JP2013074456A - Optical relay system and optical relay method incorporating optical raman amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical relay system incorporating a Raman amplifier, which exerts output constant control upon an optical amplifier on the basis of an effective span loss calculated from the input/output levels of a control supervisory signal when a wavelength interruption occurs, thereby reducing the time required for recovery from wavelength interruptions and maintaining the good transmission quality of WDM signal light.SOLUTION: The optical relay system includes a control unit which exerts output control on an optical amplifier on the basis of an effective transmission line loss in the main signal light calculated from: an effective transmission line loss in a supervisory control signal derived from an output level, i.e., the optical level of supervisory control light at one end of a fiber optic transmission line by subtracting an output level, i.e., the optical level of supervisory control light at the other end of the fiber optic transmission line therefrom; input power to the fiber optic transmission line of excited light which is output from a Raman amplifier module; and the type of fiber of the fiber optic transmission line.

Description

The present invention relates to an optical amplifier output control method in an optical repeater system in which an optical Raman amplifier is introduced.

  In recent years, with the invention of the optical amplifier (EDFA: Erbium Doped Fiber Amplifier) and the introduction to the market, the requirements for the signal-to-noise ratio have been greatly relaxed, and ultrahigh-speed optical transmission with a transmission capacity of one wavelength exceeding 10-Gbit / s The system has been put into practical use and introduced worldwide. Furthermore, a linear repeater capable of amplifying a certain wavelength band at a time using the broadband property of the optical amplifier has been introduced to further reduce the cost. Of these, optical Raman amplifiers (distributed Raman amplifiers, optical Raman amplifiers) are attracting attention. An optical Raman amplifier is an optical amplifier having a wavelength band close to 100 nm and capable of amplifying a broadband optical signal with low noise. As an amplification method, excitation light is incident on an optical fiber transmission line as an amplification medium from the receiving side. The signal light propagating through the optical fiber transmission line is amplified by the effect of stimulated Raman scattering by propagating the excitation light in the direction opposite to the propagation direction of the signal light.

  FIGS. 1A and 1B show the configuration of optical repeater transmission and the transition of optical power with respect to transmission distance when EDFAs 102-1 and 102-2 are used for optical amplification. FIGS. Shows the transition of optical power with respect to the configuration and transmission distance when EDFAs 102-3 and 102-4 and an optical Raman amplifier module are used for optical amplification. The most different point between them is the optical power input to the repeaters 100-2 and 100-4 installed downstream of the optical fiber transmission lines 101-1 and 101-2. In FIGS. 1C and 1D, optical Raman amplification is performed by the pumping light output from the pumping light source 103-2 in the optical Raman amplifier module 104-2, so that light is transmitted from the middle of the optical fiber transmission line 101-2. The power starts to increase, and the input power to the EDFA 102-4 provided in the repeater 100-4 is larger than the input power to the EDFA 102-2 provided to the repeater 100-2 in FIGS. As a result, deterioration of the signal-to-noise ratio can be reduced, and long-distance optical transmission becomes possible.

  By the way, in an optical repeater system which transmits optical fiber transmission or WDM (Wavelength Division Multiplexing) optical signals while amplifying them with an optical amplifier (EDFA) for each fixed section, the control method of the optical amplifier is always constant in gain. A constant gain control method (AGC: Auto Gain Control) or a constant output control method (ALC: Auto Level Control) that always keeps the output level of an optical signal constant is used. The constant gain control is a control method in which a gain corresponding to the transmission line loss is set when the apparatus is started up and then the set gain is held. In addition, the constant output control method sets a gain according to the transmission line loss when the apparatus is started up, and then the total output power of the optical amplifier becomes constant based on the information on the number of wavelengths of the transmitted optical signal. In this way, the gain is variably controlled.

  However, the above-described constant gain control has a problem that the output optical signal level of the optical amplifier fluctuates due to a change in transmission line loss. For example, the transmission line loss of the transmission line fiber varies with temperature. Further, for some reason, stress such as bending is applied to the transmission line fiber, and the transmission line loss may change. If constant gain control is performed under such conditions, the output light level of the optical amplifier will fluctuate in response to changes in the transmission line loss, which may deviate from the optimum signal level in terms of signal reception sensitivity. There is.

  Further, the above-described constant output control has a problem in that it takes a long time to obtain information on the number of wavelengths of the WDM optical signal, thereby causing a change in signal level. In order to realize constant output control, information on the number of wavelengths of the WDM optical signal currently amplified by the optical amplifier is required. This is because the constant output control is performed to variably control the gain of the optical amplifier with the total signal level obtained by multiplying the signal level per wavelength multiplied by the number of wavelengths as a target value. In order to detect the number of wavelengths of a WDM optical signal in which a plurality of optical signals having different wavelengths are bundled, a detector that measures the level of each wavelength and detects the presence or absence of the optical signal is required. The number of wavelengths of the WDM signal light given to the optical amplifier on the WDM optical transmission system is applied to an optical transmission apparatus provided with a multiplexer / demultiplexer on the upstream side of the optical amplifier, for example, OADM (Optical Add Drop Multiplexer). Thus, the number of wavelengths of the WDM signal light is arbitrarily changed even during operation of the communication service. Therefore, in an optical amplifier for WDM optical transmission, high-speed gain constant control is usually performed to cope with changes in the number of wavelengths of WDM signal light.

  This high-speed constant gain control only corresponds to the above-described “constant gain control”. The “constant output control” uses the wavelength number information in addition to this high-speed constant gain control. A constant output control is performed. However, it may be difficult to increase the detection time due to limitations of the detection device for detecting the wavelength number information. In view of this problem, as a control method for constant output control that does not require high-speed detection of the number of wavelengths, not only a wavelength number detection unit for detecting the number of wavelengths information is provided, but also between the immediately preceding repeater Patent Document 1 proposes a system that also includes a span loss monitor that constantly monitors a loss (span loss) in a transmission section, and controls the output signal level of an optical amplifier constant according to the wavelength number information and the span loss monitoring result. Yes.

  FIG. 2 is a schematic diagram showing a prior art optical repeater system. In such an optical repeater system using constant control, a multiplexer / demultiplexer 200 for multiplexing / demultiplexing an optical signal of a desired wavelength with respect to a WDM signal light combined with a plurality of optical signals having different wavelengths, and a WDM A first optical amplification unit 201 that amplifies the signal light; an optical fiber transmission line 202 that receives the WDM signal light amplified by the first amplification unit; and an output that is output from the other end of the optical fiber transmission line. In an optical repeater system including a second optical amplification unit 203 for amplifying WDM signal light, a wavelength for detecting the number of wavelengths of WDM signal light input to the first optical amplification unit 201 and generating wavelength number information A number detection unit 204 is provided.

