JP2008294818A - Wavelength multiplex transmission system, and optical transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To utilize a supervisory light for gain control of wavelength multiplex signal lights in a wavelength multiplex transmission system provided with a supervisory information transfer means. <P>SOLUTION: The wavelength multiplex transmission system includes an optical transmitter, an optical repeater, and an optical receiver. The optical transmitter and the optical repeater include a supervisory light transmitter for generating the supervisory light which can be amplified by an optical amplifier and has a wavelength different from a main signal. The output side of the device includes a means for multiplexing the wavelength multiplex signal light and the supervisory light, and the optical repeater and the optical receiver include a means for demultiplexing the wavelength multiplex signal light and the supervisory light at the input side of the devices to re-multiplex a part of the supervisory light as the wavelength multiplex signal light. The output side of the optical amplifier includes a means for extracting the supervisory light to detect a light intensity, and a control circuit for controlling a gain of the optical amplifier is provided to control the detected supervisory light intensity at a constant level. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wavelength division multiplexing transmission system and an optical transmission apparatus, and more particularly to a wavelength division multiplexing transmission system and an optical transmission apparatus including a monitoring information transfer means and an optical amplifier.

  In order to maintain the quality of signal light stably, optical amplifiers applied to wavelength division multiplexing transmission systems maintain a constant gain with respect to changes in the number of multiplexed wavelengths and output light with respect to optical transmission line loss fluctuations. The contradictory control of making the strength constant is required. In order to solve this problem, the wavelength multiplexing system described in Patent Document 1 includes an optical amplifier and the optical amplifier, and multiplexes pilot light having a wavelength different from that of the wavelength multiplexed signal light into the wavelength multiplexed signal light. The pilot light intensity is controlled to be constant on the output side.

JP 2001-257646 A

  The wavelength multiplexing transmission system described above does not touch on the monitoring information transfer means, but in an actual wavelength multiplexing transmission system, information for monitoring the state of the optical transmitter, optical repeater, optical receiver, and optical transmission path, Monitoring information transfer means for gathering monitoring information in an optical receiving apparatus by transferring the monitoring information of the downstream apparatus while adding the monitoring information of the downstream apparatus is widely used. When this monitoring information transfer means is provided in a wavelength division multiplexing transmission system according to the prior art, a method of newly adding a monitoring optical transmitter can be considered. However, the system having the monitoring light and the pilot light separately has a problem that the configuration is complicated and the cost increases.

  An object of the present invention is to solve the above-mentioned problems of the prior art and to efficiently control the wavelength multiplexing transmission system even when the monitoring information transfer means is provided, and to reduce the cost, and its It is to provide a control method.

  The above-mentioned problem is composed of a wavelength division multiplexing optical transmitter, an optical repeater, and a wavelength division multiplexing optical receiver. The wavelength division multiplexing optical transmitter includes a wavelength multiplexer that multiplexes signal light, and a multiplexed light that is multiplexed by the wavelength multiplexer. A first optical amplifier that amplifies a signal, a first optical transmitter that generates first monitoring light, and a first optical multiplexer that multiplexes the output of the first optical amplifier and the first monitoring light The optical repeater includes a first supervisory light extraction unit that extracts a part of the first supervisory light from the transmitted multiplexed optical signal, and a multiplex from which a part of the first supervisory light is extracted A second optical amplifier for amplifying the optical signal; a second optical transmitter for generating a second monitoring light; and a second optical multiplexing for multiplexing the output of the second optical amplifier and the second monitoring light. The wavelength division multiplexing optical receiver includes a second monitoring light extraction unit that extracts a part of the second monitoring light from the transmitted multiplexed optical signal. And a third optical amplifier that amplifies the multiplexed optical signal from which a part of the second monitoring light is extracted, and a wavelength separator that wavelength-separates the output of the third optical amplifier. The amplifier is controlled to have a constant output light intensity, and the second optical amplifier and the third optical amplifier are wavelength-multiplexed in which the intensity of the amplified first monitoring light or the second monitoring light is controlled to be constant. This can be achieved by a transmission system.

  Also, a first wavelength separator that separates the monitoring light from the transmitted multiplexed optical signal, a first branch coupler that branches the separated monitoring light, and a first output of the first branch coupler. A first photodiode to be monitored, a wavelength multiplexer that multiplexes the second output of the first branch coupler and the multiplexed optical signal from which the monitoring light is separated, and an optical amplifier that amplifies the output of the wavelength multiplexer A second branching coupler for branching the amplified multiplexed optical signal, a second wavelength separator for separating the monitoring light from the first output of the second branching coupler, and the second wavelength separator This can be achieved by an optical transmission device comprising a gain control circuit for controlling the amplification of the optical amplifier based on the output of.

