JP2001274752A - Optical transmitter and optical receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize transfer of supervisory information of an optical fiber transmission system, without having to reduce the output power of an optical fiber amplifier. SOLUTION: The transfer of supervisory information can be realized in such a way that a supervisory optical transmitter and the optical receiver which have nearly the same wavelength as that of an excitation light source of an optical fiber amplifier are provided in an optical repeater, a first optical multiplexer/demultiplexer multiplexes excitation light in the forward direction and demultiplexes a supervisory optical signal that is transmitted, while being subjected to wavelength multiplex processing, a supervisory optical receiver receives the demultiplexed signals at the input side of an optical repeater at the same time, a second optical multiplexer/demultiplexer multiplexes the excitation light in the reverse direction at the output side of the optical repeater and the supervisory optical transmitter outputs the multiplexed signal at the same time. Thus, the transfer of the supervisory information can be realized with a simple configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiving apparatus using an optical fiber amplifier, and more particularly, to a method of monitoring and transmitting monitoring information.

[0002]

BACKGROUND OF THE INVENTION Optical fiber amplifiers may be used in future optical fiber transmission systems. The system includes an optical transmitter (including a data optical transmitter for converting data into a data optical signal and an optical fiber amplifier), an optical repeater (including an optical fiber amplifier), and an optical receiver (optical fiber amplifier and a data optical signal). And a data optical receiver for reproducing data from the optical network) and an optical transmission line connecting them, and transferring the obtained monitoring information to the optical terminal. Conventionally, the monitoring information transfer technique has been described in, for example, JP-A-3-214936. In the conventional monitoring information transfer technique, (1) a data optical signal and a monitoring optical signal multiplexed with the data optical signal are simultaneously optically amplified by an optical fiber amplifier in each optical repeater;
Alternatively, a method of (2) branching an excitation light source into two and using one of them as a monitoring light signal has been used.

[0003]

Assuming that an optical fiber amplifier whose output is saturated is compared with a case where only a data optical signal is input to the optical fiber amplifier, the prior art (1) also shows that the monitoring optical signal is At the same time, since the signal is input to the optical fiber amplifier, the gain is reduced and the output power of the data optical signal is reduced. Similarly, in the above-mentioned prior art (2), the pumping light power drops because the pumping light is branched for the monitoring light signal, and the output power of the optical fiber amplifier also drops because the gain decreases. Usually, an optical repeater often uses a built-in optical fiber amplifier in an output saturated state. this is,
This is because it is necessary to increase the output power of the data optical signal as much as possible. However, the use of the above-described prior art is problematic because output power is reduced.

An object of the present invention is to solve the above problems,
That is, it is an object of the present invention to realize transmission of monitoring information of an optical fiber transmission system using an optical fiber amplifier without lowering the output power of the optical fiber amplifier, and to realize monitoring of the system. Note that the optical fiber amplifier has at least an optical fiber doped with an additive (doped fiber) and an excitation light source that outputs light (excitation light) having a wavelength λp that excites the doped fiber.

[0005]

The above objects can be attained by implementing the following items 1 and 2. 1. The transfer of the monitoring information can be realized by configuring the optical transmitter, the optical repeater (one or more), and the optical receiver constituting the optical fiber transmission system as follows.
That is, (1) the monitoring information transfer from the optical transmission device transmits an electrical signal for monitoring (hereinafter, referred to as monitoring signal) including the monitoring information in the optical transmission device.
A monitoring optical transmitter for converting a monitoring electrical signal into an optical signal (wavelength approximately λp, hereinafter abbreviated as an output monitoring optical signal); and a monitoring optical transmitter disposed after the doped fiber and opposite to the amplified data optical signal. This can be realized by providing an optical multiplexer / demultiplexer which multiplexes the pump light in the direction and simultaneously multiplexes the output monitoring optical signal in the same direction as the data optical signal. (2) The monitoring information transfer in the optical repeater is performed by monitoring the monitor optical signal 1 (wavelength approximately λp, hereinafter) that is arranged in the optical repeater before the doped fiber and multiplexed with the data optical signal and sent. At the same time as demultiplexing the input monitoring optical signal, the first pumping light (wavelength λ)
p, output from the first pumping light source) in the same direction as the data optical signal, and a monitoring optical receiver for converting the input monitoring optical signal into an input monitoring electrical signal. A controller for adding monitoring information relating to the optical repeater to the input monitoring electric signal and outputting an output monitoring electric signal, and converting the output monitoring electric signal into a monitoring light signal 2 (wavelength approximately λp, hereinafter abbreviated as an output monitoring light signal) And a second pumping light (wavelength λp, output from the second pumping light source) arranged in the opposite direction to the amplified data light signal, which is disposed after the doped fiber and is converted after the monitoring. This can be realized by providing an optical multiplexer / demultiplexer which multiplexes the output monitoring optical signal in the same direction as the data optical signal while oscillating. Further, (3) the monitoring information is received by the optical receiving apparatus. The monitoring optical signal (wavelength substantially λp) which is disposed in the optical receiving apparatus before the doped fiber and multiplexed with the data optical signal and sent. An optical multiplexer / demultiplexer that demultiplexes the pumping light in the same direction as the data optical signal while demultiplexing the input monitoring optical signal, and a monitoring light that converts the input monitoring optical signal into an input monitoring electrical signal. This can be realized by providing a receiver. 2. Monitoring of the optical transmitter, the optical repeater (one or more), the optical receiver, and the transmission line connecting these, which constitute the optical fiber transmission system, can be realized as follows. That is, (1) monitoring of the optical transmission apparatus includes, in the optical transmission apparatus, a power splitter that branches a part of the output light of the apparatus, and an optical filter that extracts only a data optical signal from one output light of the power splitter. And a power monitor for detecting the power Pd of the extracted data optical signal. The controller observes the Pd and, at the same time, if the value of Pd deviates from the normal value, judges that the optical transmitter is abnormal and issues a warning. This can be realized by generating a signal (hereinafter, the observed value of Pd and the warning signal are referred to as monitoring information in the optical transmitter).
(2) The monitoring of the transmission path and the optical repeater connected after the transmission path is performed by detecting the power Pw of the input monitoring optical signal demultiplexed by the monitoring optical receiver, and simultaneously monitoring the power Pw in the optical repeater.
A power splitter that splits a part of the device output light, an optical filter that extracts only a data optical signal from one output light of the power splitter, and a power monitor that detects a power Pd of the extracted data optical signal. The controller observes Pw and Pd, and at the same time, when only the value of Pd deviates from the normal value, judges that the optical fiber amplifier in the optical repeater is abnormal, and only the value of Pw deviates from the normal value. In this case, it is determined that the monitoring optical receiver or the monitoring optical transmitter (wavelength approximately λp) of the preceding optical repeater (or optical transmitter) is abnormal, and both Pd and Pw deviate from the normal values. If it is, it is determined that the transmission path is abnormal,
Each of them can be realized by generating a warning signal (hereinafter, the observed values of Pd and Pw, the warning signal, and the like are referred to as monitoring information in the optical repeater). Further, (3) monitoring of the transmission path and the optical receiving device connected after the transmission path detects the power Pw of the input monitoring optical signal demultiplexed by the monitoring optical receiver, and the data optical receiver The power Pd of the received data optical signal is detected, and further, the controller determines Pw and Pw.
At the same time as observing d, if only the value of Pd deviates from the normal value, it is determined that the optical fiber amplifier in the optical receiver is abnormal, and if only the value of Pw deviates from the normal value, it is used for monitoring. It is determined that the optical receiver or the monitoring optical transmitter (wavelength approximately λp) of the preceding optical repeater is abnormal, and Pd and Pw
Can be realized by determining that the transmission path is abnormal and generating a warning signal (hereinafter, the observed values of Pd and Pw, the warning signal, and the like in the optical receiving apparatus). Monitoring information).

