JP2004320486A - Optical wavelength division multiplexing network apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical wavelength division multiplexing network device in which the number of transmitting/receiving devices can be increased by eliminating the problem of coding errors due to the coherent crosstalk in an AWG multiplexing/demultiplexing circuit. <P>SOLUTION: N pieces of transmitting circuits 312 of a transmitting/receiving circuit 310 each includes a transmitter 312a for generating an electrical signal having a transmitting speed of 2.48832 Gbits/s, an error correcting coding circuit 312b for encoding this electrical signal into an electrical signal having 2.654208 Gbits/s by using a Reed-Solomon code, and an electro/optical converting circuit 312c for converting the encoded electrical signal into an optical signal having a predetermined wavelength (λ1-Nλ) by a method, such as a direct modulation, etc. N pieces of receiving circuits 311 each includes an electro/optical converting circuit 311a for converting the optical signal of each wavelength from demultiplexing circuit 313 into an electrical signal, an error correcting decoding circuit 312b for decoding the electrical signal having the transmitting speed of 2.654208 Gbits/s into an electrical signal having the transmitting speed of 2.48832 Gbits/s by using the Reed-Solomon code, and a receiver 311c receiving the electric signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a full mesh type optical wavelength division multiplexing transmission network device for transmitting an optical signal wavelength division multiplexed between a plurality of transmission / reception devices.
[0002]
[Prior art]
A method of multiplexing a plurality of optical signals having different wavelengths and transmitting the multiplexed signals through a single optical fiber, that is, a WDM (Wavelength Division Multiplexing) transmission method, can not only greatly increase the transmission capacity but also multiplexing. Addressing for assigning destination information of a signal to each of the obtained optical signals is possible. In addition, a network composed mainly of an arrayed waveguide grating (AWG, Arrayed Waveguide Grating) type multiplexing / demultiplexing circuit having a wavelength revolving property and a plurality of transmitting / receiving devices connected in a star-shaped optical fiber is By passing an optical signal (hereinafter, referred to as a WDM optical signal) wavelength-division multiplexed through an optical fiber, a full mesh type optical wavelength division multiplexing transmission network device can be constructed.
[0003]
FIG. 1 is a schematic diagram of an optical wavelength division multiplexing transmission network device described in JP-A-2000-201112 and the like. In the figure, 101 to 107 denote N transmitting / receiving apparatuses (1 to N) for transmitting and receiving WDM optical signals (λ1 to λN), and 108 denotes an N × N AWG type multiplexing / demultiplexing apparatus having N input ports and output ports. The circuits, OF1 and OF2, are optical fibers that connect the transmitting / receiving apparatuses 101 to 107 and the AWG type multiplexing / demultiplexing circuit 108.
[0004]
FIG. 2 is a configuration diagram of the optical wavelength division multiplexing transmission network device shown in FIG. In the figure, 210 to 240 are N transmission / reception devices (1, 2, i, N), and 211 to 241 are N in each of the transmission / reception devices 210 to 240 capable of receiving optical signals of different wavelengths (λ1 to λN). N receiving circuits, 212 to 242, are located in each of the transmitting / receiving apparatuses 210 to 240 and N transmitting circuits capable of transmitting optical signals of different wavelengths (λ1 to λN), and 213 to 243 are located in each of the transmitting / receiving apparatuses 210 to 240. A demultiplexing circuit for demultiplexing the input WDM optical signal for each wavelength, and a demultiplexing circuit for demultiplexing the optical signal from each of the transmitting circuits 212 to 242 in each of the transmitting and receiving devices 210 to 240. It is a wave circuit.
[0005]
Reference numeral 250 denotes an N × N AWG-type multiplexer / demultiplexer, 261 and 262 denote optical fibers connecting the transmitting / receiving device 210 and the AWG-type multiplexer / demultiplexer 250, and 271 and 272 denote the transmitting / receiving device 220 and the AWG-type multiplexer / demultiplexer. The optical fiber connecting the wave circuit 250, the optical fibers 281 and 282 connect the transmitting / receiving device 230 and the AWG type multiplexing / demultiplexing circuit 250, and the 291 and 292 connecting the transmitting / receiving device 240 and the AWG type multiplexing / demultiplexing circuit 250 Optical fiber.