  The first optical amplification unit 201 detects the total power of the first optical amplifier 205 that amplifies the input WDM signal light and the WDM signal light output from the first optical amplifier 205 to detect the first signal. The first signal output monitor 206 for generating output level information, the control number monitoring including the wavelength number information generated by the wavelength number detector 204 and the first signal output level information generated by the first signal output monitor 206 The control monitoring light transmitter 207 that transmits light (monitoring control light, OSC (Optical Supervision Channel) signal light), and the first signal output level information generated by the first signal output monitor 206 is used as the control monitoring light transmitter. A control circuit 208 for transmission to the 207, the WDM signal light amplified by the first optical amplifier 205, and the control and monitoring optical transmitter 207. And a control light output monitor 210 that monitors the output level of the control monitoring light. The multiplexer 209 combines the control monitoring light transmitted from the optical fiber transmission line and applies the resultant light to one end of the optical fiber transmission line.

  Further, the second optical amplification unit 203 includes a demultiplexer 211 that demultiplexes light output from the other end of the optical fiber transmission line 202 into WDM signal light and control monitoring light, and the demultiplexer 211 demultiplexes the light. A second optical amplifier 212 that amplifies the waved WDM signal light, and a second signal input monitor that detects the total power of the WDM signal light input to the second optical amplifier 212 and generates second signal input level information. 213, a second signal output monitor 214 that detects the total power of the WDM signal light output from the second optical amplifier 212 and generates second signal output level information, and is demultiplexed by the demultiplexer 211 A control monitoring light receiver 215 that receives the control monitoring light and obtains the wavelength number information and the first signal output level information; the first signal output level information acquired by the control monitoring light receiver 215; The second signal input level information generated by the second signal input monitor 213 is used to calculate the span loss in the optical fiber transmission line 202, and the gain set in the second optical amplifier 212 is calculated based on the span loss. At the same time, the target signal output level of the second optical amplifier 212 is calculated using the wavelength number information acquired by the control monitoring optical receiver 215, and the target signal output level and the second signal output monitor 214 generate the target signal output level. The control circuit 216 controls the second optical amplifier 212 in accordance with the corrected gain using the difference from the second signal output level information as a correction value, and monitors the input level of the control monitoring light A control monitoring light input monitor 217.

  In the conventional optical repeater system as described above, the wavelength number information and the first signal output level information about the WDM signal light output from the upstream first optical amplification unit 201 to the optical fiber transmission line 202 are controlled and monitored light. Is transmitted to the second optical amplification unit 203 on the downstream side. In the second optical amplification unit 203, the control circuit 216, as shown in FIG. 5, the total output power of the WDM signal light on the upstream side indicated by the first signal output level information and the downstream detected by the signal input monitor 213. The loss (span loss) of the optical fiber transmission line 202 is calculated using the total input power of the WDM signal light on the side, and the gain set in the second optical amplifier 212 is calculated based on the span loss.

  Further, the target signal output level of the second optical amplifier 212 is calculated using the wavelength number information of the WDM signal light, and the difference between the target signal output level and the second signal output level detected by the second signal output monitor 214 is calculated. Is calculated. Since the gain calculated based on the span loss includes the measurement error of the span loss, the error is corrected by the difference between the target value of the second signal output level calculated using the wavelength number information and the actual measurement value, and is corrected. The second optical amplifier is controlled according to the later gain. The correction using the wavelength number information in the above control is performed only to correct the error, and the execution period depends on the factor of the error, but considering mainly the temperature and the secular variation, it is in the order of seconds. It is possible to have a long period.

  According to the relay system of the prior art, the gain setting error caused by the span loss measurement error is compensated by the correction value calculated using the wavelength number information, so that the span loss of the optical fiber transmission line and the WDM signal light Even if the number of wavelengths varies, it is possible to control the optical amplifiers installed on the upstream and downstream sides of the system at high speed and with high accuracy, and it is possible to improve the signal reception sensitivity in the optical repeater system. Further, although correction using the wavelength number information is performed, the control speed (implementation cycle) can be slowed as described above. In conventional signal output level constant control using wavelength number information, it is necessary to increase the control speed as much as possible in order to suppress level fluctuations when span loss fluctuates at high speed. There was a level change in relation. However, when the number-of-wavelength information is used for correcting the error in the constant output control by the span loss monitor, the level fluctuation as in the prior art is also eliminated.

  Further, the control monitoring output monitor 210 is provided in the subsequent stage of the multiplexer 209 of the first optical amplification unit 201 installed upstream of the optical fiber transmission line 202, and the control monitoring input monitor 217 is installed downstream of the optical fiber transmission line 202. The control monitoring output monitor 210 monitors the output level of the control monitoring light transmitted from the first optical amplification unit 201 to the optical fiber transmission line 202 by being provided in the subsequent stage of the duplexer 211 of the second optical amplification unit 203. Then, the monitoring result is transmitted to the control monitoring transmitter 207. The control monitoring transmitter 207 generates the control monitoring light including the output level information of the control monitoring signal together with the wavelength number information and the signal output level information. The light is sent to the optical fiber transmission line 202. The control monitoring input monitor 217 downstream of the transmission line monitors the input level of the control monitoring light that has propagated through the optical fiber transmission line 202, and the monitoring result is transmitted to the control circuit 216. At this time, the output level information of the control monitoring light transmitted by the propagation of the control monitoring light and the input level information of the control monitoring light monitored by the control monitoring input monitor 217 are obtained when the wavelength of the WDM signal light as the main signal occurs ( This is used to calculate span loss when the number of wavelengths of WDM signal light is zero. In general, since control monitoring light is often communicated even when a wavelength interruption occurs, the first optical amplification unit 201 on the upstream side until the wavelength interruption is recovered after the occurrence of the wavelength interruption. By monitoring the amount of span loss fluctuation based on the control monitoring output level information and the control monitoring input level information of the second optical amplification unit 203 on the downstream side, the transmission quality of the WDM signal light at the time of recovery from the wavelength interruption is kept good. It becomes possible.

  FIG. 3 is a schematic diagram showing a prior art optical repeater system with a Raman amplifier module. Here, as shown in FIG. 3, the optical Raman amplifier module 318 is provided in the second optical amplification unit 303 downstream of the transmission line, and the excitation light is supplied from the excitation light source 319 provided in the optical Raman amplifier module 318 to the WDM signal light. A case will be described in which the WDM signal light attenuated in the optical fiber transmission line 302 is Raman-amplified by being sent to the optical fiber transmission line 302 in the direction opposite to the traveling direction.

