JP3503600B2 - Optical transmitting device and optical receiving device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver using an optical fiber amplifier and, more particularly, to its monitoring and monitoring information transfer method.

[0002]

Fiber optic amplifiers may be used in future fiber optic transmission systems. In the system, an optical transmitter (including a data optical transmitter and an optical fiber amplifier for converting data into a data optical signal), an optical repeater (including an optical fiber amplifier), an optical receiver (an optical fiber amplifier and a data optical signal) It is essential to monitor a data optical receiver for reproducing data from the above) and an optical transmission line connecting them, and transfer the obtained monitoring information to the optical terminal station. Conventionally, the monitoring information transfer technique is described in, for example, Japanese Patent Laid-Open No. 3-214936. In the conventional supervisory information transfer technology, (1) the optical data amplifier and the supervisory optical signal multiplexed with the optical data signal are simultaneously optically amplified by an optical fiber amplifier in each optical repeater,
Alternatively, (2) a method of branching the excitation light source into two and using one of them as a monitoring light signal has been used.

[0003]

Assuming an optical fiber amplifier whose output is in a saturated state and comparing it with a case where only a data optical signal is input to the optical fiber amplifier, in the above-mentioned prior art (1), a monitoring optical signal is also generated. At the same time, the input power to the optical fiber amplifier lowers the gain and the output power of the data optical signal decreases. Further, similarly in the above-mentioned related art (2), the pumping light power is lowered because the pumping light is branched for the monitoring light signal, and the output power of the optical fiber amplifier is also lowered because the gain is also lowered. Usually, in the optical repeater, the built-in optical fiber amplifier is often used 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-mentioned conventional technique is problematic because the output power decreases.

The object of the present invention is to solve the above problems,
That is, it is necessary to realize the monitoring information transfer of the optical fiber transmission system using the optical fiber amplifier without lowering the output power of the optical fiber amplifier, and further to realize the monitoring of the system. The optical fiber amplifier is assumed to have at least an optical fiber doped with an additive (doped fiber) and a pumping light source that outputs light (pumping light) having a wavelength λp that pumps the doped fiber.

[0005]

The above-mentioned problems can be solved by carrying out the following 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 that configure the optical fiber transmission system as follows.
That is, (1) the monitoring information transfer from the optical transmitting device is performed by monitoring the electric signal for monitoring including the monitoring information (hereinafter,
A monitoring optical transmitter for converting a monitoring electric signal (abbreviated as a monitoring electrical signal) into an optical signal (wavelength approximately λp, hereinafter abbreviated as an output monitoring optical signal) and a data optical signal that is arranged after the doped fiber and is amplified. This can be realized by providing an optical multiplexer / demultiplexer that simultaneously combines the pumping light in the same direction and the output monitoring optical signal in the same direction as the data optical signal. (2) The supervisory information transfer in the optical repeater is carried out in the optical repeater in front of the doped fiber, and the supervisory optical signal 1 (wavelength approximately λp, hereinafter At the same time as demultiplexing the input monitoring optical signal, the first pumping light (wavelength λ
p, which is output from the first pumping light source) in the same direction as the data optical signal, and a monitoring optical receiver that converts the input monitoring optical signal into an input monitoring electrical signal. A controller that adds monitoring information about the optical repeater to the input monitoring electrical signal and outputs an output monitoring electrical signal; and the output monitoring electrical signal is a monitoring optical signal 2 (wavelength approximately λp, hereinafter abbreviated as output monitoring optical signal). And a second optical pumping light (wavelength λp, output from the second optical pumping light source) in the opposite direction to the amplified optical data signal arranged after the doped optical fiber and the monitoring optical transmitter for converting into This can be realized by providing an optical multiplexer / demultiplexer that simultaneously multiplexes the output monitoring optical signal in the same direction as the data optical signal. Further, (3) the reception of the monitoring information in the optical receiving device is arranged in the optical receiving device in front of the doped fiber, and the monitoring optical signal (wavelength approximately λp) transmitted after being multiplexed with the data optical signal is sent. , Optical input / output optical signal), and an optical multiplexer / demultiplexer that simultaneously splits pumping light in the same direction as the data optical signal and a monitoring light that converts the input monitoring optical signal into an input monitoring electrical signal. It can be realized by providing a receiver. 2. Monitoring of the optical transmitters, the optical repeaters (one or more), the optical receivers, and the transmission lines that connect them to the optical fiber transmission system can be realized as follows. That is, (1) monitoring of an optical transmitter is performed by a power splitter that branches a part of the output light of the device and an optical filter that extracts only a data optical signal from one output light of the power splitter in the optical transmitter. And a power monitor for detecting the power Pd of the extracted data optical signal, and the controller observes Pd and at the same time, if the value of Pd deviates from the normal value, the controller judges that the optical transmitter is abnormal and warns. This can be realized by generating a signal (hereinafter, the observed value of Pd, the warning signal, etc. are referred to as monitoring information in the optical transmitter).
(2) The monitoring of the transmission line and the optical repeater connected after the transmission line detects the power Pw of the input monitoring optical signal demultiplexed by the monitoring optical receiver, and at the same time, in the optical repeater,
A power splitter that splits a part of the output light of the device, an optical filter that extracts only a data optical signal from one output light of the power splitter, and a power monitor that detects the power Pd of the extracted data optical signal. The controller observes Pw and Pd, and at the same time, if only the value of Pd deviates from the normal value, it is judged 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 determined that the transmission line is abnormal,
This can be realized by generating warning signals (hereinafter, the observed values of Pd and Pw, the warning signals, etc. are referred to as monitoring information in the optical repeater). Furthermore, (3) the monitoring of the transmission line and the optical receiving device connected after the transmission line 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 the controller further detects Pw and Pw.
At the same time as observing d, if only the value of Pd deviates from the normal value, it is judged that the optical fiber amplifier in the optical receiving device is abnormal, and if only the value of Pw deviates from the normal value, it is for monitoring. It is judged that the optical receiver or the monitoring optical transmitter (wavelength approximately λp) of the preceding optical repeater is abnormal, and Pd and Pw
If both of the values deviate from the normal values, it can be realized by determining that the transmission line is abnormal and generating a warning signal (hereinafter, the observed values of Pd and Pw, the warning signal, etc., can be realized in the optical receiver. Called monitoring information).