[0006]
FIG. 3 is a diagram showing the input / output relationship of the multiplexing / demultiplexing circuit in the optical wavelength division multiplexing transmission network device shown in FIG. 2 when eight transmission / reception devices are connected to an 8 × 8 AWG type multiplexing / demultiplexing circuit. It is a figure showing a wave characteristic.
[0007]
The transmitting sides of the eight transmitting / receiving apparatuses (1) to (8) are optically connected to eight input ports 1 to 8 of the AWG type multiplexing / demultiplexing circuit in order, and the eight transmitting / receiving apparatuses (1) to (8) are used. Are sequentially optically connected to the eight output ports 1 to 8 of the AWG type multiplexing / demultiplexing circuit, and eight transmission / reception devices (1) to (8) receive WDM optical signals of eight wavelengths (λ1 to λ8). Are input to the input ports 1 to 8 of the AWG-type multiplexing / demultiplexing circuit, respectively, according to the wavelength recirculation rule of the AWG-type multiplexing / demultiplexing circuit. The input WDM optical signal is split into wavelengths (λ1 to λ8) for the output ports 1 to 8 as shown in the figure, and eight wavelengths (from the output ports 1 to 8 of the AWG type multiplexing / demultiplexing circuit). λ1 to λ8) are output as shown in FIG. (1) is fed to the receiver to (8).
[0008]
That is, 64 paths can be independently set with the minimum number of wavelengths of 8, and optical signals can be sent independently on all the paths that can be set among the eight transceivers (1) to (8). it can. Also, since a specific wavelength is assigned to each path, if a wavelength corresponding to a predetermined receiving circuit is selected on the transmitting circuit side of the transmitting / receiving apparatus, an optical signal of the selected wavelength can be sent to the receiving circuit of the target transmitting / receiving apparatus. A wavelength addressing function can be realized.
[0009]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-201112
[Problems to be solved by the invention]
However, in the conventional optical wavelength division multiplexing transmission network device described above, since all the transmitting and receiving devices use optical signals of the same wavelength, for example, optical signals of wavelengths λ1 to λ8 in FIG. Signal degradation due to coherent crosstalk between optical signals of the same wavelength in the AWG type multiplexing / demultiplexing circuit becomes a problem.
[0011]
FIG. 4 is a diagram for explaining the influence of the coherent crosstalk. Since the device configuration is the same as that of FIG. 2, the description thereof will be omitted.
[0012]
Here, in a state where WDM optical signals including the optical signal of the wavelength λi are respectively input to the N input ports of the AWG type multiplexing / demultiplexing circuit 250 from all the N transmitting / receiving apparatuses 210 to 240, It is assumed that the transmission / reception device 240 is communicating with an optical signal having a wavelength λi.
[0013]
As described with reference to FIG. 3, the optical signals of the wavelength λi included in the WDM optical signals input to the N input ports of the AWG type multiplexing / demultiplexing circuit 250 are demultiplexed to different output ports. However, a coherent crosstalk XT indicated by a broken line in FIG. 4 occurs in the AWG type multiplexing / demultiplexing circuit 250, and the coherent crosstalk XT reaches the transmitting / receiving device 240 from the output port N together with the optical signal of the wavelength λi. I do. The demultiplexing circuit 243 of the transmitting / receiving device 240 cannot perform demultiplexing because the optical signal of the wavelength λi and the wavelength of the coherent crosstalk are the same, and the receiving circuit 241 having the same optical signal of the wavelength λi and the same coherent crosstalk is used. Will be received.
[0014]
This coherent crosstalk is very small at -40 dB per channel in an AWG type multiplexing / demultiplexing circuit that has recently been marketed, and therefore does not pose a problem when the number of channels is small. However, the total amount of coherent crosstalk is proportional to the number of channels of the AWG type multiplexing / demultiplexing circuit. For example, when the number of channels of the AWG type multiplexing / demultiplexing circuit is 64, coherent crosstalk from the other 63 channels is integrated. Since the total amount of crosstalk to a predetermined optical signal increases to about 18 dB, a code error occurs due to interference between the optical signal and coherent crosstalk. That is, as the number of transmission / reception devices connected to the AWG-type multiplexing / demultiplexing circuit increases, coherent crosstalk increases and a code error easily occurs, so that the scale of the network (the number of accommodated channels) is limited.