  According to the present invention, it is possible to provide a wavelength division multiplexing transmission system and a wavelength division multiplexing apparatus that do not require a new light source for gain control of an optical amplifier.

  Embodiments of the present invention will be described below with reference to the drawings using examples. The same reference numerals are assigned to substantially the same parts, and the description will not be repeated.

A first embodiment will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is a block diagram of the wavelength division multiplexing transmission system. FIG. 2 is a diagram for explaining the light intensity at each point of the wavelength division multiplexing transmission system.
A schematic configuration of a wavelength division multiplexing transmission system will be described with reference to FIG. In FIG. 1, a wavelength division multiplexing transmission system 500 includes a wavelength division multiplexing optical transmitter 100, an optical repeater 200, and a wavelength division multiplexing optical receiver 300.

  The wavelength division multiplexing optical transmission apparatus 100 includes a wavelength multiplexer 102 that multiplexes n-wave signal light on the input side, a branch coupler 103 that branches a part of the multiplexed wavelength multiplexed signal light, and a branched wavelength multiplexed signal light. Photodiode 4-1 for electrical conversion, optical amplifier 5-1, branching coupler 6-1 for branching a part of wavelength multiplexed signal light on the output side of optical amplifier 5-1, photo for optical / electrical conversion of the branched signal light A gain control circuit 9 that changes the gain of the optical amplifier 5-1 by changing the output light intensity of the diode 7-1, the pump LD 8-1 that generates pump light to be injected into the optical amplifier 5-1, and the pump LD 8-1; The monitoring optical transmitter 10-1 for generating the monitoring light and the optical multiplexer 11-1 for combining the monitoring light with the wavelength multiplexed signal light on the output side of the apparatus and outputting it to the optical transmission line.

  An optical repeater 200 that directly amplifies the wavelength multiplexed signal light attenuated through the optical transmission line 400-1 includes an optical demultiplexer 14-1 that demultiplexes the monitoring light from the wavelength multiplexed signal light on the input side of the apparatus. A branching coupler 15-1 for branching the demultiplexed monitoring light, a monitoring optical receiver 16-1 for receiving one of the branched monitoring lights, and an optical multiplexing for recombining the other branched monitoring light with the wavelength multiplexed signal light. A wave coupler 17-1, an optical amplifier 5-2, a branching coupler 6-2 for branching a part of the wavelength multiplexed signal light and the monitoring light on the output side of the optical amplifier 5-2, and a wavelength multiplexed signal for monitoring light after branching. An optical demultiplexer 20-1 that demultiplexes the light, a photodiode 7-2 that optically / electrically converts the demultiplexed monitoring light, an excitation LD 8-2 that generates excitation light to be injected into the optical amplifier 5-2, and an excitation LD8 The gain of the optical amplifier 5-2 is changed by changing the output light intensity of -2. Obtaining control circuit 23-1, monitoring optical transmitter 10-2 for generating monitoring light, optical multiplexer 11-2 for combining the monitoring light with the wavelength multiplexed signal light on the output side of the apparatus and outputting it to the optical transmission line Consists of.

  The wavelength division multiplexing optical receiver 300 that directly amplifies the wavelength multiplexed signal light attenuated through the optical transmission line 400-2 is an optical demultiplexer 14− that demultiplexes the monitoring light from the wavelength multiplexed signal light on the input side of the apparatus. 2. A branching coupler 15-2 for branching the demultiplexed monitoring light, a monitoring optical receiver 16-2 for receiving one of the branched monitoring lights, and recombining the other branched monitoring light with the wavelength multiplexed signal light The optical coupler 17-2, the optical amplifier 5-3, the branch coupler 6-3 for branching a part of the wavelength multiplexed signal light and the monitoring light at the output side of the optical amplifier 5-3, and only the monitoring light after branching. An optical demultiplexer 20-2 to extract, a photodiode 7-3 for optical / electrical conversion of the extracted monitoring light, an output of the pump LD 8-3 for generating pump light to be injected into the optical amplifier 5-3, and an output of the pump LD 8-3 Gain for changing the gain of the optical amplifier 5-3 by changing the light intensity Control circuit 23-2 comprises a wavelength separator 302 which separates the wavelength-multiplexed signal light into signal lights of n waves at the output of the device.