[0006]

According to the above means 1, the supervisory optical signal sent from the optical transmitter is received by each optical repeater, and after the supervisory information is added, the supervisory optical signal is sent again as a supervisory optical signal. Since it reaches and is received by the receiving device, it is possible to transfer the monitoring optical signal carrying the monitoring information on the optical transmitting device, each optical repeater and the transmission path to the optical receiving device.
At this time, since each optical fiber amplifier inputs only the data optical signal, there is no decrease in output power that would occur when the conventional technique is used.

According to the above means 2, (1) the optical transmitter can detect the power Pd of the data optical signal output by itself, so that it can monitor its own abnormality by observing its value, and (2) The optical repeater simultaneously transmits the power Pd of the data optical signal (passes through the transmission line and the optical fiber amplifier in the optical repeater) output by itself, and simultaneously transmits the supervisory optical signal (output from the supervisory optical transmitter in the preceding stage). , The power Pw of the optical receiver for monitoring (detected by the monitoring optical receiver) can also be detected.
The transmission line, optical fiber amplifier,
And, the abnormality of the monitoring optical receiver or the monitoring optical transmitter of the preceding stage can be monitored respectively, and (3) the optical receiving device receives the data optical signal (transmission path and the optical fiber in the optical receiving device) which it receives. At the same time as the power Pd of passing through the amplifier, the power Pw of the sent monitoring optical signal (output from the preceding monitoring optical transmitter, passing through the transmission line, detected by the monitoring optical receiver) can be detected. By observing these powers, it is possible to monitor the abnormality of the transmission line, the optical fiber amplifier, and the monitoring optical receiver or the preceding monitoring optical transmitter. That is, monitoring of the optical transmitter, 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 sake of explanation, FIG. 2 shows a typical configuration example of a relay device that can be realized by using an optical fiber amplifier. The input to this 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 a doped fiber) 1-1 and 1-2 doped with erbium (Er) and a pumping light source (wavelength λp) 2 which outputs a pumping light that gives a gain to the doped fiber. 1, 2-2
Optical multiplexers (3 terminals) 3-1 and 3-2 for multiplexing the data optical signal and the pumping 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 comprises (a) an optical filter having a dielectric multi-layered film whose reflectance has wavelength dependence on its surface, and (b) a directional coupler using two optical fibers. It can be realized and is commercially available. FIG. 3 shows a configuration example of the optical multiplexer 3-1 realized by using the dielectric multilayer filter.
The dielectric multi-layer film filter in the optical multiplexer is set so that the reflectance for light of wavelength λd is almost zero and the reflectance for light of wavelength λp is almost 100%. . 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 pumping light of wavelength λp is input from the second port, the pumping light is reflected by the filter and is also output to the third port. As a result, as shown in FIG. 3 (1), the combined light obtained by combining the optical signals of both wavelengths is obtained from the third port. That is, the data optical signal and the pumping light can be multiplexed by using the present optical multiplexer. By the same principle,
When the multiplexed light composed of the data optical signal of wavelength λd and the 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. 3 (2). And the monitoring light signal is reflected. That is, the combined light can be demultiplexed. Therefore, as shown in FIG. 4 (1), if a fourth port is newly provided in the present multiplexer to make an optical multiplexer / demultiplexer with four terminals, a single optical multiplexer / demultiplexer can be used to convert data optical signals. It is possible to demultiplex a monitoring optical signal from an input multiplexed light composed of a monitoring optical signal and output it to the fourth port, and at the same time to multiplex the data optical signal and the pumping light and output the combined light from the third port. it can. In the configuration of FIG. 4 (1), if pumping light of wavelength λp is input from the fourth port and a monitoring optical signal of wavelength λp is input from the second port, pumping combined in the opposite direction to the data optical signal is performed. At the same time that light is output 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 (input side optical multiplexer / demultiplexer) having the configuration (1) is replaced and the optical multiplexer 3-2 is replaced with the optical multiplexer / demultiplexer having the configuration shown in FIG. A monitoring optical signal can be demultiplexed by an optical multiplexer / demultiplexer on the input side from the optical signal (combined light of the data optical signal and the monitoring optical signal) input to the Can be output. That is, the optical fiber for transmitting the data optical signal can be used to transfer the monitoring information sent from the optical repeater (or the optical terminal station) in the preceding stage to the optical repeater (or the optical terminal station) in the subsequent stage. .

As described above, according to the present invention, the optical multiplexer / demultiplexer for multiplexing the pumping light into the doped fiber is used for multiplexing and demultiplexing the monitoring optical signal. It is possible to achieve the effect that the monitoring of the receiving device and the optical transmission line connecting them and the transfer of the monitoring information can be realized without causing a decrease in output power in each optical fiber amplifier.