[0006]

According to the means (1), the monitoring optical signal transmitted from the optical transmitter is received by each optical repeater, added with monitoring information, transmitted again as a monitoring optical signal, and finally transmitted as an optical signal. Since the light reaches the receiving device and is received, the monitoring optical signal carrying the monitoring information on the optical transmitting device, each optical repeater, and the transmission path can be transferred to the optical receiving device.
At this time, since each optical fiber amplifier receives only the data optical signal, the output power does not decrease as in the case of using the conventional technology.

Further, according to the above means 2, (1) the optical transmitter can detect the power Pd of the data optical signal output by itself, and can monitor its own abnormality by observing the value, and (2) The optical repeater transmits the monitoring optical signal (output from the preceding monitoring optical transmitter) simultaneously with the power Pd of the data optical signal (it passes through the transmission line and the optical fiber amplifier in the optical repeater) output by itself. , Passing through the transmission path and detected by the monitoring optical receiver), the power Pw can be detected.
By observing these powers, transmission lines, optical fiber amplifiers,
In addition, the monitoring optical receiver or the monitoring optical transmitter in the preceding stage can be monitored for abnormalities. Further, (3) the optical receiving apparatus can receive the data optical signal (transmission path and optical fiber in the optical receiving apparatus) received by itself. The power Pd of the transmitted monitoring optical signal (output from the upstream monitoring optical transmitter, passed through the transmission path, detected by the monitoring optical receiver) can be detected simultaneously with the power Pd of the monitoring optical signal. By observing these powers, abnormalities of the transmission line, the optical fiber amplifier, and the monitoring optical receiver or the monitoring optical transmitter at the preceding stage can be monitored. That is, monitoring of the optical transmission device, the optical repeater, the optical receiver, and the transmission path can be realized.

The operation of the optical multiplexer / demultiplexer used in the present invention can be explained as follows. For the purpose of explanation, FIG. 2 shows a typical configuration example of a repeater that can be realized using an optical fiber amplifier. The input to the repeater is a weak data optical signal (wavelength λd), and the output is an amplified data optical signal. This repeater includes an optical fiber (hereinafter, abbreviated as “doped fiber”) 1-1 and 1-2 doped with erbium (Er) and the like, and a pumping light source (wavelength λp) 2 for outputting pumping light for giving gain to the doped fiber. 1, 2-2
And optical multiplexers (3 terminals) 3-1 and 3-2 for multiplexing the data optical signal and the pump light, and isolators 4-1 to 4-3 for preventing oscillation of the optical fiber amplifier. And are connected as shown in FIG.

The multiplexer includes (a) an optical filter having a dielectric multilayer film whose reflectance has wavelength dependence on the surface, and (b) a directional coupler using two optical fibers. Realizable and commercially available. FIG. 3 shows a configuration example of an optical multiplexer 3-1 realized using a dielectric multilayer filter.
In the dielectric multilayer filter in the optical multiplexer, the reflectance is set to be almost zero for the light having the wavelength λd and to be almost 100% for the light having the wavelength λp. . Therefore, when a data optical signal of wavelength λd is input from the first port, the optical signal passes through the filter and is output to the third port. When the pumping light having the wavelength λp is input from the second port, the pumping light is reflected by the filter and output to the third port. As a result, as shown in FIG. 3A, multiplexed light obtained by multiplexing optical signals of both wavelengths is obtained from the third port. That is, the data optical signal and the pump light can be multiplexed using the optical multiplexer. By the same principle,
When multiplexed light composed of a data optical signal of wavelength λd and a monitoring optical signal of wavelength λp is input to the first port, the data optical signal passes through the filter and is output to the third port as shown in FIG. The monitoring light signal is reflected. That is, the multiplexed light can be split. Therefore, as shown in FIG. 4A, if a fourth port is newly provided in this multiplexer to provide a four-terminal optical multiplexer / demultiplexer, one optical multiplexer / demultiplexer can be used to combine the data optical signal with the data optical signal. The monitoring optical signal is demultiplexed from the input multiplexed light composed of the monitoring optical signal and output to the fourth port. At the same time, the data optical signal and the pumping light are multiplexed and the multiplexed light is output from the third port. it can. In the configuration of FIG. 4A, if the pumping light having the wavelength λp is inputted from the fourth port and the monitoring light signal having the wavelength λp is inputted from the second port, the pumping light multiplexed in the opposite direction to the data light signal. At the same time as outputting light from the first port, a data optical signal obtained by multiplexing the monitoring optical signal can be output from the third port (see FIG. 4 (2)).

Therefore, the optical multiplexer 3-1 of FIG.
If the optical multiplexer / demultiplexer having the configuration of (1) is replaced with an optical multiplexer / demultiplexer on the input side and the optical multiplexer / demultiplexer 3-2 is replaced with the optical multiplexer / demultiplexer having the configuration of FIG. The monitoring optical signal can be demultiplexed by the input-side optical multiplexer / demultiplexer from the optical signal (combined light of the data optical signal and the monitoring optical signal) input to the optical fiber, and the data optical signal obtained by multiplexing the monitoring optical signal is transmitted from the repeater. Can be output. That is, the monitoring information sent from the optical repeater (or optical terminal) at the preceding stage can be transferred to the optical repeater (or optical terminal) at the subsequent stage using the optical fiber for transmitting the data optical signal. .

As described above, according to the present invention, since the monitoring optical signal is multiplexed and demultiplexed by the optical multiplexer / demultiplexer for multiplexing the pumping light to the doped fiber, the optical transmission device, the optical repeater, There is an effect that monitoring of the receiving device and the optical transmission line connecting them and monitoring information transfer can be realized without causing a decrease in output power in each optical fiber amplifier.

[0012]

FIG. 1 shows a first embodiment of the optical repeater of the present invention. This device comprises an optical fiber amplifier and a monitoring device. In the optical fiber amplifier, the optical multiplexer / demultiplexer shown in FIG. 4A is used instead of the optical multiplexers 3-1 and 3-2 in the configuration of FIG. The input-side optical multiplexer / demultiplexer 5-1 demultiplexes an input monitoring optical signal from an optical signal (composed of a data optical signal and an input monitoring optical signal) input to the optical repeater, and simultaneously multiplexes pump light. The data optical signal is amplified by the doped fiber and input to the output-side multiplexer / demultiplexer 5-2, and the input monitoring optical signal is input to the monitoring device. The output-side multiplexer / demultiplexer 5-2 multiplexes the output monitoring optical signal output from the monitoring optical transmitter with the amplified data optical signal and outputs the multiplexed light, and simultaneously multiplexes the pump light in the reverse direction. The monitoring device converts the demultiplexed input monitoring optical signal into an input monitoring electrical signal and, at the same time, detects a monitoring optical receiver 6 that detects the input monitoring optical signal power Pw, and branches a part of the output light of the optical repeater. Power splitter 7
An optical filter 8 for passing only the data optical signal of the split light, a power monitor 9 for detecting the power Pd (hereinafter abbreviated as data optical signal power) of the data optical signal passing through the optical filter, A controller 10 that receives an input monitoring electrical signal, the input monitoring optical signal power, and the data optical signal power as inputs, and a monitoring optical transmitter that converts an output monitoring electrical signal output from the controller into the output monitoring optical signal. And a vessel 11. The detection of the input monitoring optical signal power Pw in the monitoring optical receiver 6 is performed, for example, by measuring a DC current flowing through a photodiode (an element that converts the input monitoring optical signal into electricity) built in the monitoring optical receiver. It can be realized by doing.