  When the wavelength of the WDM signal light, which is the main signal, does not occur, the first light is output from the signal output monitor 306 provided in the first optical amplification unit 301 upstream of the transmission line, as in the case where the Raman amplifier module 318 is not introduced. The control signal light including the first signal output level information detected and generated by the total power of the WDM signal light output from the amplifier 305 and the wavelength number information detected and generated by the wavelength number detection unit 304 is transmitted to the optical fiber transmission line 302. The second signal input level detected and generated by the second signal input monitor 313 provided in the second optical amplification unit 303 downstream of the transmission line and detected by the total power of the WDM signal light input to the second optical amplifier 312 Using the information and the wavelength number information and the signal output level information acquired by receiving the control monitoring light branched by the branching filter 311 by the control monitoring term receiver 315, the first signal From the power level information and the second signal input level information, the span loss (actually Raman gain is included, so it will be described as “effective span loss” below) is calculated. Based on this, the gain set in the second optical amplifier 312 is calculated, the target signal output level is calculated from the wavelength number information, and the difference from the output level information generated by the signal output monitor 314 provided downstream of the transmission path is calculated. The calculated gain is corrected as a correction value, and the control circuit 316 controls the optical amplifier 312 according to the corrected gain, so that the output constant control is possible.

JP 2008-85712 A

  However, in FIG. 3, which is a prior art optical repeater system having a Raman amplifier module, when a wavelength interruption of the WDM signal light as the main signal occurs, the same method as when the Raman amplifier module 318 is not installed, that is, control monitoring When an effective span loss is calculated from the output level information of the signal and the input level information of the control monitoring signal, and the output constant control of the second optical amplifier 312 is performed based on the effective span loss, the following problem occurs. .

  FIG. 4 is an optical spectrum of the control WDM signal light and the control light on the downstream side of the transmission line when the Raman amplifier is introduced. In general, as shown in FIG. 4, the Raman gain in the wavelength band of the WDM signal light that is the main signal is about several dB larger than the Raman gain in the wavelength band of the control monitoring signal. The effective span loss of the control light calculated based on the input level information of the monitoring signal (the value obtained by subtracting the Raman gain of the control light wavelength band from the actual span loss), the output level information of the main signal light, and the input level information The effective span loss of the main signal light calculated based on this (a value obtained by subtracting the Raman gain of the main signal light wavelength band from the actual span loss) also has a difference of about several dB. That is, when a wavelength interruption occurs, light with a Raman amplifier is mounted with a constant output control system that controls the signal output level of the second optical amplifier 312 based on the effective span loss calculated based on the input / output level information of the control and monitoring light. When applied to a relay system, the signal level output from the second optical amplifier 312 is set to an excessive value of about several dB, and the in-device level diagram in the second optical amplification unit 303 is distorted, so that the wavelength is cut off. The recovery of the optical amplifier is greatly delayed, and in the worst case, there is a possibility that it will spread to the failure of another optical amplifier installed in the subsequent stage.

  The present invention has been made paying attention to the above points. In an optical repeater system incorporating a Raman amplifier, constant output control based on effective span loss calculated from the input / output level of a control monitoring signal when a wavelength interruption occurs is performed. By appropriately setting the signal level output from the second optical amplifier, normalizing the in-device level diagram in the second optical amplification unit, reducing the recovery time from the wavelength interruption and the WDM signal light at the time of recovery An object of the present invention is to provide an optical repeater system and an optical amplifying apparatus that maintain good transmission quality.

  To achieve the above object, an optical repeater system according to the present invention includes a multiplexer / demultiplexer that multiplexes and demultiplexes an optical signal having a desired wavelength with respect to a WDM signal light in which a plurality of optical signals having different wavelengths are multiplexed. A first optical amplification unit that amplifies the WDM signal light, an optical fiber transmission line to which the WDM signal light amplified by the first amplification unit is input at one end, and an output from the other end of the optical fiber transmission line A second optical amplifying unit for amplifying the WDM signal light; and a wavelength number detection for detecting the number of wavelengths of the WDM signal light input to the first optical amplifying unit and generating wavelength number information. The first optical amplification unit detects a total power of the WDM signal light output from the first optical amplifier and a first optical amplifier that amplifies the input WDM signal light; Generate level information A signal output monitor; a control monitoring light transmitter that transmits control monitoring light including the wavelength number information generated by the wavelength number detection unit and the first signal output level information generated by the first signal output monitor; A multiplexer / demultiplexer that multiplexes the WDM signal light amplified by the first optical amplifier and the control monitoring light transmitted from the control monitoring light transmitter and applies the resultant light to one end of the optical fiber transmission line; and the control monitoring light A control monitoring output monitor that demultiplexes a part of the control monitoring light transmitted from the transmitter by the multiplexer / demultiplexer and monitors an output level of the control monitoring light.

  The second optical amplifying unit further includes: a demultiplexer that demultiplexes light output from the other end of the optical fiber transmission path into WDM signal light, control monitoring light, and part of control monitoring light; and A second optical amplifier for amplifying the WDM signal light demultiplexed by the detector; a second signal input monitor for detecting the total power of the WDM signal light input to the second optical amplifier and generating signal input level information; Receiving a second signal output monitor for detecting the total power of the WDM signal light output from the second optical amplifier and generating second signal output level information, and the control monitoring light demultiplexed by the demultiplexer A control monitoring light receiver for acquiring the wavelength number information and the first signal output level information, and a control monitoring signal input monitor for monitoring an input level of a part of the control monitoring light demultiplexed by the branching filter And the optical fiber transmission line The effective span loss of the main signal is calculated, the gain set in the second optical amplifier is calculated based on the effective span loss, and the wavelength number information acquired by the control and monitoring optical receiver is used. The target signal output level of the second optical amplifier is calculated, and the calculated gain is corrected using the difference between the target signal output level and the second signal output level information generated by the second signal output monitor as a correction value. And a control circuit that controls the second optical amplifier according to the corrected gain, and a Raman amplifier module that amplifies the WDM signal light attenuated by the optical fiber transmission line.

  Further, the Raman amplifier module includes a pumping light source for sending pumping light for Raman amplification of the WDM signal light to the optical fiber transmission line, the WDM signal light propagated from the optical fiber transmission line, and the control. A multiplexer that multiplexes the monitoring light and the excitation light in the backward direction, an excitation light power detection unit that detects an output power of the excitation light output from the excitation light source, and output level information of the control monitoring signal; Based on the effective span loss of the control monitoring signal calculated from the input level information, the output power information of the pumping light detected by the pumping light power detector, and the fiber type information of the optical fiber transmission line, And a reference table that is referred to in order to calculate a Raman gain and to calculate an effective span loss of the main signal using the Raman gain of the main signal wavelength band.

  In the optical repeater system of the present invention as described above, when a wavelength interruption of the WDM signal light that is the main signal occurs, the output level information of the control monitoring light output from the first optical amplification unit to the optical fiber transmission line is The control monitoring light is transmitted to the second optical amplification unit. The control circuit of the second optical amplification unit performs control monitoring using the output level of the control monitoring light indicated by the output level information of the control monitoring light and the input level information of the control monitoring signal detected by the control monitoring signal input monitor. An effective span loss of light is calculated, and the reference table is calculated based on the effective span loss of the control and monitoring light, the output power information of the pumping light detected by the pumping light power detector, and the fiber type information of the transmission path. The effective span loss of the main signal light is calculated with reference, and the gain set in the second optical amplifier is calculated based on the effective span loss of the main signal. The gain calculated based on the effective span loss is corrected using the calculated difference, and the second optical amplifier is controlled according to the corrected gain.