[0015]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to eliminate the problem of code errors due to coherent crosstalk in an AWG type multiplexing / demultiplexing circuit and to increase the number of transmission / reception devices. It is an object of the present invention to provide a wavelength division multiplex transmission network device.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method for transmitting / receiving a wavelength division multiplexed optical signal to / from an N × N arrayed waveguide grating type multiplexer / demultiplexer having N (N is a plurality) input ports and output ports. A full-mesh type optical wavelength division multiplexing transmission network device configured by optically connecting M (M is an integer of 2 or more and N or less) N transmission / reception devices, wherein the array waveguide diffraction grating type multiplexing / demultiplexing circuit is provided. Has a demultiplexing characteristic of a periodic input / output relationship. The transmitting / receiving apparatus includes: M transmitting circuits capable of transmitting optical signals of different wavelengths; and a multiplexer for multiplexing optical signals from the transmitting circuits. Wave circuit, a demultiplexing circuit for demultiplexing the wavelength division multiplexed optical signal from the arrayed waveguide diffraction grating type multiplexing / demultiplexing circuit for each wavelength, and an optical signal for each wavelength from the demultiplexing circuit can be received. M receiving circuits, wherein at least one of the M transmitting circuits is Encoding means for adding an error correction signal to the optical signal by encoding, and at least one of the M receiving circuits, which is a transmission partner of the transmission circuit having the encoding means, converts the optical signal with the error correction signal into an error signal. Its main feature is that it comprises a decoding means for decoding based on the correction information.
[0017]
According to this optical wavelength division multiplexing transmission network device, a transmission circuit for transmitting an optical signal to which an error correction signal is added by encoding and a reception circuit for decoding the optical signal with the error correction signal based on the error correction information are provided. Is used as a transmission / reception device, so that even if a code error occurs due to coherent crosstalk in an arrayed waveguide diffraction grating type multiplexing / demultiplexing circuit, the error can be corrected and stable communication can be performed. By eliminating the problem of errors, the number of transmission / reception devices can be increased, and a large-scale, multi-channel, full-mesh type optical wavelength division multiplexing transmission network device can be constructed.
[0018]
The above and other objects, constitutional features, and operational effects of the present invention will become apparent from the following description and the accompanying drawings.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 5 is a configuration diagram of an optical wavelength division multiplexing transmission network device to which the present invention is applied. In the figure, reference numerals 310 to 340 denote N transmission / reception devices (1, 2, i, N), and reference numerals 311 to 341 denote Ns which can receive optical signals of different wavelengths (λ1 to λN) in the transmission / reception devices 310 to 340. N receiving circuits, 312 to 342, are located in each of the transmitting / receiving devices 310 to 340, and N transmitting circuits capable of transmitting optical signals of different wavelengths (λ1 to λN), and 313 to 343 are located in each of the transmitting / receiving devices 310 to 340. A demultiplexing circuit 314 to 344 for demultiplexing the input WDM optical signal for each wavelength is provided in each of the transmission / reception devices 310 to 340 to combine the optical signals from the transmission circuits 312 to 342. It is a wave circuit.
[0020]
Further, 350 is an N × N AWG type multiplexer / demultiplexer, 361 and 362 are optical fibers connecting the transmission / reception device 310 and the AWG type multiplexer / demultiplexer 350, and 371 and 372 are transmission / reception device 320 and AWG type multiplexer / demultiplexer. An optical fiber for connecting the circuit 350, 381 and 382 are optical fibers for connecting the transmitting / receiving device 330 and the AWG type multiplexing / demultiplexing circuit 350, and 391 and 392 are for connecting the transmitting / receiving device 340 and the AWG type multiplexing / demultiplexing circuit 350. Optical fiber.
[0021]
This optical wavelength division multiplexing transmission network device is different from the conventional optical wavelength division multiplexing transmission network device shown in FIG. 2 in that each of N transmission circuits 312 to 342 provided in each of the transmission / reception devices 310 to 340 has an optical transmission line. The point that it has a function of adding an error correction signal to the signals (λ1 to λN), and the N receiving circuits 311 to 341 provided in each of the transmission / reception devices 310 to 340 each include an optical signal (λ1 to λN) to which an error correction signal is added. ) Based on the error correction information. Hereinafter, these points will be described in detail with reference to FIG.