The wavelength λd of the data optical signal is, for example, 1.
Considering light in the 55 μm band, when an optical fiber doped with erbium or the like as an additive is used as a doped fiber, the gain can be given to the doped fiber by using pumping light having a wavelength of about 1.48 μm (= λp). . The optical fiber used as the transmission line has a wavelength of 1.48 μm.
In the vicinity, since the transmission loss is about the same as the wavelength of 1.55 μm, the output monitoring optical signal having a wavelength of about 1.48 μm, which is multiplexed with the data optical signal and output, is the same as the data optical signal in the next stage optical relay Device (or optical receiver). However, the wavelengths of λd and λp need not be limited to the above-mentioned wavelengths.

The controller determines whether the optical transmission line, the optical fiber amplifier, and the monitoring device are normal based on the observed values of the input monitoring optical signal power and the data optical signal power.
The determination result is added to the input monitoring electric signal and output as an output monitoring electric signal. Specifically, Pw and Pd are observed by the controller, and when only the value of Pd deviates from the normal value, it is determined that the optical fiber amplifier in the optical repeater is abnormal, and only the value of Pw is the normal value. If it deviates from that, it is determined that the monitoring optical receiver or the monitoring optical transmitter (wavelength approximately λp) of the preceding optical repeater (or optical transmitter) is abnormal, and both Pd and Pw are normal values. If it deviates from the transmission path, it is determined that the transmission path is abnormal. This is because while the data optical signal passes through both the transmission line and the optical fiber amplifier in the optical repeater, the incoming input monitoring optical signal passes only through the transmission line, so both Can be determined to be abnormal on the transmission line only when
This is because if either one deviates from the normal value, it can be determined that the rest is abnormal. In addition, the controller includes necessary information (signals required for monitoring the optical repeater, information about other devices in the optical terminal, control signals for controlling each optical repeater at the subsequent stage, control signals for controlling the optical receiver, A control signal for controlling each optical repeater or an optical fiber amplifier built in the optical receiver can be input as appropriate, and is added to the input monitoring electric signal and output as an output monitoring electric signal. Further, it is possible to read the input monitoring electric signal received from the controller and the monitoring information obtained by the optical repeater. The controller can also control the operation of the optical repeater and the built-in optical fiber amplifier based on the control information added to the received input monitoring electric signal and transferred. The detection of the input monitoring optical signal power (or the voltage signal proportional to the power) in the monitoring optical receiver is performed as follows.
For example, a part of the received input monitoring electric signal is branched,
It can be realized by measuring the power or the peak value. The input monitoring optical signal power can also be detected by detecting a DC current (or a voltage proportional to the DC current) flowing through the photodiode built in the monitoring optical receiver.

As described above, according to the present embodiment, the optical transmission line and the optical repeater (optical fiber amplifier and monitoring device) are monitored with a simple configuration, and the optical repeater (and optical terminal) at the preceding stage is monitored. There is an effect that the monitoring information of the optical repeater is added to the monitor information from the station) and can be transferred to the optical repeater (and the optical terminal) at the subsequent stage. Also, the operation can be controlled by the transferred control information.

The above effects of the present invention are not limited to the configuration of the present embodiment. For example, the above-described effects can be obtained regardless of the specific internal configuration of the optical multiplexer / demultiplexer as long as it can multiplex and demultiplex the two wavelengths λd and λp. Also,
Optical isolators can be placed in different places,
Even if the number used is different or not used, the above effect can be obtained. Further, the method of exciting the doped fiber may be different from that of FIG. That is, the above-described effects can be obtained regardless of whether the pumping light travels in the forward direction, the reverse direction, or the bidirectional direction with respect to the data optical signal. The above-described effect can be obtained even when the number of excitation light sources is further increased. Further, even if the number of doped fibers is different from the case of FIG. 1, the above effect can be obtained. In addition, the power splitter 7,
Even without the optical filter 8 and the power monitor 9, the optical transmission line (or the monitoring optical receiver, the controller, and the
It is possible to monitor the monitoring optical transmitter of the preceding optical repeater and to transfer the monitoring information, and only these functions are useful for an optical fiber amplifier transmission system using an optical fiber amplifier. Further, the above-described effect can be obtained even when an optical component such as an optical filter is inserted. Further, the above-described effect can be obtained even if the input monitoring electric signal is used as it is as the output monitoring electric signal.

FIG. 5 shows that, when an optical fiber amplifier is used as an optical booster amplifier in an optical transmitter in an optical terminal, the optical booster amplifier is monitored, and the obtained monitoring information is transmitted to a subsequent optical repeater. 1 shows an embodiment of an optical transmission device for transferring. The optical transmitter includes a data optical transmitter for converting data into a data optical signal having a wavelength λd, an optical fiber amplifier for amplifying the data optical signal, and a monitoring device. The optical fiber amplifier includes a doped fiber 1, pumping light sources 2-1 and 2-2, an optical multiplexer 3 for multiplexing pumping light from the pumping light source 2-1 with a data optical signal, and a pumping light source 2-.
It comprises an optical multiplexer / demultiplexer 5 for multiplexing the pump light from 2 and the data optical signal in opposite directions and multiplexing the output monitoring optical signal, and optical isolators 4-1 and 4-2. Therefore,
With this configuration, the output monitoring optical signal is multiplexed with the data optical signal, transmitted from the optical transmission device, and transferred to the next-stage optical repeater. The optical multiplexer 3 has, for example, the configuration shown in FIG.
The optical multiplexer / demultiplexer 5 has, for example, the configuration shown in FIG. The monitoring device includes a power splitter 7 for branching a part of the output light of the optical booster amplifier, an optical filter 8 for passing only the data optical signal of the branched light, and a data light for the data optical signal passing through the optical filter. A power monitor 9 for detecting signal power, the data optical signal power, and other necessary information (parity check signal, other signals necessary for monitoring the optical repeater, control signals for controlling each optical repeater, optical reception A controller 10 which receives control signals for controlling the apparatus, control signals for controlling the optical fiber amplifiers incorporated in the respective optical repeaters and optical receivers, and an output monitoring electric signal output from the controller. And a monitoring optical transmitter 11 for converting the optical signal into an optical signal.
The controller determines whether the transmitter or the optical fiber amplifier is normal by monitoring whether the data optical signal power is normal. The monitoring optical transmitter adds the necessary information to the obtained determination result (monitoring information) and converts it into an output monitoring optical signal.

According to this embodiment, it is possible to transfer the monitoring information of the optical fiber amplifier used as the optical booster amplifier to the subsequent optical repeater and to transfer information other than the monitoring information. . For example, as described above, if the control signal for controlling the optical fiber amplifier built in each optical repeater is transferred, the operation and the like of each optical fiber amplifier can be controlled from the optical terminal station containing the optical transmitter.

