JPH04256233A - Optical communication system - Google Patents

Abstract

PURPOSE:To easily maintain and operate a system without necessity for newly providing a different line for transmitting management information for giving the notice of an abnormal place in the system to a downstream. CONSTITUTION:An optical fiber amplifier successively monitors the state of a transmission system and detects the abnormality. When the abnormality of an exciting light source 108 is detected, e.g. a wave length control circuit 110 controls the temperature of the exciting light source 108, controls the wave length of exciting light and gives the notice of the abnormality to a reception- side. An optical receiver 113 branch-detects exciting light from a transmitted signal light in a branching the presence or absence of abnormality at an upstream is discriminated in an abnormality detector 118.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system using an optical fiber amplifier.

0002

[Prior Art] In optical communication systems that use optical fibers as transmission lines, optical signals are attenuated due to transmission line losses. Therefore, a means for amplifying the attenuated signals is provided to compensate for the optical fiber transmission line losses. ing. As a means of compensating for this transmission line loss, there is a method of installing an optical repeater between optical fiber transmission lines. FIG. 3 shows an example of an optical communication system using one stage of optical repeaters.

On the transmitting side, an electrical signal modulated by a signal source 301 is converted into an optical signal by an optical transmitter 302 and sent to a first optical fiber transmission line 303. This optical signal suffers a transmission loss while passing through the optical fiber transmission line, is attenuated, and is sent to the optical repeater 304.
is input. The optical repeater 304 converts the optical signal into an electrical signal, amplifies and regenerates the attenuated signal, converts it into an optical signal again, and sends the optical signal to the second optical fiber transmission line 305. The optical receiver 306 converts the input signal light into an electrical signal and demodulates the received signal.

[0004] In such an optical communication system, in addition to the main information, management information such as abnormalities in the system is included in the optical signal to be transmitted, making it easier to operate, maintain, and manage the system. I have to. For example, in the case of an electric optical repeater as described above, an abnormality occurs on the upstream side of the optical repeater, that is, the signal source 301 and the optical transmitter 302 in FIG.
An abnormality in the transmission line optical fiber 303 is detected in the optical repeater 304 by monitoring the electrical signal after optical/electrical conversion. When an abnormality is detected on the upstream side, the management information portion of the transmission signal is electrically processed and converted into electricity/optical along with the main information, and sent to the downstream side. Similarly, if an abnormality occurs within the optical repeater 304, the management information portion is electrically processed and then converted into an optical signal and sent to the downstream side. Further downstream of the optical repeater 304, the presence or absence of an upstream abnormality can be detected by monitoring the management information portion after converting the optical signal into an electrical signal. With such a configuration, an abnormality occurring on the upstream side of the system can be detected on the downstream side of the system, making it possible to easily operate, maintain, and manage the system.

By the way, recent research has revealed that an optical fiber amplifier whose core portion is doped with, for example, erbium is effective as a means for compensating transmission line loss of an optical fiber. This optical fiber amplifier can directly amplify optical signals in the optical state without converting them to electrical signals, and has the characteristics of high gain, low noise, and good compatibility with transmission fibers. There is. When an optical fiber amplifier is used, it does not require the optical/electrical conversion and electrical/optical conversion processes in optical signal amplification described above, and is therefore considered promising as a compact optical signal amplification means with low power consumption.

However, when an optical fiber amplifier is used in the transmission line, the optical signal is directly amplified and no optical/electrical or electrical/optical conversion is involved, so it is necessary to monitor the transmitted signal to detect abnormalities. Accordingly, the management information portion cannot be signal-processed and transmitted. Therefore, it is necessary to provide a separate line for transmitting management information in addition to a line for transmitting main information, which poses the problem of difficulty in maintaining, managing, and operating the system.

[0007]

[Problems to be Solved by the Invention] As stated above, in optical communication systems using optical fiber amplifiers, there is no effective means of transmitting management information from upstream to downstream, so a separate line for transmitting management information is provided. However, there was a problem in that the system was difficult to maintain, manage, and operate. The present invention has been made to solve the above problems, and provides an optical communication system using an optical fiber amplifier that does not require a separate line for transmitting management information and can easily maintain, manage, and operate the system. The purpose is to provide. [Structure of the invention]

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention uses an optical fiber as a transmission line, interposes an optical fiber amplifier between an optical transmitter and an optical receiver, and provides input to the optical fiber amplifier. In an optical communication system that transmits information by combining pump light from a pump light source with a transmitted signal light and optically amplifying the signal light, the optical fiber amplifier is provided with the optical transmitter, the optical wavelength control means for changing the wavelength of the pump light source according to the abnormal state when an abnormality occurs in the fiber amplifier or the optical fiber transmission line; The present invention is characterized in that it is configured to include means for identifying the wavelength and monitoring the presence or absence of an abnormality.