[0012]

1 shows a first embodiment of an optical repeater according to the present invention. This device consists of 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 the input monitoring optical signal from the optical signal (composed of the data optical signal and the input monitoring optical signal) input to the optical repeater and simultaneously multiplexes the pumping 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 combines the output monitor optical signal output from the monitor optical transmitter with the amplified data optical signal and outputs the amplified data optical signal, and simultaneously combines the pump light in the opposite direction. The monitoring device splits the demultiplexed input monitoring optical signal into an input monitoring electrical signal and, at the same time, monitors the optical receiver 6 for detecting the input monitoring optical signal power Pw and a part of the output light of the optical repeater. Power splitter 7
An optical filter 8 that passes only the data optical signal of the branched light; a power monitor 9 that detects the power Pd of the data optical signal that has passed through the optical filter (hereinafter abbreviated as data optical signal power); An input monitoring electrical signal, a controller 10 that receives the input monitoring optical signal power, and the data optical signal power, and a monitoring optical transmission that converts the output monitoring electrical signal output from the controller into the output monitoring optical signal. It is configured with a container 11. The detection of the input monitoring optical signal power Pw in the monitoring optical receiver 6 is performed by, for example, measuring a direct current flowing through a photodiode (element for converting the input monitoring optical signal into electricity) built in the monitoring optical receiver. It can be realized by doing.

As the wavelength λd of the data optical signal, for example, 1.
Considering light in the 55 μm band and using an optical fiber doped with erbium or the like as an additive as a doped fiber, a gain can be imparted to the doped fiber by using pumping light having a wavelength near 1.48 μm (= λp). . The optical fiber used as a transmission line has a wavelength of 1.48 μm.
Since there is a transmission loss of about the same as the wavelength of 1.55 μm in the vicinity, the output monitoring optical signal of the wavelength of about 1.48 μm, which is output after being multiplexed with the data optical signal, is the same as the data optical signal in the next optical relay. The device (or the optical receiving device) can be reached. However, the wavelengths of λd and λp need not be limited to the above wavelengths.

The controller judges whether or not the optical transmission line, the optical fiber amplifier, and the monitoring device are normal from 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 as the output monitoring electric signal. Specifically, the controller observes Pw and Pd, 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 is deviated from the above, 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 is deviated, it is determined that the transmission line is abnormal. This is because the data optical signal passes through both the transmission line and the optical fiber amplifier in the optical repeater, while the input monitoring optical signal sent through passes through the transmission line only. It can be judged that there is an abnormality in the transmission line only when is deviated from the normal value,
This is because if either one deviates from the normal value, it can be determined that the remaining portion is abnormal. Further, the controller has necessary information (a signal necessary for monitoring the optical repeater, information about other devices in the optical terminal station, a control signal for controlling each optical repeater in the subsequent stage, a control signal for controlling the optical receiving device, A control signal for controlling an optical fiber amplifier incorporated in each optical repeater or optical receiving device) can be appropriately input, and 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 present optical repeater or the built-in optical fiber amplifier based on the control information transferred in addition to the received input monitoring electric signal. The detection of the input monitoring optical signal power (or the voltage signal proportional to the power) in the monitoring optical receiver is performed by
For example, by branching a part of the received input monitoring electrical signal,
It can be realized by measuring the power or peak value. The input monitoring optical signal power can also be detected by detecting a direct current (or a voltage proportional to the direct current) flowing in the photodiode built in the monitoring optical receiver.

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

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

In FIG. 5, when the optical fiber amplifier is used as the optical booster amplifier in the optical transmitter in the optical terminal station, the optical booster amplifier is monitored and the obtained monitoring information is sent to the optical repeater in the subsequent stage. An example of an optical transmitter for transfer is shown. The optical transmitter includes a data optical transmitter that converts data into a data optical signal having a wavelength λd, an optical fiber amplifier that amplifies 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 and a data optical signal, and a pumping light source 2-.
It is composed of an optical multiplexer / demultiplexer 5 for multiplexing the pumping light from 2 and the data optical signal in opposite directions and for 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, sent out from the optical transmitter, and transferred to the optical repeater at the next stage. 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 that branches a part of the output light of the optical booster amplifier, an optical filter 8 that passes only the data optical signal of the split light, and a data light of the data optical signal that has passed 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 required for monitoring optical repeaters, control signals for controlling each optical repeater, optical reception A control signal for controlling the device, a control signal for controlling an optical fiber amplifier incorporated in each optical repeater or an optical receiving device), and an output monitoring electric signal output from the controller 10 It is composed of a monitoring optical transmitter 11 for converting 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 judgment 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 optical repeater in the subsequent stage, and also to transfer the information other than the monitoring information. . For example, as described above, by transferring a control signal for controlling the optical fiber amplifier incorporated in each optical repeater, the operation of each optical fiber amplifier can be controlled from the optical terminal station incorporating the optical transmitter.