The above effects of the present invention are not limited to the configuration of the present embodiment. For example, the above-described effects can be obtained regardless of the specific internal configuration of the optical multiplexer / demultiplexer as long as it can multiplex and demultiplex the two wavelengths λd and λp. Also,
Optical isolators can be placed in different places,
Even if the number used is different or not used, the above effect can be obtained. The method of exciting the doped fiber may be different from that of FIG. That is, the above-described effects can be obtained regardless of whether the pumping light travels in the forward direction, the reverse direction, or the bidirectional direction with respect to the data optical signal. The above-described effect can be obtained even when the number of excitation light sources is further increased. Further, even if the number of doped fibers is different from the case of FIG. 5, the above effect can be obtained. In addition, the power splitter 7,
The optical filter 8 and the power monitor 9 may not be provided. Even if the output monitoring optical signal of wavelength λp does not carry monitoring information on the optical booster amplifier, if the next-stage optical repeater monitors the power of the monitoring optical signal of wavelength λp, the next-stage optical repeater The apparatus is useful because it can monitor the optical transmission line for abnormalities and the like. Further, the above-described effect can be obtained even when an optical component such as an optical filter is inserted.

FIG. 6 shows a case where an optical fiber amplifier is used as an optical preamplifier in an optical receiver in an optical terminal.
An embodiment of an optical receiving apparatus for receiving monitoring information from a preceding stage and monitoring an optical transmission line and an optical preamplifier will be described. The optical receiving device includes an optical fiber amplifier for amplifying the data optical signal, a monitoring device, and a device for regenerating data from the amplified data optical signal and for transmitting the data optical signal power Pd.
And a data optical receiver for detecting The optical fiber amplifier is composed of doped fibers 1-1 and 1-2.
An excitation light source 2, an optical multiplexer 5 for demultiplexing the input monitoring optical signal and multiplexing the excitation light and the data optical signal from the excitation light source 2, optical isolators 4-1 and 4-2, And an optical filter 12 for removing noise. The optical multiplexer / demultiplexer 5 has, for example, the configuration shown in FIG. The monitoring device is
A monitoring optical receiver for converting the demultiplexed input monitoring optical signal into an input monitoring electrical signal and detecting an input monitoring optical signal power; the input monitoring electrical signal; the input monitoring optical signal power; Controller 1 which receives data optical signal power and outputs monitoring information of the entire optical transmission system
0. The detection of the data optical signal power in the optical receiver can be realized by, for example, branching a part of the received data signal and measuring the power or the peak value. Alternatively, it can also be realized by measuring a direct current flowing through a photodiode (element for converting a data optical signal into an electric signal) built in the data optical receiver.

The controller determines whether the optical transmission line, the optical fiber amplifier, and the monitoring device are normal based on the observed values of the input monitoring optical signal power and the data optical signal power.
The judgment result is added to the input monitoring electric signal and output.
Specifically, Pw and Pd are observed by the controller, and when only the value of Pd deviates from the normal value, it is determined that the optical fiber amplifier in the optical receiver is abnormal, and only the value of Pw is the normal value. If it deviates from that, the monitoring optical receiver or the monitoring optical transmitter of the preceding optical repeater (wavelength approximately λp)
Is determined to be abnormal, and if both Pd and Pw deviate from the normal values, it is determined that the transmission path is abnormal. The reason for this determination is the same as in the case of the optical repeater.
Further, the controller can control the operation of the built-in optical fiber amplifier or the like based on the control signal added to the received input monitoring electric signal.

According to this embodiment, an effect is obtained that monitoring information of the entire optical transmission system can be obtained.

The effect of the present invention is not limited to the configuration of the present embodiment. For example, the above-described effects can be obtained regardless of the specific internal configuration of the optical multiplexer / demultiplexer as long as it can multiplex and demultiplex the two wavelengths λd and λp. Also,
Optical isolators can be placed in different places,
Even if the number used is different or not used, the above effect can be obtained. The method of exciting the doped fiber may be different from that of FIG. That is, the above-described effects can be obtained regardless of whether the pumping light travels in the forward direction, the reverse direction, or the bidirectional direction with respect to the data optical signal. The above-described effect can be obtained even when the number of excitation light sources is further increased. Further, even if the number of doped fibers is different from the case of FIG. 6, the above effect can be obtained. Further, the above-described effect can be obtained even when an optical component such as an optical filter is inserted.

FIG. 7 shows an embodiment of an optical transmission system to which the monitoring method and the monitoring information transfer method of the present invention are applied.
The system includes an optical transmission device according to the present invention, which converts data into a data optical signal, amplifies and outputs the data, and an optical transmission line (a first optical transmission line to an (N + 1) th optical transmission line,
Here, N is an integer of 1 or more, and an optical repeater of the present invention for amplifying the attenuated data optical signal (first optical repeater to N + th optical repeater).
1 optical repeater) and the optical receiver of the present invention that reproduces data after amplifying the data optical signal. In addition to the data, the optical transmission device needs information (parity check signal, other signals necessary for monitoring the optical repeater,
Information on other devices in the optical terminal, control signals for controlling each optical repeater, control signals for controlling optical receivers, control signals for controlling optical fiber amplifiers incorporated in each optical repeater and optical receiver, and the like. And the like, and output is light in which the data optical signal and the first monitoring optical signal are multiplexed. The first optical repeater amplifies the transmitted data optical signal, and adds new monitoring information and other necessary information to the transmitted first monitoring optical signal to form a second monitoring optical signal. And multiplexes the output data optical signal. Hereinafter, the second to N-th optical repeaters perform the same operation as the first optical repeater. In the optical receiving device, the transmitted data optical signal is received after amplification, and the data is reproduced. In addition, monitoring information on the optical fiber amplifier in the present optical receiving device is added to the (N + 1) th optical monitoring optical signal signal and output. I do.

According to this embodiment, there is an effect that monitoring information of the entire optical transmission system can be obtained with a simple configuration. At the same time, the operation of each device can be controlled based on the control signal added to the monitoring signal. The configuration of the optical transmission system is not limited to the above embodiment. For example, even if the optical transmission device does not include an optical fiber amplifier, the above-described effects relating to monitoring can be obtained by providing a monitoring optical transmitter, an optical multiplexer for multiplexing a monitoring optical signal and a data optical signal.
The same applies to the optical receiving apparatus. Even if an optical fiber amplifier is not built in, the above-mentioned effect on monitoring can be obtained by providing an optical multiplexer for splitting the (N + 1) th monitoring optical signal from the data optical signal.

FIG. 8 shows an optical fiber amplifier in the optical receiving apparatus shown in FIG. 6 in which the driving current of the pumping light source 2 is adjusted so that the data optical signal power input to the data optical receiver is substantially constant. An embodiment in the case where an automatic gain control circuit for controlling the gain of FIG. In the figure, a data optical receiver includes a photodiode, a resistor connected in series with the photodiode, an amplifier circuit for amplifying received data, a circuit for extracting timing from an output signal of the amplifier circuit, It comprises a circuit and a DC voltage detector for detecting a DC voltage generated in the resistor. The output of the identification reproducing circuit is reproduced data, and the output of the DC voltage detector is a voltage signal proportional to the data optical signal power. Therefore, if the voltage signal proportional to the data optical signal power is controlled to have a constant value, the power of the data optical signal input to the photodiode also becomes constant. To perform such control, an automatic gain control circuit
The control circuit outputs a control signal by detecting a difference between a signal proportional to the data light signal power and a reference signal, and a drive circuit that controls a current flowing to the excitation light source based on the control signal. The value of the control signal is set so that the difference becomes zero. If the difference becomes zero, the signal proportional to the data optical signal power is always constant (equal to the reference signal), and as a result, the power of the data optical signal input to the photodiode is also constant. When added to the present optical receiving device, an effect that the power of the input data optical signal to the data optical receiver can be set optimally regardless of the power fluctuation of the data optical signal input to the present optical receiving device can also be obtained. If the optical receiving device of FIG. 8 is applied to the optical transmission system of FIG. 7, the performance of the optical transmission system can be further improved.