[0022]
FIG. 6 is a detailed diagram of the transmission / reception device 310 in the optical wavelength division multiplexing transmission network device shown in FIG. In the figure, reference numeral 311 denotes N receiving circuits, 312 denotes N transmitting circuits, 313 denotes a demultiplexing circuit, 314 denotes a multiplexing circuit, 361 and 362 denote optical fibers, and the demultiplexing circuit 313 and the multiplexing circuit 314 Uses a 1 × N AWG type multiplexing / demultiplexing circuit.
[0023]
The N transmission circuits 312 use a transmitter 312a that generates an electric signal of OC-48 (transmission rate of 2.48832 Gbit / s) and a Reed-Solomon (255,241) code using the electric signal from the transmitter 312a. And an error correction encoding circuit 312b for encoding an electric signal of 2.654208 Gbit / s into a predetermined wavelength (λ1 to λN) by a technique such as direct modulation. And an electric / optical conversion circuit 312c such as a semiconductor laser diode for converting the optical signal into an optical signal. Incidentally, the Reed-Solomon code is a type of block code, and is an error correction code capable of performing error correction in units of a plurality of bits (for example, in units of bytes).
[0024]
The optical signals from the N transmission circuits 312 are multiplexed by the multiplexing circuit 314 and transmitted to the AWG type multiplexing / demultiplexing circuit 350 through the optical fiber 362. Also, the WDM optical signal input from the AWG type multiplexing / demultiplexing circuit 350 to the demultiplexing circuit 313 via the optical fiber 361 is demultiplexed into optical signals for each wavelength and sent to the N receiving circuits 311.
[0025]
The N receiving circuits 311 include an optical / electrical conversion circuit 311a such as a photodiode for converting an optical signal for each wavelength from the demultiplexing circuit 313 into an electric signal, and an encoded signal from the optical / electrical conversion circuit 311a. An error correction decoding circuit 312b for decoding an electric signal (transmission rate 2.654208 Gbit / s) into an OC-48 (transmission rate 2.48832 Gbit / s) electric signal using a Reed-Solomon (255,241) code; A receiver 311c for receiving the electric signal from the error correction decoding circuit 312b.
[0026]
Although not shown, the transmission / reception devices 320, 330, and 330 other than the transmission / reception device 310 have the same configuration as the transmission / reception device 310.
[0027]
As described above, according to the above-described optical wavelength division multiplexing transmission network device, the transmission circuit that transmits the optical signal to which the error correction signal is added by encoding and the optical signal to which the error correction signal is added are decoded based on the error correction information. Is used as a transmission / reception device, even when a code error occurs in the AWG type multiplexing / demultiplexing circuit 350 due to coherent crosstalk, stable communication can be performed by correcting the code error, and By eliminating the problem of the code error described above, the number of transmission / reception devices can be increased, and a large-scale, multi-channel, full-mesh type optical wavelength division multiplexing transmission network device can be constructed.
[0028]
According to experiments, the effect (gain) of improving the receiving sensitivity by the error correction is about 5 dB, which is equivalent to about 3.2 times when converted into an effect of increasing the number of channels. That is, according to the literature (K. Noguchi, OECC 2002, 10A1-2, pp. 72-73), the maximum number of channels in the case of the conventional optical wavelength division multiplexing transmission network device was about 100, In a division multiplex transmission network device, it is sufficiently possible to increase the number of channels to about 300.
[0029]
In the above-described embodiment, encoding means for adding an error correction signal to an optical signal by encoding is provided in all of the N transmission circuits 312 to 342 in each of the transmission / reception devices 310 to 340, and the N reception circuits 311 341 are provided with decoding means for decoding the optical signal with the error correction signal added thereto based on the error correction information. However, at least one of the N transmission circuits 312 to 342 is encoded by encoding. An encoder for adding an error correction signal to an optical signal is provided, and an optical signal with an error correction signal added to at least one of the N receiving circuits 311 to 341 corresponding to a transmission partner of the transmission circuit including the encoder is error-corrected. Decoding means for decoding based on information may be provided.
[0030]
In short, in the above-mentioned optical wavelength division multiplexing transmission network device, the destination of a signal can be routed as light even if the transfer speed is increased by the above-mentioned encoding, so that the above-mentioned code is transmitted only to a predetermined transmitting circuit of the transmitting / receiving device. If the decoding means is provided only in a predetermined receiving circuit of another transmission / reception apparatus which is a transmission partner of the transmission circuit, communication by an encoded optical signal and light not encoded are provided. It is also possible to construct a network in which communication using signals is mixed.