  Further, the effective span loss of the main signal light can be calculated by adding the Raman gain difference to the effective span loss of the control monitoring light. Also, the target signal output level of the second optical amplifier 712 is calculated using the wavelength number information of the WDM signal light, and the difference between the target signal output level and the signal output level detected by the second signal output monitor 714 is calculated. Is done. Since the gain calculated based on the effective span loss of the main signal includes an error in measuring the effective span loss, the target value and the actual measurement value of the signal output level calculated using the wavelength number information are corrected for the error. The second optical amplifier 712 is controlled according to the corrected gain.

  In the optical repeater system of the present invention as described above, the reference table corresponds to the difference between the Raman gain of the main signal and the Raman gain of the control monitoring light (Raman gain difference) corresponding to the output power of the pumping light and the fiber type. Is stored. The profile of the Raman gain in the wavelength direction is uniquely determined by the output power of the pump light and the fiber type. Therefore, for example, in a transmission line of a certain fiber type, the Raman gain of the wavelength band of the main signal light and the Raman gain of the wavelength band of the control monitoring light when the output power of the pump light is changed are measured, By calculating the difference between these measured values, a table of Raman gain differences (Raman gain in the wavelength band of the main signal light-Raman gain in the wavelength band of the control monitoring light) corresponding to a certain fiber type and the output power of the pumping light can be obtained. Can be created. Further, the reference can be created by changing the fiber type and performing the same operation. The reference table may be created from a Raman gain profile obtained by calculation instead of an actual measurement value of Raman gain.

  According to the present invention, even when a wavelength interruption of the WDM signal light that is the main signal occurs, the signal level output from the second optical amplifier is appropriately set, and the in-device level diagram in the second optical amplification unit is set. Thus, it is possible to reduce the recovery time from wavelength interruption and to maintain good transmission quality of the WDM signal light at the time of recovery.

1 is a schematic diagram showing a method of optical amplification in optical repeater transmission. (a) Configuration diagrams in the case of using an EDFA for optical amplification (b) Optical power with respect to transmission distance in the case of (a) is shown. (c) Configuration diagrams when an EDFA and an optical Raman amplifier are used for optical amplification. (d) Optical power with respect to transmission distance in the case of (c). 1 is a schematic diagram showing a prior art optical repeater system. 1 is a schematic diagram illustrating a prior art optical repeater system with a Raman amplifier module. It is the optical spectrum of the control WDM signal light and the control light in the downstream of the transmission line when the Raman amplifier is introduced. It is a graph which shows the optical level with respect to the transmission distance of WDM signal light at the time of Raman amplifier non-introduction. It is a graph which shows the optical level with respect to the transmission distance of the control monitoring light at the time of Raman amplifier introduction. It is a graph which shows the optical level with respect to the transmission distance of noise light at the time of Raman amplifier introduction. It is a block diagram of the optical transmission system of the 1st Embodiment of this invention. It is a block diagram of the optical transmission system of the 2nd Embodiment of this invention. It is a block diagram of the optical transmission system of the 3rd Embodiment of this invention. It is a schematic diagram in the case where there is an influence of the wavelength dependence of the Raman gain in the wavelength band of the control monitoring light in the optical spectrum of the control WDM signal light and the control monitoring light in the downstream of the transmission path when the Raman amplifier is introduced. Schematic diagram of the optical spectrum of the control WDM signal light and control light downstream of the transmission line when the Raman amplifier is introduced, using an optical filter to prevent the influence of the wavelength dependence of the Raman gain in the wavelength band of the control monitoring light It is. In the optical spectrum of the control WDM signal light and control light downstream of the transmission line when the Raman amplifier is introduced, the number of wavelengths of the pump light is increased so that the wavelength dependence of the Raman gain is not affected in the wavelength band of the control light. FIG. It is the schematic which shows an example of the table for a reference used in 1st Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 7 is a block diagram showing a configuration of a main part of the optical repeater system in which the Raman amplifier according to the first embodiment of the present invention is introduced.

  In FIG. 7, the optical repeater system according to the present embodiment includes an optical multiplexer / demultiplexer 700 that multiplexes / demultiplexes an optical signal having a desired wavelength with respect to a WDM signal light combined with a plurality of optical signals having different wavelengths, and a WDM. A first optical amplification unit 701 that amplifies signal light, an optical fiber transmission line 702 to which the WDM signal light amplified by the first amplification unit 701 is input at one end, and an output from the other end of the optical fiber transmission line 702 A second optical amplification unit 703 that amplifies the WDM signal light to be generated, and detects the number of wavelengths of the WDM signal light input to the first optical amplification unit 701 to generate wavelength number information A number detection unit 704 is provided.

  The first optical amplification unit 701 detects the total power of the first optical amplifier 705 that amplifies the input WDM signal light and the WDM signal light output from the first optical amplifier 705 to detect the first signal. A first signal output monitor 706 for generating output level information, and control monitoring including the wavelength number information generated by the wavelength number detector 704 and the first signal output level information generated by the first signal output monitor 706 A control monitoring optical transmitter 707 for transmitting light; and the WDM signal light amplified by the first optical amplifier 705 and the control monitoring light transmitted from the control monitoring optical transmitter 707 to combine the optical fiber transmission line. A multiplexer / demultiplexer 709 to be supplied to one end of 702, and a part of the control monitoring light transmitted from the control / monitoring light transmitter 707 is demultiplexed by the multiplexer / demultiplexer 709 to output the control monitoring light Has a control monitor output monitor 710 for monitoring the level, the.

  The wavelength number information detected by the wavelength number detector 704 and the first signal output level information detected by the first signal output monitor 706 are transmitted via the control lines indicated by thin arrow lines in FIG. It is transmitted to the control monitoring light transmitter 707 and included in the control monitoring signal.

  Further, the second optical amplification unit 703 includes a demultiplexer 711 that demultiplexes light output from the other end of the optical fiber transmission line 702 into a part of WDM signal light, control monitoring light, and control monitoring light; A second optical amplifier 712 that amplifies the WDM signal light demultiplexed by the demultiplexer 711 and a total power of the WDM signal light input to the second optical amplifier 712 are detected to generate signal input level information. A signal input monitor 713, a second signal output monitor 714 that detects the total power of the WDM signal light output from the second optical amplifier 712 and generates second signal output level information, and the demultiplexer 711 A control monitoring light receiver 715 that receives the transmitted control monitoring light and obtains the wavelength number information and the first signal output level information, and a part of the control monitoring light demultiplexed by the branching unit 711 Enter A control monitoring signal input monitor 717 for monitoring the level and an effective span loss of the main signal in the optical fiber transmission line 702 (a value obtained by subtracting the Raman gain from the actual span loss) are calculated, and based on the effective span loss. The gain set in the second optical amplifier 712 is calculated, and the target signal output level of the second optical amplifier 712 is calculated using the wavelength number information acquired by the control monitoring optical receiver 715, and the target signal Control for correcting the calculated gain using a difference between an output level and second signal output level information generated by the second signal output monitor 714 as a correction value, and controlling the second optical amplifier according to the corrected gain A circuit 716 and a Raman amplifier module 718 for amplifying the WDM signal light attenuated by the optical fiber transmission line 702. .