FIG. 9 shows a second embodiment of the optical repeater of the present invention. In this embodiment, the optical multiplexer / demultiplexer 5-1 on the input side of the first embodiment shown in FIG. 1 is replaced with optical multiplexers 3-2 and 3-1 (the configuration is the same as that of the optical multiplexers 3-1 and 3-1 in FIG. 2). 3-2),
The optical multiplexer (3-2) demultiplexes the input monitoring optical signal from the optical signal (consisting of the data optical signal and the input monitoring optical signal) (using the optical multiplexer (3-2) as an optical demultiplexer). The data optical signal and the excitation light (the excitation light source 2-1) are output from the optical multiplexer 3-1.
Output from). Other configurations are the same as those in FIG. In this embodiment, the wavelength λp ′ of the pump light output from the pump light source 2-1 does not necessarily have to be equal to λp. For example, when λp is approximately 1.48 μm, λp ′ is approximately 0.98 μm.
m may be used. It is known that when the wavelength of the pump light is approximately 0.98 μm, the noise figure of the optical fiber amplifier can be lower than when the wavelength of the pump light is approximately 1.48 μm. Therefore, according to the present embodiment, the same effect as that of the first embodiment of the optical repeater can be obtained, and at the same time, the effect that the noise figure of the optical repeater can be reduced can be obtained. The same effect can be obtained by performing the same replacement (to the optical multiplexers 3-2 and 3-1) on the optical multiplexer / demultiplexer 5 of the optical receiver shown in FIG. That is, since the noise figure of the optical fiber amplifier can be reduced, the receiving sensitivity of the optical receiver can be improved. If the optical repeater and the optical receiver described here are applied to the optical transmission system of FIG. 7, the interval between the optical repeaters and the interval between the optical repeater and the optical receiver can be increased.

FIG. 10 shows a third embodiment of the optical repeater of the present invention. In this embodiment, the optical multiplexer / demultiplexer 5-2 on the output side of the second embodiment shown in FIG. 9 is replaced with optical multiplexers 3-2 'and 3-1' (the configuration is the optical multiplexer 3--3 in FIG. 9). 1 and 3-2), the optical multiplexer 3-2 'multiplexes the pump light source 2-2 in the opposite direction to the data optical signal, and the optical multiplexer 3-1' multiplexes the data optical signal and the output monitoring light. It combines signals. Other configurations are the same as those in FIG. In this embodiment, the excitation light source 2-1
(Wavelength λp ′) and the pumping light output from the pumping light source 2-2 (wavelength λp ″) are not necessarily the wavelength of the monitoring light signal.
It does not have to be equal to λw. For example, λp 'and λ
p ″ may be approximately 0.98 μm, and λw may be approximately 1.48 μm or approximately 1.60 μm.
p ′ and λp ″ (for example, approximately 1.
48 μm), λw and λp ″ may be equal (for example, approximately 1.48 μm), and λp ′ may be approximately 0.98 μm. As described above, when the wavelength of the excitation light is approximately 0.98 μm, the optical fiber It is known that the noise figure of the amplifier can be made smaller than the case where the wavelength of the pump light is about 1.48 μm, and the wavelength λw may be another value, for example, out of band (gain) of the optical fiber amplifier. Or a wavelength band having a low gain) and having a sufficiently low transmission loss of the transmission line optical fiber.Therefore, according to the present embodiment, the second wavelength of the optical repeater can be selected. The optical repeater having a smaller noise figure can be realized as compared with the embodiment.If the optical repeater of this embodiment is applied to the optical transmission system of FIG. In this case, The wavelength λw of Miko signals to unify in an optical transmission system, an optical multiplexer 3-2 'for the light demultiplexer 5 of the optical transmitting apparatus shown in FIG. 5 3
-1 ', and the optical multiplexer / demultiplexer 5 of the optical transmitter shown in FIG. 6 needs to be replaced with the optical multiplexers 3-2 and 3-1. If the optical transmitter, optical repeater, and optical receiver described here are applied to the optical transmission system of FIG. 7, the relay interval and the total transmission distance (total transmission distance from the optical transmitter to the optical receiver) are reduced. Can be longer.

FIG. 11 shows a fourth embodiment of the optical repeater of the present invention. In this embodiment, the doped fiber 1-2 on the output side is used to increase the output power of the optical repeater of the first embodiment.
The power of the pumping light supplied to is increased by bidirectional pumping. The number of excitation light sources is set to four in order to increase the power of the excitation light. Two of the four (excitation light source 2-2
1 and 2-2-2) are light sources for exciting the doped fiber 1-2 in the forward direction, and the respective output lights are polarization-synthesized (synthesis in the orthogonal polarization state) by the polarizing prism. The light is input to the doped fiber 1-2 via the optical multiplexer 3-1. On the other hand, the pump light sources 2-2-3 and 2-2-4 are light sources for pumping the doped fiber 1-2 in the opposite direction, and the respective output lights are polarized and synthesized by the polarizing prism, and the optical multiplexer is used. The signal is input to the doped fiber 1-2 via 5-2. Therefore, according to this embodiment, the same effect as that of the first embodiment of the optical repeater can be obtained, and at the same time, the effect that the output power of the optical repeater can be increased. The same effect can be obtained by performing the same bidirectional pumping on the doped fiber 1 of the optical transmitter shown in FIG. That is, the output power of the optical fiber amplifier can be increased. If the optical transmission device or the optical repeater described here is applied to the optical transmission system of FIG. 7, the interval between the optical repeaters and the interval between the optical transmitter and the optical repeater can be increased. However, even if the number of pumping light sources is less than four, if the number is two or more, the output power can be increased, and thus the relay interval can be lengthened. Also,
The wavelengths of the excitation light sources 2-2-1, 2, 3, and 4 are approximately 0.98 μ.
m, or approximately 1.48 μm, or both may be combined.

