength division multiplexing passive optical network system according to claim 7, wherein an optical element using an integrated optical technology, a micro optical technology, or an optical fiber technology is used for the 2xN optical multiplexer / demultiplexer.   The wavelength division multiplexing passive optical network system according to claim 7, wherein an arrayed waveguide grating wavelength division multiplexer / demultiplexer is used as the 2xN optical multiplexer / demultiplexer.   When a failure occurs in the optical network, the connection of the first 1x2 spatial optical switch and the second 1x2 spatial optical switch is switched, and the 2xN optical multiplexer / demultiplexer of the second optical cable, the central base station and the remote branch node are switched. 8. The wavelength division multiplexing passive optical network system according to claim 7, wherein the optical path is controlled so that the input terminal setting with the multiplexer is changed by synchronization.   8. The wavelength division multiplexing passive optical network system according to claim 7, wherein the wavelength is automatically assigned by the wavelength change of the injected incoherent light when a failure is recovered in the optical network.

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