  The Raman amplifier module 718 includes a pumping light source 719 for sending pumping light for Raman amplification of the WDM signal light to the optical fiber transmission line 712, and the WDM signal propagated from the upstream of the optical fiber transmission line 702. A light combiner 720 for combining light, the control monitoring light, and the pump light in the reverse direction, a pump light power detector 721 for detecting the output power of the pump light output from the pump light source 719, and a control The effective span loss of the control monitoring signal calculated from the output level information and the input level information of the monitoring signal, the output power information of the pumping light detected by the pumping light power detection unit 721, and the fiber type information of the transmission path 702 Based on this, the Raman gain of the main signal wavelength band is calculated, and the effective span loss of the main signal is calculated using the Raman gain of the main signal wavelength band. Has a reference table 722 to be referred to because the.

  Here, the fiber type information of the transmission line will be described. The fiber type information is determined by data or data when the fiber cable is laid on the transmission line, or transmission line information such as chromatic dispersion or loss of the fiber transmission line is measured immediately before service-in, and the information is It becomes clear by the method of determining based on. As an example of the latter method, each fiber has a difference in chromatic dispersion of the fiber, for example. When the chromatic dispersion is about 16 to 20 ps / nm / km, SMF (Single mode fiber), 3 to 5 ps / nm / km. If it is approximately, it can be determined as DSF (Dispersion shift fiber) or the like.

FIG. 11 shows an example of the reference table 722. The reference table shows the Raman gain of the main signal and the Raman gain of the control monitoring light corresponding to the output power of the pumping light (PP _ump1 , P _pump2 ...) And the fiber type (SMF, DSF...). The difference (Raman gain difference) is stored. Here, a table creation algorithm will be described. The profile of the Raman gain in the wavelength direction has a shape as shown in FIG. 4, and the profile is uniquely determined by the output power of the pumping light and the fiber type. Therefore, for example, in a transmission line of a certain fiber type, the Raman gain of the wavelength band of the main signal light and the Raman gain of the wavelength band of the control monitoring light when the output power of the pump light is changed are measured, By calculating the difference between these measured values, a table of Raman gain differences (Raman gain in the wavelength band of the main signal light-Raman gain in the wavelength band of the control monitoring light) corresponding to a certain fiber type and the output power of the pumping light can be obtained. Can be created. Furthermore, the reference type 722 as shown in FIG. 11 can be created by changing the fiber type and performing the same operation. The reference table may be created from a Raman gain profile obtained by calculation instead of an actual measurement value of Raman gain.

When the wavelength of the WDM signal light that is the main signal has not been interrupted, the wavelength number information and the first signal output level for the WDM signal light output from the upstream first optical amplification unit 701 to the optical fiber transmission line 702 Information is transmitted to the second optical amplification unit 703 on the downstream side using the control monitoring light. In the second optical amplification unit 703, the total output power of the WDM signal light on the upstream side indicated by the first signal output level information and the total input power of the WDM signal light on the downstream side detected by the signal input monitor 713 are calculated. Is used to calculate the effective span loss L _Signal-EFF [dB] of the WDM signal light, and the gain G _EDFA [dB] = L _Signal set in the second optical amplifier 712 based on the effective span loss of the WDM signal light. _-EFF is calculated.

Further, the target signal output level P _{OUTtarget-Signal} [dBm] = P _OUTperλ · 10 of the second optical amplifier 712 using the wavelength number information N [wave] of the WDM signal light and the output power P _OUTperλ [dBm] per wavelength. · Log (N) is calculated, the difference between the target signal output level P _{OUTtarget-signal} and the signal output level P _{OUTExp-signal} detected by the second signal output monitor 714 is calculated. Since the gain calculated based on the effective span loss includes the measurement error of the effective span loss, the difference between the target value of the signal output level calculated by using the wavelength number information and the measured value is corrected for the error. The second optical amplifier 712 is controlled according to the corrected gain.

When the wavelength of the main signal WDM signal light is interrupted, the output level information of the control monitoring light output from the upstream first optical amplification unit 701 to the optical fiber transmission line 702 is downstream using the control monitoring light. To the second optical amplification unit 703 on the side. In the second optical amplification unit 703, the wavelength number of the WDM signal light that is the main signal is zero because the wavelength number of the WDM signal light is zero from the wavelength number information acquired by the control monitoring light receiver 715 in the control circuit 716. _6A , the control monitoring light output level P _{control monitoring-} OUT [dBm] on the upstream side indicated by the control monitoring light output level information, and the control monitoring signal are determined. effective span loss L _{control monitoring -EFF} of using the input level P _{control monitoring -IN} of the detected control and monitoring signals input monitor 717 [dBm] control monitor light [dB] = P _{control monitoring -OUT} -P _{control monitoring -IN} is calculated, effective span loss L _{control monitoring -EFF} [dB] of the _{control monitoring} light, output power information P _Pump-OUT [dBm] of the pumping light detected by the pumping light power detection unit 721 and the transmission Fiber type information of the path 702 The reference to the reference table 722 calculates a difference .DELTA.G _Raman [dB] of the main signal wavelength band Raman gain G _Raman-Signal [dB] and the Raman gain G _{Raman- control monitoring} of the control monitor signal wavelength band [dB] in The effective span loss L _Signal-EFF [dB] = L _{control monitoring -EFF} + ΔG _Raman of the main signal is calculated using the Raman gain difference ΔG _Raman and the effective span loss L _{control monitoring -EFF of the control monitoring light.} Then, a gain G _EDFA [dB] = L _Signal-EFF set in the second optical amplifier 712 is calculated based on the effective span loss of the main signal.

  Note that the reference table is not limited to the table format as shown in FIG. 11, and a table for each optical fiber type can be input from an OpS (operation system) of an upper layer of the optical repeater system by holding a table for each fiber type. May be.

Further, the target signal output level P _{OUTtarget-Signal} [dBm] = P _OUTperλ · 10 of the second optical amplifier 712 using the wavelength number information N [wave] of the WDM signal light and the output power P _OUTperλ [dBm] per wavelength. · Log (N) is calculated, the difference between the target signal output level P _{OUTtarget-signal} and the signal output level P _{OUTExp-signal} detected by the second signal output monitor 714 is calculated. Since the gain calculated based on the effective span loss of the main signal includes an error in measuring the effective span loss, the target value and the actual measurement value of the signal output level calculated using the wavelength number information are corrected for the error. The second optical amplifier 712 is controlled according to the corrected gain.