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

FIG. 6 shows the 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 device for receiving the monitoring information from the preceding stage and monitoring the optical transmission line and the optical preamplifier will be shown. The optical receiving device includes an optical fiber amplifier for amplifying a data optical signal, a monitoring device, and a data optical signal power Pd for reproducing data from the amplified data optical signal.
And an optical receiver for data for detecting. The optical fiber amplifier is a doped fiber 1-1, 1-2.
A pumping light source 2, an optical multiplexer 5 for demultiplexing an input monitoring optical signal and multiplexing the pumping light from the pumping light source 2 and a data optical signal, optical isolators 4-1 and 4-2, and an optical The optical filter 12 removes noise. The optical multiplexer / demultiplexer 5 has, for example, the configuration shown in FIG. The monitoring device is
An optical receiver 6 for monitoring, which converts the demultiplexed input monitoring optical signal into an input monitoring electrical signal and detects the input monitoring optical signal power, the input monitoring electrical signal, the input monitoring optical signal power, and the A controller 1 that receives data optical signal power as input and outputs monitoring information of the entire optical transmission system
It is composed of 0 and 0. The detection of the data optical signal power in the optical receiver can be realized, for example, by branching a part of the received data signal and measuring the power or peak value thereof. 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 judges whether or not the optical transmission line, the optical fiber amplifier, and the monitoring device are normal from 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, the controller observes Pw and Pd, 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 the above, the monitoring optical receiver or the monitoring optical transmitter of the preceding optical repeater (wavelength approximately λp)
Is abnormal, and if both Pd and Pw deviate from normal values, it is determined that the transmission path is abnormal. The reason why this determination can be made is the same as in the case of the optical repeater.
The controller can also 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, it is possible to obtain the effect that the monitoring information of the entire optical transmission system can be obtained.

The effects of the present invention are not limited to the configuration of this embodiment. For example, as long as the optical multiplexer / demultiplexer can combine and demultiplex two wavelengths λd and λp, the above effects can be obtained regardless of the specific internal configuration. Also,
Optical isolators are placed in different places,
The above effect can be obtained even if the number used is different or not used. The method of pumping the doped fiber may be different from that shown in FIG. That is, the above effect can be obtained whether the traveling direction of the pumping light is the forward direction, the reverse direction, or the bidirectional direction with respect to the traveling direction of the data optical signal. Further, the above effect can be obtained even if the number of excitation light sources is further increased. Further, the above effect can be obtained even when the number of doped fibers is different from the case of FIG. Further, the above 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 present system includes an optical transmission device of the present invention that 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 through which the data optical signal propagates.
However, N is an integer of 1 or more, and an optical repeater of the present invention (first optical repeater to Nth +) that amplifies the attenuated data optical signal.
1 optical repeater) and the optical receiving apparatus of the present invention which reproduces data after amplifying a data optical signal. In addition to data, the optical transmission device appropriately requires information (parity check signal, other signals required for optical repeater monitoring,
Information about other devices in the optical terminal station, control signals for controlling each optical repeater, control signals for controlling the optical receiver, control signals for controlling the optical fiber amplifier incorporated in each optical repeater or optical receiver, etc. (For example, control information regarding the device), and the output is the light obtained by multiplexing the data optical signal and the first monitoring optical signal. The first optical repeater amplifies the transmitted data optical signal, adds new monitoring information and other necessary information to the transmitted first monitoring optical signal, and amplifies the amplified second monitoring optical signal. The multiplexed data optical signal is output. Hereinafter, the second to Nth optical repeaters also operate similarly to the first optical repeater. In the optical receiving device, the transmitted data optical signal is received after being amplified, data is reproduced, and monitoring information regarding the optical fiber amplifier in the present optical receiving device is added to the N + 1th optical monitoring optical signal signal and output. To do.

According to this embodiment, it is possible to obtain the monitoring information of the entire optical transmission system with a simple structure. 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 this optical transmission system is not limited to the above embodiment. For example, even if the optical transmitter does not have an optical fiber amplifier built-in, the above-mentioned effects regarding monitoring can be obtained by providing an optical transmitter for monitoring and an optical multiplexer for multiplexing the monitoring optical signal and the data optical signal.
Further, the same applies to the optical receiving device, and even if the optical fiber amplifier is not built in, if the optical multiplexer for demultiplexing the (N + 1) th monitoring optical signal from the data optical signal is provided, the above-mentioned monitoring effect can be obtained.

FIG. 8 is an optical fiber amplifier in which the drive current of the pumping light source 2 is adjusted so that the power of the data optical signal input to the data optical receiver in the optical receiving apparatus shown in FIG. 6 becomes substantially constant. An example in which an automatic gain control circuit for controlling the gain of is provided is shown. In the figure, the data optical receiver comprises a photodiode, a resistor connected in series with the photodiode, an amplifier circuit for amplifying the received data, a circuit for extracting timing from the amplifier circuit output signal, and an identification reproduction It is composed of a circuit and a DC voltage detector for detecting a DC voltage generated in the resistor. The output of the identification reproduction 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. In order to perform such control, the automatic gain control circuit
The control circuit detects a difference between the signal proportional to the data optical signal power and the reference signal and outputs a control signal, and the drive circuit controls the current flowing to the pumping light source by 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 becomes constant (equal to the reference signal), and as a result, the power of the data optical signal input to the photodiode becomes constant. When added to the present optical receiver, it is possible to obtain the effect that the input data optical signal power to the data optical receiver can be optimally set regardless of the power fluctuation of the data optical signal input to the present optical receiver. If the optical receiver 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 according to 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 structure is the same as that of the optical multiplexer 3-1 of FIG. 2). Equal to 3-2),
The input multiplexer optical signal is demultiplexed from the optical signal (composed of the data optical signal and the input supervisory optical signal) by the optical multiplexer 3-2 (the optical multiplexer 3-2 is used as an optical demultiplexer), and A data optical signal and pumping light (pumping light source 2-1
Output from). Other configurations are the same as those in FIG. In this embodiment, the wavelength λp ′ of the pumping light output from the pumping light source 2-1 does not necessarily have to be equal to λp. For example, λp is about 1.48 μm and λp ′ is about 0.98 μm.
It may be m. It is known that when the wavelength of pumping light is approximately 0.98 μm, the noise figure of the optical fiber amplifier can be made lower than when the wavelength of pumping light is approximately 1.48 μm. 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 noise figure of the optical repeater can be lowered can be obtained. The same effect can be obtained by performing the same replacement (to the optical multiplexers 3-2 and 3-1) for 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 lowered, the receiving sensitivity of the optical receiving device can be improved. If the optical repeater and the optical receiver described here are applied to the optical transmission system in FIG. 7, the optical repeater interval and the interval between the optical repeater and the optical receiver can be lengthened.