[0031]
Further, in the above-described embodiment, the Reed-Solomon (255, 241) code is used as the error correction code. However, other codes, for example, a Hamming code, BCH-1 and BCH-2 are used as error correction codes. It may be used as a correction code.
[0032]
Furthermore, in the above-described embodiment, the signal using the OC-48 (transmission rate of 2.48832 Gbit / s) signal is used as the original signal before and after the decoding, but another signal, for example, the OC-192 ( A signal having a transmission rate of 9.95328 Gbit / s) or a signal having a transmission rate of 40 Gbit / s may be used as the original signal.
[0033]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to eliminate the problem of code errors due to coherent crosstalk in an arrayed waveguide diffraction grating type multiplexing / demultiplexing circuit, and to increase the number of transmission / reception devices. Network equipment can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a conventional optical wavelength division multiplex transmission network device. FIG. 2 is a configuration diagram of the optical wavelength division multiplex transmission network device shown in FIG. 1. FIG. 3 is an optical wavelength division multiplex transmission network shown in FIG. FIG. 4 is a diagram showing the demultiplexing characteristics of the input / output relationship of the multiplexing / demultiplexing circuit when eight transmission / reception devices are connected to an 8 × 8 AWG type multiplexing / demultiplexing circuit. FIG. 5 is a diagram for explaining the influence of coherent crosstalk in a circuit. FIG. 5 is a configuration diagram of an optical wavelength division multiplexing transmission network device to which the present invention is applied. FIG. 6 is a transmission / reception device 310 in the optical wavelength division multiplexing transmission network device shown in FIG. Detailed view of [Description of reference numerals]
310, 320, 330, 340 transmission / reception device, 311, 321, 331, 341 reception circuit, 311a optical / electrical conversion circuit, 311b error correction decoding circuit, 311c receiver, 312, 322, 332, 342 ... transmitting circuit, 312a ... transmitter, 312b ... error correction coding circuit, 312c ... electric / optical conversion circuit, 313, 323, 333, 343 ... demultiplexing circuit, 314, 324, 334, 344 ... multiplexing circuit, 350 ... AWG-type multiplexing / demultiplexing circuits, 361,362,371,372,381,382,391,392.

Claims (3)

M units (M is 2 or more and N or less) for transmitting / receiving wavelength division multiplexed optical signals to / from an N × N arrayed waveguide grating type multiplexing / demultiplexing circuit having N (N is a plurality) input ports and output ports Integer) optical wavelength division multiplexing transmission network device configured by optically connecting transmission / reception devices,
The array waveguide diffraction grating type multiplexing / demultiplexing circuit has a demultiplexing characteristic of a periodic input / output relationship,
The transmission / reception device includes M transmission circuits capable of transmitting optical signals of different wavelengths, a multiplexing circuit for multiplexing the optical signals from the transmission circuits, and an array waveguide diffraction grating type multiplexing / demultiplexing circuit. A demultiplexing circuit for demultiplexing the wavelength division multiplexed optical signal for each wavelength, and M receiving circuits capable of receiving an optical signal for each wavelength from the demultiplexing circuit;
At least one of the M transmission circuits includes an encoding unit that adds an error correction signal to the optical signal by encoding, and at least one of the M reception circuits corresponding to a transmission destination of the transmission circuit including the encoding unit is included. One comprises decoding means for decoding the optical signal of the error correction signal addition based on the error correction information,
An optical wavelength division multiplexing transmission network device, characterized in that: The coding means includes a coding circuit for coding an electric signal having a predetermined transmission rate by an error correction code, and an electric / optical conversion for converting the coded electric signal from the coding circuit into an optical signal of a predetermined wavelength. Circuit and
The decoding means includes: an optical / electrical conversion circuit for converting an optical signal of a predetermined wavelength into an electric signal; and a decoding circuit for decoding an encoded electric signal from the optical / electrical conversion circuit by an error correction code. Including,
The optical wavelength division multiplexing transmission network device according to claim 1, wherein: The error correction code used for encoding and decoding is a Reed-Solomon code,
3. The optical wavelength division multiplexing transmission network device according to claim 1, wherein:

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