Note that as shown in FIG. 10A, the control monitoring light may vary in the wavelength direction due to manufacturing variations and temperature characteristics. Since the Raman gain in the wavelength band of the control and monitoring light striking the wavelength dependence, the Raman gain G of the Raman gain G _Raman-Signal [dB] and the control monitor signal wavelength band of the main signal wavelength band above _{Raman- control monitoring} [dB The difference ΔG _Raman [dB] may also vary, and an error may occur in the output control of the second optical amplifier 712. Therefore, an optical equalizer or an optical filter is provided immediately before the control monitoring light input monitor 717 so that the wavelength dependence of the Raman gain does not appear in the wavelength band of the control monitoring light as shown in FIG. By increasing the number of wavelengths of the excitation light source 719 provided in the Raman amplifier module 718 and broadening the Raman gain as shown in FIG. 10C, the wavelength dependence of the Raman gain does not appear, or the control monitoring light By averaging the input level values of the control monitoring light monitored a plurality of times by the input monitor 717, the variation in the Raman gain difference ΔG _Raman is suppressed, and the output of the second Hikari amplifier 712 is reduced. Control is performed normally. However, in the present invention, since the output control of the second optical amplifier 712 is corrected based on the wavelength number information acquired by the wavelength number detector 704, it is considered that no large error occurs.

  FIG. 8 is a block diagram showing a configuration of a main part of an optical repeater system in which a Raman amplifier according to the second embodiment of the present invention is introduced. In FIG. 8, the optical repeater system of this embodiment includes an optical multiplexer / demultiplexer 800 that multiplexes / demultiplexes an optical signal of a desired wavelength with respect to a WDM signal light in which a plurality of optical signals having different wavelengths are combined, and a WDM. A first optical amplification unit 801 that amplifies signal light, an optical fiber transmission line 802 to which the WDM signal light amplified by the first amplification unit 801 is input at one end, and an output from the other end of the optical fiber transmission line 802 A second optical amplification unit 803 that amplifies the WDM signal light, and detects the number of wavelengths of the WDM signal light input to the first optical amplification unit 801 to generate wavelength number information A number detection unit 804 is provided.

  The first optical amplification unit 801 detects the total power of the first optical amplifier 805 that amplifies the input WDM signal light and the WDM signal light output from the first optical amplifier 805 to detect the first signal. A first signal output monitor 806 for generating output level information, control monitoring including the wavelength number information generated by the wavelength number detector 804 and the first signal output level information generated by the first signal output monitor 806 A control monitoring optical transmitter 807 for transmitting light; and the optical fiber transmission line by combining the WDM signal light amplified by the first optical amplifier 805 and the control monitoring light transmitted from the control monitoring optical transmitter 807 An optical multiplexer / demultiplexer 809 provided to one end of 802, and the noise light (ASE: Amplified Spontaneous Emission) output from the first optical amplifier 805. a noise light output monitor 810 that branches a part of (ion) and monitors the output level of the noise light.

  Further, the second optical amplification unit 803 includes a demultiplexer 811 that demultiplexes light output from the other end of the optical fiber transmission line 802 into WDM signal light, control monitoring light, and part of control monitoring light, A second optical amplifier 812 that amplifies the WDM signal light demultiplexed by the demultiplexer 811 and a total power of the WDM signal light input to the second optical amplifier 812 are detected to generate signal input level information. A signal input monitor 813, a second signal output monitor 814 that detects the total power of the WDM signal light output from the second optical amplifier 812 and generates second signal output level information, and the demultiplexer 811 demultiplexes the signal. A control and monitoring light receiver 815 for receiving the transmitted control and monitoring light to obtain the wavelength number information and the first signal output level information; and the second amplification of the noise light output from the first amplifier. A noise light input monitor 817 for monitoring the input level to the knit unit and an effective span loss of the main signal in the optical fiber transmission line 802 (a value obtained by subtracting the Raman gain from the actual span loss) are calculated, and the effective span loss is calculated. And calculating a target signal output level of the second optical amplifier 812 using the wavelength number information acquired by the control monitoring optical receiver 815, and calculating a gain to be set in the second optical amplifier 812 based on The calculated gain is corrected using a difference between the target signal output level and the second signal output level information generated by the second signal output monitor 814 as a correction value, and the second optical amplifier is adjusted according to the corrected gain. A control circuit 816 for controlling, and a Raman amplifier module 818 for amplifying the WDM signal light attenuated by the optical fiber transmission line 802. It is.

  The Raman amplifier module 818 includes a pumping light source 819 for sending pumping light for Raman amplification of the WDM signal light to the optical fiber transmission line 812, and the WDM signal transmitted from the upstream of the optical fiber transmission line 802. And a multiplexer 820 that multiplexes the light, the control monitoring light, and the excitation light in the reverse direction.

In the optical repeater system configured as described above, when there is no wavelength interruption of the WDM signal light that is the main signal, the WDM signal light output from the first optical amplification unit 801 on the upstream side to the optical fiber transmission line 802. The number of wavelengths information and the first signal output level information are transmitted to the second optical amplification unit 803 on the downstream side using the control monitoring light. In the second optical amplifying unit 803, the control circuit 816 uses the upstream total WDM signal light output power indicated by the first signal output level information and the downstream WDM signal light detected by the signal input monitor 813. The effective span loss L _Signal-EFF [dB] of the WDM signal light is calculated using the total input power of the WDM signal light, and the gain G _EDFA set in the second optical amplifier 812 based on the effective span loss of the WDM signal light is calculated. dB] = L _Signal-EFF is calculated. Further, the target signal output level P _{OUTtarget-Signal} [dBm] = P _OUTperλ · 10 of the second optical amplifier 812 using the wavelength number information N [wave] of the WDM signal light and the output power P _OUTperλ [dBm] per wavelength. · Log (N) is calculated, the difference between the target signal output level P _{OUTtarget-signal} and the signal output level P _{OUTExp-signal} detected by the second signal output monitor 814 is calculated. Since the gain calculated based on the effective span loss includes the measurement error of the effective span loss, the difference between the target value of the signal output level calculated by using the wavelength number information and the measured value is corrected for the error. The second optical amplifier 812 is controlled in accordance with the corrected gain.

When the wavelength of the WDM signal light, which is the main signal, is interrupted, the output level information of the control monitoring light output from the upstream first optical amplification unit 801 to the optical fiber transmission line 802 uses the control monitoring light. This is transmitted to the second optical amplification unit 803 on the downstream side. In the second optical amplifying unit 803, the wavelength number of the WDM signal light that is the main signal is zero because the wavelength number of the WDM signal light is zero from the wavelength number information acquired by the control monitoring light receiver 715 in the control circuit 816. 6b, the noise light output level information P _ASE-OUT [dBm] output from the first amplifier and the noise light input monitor 817 detect the noise light output level information P _ASE-OUT [dBm]. The effective span loss L _ASE-EFF [dB] = P _ASE-OUT −P _ASE-IN of the noise light is calculated using the input level P _ASE-IN [dBm] of the noise light, and the effective light of the noise light is calculated. Based on the span loss L _ASE-EFF [dB], the gain G _EDFA [dB] = L _ASE-EFF set in the second optical amplifier 812 is calculated.