[0009]

[Operation] In the optical communication system with the above configuration, an optical fiber amplifier sequentially monitors the state of the transmission system and detects an abnormality. When an abnormality is detected, the temperature of the pumping light source is controlled to change the wavelength of the pumping light. control and inform the receiving side of the presence or absence of an abnormality.
The optical receiver separates and detects the pumping light from the transmitted signal light and identifies the wavelength of the pumping light, thereby determining the presence or absence of an upstream abnormality.

0010

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

FIG. 1 is a diagram illustrating a first embodiment of the present invention, and is an example of an optical communication system using one stage of optical fiber amplifiers as intermediate amplifiers. In the figure, 101 is a signal source, and an optical transmitter 102 uses wavelength 1 based on the signal source 101.
．． The 5 μm band light source is modulated and sent to the first optical fiber transmission line 103 as signal light. This signal light undergoes loss through the optical fiber and is attenuated to the optical fiber amplifier 104.
The signal is input to the input port 105 of the .

In the optical fiber amplifier 104, the input signal light and the output from the pumping light source 108, for example, 1.48μ.
The m-band pumping light is multiplexed by a multiplexer 106, and an amplification optical fiber 107 whose core portion is doped with erbium is formed.
is input. The erbium-doped fiber has an amplification effect, and an optical signal in the 1.5 μm band is amplified and output. From the output port 111, the amplified 1.5 μm band signal light and the remaining portion of the 1.48 μm pump light are output, and the second
The signal is sent out to the optical fiber transmission line 112 of. In other words, the signal light passes through the optical fiber amplifier 104.
The loss of the transmission line optical fiber 103 is compensated for.

The output intensity of the pumping light source 108 is monitored by a pumping light output monitor 109, and when the output intensity decreases from the initial value due to deterioration of the pumping light source 108, a wavelength control circuit 110 changes the wavelength of the pumping light source 108 to a predetermined value. control to the value of That is, when an abnormality occurs in the output of the excitation light source, by changing the wavelength of the excitation light source, it is possible to notify the downstream side that the abnormality has occurred. The semiconductor laser diode used as the light emitting element of the excitation light source has a wavelength change characteristic of several angstroms per degree Celsius, and the wavelength can be set to a predetermined value by controlling the temperature of the light emitting element.

In the optical receiver 113, the input port 1
1.5μm band signal light input from 14 and 1.48μ
The m-band excitation light is separated by a demultiplexer 115, and the 1.5
The μm band signal is input to the light receiving element 116 and undergoes optical/electrical conversion to become a received signal. Furthermore, the wavelength of the excitation light in the 1.48 μm band is identified by the wavelength monitor 117, and if an abnormality occurs on the upstream side, the presence or absence of the abnormality is detected by the abnormality detector 118 based on the change in the wavelength of the excitation light. .

According to such a configuration, by monitoring the wavelength of the excitation light source propagated through the same optical fiber transmission line as the signal light, abnormalities occurring in the system can be detected downstream, so management information transmission is This makes it possible to easily maintain, manage, and operate the system without having to install a separate line for the system.

FIG. 2 is a diagram illustrating a second embodiment of the present invention, which can be installed in an optical transmitter as a post amplifier, installed in a repeater as an intermediate amplifier, or installed in an optical receiver. This is an example of an optical fiber amplifier that can be used as a preamplifier.

The optical fiber amplifier used in the first embodiment has functions for detecting the states of the input signal light and output signal light, the drive current of the light emitting element in the excitation light source, and various abnormalities on the upstream side. The difference is that

That is, in the optical fiber amplifier 201, the input port 202 receives the signal light in the 1.5 μm band and the signal light in the 1.5 μm band.
．． Excitation light of 48 μm is input. This is because when a plurality of optical fiber amplifiers are connected to an optical fiber transmission line with the same configuration, the remaining part of the pumping light from the upstream optical fiber amplifier is also input to the next optical fiber amplifier. Duplexer 2
At step 03, the pumping light component and the signal light are separated, and the pumping light component is input to the wavelength monitor 204. Wavelength monitor 204
monitors the wavelength of the excitation light, and if an abnormality occurs on the upstream side, a change in the wavelength of the excitation light is detected, and the wavelength control circuit 215 adjusts the wavelength of the excitation light source 208 to a predetermined value according to the monitoring result. controlled by.

The signal light component split by the splitter 203 is input to the splitter 205, and the optical splitter 205 splits the signal light at a predetermined splitting ratio between the splitter 207 and the input light monitor 20.
It branches to 6 and outputs it. The input light monitor 206 monitors the state of the input signal light, a part of which has been branched by the splitter 205, and if an abnormality is found in the input signal light, the wavelength control circuit 215 changes the wavelength of the excitation light source to a predetermined value. Controlled by value.