FIG. 10 shows a third embodiment of the optical repeater according to 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-of FIG. 9). 1 and 3-2), the pump light source 2-2 is multiplexed in the opposite direction to the data optical signal by the optical multiplexer 3-2 ′, and the data optical signal and the output monitoring light are coupled by the optical multiplexer 3-1 ′. 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 ″) is not necessarily the wavelength of the monitoring optical 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. Of course, λw is λ
p ′ and λp ″ may be equal (eg, approximately 1.
48 μm), λw and λp ″ may be equal (for example, about 1.48 μm), and λp ′ may be about 0.98 μm. As described above, when the wavelength of the excitation light is about 0.98 μm, the optical fiber It is known that the noise figure of the amplifier can be made smaller than that when the wavelength of the pumping light is approximately 1.48 μm, and the wavelength λw may have other values, for example, outside the band of the optical fiber amplifier (gain. It is also possible to select other wavelengths that do not have a wavelength or have a low gain) and have a sufficiently low transmission loss of the transmission path optical fiber. The effect that an optical repeater having a noise figure smaller than that of the embodiment can be realized is also obtained by applying the optical repeater of the present embodiment to the optical transmission system of Fig. 7. Yes, 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 for the optical multiplexer / demultiplexer 5 of the optical transmitter shown in FIG. 6, the optical multiplexers 3-2 and 3-1 must be replaced, respectively. If the optical transmitter, the optical repeater, and the optical receiver described here are applied to the optical transmission system in FIG. 7, the relay interval and the total transmission distance (total transmission distance from the optical transmitter to the optical receiver) can be calculated. Can be long.

FIG. 11 shows an optical repeater according to a fourth embodiment of the present invention. In this embodiment, in order to increase the output power of the optical repeater of the first embodiment, the doped fiber 1-2 on the output side is used.
The power of the pumping light supplied to is increased by bidirectional pumping. The number of pumping light sources is four in order to increase the power of pumping light. 2 out of 4 (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-combined (combined in orthogonal polarization states) by the polarization prism, The light is input to the doped fiber 1-2 via the optical multiplexer 3-1. On the other hand, the pumping light sources 2-2-3 and 2-2-4 are light sources for pumping the doped fiber 1-2 in the opposite directions, and the respective output lights are polarization-combined by the polarization prism and the optical multiplexer. It 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 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 transmitter and the optical repeater described here are applied to the optical transmission system of FIG. 7, the optical repeater interval and the interval between the optical transmitter and the optical repeater can be lengthened. However, even if the number of pumping light sources is less than 4, if the number of pumping light sources is 2 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, 4 are approximately 0.98μ.
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 and the present embodiment of the optical repeater is that (1) the wavelength of the pumping 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) sent by
The optical multiplexer / demultiplexer 13 multiplexes the excitation light output from the optical multiplexer / demultiplexer 13. The wavelengths λd, λp, and λp ′ are, for example, approximately 1.55 μm, approximately 1.48 μm, and approximately 0.98 μm, which are suitable wavelength settings. Where λ
p may be another wavelength. For example, it may be another wavelength outside the band of the optical fiber amplifier. As an example in FIG.
The structure of the optical multiplexer / demultiplexer 13 using a dielectric multilayer film filter and the input / output relationship of light are shown. The data optical signal input from the first port and the input monitoring optical signal are transmitted by the former and reflected by the latter by the dielectric multilayer filter. The reflected input monitoring optical signal is output from the fourth port and input to the monitoring optical receiver. On the other hand, the pumping light is input from the second port, is reflected by the dielectric multilayer filter, is multiplexed with the transmitted data optical signal, and is output from the third port. That is, the dielectric multilayer filter transmits the wavelength λd and transmits the wavelengths λp and λ.
It reflects p '. Such an input / output relationship can be realized by making the dielectric multilayer filter have wavelength dependence of reflectance and transmittance as shown in FIG. 14A, for example. That is, it has a reflection characteristic (reflectance of about 1 and transmittance of about 0) for a wavelength of about 1.5 μm or less.
For wavelengths of 5 μm or more, it may have a transmission characteristic (transmittance is about 1 and reflectance is about 0). However, if the wavelength λd is transmitted and the wavelengths λp and λp ′ are reflected, the characteristics of reflectance and transmittance other than those shown in FIG. 14A may be used. Further, a filter other than the dielectric multilayer filter may be used. Further, if the above-mentioned optical multiplexing and demultiplexing are realized for the wavelength λd and the wavelengths λp and λp ′, the relation between reflection and transmission may be reversed. 14 (b) and (c) show
13 shows the transmittance characteristics of the optical filter 14 in FIG. In the optical filter 14, when the characteristics of the reflectance and the transmittance of the optical multiplexer / demultiplexer 13 are imperfect, a part of the excitation light of the wavelength λp ′ is transmitted through the dielectric multilayer film filter, and FIG.
It is provided in order to prevent the output from the fourth port and the input to the monitoring optical receiver. As an example, FIG.
The wavelength λp ′ can be removed by providing the optical filter 14 with the transmittance characteristic as shown in (b) or (c). Of course, other transmittance characteristics may be used as long as the transmittance is high near the wavelength λp. Further, if the imperfections of the optical multiplexer / demultiplexer 13 are removed and the input / output relationship as shown in FIG. 13A is almost realized, the optical filter 14 need not be used. Further, even when the monitoring optical receiver does not respond to the wavelength λp ′ (the light receiving sensitivity is almost zero), it is not necessary to use the optical filter 14. 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, since the pumping light wavelength of approximately 0.98 μm can be used, the noise figure of the optical repeater can be lowered. . Further, since the demultiplexing of the input monitoring optical signal and the demultiplexing of the pumping light of about 0.98 μm can be performed by one optical multiplexer / demultiplexer, the optical component is more optical than that of the second embodiment (FIG. 9). The number of points can be reduced, and at the same time, the attenuation of the data optical signal can be reduced. When the optical repeater shown in FIG. 12 is applied to the optical transmission system shown in FIG. 7, the noise figure of the optical repeater is lowered, so that the interval between the optical repeaters can be increased.
There is also an effect that the performance of the optical transmission system can be further improved. The optical fiber amplifier in the optical repeater of this embodiment may be bidirectionally pumped. In this case, the noise figure can be further reduced and the gain can be further improved.