FIG. 12 shows a fifth embodiment of the optical repeater of the present invention. The difference between the first embodiment of the optical repeater and the present embodiment is that (1) the wavelength of the pump light source 2-1 is λp ′ (≠ λp), and (2) it is multiplexed with the data optical signal (wavelength λd). Of the input monitoring optical signal (wavelength λp)
The multiplexing of the pumping light output from 1 is performed by the optical multiplexer / demultiplexer 13 in two points. As the wavelengths λd, λp, and λp ′, for example, approximately 1.55 μm, approximately 1.48 μm, and approximately 0.98 μm are appropriate wavelength settings. Where λ
p may be another wavelength. For example, another wavelength outside the band of the optical fiber amplifier may be used. FIG. 13 shows an example.
The configuration of an optical multiplexer / demultiplexer 13 using a dielectric multilayer filter and the input / output relationship of light are shown. The data optical signal and the input monitoring optical signal input from the first port are transmitted through the dielectric multilayer filter, and the latter are reflected. The reflected input monitoring optical signal is output from the fourth port and input to the monitoring optical receiver. On the other hand, the excitation light is input from the second port, reflected by the dielectric multilayer filter, multiplexed with the transmitted data optical signal, and output from the third port. That is, the dielectric multilayer filter transmits the wavelength λd and transmits the wavelengths λp and λp.
Reflects p '. Such an input / output relationship can be realized by giving the dielectric multilayer filter a wavelength dependence of the reflectance and the transmittance as shown in FIG. 14A, for example. That is, for a wavelength of about 1.5 μm or less, it has reflection (reflectance is about 1 and transmittance is about 0).
For a wavelength of 5 μm or more, transmission characteristics (a transmittance is approximately 1 and a reflectance is approximately 0) may be provided. However, if the wavelength λd is transmitted and the wavelengths λp and λp ′ are reflected, characteristics of the reflectance and the transmittance other than those in FIG. 14A may be used. Further, a filter other than the dielectric multilayer filter may be used. If the above-described optical multiplexing and optical demultiplexing are realized with respect to the wavelength λd and the wavelengths λp and λp ′, the relationship between reflection and transmission may be reversed. 14 (b) and (c)
13 shows transmittance characteristics of the optical filter 14 in FIG. When the characteristics of the reflectance and the transmittance of the optical multiplexer / demultiplexer 13 are incomplete, the optical filter 14 transmits a part of the excitation light having the wavelength λp ′ through the dielectric multilayer filter, as shown in FIG.
Is provided to prevent output from the fourth port and input to the monitoring optical receiver. FIG. 14 as an example
If the optical filter 14 has the transmittance characteristic as shown in (b) or (c), the wavelength λp 'can be removed. Of course, other transmittance characteristics may be used as long as the transmittance is high near the wavelength λp. Further, if the imperfection of the optical multiplexer / demultiplexer 13 is removed and the input / output relationship as shown in FIG. 13A is substantially realized, the optical filter 14 does not need to be used. The optical filter 14 does not need to be used even when the monitoring optical receiver does not respond to the wavelength λp ′ (the light receiving sensitivity is almost zero). According to this embodiment, the same effect as that of the first embodiment of the optical repeater can be obtained, and at the same time, the pumping wavelength of about 0.98 μm can be used, so that the noise figure of the optical repeater can be reduced. . Further, since the demultiplexing of the input monitoring optical signal and the multiplexing of the pump light of approximately 0.98 μm can be performed by one optical multiplexer / demultiplexer, the optical components are more improved than in the second embodiment of the optical repeater (FIG. 9). At the same time, the number of points can be reduced, and at the same time, the attenuation of the data optical signal can be reduced. If the optical repeater of FIG. 12 is applied to the optical transmission system of FIG.
The effect that the performance of the optical transmission system can be further improved is also obtained. The optical fiber amplifier in the optical repeater of the present embodiment may be bidirectionally pumped. In that case, the effect that the noise figure can be further reduced and the gain can be further improved can be obtained.

FIG. 15 shows a sixth embodiment of the optical repeater of the present invention. The difference between the fifth embodiment of the optical repeater and the present embodiment is that (1) the wavelength of the pump light source 2-2 is also λp ′ (≠ λp), and (2) output monitoring to a data optical signal (wavelength λd). The multiplexing of the optical signal (wavelength λp) and the pump light output from the above 2-2 is performed by the optical multiplexer / demultiplexer 13-2. The optical multiplexer / demultiplexer 13-1 in the figure is the same as 13 in FIG. The method and configuration of the optical multiplexer / demultiplexer 13-2 are the same as those of the fifth embodiment, but the input / output relationship of light is as shown in FIG. That is, the data optical signal is input from the first port, passes through the dielectric multilayer filter, and is output to the third port. Excitation light is input from the fourth port, is reflected by the dielectric multilayer filter, and is output to the first port. The output monitoring optical signal is input from the second port, reflected by the dielectric multilayer filter, and output to the third port. The optical filter 14-1 is used for the reason described in the fifth embodiment, and may not be used in some cases. Similarly, the optical filter 14-2 is provided to prevent a part of the excitation light having the wavelength λp 'from passing through the dielectric multilayer filter and entering the monitoring optical transmitter. Otherwise, it may not be used. According to this embodiment, the same effect as that of the fifth embodiment of the optical repeater can be obtained, and at the same time, the noise factor of the optical repeater can be further reduced because the wavelength of the pump light on the output side is approximately 0.98 μm. The effect is obtained. Further, since the output monitoring optical signal and the pump light can be multiplexed into the data optical signal by one optical multiplexer / demultiplexer, the number of optical components can be reduced as compared with the third embodiment (FIG. 10) of the optical repeater. At the same time, the effect that the attenuation applied to the data optical signal can be reduced is obtained. FIG. 7 shows the optical repeater of FIG.
When applied to the optical transmission system, the noise figure of the optical repeater is further reduced, so that the interval between the optical repeaters can be further lengthened, and the effect that the performance of the optical transmission system can be further improved can be obtained. The optical fiber amplifier in the optical repeater of the present embodiment may be bidirectionally pumped. In that case, the effect that the noise figure can be reduced and the gain can be improved can also be obtained.

FIG. 17 shows another embodiment of the optical receiver. The difference between the embodiment of the optical receiver shown in FIG. 6 and this embodiment is that (1) the wavelength of the pump light source 2 is λp ′ (≠ λp), and (2) it is multiplexed with the data optical signal (wavelength λd). The optical multiplexer / demultiplexer 13-1 combines the demultiplexing of the input monitoring optical signal (wavelength [lambda] p) transmitted and the pumping light output from the above 2 with the optical multiplexer / demultiplexer 13-1. Wavelengths λd, λp, and λp ′
Is the same as that of the fifth embodiment of the optical repeater, and the same is true of the method of realizing the optical multiplexer / demultiplexer 13-1. Further, the same optical filter 14 as that in FIG. 12 is used for the same reason. According to this embodiment, the same effect as the embodiment of the optical receiver shown in FIG. 6 is obtained, that is, the effect that monitoring information of the entire optical transmission system can be obtained, and at the same time, the wavelength of the pump light is set to about 0.98 μm. Since it can be used, the effect that the noise figure of the optical fiber amplifier in the optical receiver can be reduced can be obtained. When the optical receiver of FIG. 17 is applied to the optical transmission system of FIG. 7, the noise figure of the optical receiver is reduced, so that the interval between the optical repeater and the optical receiver can be increased, and the performance of the optical transmission system is improved. There is also an effect that it can be performed. The optical fiber amplifier in the optical receiver according to the present embodiment may be bidirectionally pumped. In that case, the effect that the noise figure can be further reduced and the gain can be further improved can be obtained.

FIG. 18 shows another embodiment of the optical transmitter. The difference between the embodiment of the optical transmitter shown in FIG. 5 and this embodiment is that (1) the wavelength of the pump light source 2-2 is set to λp ′ (≠ λp).
(2) The output monitoring optical signal (wavelength λp) to the data optical signal (wavelength λd) and the multiplexing of the pump light output from 2-2 are performed by the optical multiplexer / demultiplexer 13-2. It is. The settings of the wavelengths λd, λp, and λp ′ are the same as in the fifth embodiment of the optical repeater. The method of realizing the optical multiplexer / demultiplexer 13-2 is the same as that of the sixth embodiment of the optical repeater. According to this embodiment, the same effect as that of the embodiment of the optical transmitting apparatus shown in FIG. 5 is obtained, and at the same time, approximately 0.98 μm can be used as the pumping light wavelength. This has the effect of reducing the index. The wavelength of the pump light source 2-1 may be either λp ′ or λp, but the noise figure of the optical fiber amplifier can be lower in the case of λp ′. If the optical receiver of FIG. 18 is applied to the optical transmission system of FIG. 7, the noise figure of the optical transmitter is reduced, so that the interval between the optical transmitter and the optical repeater can be increased, and the performance of the optical transmission system is improved. There is also an effect that it can be performed. The optical fiber amplifier in the optical transmitter according to the present embodiment may be bidirectionally pumped. In that case, the effect of reducing the noise figure and improving the gain and output power can also be obtained.