For example, if the NF (Noise Fogue) of the first optical amplifier 805 is 5 [dB], the actual span loss is 30 [dB], and the Raman gain is 15 [dB], the output level P _ASE-OUT = −28 [dBm]. = −53 (the amount of optical noise per 0.1 nm in the case of NF5 [dB], optical amplifier 0 [dBm] input) +25 (main signal wavelength band 30 nm), input level P _{ASE-IN of the} noise light = −43 [dBm] = − 28 (output level) −30 (actual span loss) +15 (Raman gain), which is a realizable light level. Further, the target signal output level P _{OUTtarget-Signal} [dBm] = P _OUTperλ · 10 of the second optical amplifier 812 using the wavelength number information N [wave] of the WDM signal light and the output power P _OUTperλ [dBm] per wavelength. · Log (N) is calculated, the difference between the target signal output level P _{OUTtarget-signal} and the signal output level P _{OUTExp-signal} detected by the second signal output monitor 814 is calculated. Since the gain calculated based on the effective span loss of the main signal includes an error in measuring the effective span loss, the target value and the actual measurement value of the signal output level calculated using the wavelength number information are corrected for the error. The second optical amplifier 812 is controlled according to the corrected gain.

  FIG. 9 is a block diagram showing a configuration of a main part of an optical repeater system in which a Raman amplifier according to the third embodiment of the present invention is introduced.

  In FIG. 9, the optical repeater system according to the present embodiment includes a multiplexer / demultiplexer 900 that multiplexes and demultiplexes an optical signal having a desired wavelength with respect to a WDM signal light in which a plurality of optical signals having different wavelengths are combined, and a WDM. A first optical amplification unit 901 that amplifies signal light, an optical fiber transmission line 902 to which the WDM signal light amplified by the first amplification unit 901 is input at one end, and an output from the other end of the optical fiber transmission line 902 A second optical amplification unit 903 that amplifies the WDM signal light to be generated, and detects the number of wavelengths of the WDM signal light input to the first optical amplification unit 901 to generate wavelength number information A number detection unit 904 is provided.

  The first optical amplification unit 901 detects a total power of the first optical amplifier 905 that amplifies the input WDM signal light and the WDM signal light output from the first optical amplifier 905 to detect the first signal. A first signal output monitor 906 that generates output level information, and control monitoring that includes the wavelength number information generated by the wavelength number detector 904 and the first signal output level information generated by the first signal output monitor 906 A control monitoring optical transmitter 907 for transmitting light; and the WDM signal light amplified by the first optical amplifier 905 and the control monitoring light transmitted from the control monitoring optical transmitter 907 to combine the optical fiber transmission line. When the number of wavelengths of the WDM signal light amplified by the first optical amplifier becomes zero, dummy light is transmitted instead of the main signal in the optical fiber. It has a dummy light source 910 to be sent to 902, a.

  Further, the second optical amplification unit 903 includes a demultiplexer 911 that demultiplexes the light output from the other end of the optical fiber transmission line 902 into a part of the WDM signal light, the control monitoring light, and the control monitoring light; A second optical amplifier 912 that amplifies the WDM signal light demultiplexed by the demultiplexer 911 and a total power of the WDM signal light input to the second optical amplifier 912 are detected to generate signal input level information. The signal input monitor 913, the second signal output monitor 914 that detects the total power of the WDM signal light output from the second optical amplifier 912 and generates second signal output level information, and the demultiplexer 911 A control and monitoring light receiver 915 that receives the transmitted control and monitoring light and obtains the wavelength number information and the first signal output level information; and an effective scan of the main signal in the optical fiber transmission line 902. Is calculated by subtracting the Raman gain from the actual span loss, the gain set in the second optical amplifier 912 is calculated based on the effective span loss, and obtained by the control monitoring optical receiver 915. The target signal output level of the second optical amplifier 912 is calculated using the obtained wavelength number information, and the difference between the target signal output level and the second signal output level information generated by the second signal output monitor 914 is corrected. A control circuit 916 that corrects the calculated gain as a value and controls the second optical amplifier according to the corrected gain, and a Raman amplifier module 917 that amplifies the WDM signal light attenuated by the optical fiber transmission line 902 are provided. doing.

  The Raman amplifier module 917 includes a pumping light source 918 for sending pumping light for Raman amplification of the WDM signal light to the optical fiber transmission line 912, and the WDM signal transmitted from the upstream of the optical fiber transmission line 902. And a multiplexer 919 that multiplexes the light, the control monitoring light, and the excitation light in the reverse direction.

In the optical repeater system configured as described above, when there is no wavelength interruption of the WDM signal light that is the main signal, the WDM signal light output from the first optical amplification unit 901 on the upstream side to the optical fiber transmission line 902 The number-of-wavelength information and the first signal output level information are transmitted to the second optical amplification unit 903 on the downstream side using the control monitoring light. In the second optical amplifying unit 903, the control circuit 916 uses the total output power of the upstream WDM signal light indicated by the first signal output level information and the downstream WDM signal light detected by the signal input monitor 913. The effective span loss L _Signal-EFF [dB] of the WDM signal light is calculated using the total input power of the WDM signal light, and the gain G _EDFA set in the second optical amplifier 912 based on the effective span loss of the WDM signal light is calculated. dB] = L _Signal-EFF is calculated. Further, the target signal output level P _{OUTtarget-Signal} [dBm] = P _OUTperλ · 10 of the second optical amplifier 912 using the wavelength number information N [wave] of the WDM signal light and the output power P _OUTperλ [dBm] per wavelength. · Log (N) is calculated, the difference between the target signal output level P _{OUTtarget-signal} and the signal output level P _{OUTExp-signal} detected by the second signal output monitor 914 is calculated. Since the gain calculated based on the effective span loss includes the measurement error of the effective span loss, the difference between the target value of the signal output level calculated by using the wavelength number information and the measured value is corrected for the error. The second optical amplifier 912 is controlled according to the corrected gain.