Next, control of the wavelength multiplexing optical transmitter 100, the optical repeater 200, and the wavelength multiplexing optical receiver 300 will be described.
In the wavelength division multiplexing optical transmitter 100, the gain control circuit 9 has a ratio of light intensity detected by optical / electrical conversion by the photodiode 4-1 and light intensity detected by optical / electrical conversion by the photodiode 7-1. The gain of the optical amplifier 5-1 is controlled so as to be constant. Thereby, even when the number of wavelengths input to the optical transmission device 100 changes, the output light intensity of each signal light can be made constant. Since the wavelength multiplexing section from the wavelength multiplexer 102 to the optical amplifier 5-1 is incorporated in the optical transmission device, it is not necessary to consider the loss variation that occurs in the case of the optical transmission line, and the output light intensity constant control. There is no particular need for.

  In the optical repeater 200 and the wavelength division multiplexing optical receiver 300, the gain control circuit 23 uses the optical amplifier 5 so that the monitoring light intensity detected by optical / electrical conversion by the photodiodes 7-2 and 7-3 is constant. -2, 5-3 control gain. As a result, the gain of each signal light can be made constant with respect to the change in the number of multiplexed wavelengths, and the output light intensity can be made constant with respect to the loss variation of the optical transmission line.

  With reference to FIG. 2, a level diagram of wavelength multiplexed signal light and monitoring light will be described. In FIG. 2, the wavelength multiplexed signal light is amplified by the optical amplifier 5-1 of the optical transmission apparatus 100 and then attenuated through the optical transmission line 400-1. The wavelength multiplexed signal light is amplified again by the optical amplifier 5-2 of the optical repeater 200 and then attenuated through the optical transmission line 400-2. The wavelength multiplexed signal light is amplified three times by the optical amplifier 5-3 of the wavelength multiplexed optical receiver 300. The supervisory light is attenuated through the optical transmission line 400-1 and the optical transmission line 400-2, branched by the branch coupler 15, and then received by the supervisory optical transmitter 16. The other monitoring light is amplified by optical amplifiers 5-2 and 5-3. The minimum light intensity that can be received by the monitoring optical receiver 16 is -32 dBm. In order to enable transmission of the monitoring light, it is necessary to distribute the branching ratio of the branch coupler 15 so that the monitoring light is output to the monitoring optical receiver 16 with a receivable light intensity. Here, the branching ratio of the branching coupler 15 is distributed 95: 5 between the monitoring optical receiver side and the optical amplifier side.

  Next, a method for controlling the gain of the optical amplifier in consideration of the light intensity difference between the wavelength multiplexed signal light and the monitoring light will be described. The difference between the signal light intensity per wavelength of the wavelength multiplexed signal light and the monitoring light intensity is mainly the difference in light intensity when output from the optical transmitter 100 or the optical repeater 200, and the optical repeater 200 or the wavelength multiplexed light. This is caused by the difference in loss that the signal light and the monitoring light suffer in the optical circuit on the input side of the receiving apparatus 300. In this embodiment, the monitoring light intensity on the output side of the optical amplifiers 5-2 and 5-3 is 16 dB lower than the signal light intensity per wavelength of the wavelength multiplexed signal light. Therefore, in order to set the signal light intensity per wavelength of the wavelength multiplexed signal light to a predetermined light intensity, the monitoring light intensity may be controlled to a level relatively lower by 16 dB.

  Here, the description has been made assuming that the amplification factors of the optical amplifier for the optical signal and the monitoring light are the same. However, the amplification factor with respect to the wavelength of the monitoring light need not be the same as the amplification factor of the signal light. The wavelength of the monitoring light may be any wavelength that can be amplified by the optical amplifier, and can be selected from wavelengths in the vicinity of less than 1530 nm or more than 1560 nm when the optical signal is C-band (1530-1560 nm).

Here, the optical multiplexer 11-2 of the optical repeater 200 uses a dielectric multilayer filter, and the monitoring light output from the optical amplifier 5-2 is the dielectric multilayer filter of the optical multiplexer 11-2. Therefore, the influence on the transmission of the monitoring light output from the monitoring optical transmitter 10-2 can be ignored. Alternatively, the branching coupler 6-2 that branches a part of the wavelength multiplexed signal light and the monitoring light on the output side of the optical amplifier 5-2 is replaced with an optical demultiplexer that extracts the monitoring light, and the optical demultiplexer You may make it the structure which interrupts | blocks the monitoring light of the waver 11-2 direction.
Note that the wavelength division multiplexing optical transmitter, the optical repeater, and the wavelength division optical receiver are all referred to as an optical transmission apparatus.

  Hereinafter, Example 2 will be described with reference to FIG. Here, FIG. 3 is a block diagram of a single-core bidirectional wavelength division multiplexing optical transmission system. In FIG. 3, the wavelength multiplexed signal light and the monitoring light traveling from one right to the left on the optical transmission line are the wavelength multiplexed signal light and the monitoring light traveling from the left to the right, and the directional coupler 50- 1-50-4, multiplexed / separated. The directional coupler 50 is an optical component having three input / output ports. The directional coupler 50 outputs the optical signal input from the first port from the second port. The directional coupler 50 outputs the optical signal input from the second port from the third port. Furthermore, the directional coupler 50 outputs the optical signal input from the third port from the first port.