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 this embodiment is that (1) the wavelength of the pumping light source 2-2 is also λp ′ (≠ λp), and (2) output monitoring to the data optical signal (wavelength λd) is performed. The two points are that the optical signal (wavelength λp) and the pumping light output from the above 2-2 are multiplexed by the optical multiplexer / demultiplexer 13-2. The optical multiplexer / demultiplexer 13-1 in the figure is the same as 13 in FIG. Further, the method and structure for realizing the optical multiplexer / demultiplexer 13-2 are the same as in the case 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, transmitted through the dielectric multilayer filter, and output to the third port. Excitation light is input from the fourth port, reflected by the dielectric multilayer filter, and 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 in order to prevent a part of the excitation light of the wavelength λp ′ from being transmitted through the dielectric multilayer filter and input to the monitoring optical transmitter, and is necessary. If not, it may not be used. According to this embodiment, the same effect as that of the fifth embodiment of the optical repeater is obtained, and at the same time, the wavelength of the pumping light on the output side is approximately 0.98 μm, so that the noise figure of the optical repeater can be further lowered. Get the effect. Further, since the output monitoring optical signal and the pumping light for the data optical signal can be combined 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, there is an effect that the attenuation that the data optical signal undergoes can be reduced. The optical repeater of FIG. 15 is shown in FIG.
When applied to the above optical transmission system, the noise figure of the optical repeater is further lowered, so that the interval between the optical repeaters can be further lengthened and the performance of the optical transmission system can be further improved. The optical fiber amplifier in the optical repeater of this embodiment may be bidirectionally pumped. In that case, the noise figure can be reduced and the gain can be improved.

FIG. 17 shows another embodiment of the optical receiver. The difference between the embodiment of the optical receiving apparatus shown in FIG. 6 and this embodiment is that (1) the wavelength of the pumping light source 2 is λp ′ (≠ λp), and (2) it is combined with the data optical signal (wavelength λd). The two points are that the optical demultiplexer 13-1 performs demultiplexing of the input monitoring optical signal (wavelength λp) that has been sent and is multiplexed with the pumping light output from 2 above. Wavelengths λd, λp, and λp '
The setting is the same as in the case of the fifth embodiment of the optical repeater, and the method of realizing the optical multiplexer / demultiplexer 13-1 is also the same. Further, the same optical filter 14 as in the case of FIG. 12 is used for the same reason. According to this embodiment, the same effect as that of the embodiment of the optical receiver shown in FIG. 6, that is, the effect that the monitoring information of the entire optical transmission system can be obtained, and at the same time, the pumping light wavelength is 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 lowered is 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 lowered, so that the interval between the optical repeater and the optical receiver can be lengthened, and the performance of the optical transmission system is improved. The effect that it can be obtained is also obtained. The optical fiber amplifier in the optical receiver of this embodiment may be bidirectionally pumped. In this case, the noise figure can be further reduced and the gain can be further improved.

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 pumping light source 2-2 is λp ′ (≠ λp).
(2) Two points in which the output monitoring optical signal (wavelength λp) to the data optical signal (wavelength λd) and the pumping light output from the above 2-2 are multiplexed by the optical multiplexer / demultiplexer 13-2. Is. The settings of the wavelengths λd, λp, and λp ′ are the same as in the case of the fifth embodiment of the optical repeater. The method of implementing the optical multiplexer / demultiplexer 13-2 is the same as in the case of the sixth embodiment of the optical repeater. According to this embodiment, the same effect as that of the embodiment of the optical transmitter shown in FIG. 5 can be obtained, and at the same time, 0.98 μm can be used as the pumping light wavelength, so that the noise of the optical fiber amplifier in the optical receiver is reduced. The effect is that the index can be lowered. The wavelength of the pumping light source 2-1 may be either λp ′ or λp, but in the case of λp ′, the noise figure of the optical fiber amplifier can be made lower. When the optical receiver of FIG. 18 is applied to the optical transmission system of FIG. 7, the noise figure of the optical transmitter is lowered, so that the distance between the optical transmitter and the optical repeater can be lengthened and the performance of the optical transmission system is improved. The effect that it can be obtained is also obtained. The optical fiber amplifier in the optical transmitter of this embodiment may be bidirectionally pumped. In this case, the noise figure can be reduced, and the gain and the output power can be improved.