When the wavelength of the WDM signal light, which is the main signal, occurs, the output level information of the dummy light output from the first optical amplification unit 901 on the upstream side to the optical fiber transmission line 902 is obtained using the control monitoring light. This is transmitted to the second optical amplification unit 903 on the downstream side. In the second optical amplifying unit 903, the wavelength number of the WDM signal light that is the main signal is zero because the wavelength number of the WDM signal light is zero from the wavelength number information acquired by the control monitoring light receiver 715 in the control circuit 916. Is determined to occur, the dummy light output level information P _Dummy-OUT [dBm] and the dummy light input level P _Dummy-IN [dBm] detected by the first signal input monitor 913 are used. The effective span loss L _Dummy-EFF [dB] = P _Dummy-OUT −P _Dummy-IN of the dummy light is calculated, and based on the effective span loss L _Dummy-EFF [dB] of the dummy light, The gain G _EDFA [dB] = L _Dummy-EFF set in the two optical amplifier 912 is calculated. Further, the target signal output level P _{OUTtarget-Signal} [dBm] = P _OUTperλ · 10 of the second optical amplifier 812 using the wavelength number information N [wave] of the WDM signal light and the output power P _OUTperλ [dBm] per wavelength. · Log (N) is calculated, the difference between the target signal output level P _{OUTtarget-signal} and the signal output level P _{OUTExp-signal} detected by the second signal output monitor 914 is calculated. Since the gain calculated based on the effective span loss of the main signal includes an error in measuring the effective span loss, the target value and the actual measurement value of the signal output level calculated using the wavelength number information are corrected for the error. The second optical amplifier 912 is controlled according to the corrected gain.

100-1, 100-2, 100-3, 100-4 Repeater 101-1, 101-2 Optical fiber transmission line 102-1, 102-2, 102-3, 102-4 EDFA
103-1, 103-2 Excitation light sources 104-1, 104-2 Optical Raman amplifier modules 200, 300, 700, 800, 900 MUX / DEMUX 201, 301, 701, 801, 901 First optical amplification units 202, 302 , 702, 802, 902 Optical fiber transmission lines 203, 303, 703, 803, 903 Second optical amplification units 204, 304, 704, 804, 904 Wavelength number detectors 205, 305, 705, 805, 905 First optical amplifier 206, 306, 706, 806, 906 First signal output monitor 207, 307, 707, 807, 907 Control monitoring optical transmitter 208, 308, 708, 808, 908 Control circuit 209, 309, 709, 809, 909 Waver 210, 310, 710 Control monitoring light output monitor 211, 311, 711, 8 1,911 Demultiplexers 212, 312, 712, 812, 912 Second optical amplifiers 213, 313, 713, 813, 913 Second signal input monitors 214, 314, 714, 814, 914 Second signal output monitors 215, 315 , 715, 815, 915 Control monitoring light receiver 216, 316, 716, 816, 916 Control circuit 217, 317, 717 Control monitoring light input monitor 318, 718, 818, 917 Optical Raman amplifier modules 319, 719, 819, 918 Excitation light sources 320, 720, 820, 919 Multiplexer 721 Excitation light power detection unit 722 Reference table 810 Noise light output monitor 817 Noise light input monitor 910 Dummy light source

Claims (9)

  An optical transmitter for sending an optical signal including the first signal light and the second signal light to an optical fiber transmission line, an optical fiber transmission line through which the optical signal propagates, and light propagated through the optical fiber transmission line An optical receiver for receiving a signal; an optical amplifier for amplifying the optical signal including at least the first signal light attenuated by an optical fiber transmission line in a predetermined section; and transmitting the optical signal to a subsequent optical fiber; and the optical fiber An optical amplifying unit including at least one Raman amplifier module that sends pumping light to the transmission line in a direction opposite to the traveling direction of the optical signal and distributes and amplifies the optical signal on the optical fiber transmission line; The output level that is the optical level of the second signal light at the other end of the optical fiber transmission path is subtracted from the output level that is the optical level of the second signal light at one end of the fiber transmission path. The first signal calculated from the transmission line loss of the second signal light, the input power of the pumping light output from the Raman amplifier module to the optical fiber transmission line, and the fiber type of the optical fiber transmission line An optical repeater system comprising: a control unit that performs output control of the optical amplifier based on an optical transmission line loss. The second signal light includes line monitoring, transmission of wavelength number information, transmission of input level information of the optical signal to the optical fiber transmission line, transmission of input level information of the signal light to the optical fiber transmission line Control monitoring light for the purpose of
2. The optical repeater system according to claim 1, wherein a wavelength band of the control monitoring light is different from a wavelength band of the first signal light which is a main signal.   2. The optical repeater according to claim 1, wherein the second signal light is the same wavelength band as the first signal light which is a main signal and is noise light output from the optical transmitter. system   The second signal light has the same wavelength band as the first signal light, which is the main signal, and the first signal light propagating through the optical fiber transmission line does not propagate even one wavelength. 2. The optical repeater system according to claim 1, wherein the optical repeater system is dummy light that propagates in a disconnected state.   The output level which is the optical level of the second signal light at the other end of the optical fiber transmission line is monitored by the output level monitor for the second signal light provided in the optical amplification unit, The optical relay system according to claim 1, wherein the output level monitor includes a mechanism for installing an optical filter to avoid the influence of wavelength dependence of Raman gain.   The Raman amplifier module includes one or more excitation light sources that transmit the excitation light to the optical fiber transmission line, and the excitation light source includes a wavelength band of the first signal light that is a main signal and the second light source. 2. The optical repeater system according to claim 1, wherein the wavelength arrangement of the pumping light is realized so that the Raman gain is not wavelength-dependent in the wavelength band of the signal light.   The output level which is the optical level of the second signal light at the other end of the optical fiber transmission line is a wavelength of Raman gain as an average value of two or more measurement results of values monitored by the output level monitor. The optical repeater system according to claim 1, further comprising a mechanism for avoiding the influence of dependence.   2. The optical repeater system according to claim 1, wherein the optical repeater system includes a wavelength number detection unit that detects the number of wavelengths of the optical signal propagating through the optical fiber transmission line, and the wavelength number detection unit includes the wavelength number detection unit. When there is a change in the number of wavelengths of the optical signal, the wavelength number information is transmitted to the control circuit of the optical amplifier installed in the optical amplification unit via the control monitoring light, and the control circuit The optical power output from the optical amplifier is corrected based on the numerical information.   An optical signal including the first signal light and the second signal light is transmitted from the optical transmitter to the optical fiber transmission line, and the optical signal propagated through the optical fiber transmission line is received by the optical receiver. The optical signal including at least the first signal light attenuated in the optical fiber transmission line is amplified by an optical amplifier and sent to the optical fiber following the subsequent stage, and the traveling direction of the optical signal is opposite to the optical fiber transmission line. Pumping light is transmitted in the direction, and the optical signal is distributed Raman amplified on the optical fiber transmission line, and the optical fiber transmission line is output from an output level that is an optical level of the second signal light at one end of the optical fiber transmission line. The transmission path loss of the second signal light obtained by subtracting the output level that is the optical level of the second signal light at the other end of the optical fiber, and the pumping light output from the Raman amplifier module to the optical fiber transmission path Enter An optical repeater method comprising: controlling output of the optical amplifier based on force power and a transmission line loss of the first signal light calculated from a fiber type of the optical fiber transmission line.

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