  Here, the two monitoring lights traveling in the reverse direction on one optical transmission line can be amplified by an optical amplifier and have a different wavelength from the main signal. However, considering that the reflected return light from the optical connector (not shown) that connects the device and the optical transmission path affects the transmission characteristics of the monitoring light and the gain control of the optical amplifier as crosstalk, it is necessary to set to a different wavelength. desirable.

It is a block diagram of a wavelength division multiplexing transmission system. It is a figure explaining the light intensity for every point of a wavelength division multiplexing transmission system. 1 is a block diagram of a single-core bidirectional wavelength division multiplexing optical transmission system. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 4 ... Photodiode, 5 ... Optical amplifier, 6 ... Branch coupler, 7 ... Photodiode, 8 ... Excitation LD, 9 ... Gain control circuit, 10 ... Surveillance optical transmitter, 11 ... Optical multiplexer, 14 ... Optical multiplexer DESCRIPTION OF SYMBOLS 15 ... Branch coupler, 16 ... Surveillance optical receiver, 17 ... Optical multiplexer, 20 ... Optical multiplexer, 23 ... Gain control circuit, 50 ... Directional coupler, 100 ... Wavelength division multiplexing optical transmitter, 102 ... Wavelength Multiplexer, 103 ... Branch coupler, 200 ... Optical repeater, 300 ... Wavelength multiplexed optical receiver, 302 ... Wavelength separator, 400 ... Optical transmission line.

Claims (5)

In a wavelength division multiplexing transmission system comprising a wavelength division multiplexing transmitter, an optical repeater, and a wavelength division multiplexing receiver,
The wavelength division multiplexing optical transmitter includes a wavelength multiplexer that multiplexes signal light, a first optical amplifier that amplifies a multiplexed optical signal multiplexed by the wavelength multiplexer, and a first light that generates first monitoring light. A transmitter, and a first optical multiplexer that multiplexes the output of the first optical amplifier and the first monitoring light,
The optical repeater includes: a first monitoring light extraction unit that extracts a part of the first monitoring light from a transmitted multiplexed optical signal; and a multiplexed light from which a part of the first monitoring light is extracted. A second optical amplifier that amplifies the signal; a second optical transmitter that generates second monitoring light; and a second optical signal that multiplexes the output of the second optical amplifier and the second monitoring light. A waver,
The wavelength multiplexing optical receiver is configured to extract a second monitoring light extraction unit that extracts a part of the second monitoring light from the transmitted multiplexed optical signal, and a part of the second monitoring light. A third optical amplifier that amplifies the multiplexed optical signal; and a wavelength separator that wavelength-separates the output of the third optical amplifier.
The first optical amplifier has an output light intensity controlled to be constant, and the second optical amplifier and the third optical amplifier are configured to transmit the amplified first monitoring light or the second monitoring light. A wavelength division multiplexing transmission system characterized in that the intensity is controlled to be constant. The wavelength division multiplexing transmission system according to claim 1,
The wavelength division multiplexing optical transmitter further includes a first directional coupler at an output end,
The optical repeater further includes a second directional coupler at an input end and a third directional coupler at an output end,
The wavelength division multiplexing optical receiver further includes a fourth directional coupler at an input end,
Bidirectional transmission is performed between the first directional coupler and the second directional coupler and between the third directional coupler and the fourth directional coupler. A wavelength division multiplexing transmission system.   A first wavelength separator for separating the monitoring light from the transmitted multiplexed optical signal; a first branching coupler for branching the separated monitoring light; and a first output of the first branching coupler. A wavelength division multiplexer that multiplexes the second output of the first branch coupler and the multiplexed optical signal from which the monitoring light is separated, and amplifies the output of the wavelength multiplexer An optical amplifier, a second branch coupler for branching the amplified multiplexed optical signal, a second wavelength separator for separating the monitoring light from the first output of the second branch coupler, and the second wavelength An optical transmission device comprising: a gain control circuit that controls amplification of the optical amplifier based on an output of the separator. The optical transmission device according to claim 3,
A transmitter for transmitting a second monitoring light; and a second wavelength multiplexer for multiplexing the second monitoring light and the second output of the second branch coupler. Optical transmission equipment. The optical transmission device according to claim 3,
An optical transmission device further comprising a third wavelength separator for wavelength-separating the second output of the second branch coupler.

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