The configuration of the present invention is not limited to the above embodiment. Further, even if the optical transmission path is branched and the data optical signal (combined with the monitoring optical signal) is distributed to the plurality of optical receiving devices, the above 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 replaced, and the monitoring optical transmitter of the optical transmitting device is replaced with the monitoring optical receiver to monitor the optical receiving device. The optical receiver for monitoring needs to be replaced with the optical transmitter for monitoring. Further, the above effect can be obtained even if the optical receiving device collectively determines the abnormality that is performed in the optical transmitting device, each optical repeating device, and the controller of the optical receiving device. In this case, the optical transmitter and each optical repeater need only add the observed power value as monitoring information and transmit it. As the combination of the wavelengths of the data optical signal, the pumping light, and the monitoring optical signal, the wavelengths of the above embodiments may be appropriately combined and used. Further, 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. Moreover, the wavelength of the pumping light may be different for each optical repeater. The wavelength of the data optical signal may be about 1.3 μm. In this case, the gain can be given to the doped fiber by setting λp to a value near 1 μm and using neodymium or the like as an additive to the doped fiber. Further, the operation of the optical receiving apparatus of FIGS. 8 and 17 and the optical repeating apparatus of FIGS. 9, 10, 11, 12, and 15 can be controlled by the control signal added to the monitoring information and sent. Further, the optical transmission system, the optical repeater, and the optical receiver of the above-described embodiments may be combined appropriately to form an optical transmission system. Further, the optical multiplexer, the optical demultiplexer, and the optical filter incorporated in the optical multiplexer / demultiplexer used in each of the embodiments are the optical multiplexer, the optical demultiplexer, and the optical filter included in the embodiment if the functions such as the optical multiplexer / demultiplexer are fulfilled. The same effect can be obtained even when operating 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 of the directional coupler type, the wavelength relationship of coupling and non-coupling may be reversed. The same effect can be obtained even if the wavelength of the monitoring optical signal is approximately 1.3 μm. Moreover, a plurality of wavelengths of the monitoring optical signal may be mixed in the optical transmission system.

Further, in the optical fiber transmission system using the above optical fiber amplifier, the power of the data optical signal input to the transmission line optical fiber is high (several milliwatts or more), so that stimulated Brillouin scattering is caused in the optical fiber. (S
In some cases, the (BS) phenomenon occurs and the data optical signal is reflected and returned to the input end. SB
S is a phenomenon that appears when the power of one optical frequency exceeds the SBS threshold peculiar to the optical fiber. For example, the power is dispersed into a plurality of optical frequencies, and the power is the SBS threshold at any optical frequency. It is known that SBS will not occur unless the value is exceeded. Therefore, with respect to the above problem, for example, an SBS suppressor having a configuration as shown in FIG. 19 should be connected to the output end of an optical transmitter or an optical repeater and the output light should be input to a transmission line optical fiber. Can be solved by The SBS suppressing device shown in FIG. 19 is composed of at least a light source for phase modulation in an optical fiber, a modulation signal source for light intensity modulating the light source, and an optical multiplexer for multiplexing the intensity-modulated pumping light into a data optical signal. To be done. In this configuration, the output light intensity from the phase modulation light source in the optical fiber is changed to generate a change in the refractive index in the optical fiber by utilizing a nonlinear optical phenomenon. If there is a change in the refractive index, the data optical signal undergoes optical phase modulation and the signal spectrum is expanded. As the spectrum broadens, the power can be distributed over multiple optical frequencies. Therefore, even when the power exceeds the SBS threshold value at a certain optical frequency in the data optical signal, by using this device, the power of the optical frequency is dispersed into a plurality of frequencies and each power is SBS.
Since it can be lower than the threshold value, the occurrence of SBS can be avoided. FIG. 20 shows an example of the signal waveform of each part. FIG. 11A shows a 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. 7B shows intensity modulated light, the intensity of which changes according to 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 the 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 in which the data optical signal input to the transmission path optical fiber is represented 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. 3D 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. Of the data "1" in the figure, the underlined "1" has undergone phase modulation, and in the case of the figure, it has undergone a phase change of approximately 180 degrees. As a result, the signal spectrum of the data optical signal is broadened, so that the occurrence of SBS is suppressed.
That is, it is possible to increase the power of the data optical signal that can be input to the transmission line optical fiber by using the device of this configuration. As described above, FIG.
The greater the amount of change in light intensity at 0 (b), the greater the amount of phase modulation that can be applied to the data optical signal. The required change amount depends on the spectrum and intensity of the data optical signal, the characteristics of the optical fiber, and the like, but as a guideline, a change amount of approximately 10 milliwatts or more is required. As the wavelength of the excitation light, for example, about 1.48 μm can be used.

FIG. 21 shows the SBS suppressing function shown in FIG.
An example in which the optical transmission device is added to the optical transmission device will be described. In this embodiment, the monitoring optical transmitter of FIG. 5 is also used as a light source for optical fiber phase modulation for SBS suppression, and the monitoring effect of FIG. 5 and the SBS suppression effect of FIG. We have realized an optical transmitter that has both. The difference from the transmitting device in FIG. 5 is that a modulation signal source and a circuit for superimposing the modulation signal from the signal source on the monitoring electric signal are added. Further, the monitoring optical transmitter also serves as a light source for phase modulation in the optical fiber, which is indicated by 15 in this embodiment. FIG. 22 shows an example of the signal waveform of each part. The same figure (a)
Is a monitoring electric signal output from the controller, which is a low-speed digital signal (may be an analog signal). FIG. 11B shows a monitoring electric signal on which the modulation signal from the modulation signal source is superimposed. The frequency of the modulated signal to be superimposed needs to be set sufficiently higher than the transmission speed of the monitoring electric signal and the band of the monitoring optical receiver. 1 (c) is 1
5 is a supervisory optical signal output from the optical disc 5, and a modulation signal is superimposed on it. Since the optical intensity changes due to the superimposed modulation signal, it is possible to perform phase modulation on the data optical signal.
S can be suppressed. Furthermore, since the band of the monitoring optical receiver of the optical repeater (or optical receiving device) in the subsequent stage does not follow the frequency of the modulated signal, only low-speed monitoring information can be extracted and received from the monitoring optical signal. . Therefore, according to the present embodiment, it is possible to obtain an effect that it is possible to realize an optical transmitter having a simple configuration and an effect related to the monitoring in FIG. 5 and an effect related to the SBS suppression in FIG.