The signal light split by the splitter 205 and input to the multiplexer 207 is combined with the output light from the pumping light source 208 and input to the erbium-doped amplification fiber 211. The input signal light is optically amplified to a predetermined value to ensure loss in the optical fiber transmission line. The output intensity and drive current of the excitation light source 208 are monitored by an excitation light output monitor 210 and a drive current monitor 209, respectively, and if the output intensity decreases from the initial value due to deterioration of the excitation light source 208 or if there is an abnormality in the drive current. Then, the wavelength control circuit 215 controls the wavelength of the excitation light source 208 to a predetermined value.

A part of the remaining part of the optical signal and pump light that has been optically amplified by the amplifying optical fiber 211 is split by a splitter 212 and inputted to a splitter 213, and the rest is input to a splitter 213 downstream of the output port 216. It is sent out to an optical fiber transmission line. The demultiplexer 213 demultiplexes the signal light and the excitation light, and the signal light component is input to the output light monitor 214 . The output light monitor 214 monitors the state of the output signal light, and if an abnormality is detected in the output signal light, the wavelength control circuit 215
The wavelength of the excitation light source 208 is controlled to a predetermined value.

[0022] According to such a configuration, upstream abnormality information is transferred to the downstream optical fiber amplifier, and the information can be further transferred downstream, so that even in a system in which optical fiber amplifiers are connected in multiple stages, , abnormalities occurring upstream can be reliably detected downstream. Furthermore, by changing the wavelength of the excitation light source to be controlled depending on the type of abnormality, it is possible to distinguish and detect the type of abnormality, making maintenance, management, and operation of the system easier.

[0023]

As described above, in the optical communication system of the present invention, there is no need to provide a separate line for transmitting management information, and the system can be easily maintained, managed, and operated.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing the configuration of a second embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a conventional optical communication system.

[Explanation of symbols]

104,201 Optical fiber amplifier 107,21
1 Amplification optical fiber 108, 208 Pumping light source 110, 215 Wavelength control circuit

Claims (7)

[Claims] [Claim 1] An optical fiber amplifier is interposed between an optical transmitter and an optical receiver using an optical fiber as a transmission line, and pump light from a pump light source is combined with the transmitted signal light input to the optical fiber amplifier. Compensates for transmission loss by amplifying light,
In an optical communication system for transmitting information, the excitation light source is provided in the optical fiber amplifier, and when an abnormality occurs in the optical transmitter, the optical fiber amplifier, or the optical fiber transmission line, the excitation light source What is claimed is: 1. An optical communication system comprising: wavelength control means for changing the wavelength of the input light; and means provided in the optical receiver for identifying the wavelength of excitation light among the input light and monitoring the presence or absence of an abnormality. 2. The optical communication system according to claim 1, wherein the wavelength of the excitation light source is controlled by controlling the temperature of the excitation light source. 3. The optical fiber amplifier includes means for identifying the wavelength of the pumping light among the input lights and detecting the presence or absence of an upstream abnormality, and when an abnormality is detected by this means, the temperature of the pumping light source is determined. 2. The optical communication system according to claim 1, wherein the wavelength is changed to a predetermined value by changing the wavelength. 4. The optical fiber amplifier includes means for monitoring the output state of the pumping light source, and pumping light output abnormality detection means for detecting an abnormality in the pumping light output from the monitor information, and the detecting means detects an abnormality in the pumping light output. 2. The optical communication system according to claim 1, wherein when the excitation light source is detected, the temperature of the excitation light source is changed to change its wavelength to a predetermined value. 5. The optical fiber amplifier includes means for monitoring a drive current of a pumping light source, and drive current abnormality detection means for detecting an abnormality in the drive current from the monitor information,
2. The optical communication system according to claim 1, wherein when an abnormality is detected by this means, the temperature of the excitation light source is changed to change its wavelength to a predetermined value. 6. The optical fiber amplifier comprises means for separating signal light from input light and monitoring its state, and input signal abnormality detection means for detecting an abnormality in the input signal light from the monitor information, the means 2. The optical communication system according to claim 1, wherein when an abnormality is detected in the optical communication system, the temperature of the excitation light source is changed to change the wavelength thereof to a predetermined value. 7. The optical fiber amplifier includes means for monitoring the state of the signal light among the output lights, and output signal abnormality detection means for detecting an abnormality in the output signal light from the monitor information, and the means detects an abnormality. 2. The optical communication system according to claim 1, wherein when the excitation light source is detected, the temperature of the excitation light source is changed to change its wavelength to a predetermined value.