The configuration of the present invention is not limited to the above embodiment. Further, even if the optical transmission line is branched and the data optical signal (combined with the monitoring optical signal) is distributed to a plurality of optical receiving devices, the above-described effect can be obtained. Further, the above effect can be obtained even when the traveling direction of the monitoring optical signal is opposite to the traveling direction of the data optical signal. In this case, the monitoring optical transmitter and the monitoring optical receiver in each optical repeater are exchanged, the monitoring optical transmitter of the optical transmitting device is replaced with the monitoring optical receiver, and the monitoring of the optical receiving device is performed. It is necessary to replace the monitoring optical transmitter with a monitoring optical transmitter. In addition, the above-described effect can be obtained even if the determination of abnormality performed in the optical transmission device, each optical repeater, and the controller of the optical reception device is collectively performed in the optical reception device. In this case, the optical transmission device and each optical repeater need only add the observed power value as monitoring information and transmit it. The combination of the wavelengths of the data optical signal, the pumping light, and the monitoring optical signal may be used by appropriately combining the wavelengths of the above embodiments. The effect of the present invention can be obtained even if a plurality of wavelengths of the monitoring optical signal are used in the optical fiber transmission system. Further, the wavelength of the pump light may be different for each optical repeater. Further, the wavelength of the data optical signal may be approximately 1.3 μm. In this case, the gain can be imparted to the doped fiber by setting λp to a value in the vicinity of 1 μm, for example, and using neodymium or the like as an additive to the doped fiber. Further, the operations of the optical receivers of FIGS. 8 and 17 and the optical repeaters of FIGS. 9, 10, 11, 12, and 15 can also be controlled by the control signal transmitted in addition to the monitoring information. Further, an optical transmission system may be configured by appropriately combining the optical transmitter, the optical repeater, and the optical receiver of the above-described embodiment. In addition, the optical multiplexer, optical demultiplexer, and optical filter incorporated in the optical multiplexer / demultiplexer used in each of the embodiments can be used as an optical multiplexer, an optical demultiplexer, and an optical filter. The same effect can be obtained even if the operation is performed according to a principle different from the principle described in. For example, when the optical filter is a dielectric multilayer filter, the relationship between transmission and reflection for each wavelength may be reversed. When the optical filter is a directional coupler type, the wavelength relationship between coupling and non-coupling may be reversed. The same effect can be obtained even when the wavelength of the monitoring light signal is approximately 1.3 μm. Further, a plurality of wavelengths of the monitoring optical signal may be mixed in the optical transmission system.

In an optical fiber transmission system using an optical fiber amplifier as described above, since the power of a data optical signal input to a transmission line optical fiber is high (several milliwatts or more), stimulated Brillouin scattering occurs in the optical fiber. (S
(BS) phenomenon may occur, causing a problem that the data optical signal is reflected and returned to the input terminal. SB
S is a phenomenon that occurs when the power of one optical frequency exceeds the SBS threshold unique to the optical fiber. For example, the power is distributed to a plurality of optical frequencies and the power at any optical frequency is higher than the SBS threshold. It is known that the SBS will not occur if it is not exceeded. Therefore, to solve the above problem, for example, an SBS suppressing device having a configuration as shown in FIG. 19 is connected to the output end of an optical transmission device or an optical repeater, and the output light is input to a transmission line optical fiber. Can be solved. The SBS suppressing apparatus in FIG. 19 includes at least a light source for phase modulation in an optical fiber, a signal source for modulation for modulating the light intensity of the light source, and an optical multiplexer for multiplexing the intensity-modulated pump light into a data optical signal. Is done. In this configuration, a change in the refractive index utilizing a nonlinear optical phenomenon is generated in the optical fiber by changing the intensity of the output light from the phase modulation light source in the optical fiber. If there is a change in the refractive index, the data optical signal is subjected to optical phase modulation and the signal spectrum is expanded. As the spectrum spreads, the power can be distributed over multiple optical frequencies. Therefore, even if the power exceeds the SBS threshold at a certain optical frequency in the data optical signal, the power of the optical frequency is distributed to a plurality of frequencies by using the present apparatus, and each power is set to the SBS.
Since it can be lower than the threshold value, the occurrence of SBS can be avoided. FIG. 20 shows a waveform example of a signal of each unit. FIG. 3A shows the modulation current of the phase modulation light source in the optical fiber output from the modulation signal source, and the current value periodically fluctuates up and down. The optimum period is determined by the spectrum and intensity of the data optical signal, the characteristics of the optical fiber, and the like. At this time, the lower current value may be zero. FIG. 3B shows intensity-modulated light, the intensity of which changes in accordance with the signal of FIG. At this time, the lower light intensity may be zero. It is known that the amount of change in the refractive index caused by the nonlinear optical phenomenon in an optical fiber depends on the amount of change in the light intensity. Therefore, the amount of change in light intensity can be increased by increasing the difference between the maximum value and the minimum value of the light intensity. FIG. 20C is a diagram showing the data optical signal input to the transmission line optical fiber by the electric field amplitude. When the data is “0”, the amplitude is substantially zero and the data is “1”. In the case of, there is no sudden change in the phase. On the other hand, FIG. 6D shows the electric field amplitude of the data optical signal output from the optical fiber. Phase modulation is performed in the optical fiber corresponding to the intensity change in FIG. Among the data '1' in the figure, the underlined '1' has undergone phase modulation, and in the case of the figure, has undergone a phase change of about 180 degrees. As a result, the signal spectrum of the data optical signal is broadened, and therefore, the occurrence of SBS is suppressed.
That is, the use of the device having the above configuration has an effect that the power of the data optical signal that can be input to the transmission line optical fiber can be increased. As described above, FIG.
The larger the change in the light intensity at 0 (b), the larger the phase modulation can be applied to the data optical signal. The required amount of variation depends on the spectrum and intensity of the data optical signal, the characteristics of the optical fiber, and the like, but a variation of approximately 10 milliwatts or more is required as a guide. Further, as the wavelength of the excitation light, for example, approximately 1.48 μm can be used.

FIG. 21 shows the function of the SBS suppression in FIG.
An embodiment in the case where the optical transmission device is added to the optical transmission device of FIG. In the present embodiment, the monitoring optical transmitter of FIG. 5 is also used as a light source for phase modulation in an optical fiber for SBS suppression, and the effect of monitoring in FIG. 5 and the effect of SBS suppression of FIG. An optical transmission device having both of the above is realized. The configuration difference from the transmission apparatus of FIG. 5 is that a signal source for modulation and a circuit for superimposing a modulation signal from the signal source on a monitoring electric signal are added. Further, the monitoring optical transmitter also serves as a light source for phase modulation in the optical fiber, and is denoted by reference numeral 15 in this embodiment. FIG. 22 shows an example of a signal waveform of each unit. FIG.
Is a monitoring electric signal output from the controller and is a low-speed digital signal (an analog signal may be used). FIG. 2B shows a monitoring electric signal on which a modulation signal from a modulation signal source is superimposed. The frequency of the superimposed modulation signal needs to be set sufficiently higher than the transmission speed of the monitoring electric signal and the band of the monitoring optical receiver. FIG.
5 is a monitoring light signal output from the control signal 5, and a modulated signal is superimposed thereon. Since the light intensity is changed by the superimposed modulation signal, the data optical signal can be phase-modulated.
S can be suppressed. Furthermore, since the band of the monitoring optical receiver of the subsequent optical repeater (or optical receiving device) does not follow the frequency of the modulation signal, only low-speed monitoring information can be extracted and received from the monitoring optical signal. . Therefore, according to the present embodiment, there is obtained an effect that an optical transmission device having both the effect on monitoring in FIG. 5 and the effect on SBS suppression in FIG. 19 can be realized with a simple configuration.