FIG. 23 shows the SBS suppressing function shown in FIG.
An example in which the optical repeater is added to the optical repeater will be described. In the present embodiment, the monitoring optical transmitter of FIG. 1 is also used as a light source for phase modulation in the optical fiber for SBS suppression, and the monitoring effect of FIG. 1 and the SBS suppression effect of FIG. We have realized an optical transmitter that has both. The difference from the transmitter 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, which is also shown at 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 optical signal from 15. Figure 2
SBS can be suppressed by the same principle as in the case of 1. Furthermore, the optical repeater (or optical receiver) in the latter stage
Since the band of the optical receiver for monitoring does not follow the frequency of the modulated signal, only low-speed monitoring information can be extracted and received from the monitoring optical signal. Therefore, according to the present embodiment, it is possible to obtain an effect that an optical repeater having the effect of monitoring in FIG. 1 and the effect of suppressing SBS in FIG. 19 can be realized with a simple configuration.

When the device of FIG. 21 or 23 is applied to the system of FIG. 7, SBS generation 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 lengthened. You can also get the effect.

[0039]

As described above, according to the present invention, the output power of the optical transmitter, the optical repeater, the optical receiver, and the monitoring of the optical transmission line connecting them and the transfer of the monitoring information are reduced to each optical fiber amplifier. The effect that it can be realized without causing

[Brief description of 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 the operation of the optical multiplexer.

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

FIG. 5 is a diagram showing an embodiment of an optical transmitter.

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

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

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

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

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

FIG. 11 is a diagram showing a fourth embodiment of an optical repeater.

FIG. 12 is a diagram showing a fifth embodiment of an optical repeater.

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

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

FIG. 15 is a diagram showing a sixth embodiment of an optical repeater.

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

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

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

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

20 is a diagram showing a signal waveform in each part of FIG.

FIG. 21 is a diagram showing an embodiment of an optical transmitter having an SBS suppressing function.

22 is a diagram showing a signal waveform in each part of FIG.

FIG. 23 is a diagram showing an example of an optical repeater having an SBS suppressing function.

[Explanation of symbols]

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H04B 17/00 H04B 9/00 J 17/02 E H04J 14/00 14/02 (72) Inventor Hiroyuki Nakano Higashi Koikeku, Tokyo Kokubunji City 1-chome 280 Central Research Laboratory, Hitachi, Ltd. (72) Ryoji Wuhou 1-280 Higashi Koikekubo, Kokubunji, Tokyo 1-280 Central Research Laboratory, Hitachi, Ltd. (72) Hironari Matsuda 4-6, Kanda Surugadai, Chiyoda-ku, Tokyo Address, Hitachi, Ltd. (56) Reference JP-A-57-83899 (JP, A) JP-A-4-22925 (JP, A) JP-A-2-297027 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 H01S 3/06 H01S 3/10 H04B 17/00 H04B 17/02

Claims (4)

(57) [Claims] 1. An optical data signal and an optical supervisory signal containing supervisory information of an optical transmission system are multiplexed and transmitted on an optical transmission line.
A method of transmitting an optical signal in an optical transmission system, wherein pumping light used for amplification of the optical supervisory signal is output, and the output pumping light and the optical data signal are combined by a first optical multiplexer. Inputting the multiplexed pumping light and optical data signal into an optical fiber, amplifying the optical data signal using the pumping light by the optical fiber, outputting the optical supervisory signal, and amplifying An optical data signal and the output optical supervisory signal are multiplexed by a second optical multiplexer, the multiplexed optical data signal and the optical supervisory signal are sent to the optical transmission line, and the optical supervisory signal Is outside the amplification band of the optical fiber, and the loss of the optical supervisory signal in the optical transmission line is about the same as the loss of the optical data signal in the optical transmission line. Transmission of optical monitoring signal Method. 2. The method for transmitting an optical supervisory signal according to claim 1, wherein the wavelength of the optical supervisory signal is in the range of 1.48 μm to 1.60 μm. 3. An optical data signal and an optical supervisory signal containing supervisory information of an optical transmission system are multiplexed and transmitted on an optical transmission line.
A method of receiving an optical supervisory signal in an optical transmission system, which receives the optical data signal and the optical supervisory signal that have been multiplexed and transmitted on the optical transmission path, and the received optical data signal and the An optical supervisory signal is separated, the separated optical supervisory signal is received, pumping light used for amplification of the optical data signal is output, and the separated optical data signal and the output pumping light are combined. Wavelength, input the multiplexed pumping light and optical data signal to an optical fiber, the optical fiber, the optical data signal is amplified by using the pumping light, the wavelength of the optical supervisory signal is the optical Outside the amplification band of the fiber, the loss of the optical supervisory signal in the optical transmission line is a wavelength that is about the same as the loss of the optical data signal in the optical fiber of the optical supervisory signal, Receiving Method. 4. The method of receiving an optical supervisory signal according to claim 3, wherein the wavelength of the optical supervisory signal is in the range of 1.48 μm to 1.60 μm.