FIG. 23 shows the function of the SBS suppression in FIG.
An embodiment in the case of adding to the optical repeater of FIG. In the present embodiment, the monitoring optical transmitter of FIG. 1 is also used as a light source for phase modulation in an optical fiber for SBS suppression, and the effects related to the monitoring of FIG. 1 and the effects of SBS suppression of FIG. An optical transmission device having both of the above is realized. The configuration difference from the transmission apparatus of FIG. 1 is that a modulation signal source and a circuit for superimposing a modulation signal from the signal source on a monitoring electric signal are added. Further, the monitoring optical transmitter also serves as a light source for phase modulation in the optical fiber, and is denoted by reference numeral 15 in this embodiment. As in the case of FIG. 21, the modulation signal from the modulation signal source is superimposed on the monitoring electric signal, and as a result, the modulation signal is also superimposed on the output monitoring light signal from 15. FIG.
SBS can be suppressed based on the same principle as in the case of 1. In addition, the subsequent optical repeater (or optical receiver)
Since the band of the monitoring optical receiver does not follow the frequency of the modulated signal, only low-speed monitoring information can be extracted from the monitoring optical signal and received. Therefore, according to the present embodiment, there is obtained an effect that an optical repeater having both the effect on monitoring in FIG. 1 and the effect on SBS suppression in FIG. 19 can be realized with a simple configuration.

If the apparatus of FIG. 21 or FIG. 23 is applied to the system of FIG. 7, the occurrence of SBS can be suppressed, so that the input power of the data optical signal to the optical fiber can be increased, and as a result, the transmission distance can be extended. The effect is also obtained.

[0039]

As described above, according to the present invention, the monitoring of the optical transmitter, the optical repeater, the optical receiver, and the optical transmission line connecting them, and the transfer of the monitoring information are performed to each optical fiber amplifier to reduce the output power. This can be achieved without causing the problem.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of an optical repeater;

FIG. 2 is a basic configuration diagram of an optical fiber amplifier repeater using an optical fiber amplifier;

FIG. 3 is a diagram showing an operation of the optical multiplexer.

FIG. 4 is a diagram showing the operation of an optical multiplexer / demultiplexer.

FIG. 5 is a diagram illustrating an embodiment of an optical transmission device.

FIG. 6 is a diagram illustrating an embodiment of an optical receiver.

FIG. 7 is a diagram illustrating an embodiment of an optical transmission system.

FIG. 8 is a diagram illustrating an embodiment of an optical receiver having an automatic gain control circuit.

FIG. 9 is a diagram showing a second embodiment of the optical repeater.

FIG. 10 is a diagram showing a third embodiment of the optical repeater;

FIG. 11 is a diagram illustrating a fourth embodiment of the optical repeater.

FIG. 12 is a diagram illustrating a fifth embodiment of the optical repeater.

FIG. 13 is a diagram illustrating a configuration of an optical multiplexer / demultiplexer and an input / output relationship of light.

FIG. 14 is a diagram showing the wavelength dependence of the reflectance and transmittance of each filter.

FIG. 15 is a diagram illustrating a sixth embodiment of the optical repeater.

FIG. 16 is a diagram illustrating a configuration of an optical multiplexer / demultiplexer and an input / output relationship of light.

FIG. 17 is a diagram illustrating another embodiment of the optical receiver.

FIG. 18 is a diagram illustrating another embodiment of the optical transmitter.

FIG. 19 is a diagram showing an embodiment of a stimulated Brillouin scattering (SBS) suppressor.

FIG. 20 is a diagram showing signal waveforms at various parts in FIG. 19;

FIG. 21 is a diagram illustrating an embodiment of an optical transmission device having an SBS suppressing function.

FIG. 22 is a diagram showing signal waveforms at various parts in FIG. 21;

FIG. 23 is a diagram illustrating an embodiment of an optical repeater having an SBS suppressing function.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Doped fiber, 2 ... Excitation light source, 3 ... Optical multiplexer, 4
... optical isolator, 5 ... optical multiplexer / demultiplexer, 6 ... optical receiver for monitoring, 7 ... power splitter, 8 ... optical filter, 9 ... power monitor, 10 ... controller, 11 ... optical transmitter for monitoring, 12 ... optical filter Reference numeral 13 denotes an optical multiplexer / demultiplexer, 14 denotes an optical filter, 15 denotes a monitoring optical transmitter and a light source for phase modulation in an optical fiber.

[Procedure amendment]

[Submission date] March 8, 2001 (2001.3.8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Optical transmitter and optical receiver

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04J 14/00 H04B 9/00 J 14/02 E H04B 17/00 17/02 (72) Inventor Yukio Nakano 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Hiroyuki Nakano 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Ryoji Takeyari Tokyo Hitachi, Ltd. Central Research Laboratory, Hitachi, Ltd. (72) Inventor Hironari Matsuda 4-6-1, Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd.

Claims (5)

[Claims] Amplifying an optical data signal using an optical amplifier; transmitting an optical supervisory signal having a wavelength of approximately 1.48 μm; and wavelength-multiplexing the amplified optical data signal and the optical supervisory signal. And transmitting the monitoring information to the optical monitoring signal. 2. A monitoring system comprising the steps of: amplifying an optical data signal using an optical amplifier; transmitting an optical monitoring signal; and wavelength-multiplexing the amplified optical data signal and the optical monitoring signal. In the method for transmitting information, the optical supervisory signal includes supervisory information of an optical amplifier, and the wavelength of the optical supervisory signal is outside the amplification band of the doped fiber, and the wavelength in the transmission line is substantially equal to the optical data signal loss. A transmission method of monitoring information, characterized in that: 3. A monitoring system comprising the steps of: amplifying an optical data signal using an optical amplifier; transmitting an optical monitoring signal; and wavelength-multiplexing the amplified optical data signal and the optical monitoring signal. A method for transmitting information, wherein the optical supervisory signal includes supervisory information of an optical amplifier, the wavelength of which is in a range of 1.48 μm to 1.60 μm,
In addition, a method of transmitting monitoring information, which is outside the amplification band of the optical amplifier. 4. A step of separating an optical data signal transmitted by wavelength division multiplexing from an optical monitoring signal for monitoring an optical transmission system, a step of transmitting pump light, and a step of transmitting the separated optical data signal. Wavelength multiplexing the pumping light, optically amplifying the separated optical data signal, and receiving the separated optical monitoring signal, wherein the wavelength of the optical monitoring signal is A method for receiving monitoring information, characterized in that a loss in a transmission path outside a band is substantially the same as a loss of an optical data signal. 5. A method for separating an optical data signal transmitted by wavelength division multiplexing from an optical monitoring signal for monitoring an optical transmission system, transmitting an excitation light, and the separated optical data signal. Optically amplifying the optical data signal, wavelength-multiplexing the amplified optical data signal and the pump light in mutually opposite directions, and receiving the separated optical monitoring signal, wherein the wavelength of the optical monitoring signal is A method of receiving monitoring information, wherein a loss in a transmission line outside a band of optical amplification is substantially equal to a wavelength of a loss of an optical data signal.