JPH06326667A - Method and system for transferring alarm by multi-stage repeating - Google Patents

Abstract

PURPOSE:To realize a method or a system for transferring an alarm by multi- stage repeating capable of superimposing alarm information respectively to main signal light by plural light direct amplifiers. CONSTITUTION:The light direct amplifier 111 to 11N connected serially into multiple stages through an optical fiber 12 is constituted of a rare earth element added fiber to input signal light respectively from an input terminal, a wavelength dividing multiplex coupler which injects exciting light to the rare earth element added fiber to which this signal light is inputted and outputs the signal light after amplification to an output terminal, an excitation light source to output this exciting light, and a light source drive circuit which modulates this exciting light source by frequency peculiar to each light direct amplifier by the alarm information 141 to 14N, and inputs it to the wavelength dividing multiplex coupler as the exciting light of different intensity. The alarm information 141 to 14N is multiplexed to the main signal light by frequency-multiplexing, and the transfer of these information becomes possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multistage relay alarm transfer method and a multistage relay alarm transfer system for transmitting alarm information when an optical direct amplifier is used as an optical intermediate repeater.

[0002]

2. Description of the Related Art In a multi-stage repeater optical communication system that repeats signal light in multiple stages using an optical direct amplifier, some sort of failure may occur in the repeater. Therefore, for example, Japanese Patent Laid-Open No.
In Japanese Patent No. 266245, the excitation light is modulated with a pulse pattern having a period shorter than the relaxation time of the excited carriers, and is incident on an optical fiber doped with a rare earth element, and this pulse pattern and backscattering from an optical fiber transmission line. The time correlation with light is obtained to measure the optical loss and breakage position of the optical fiber transmission line.

However, with such a monitoring method, although the transmission line itself can be monitored, it is not possible to obtain information related to a failure in the relay device. Therefore, the relay device side also creates alarm information and transmits it to the downstream side. In a conventional multi-stage relay alarm transfer system in which repeaters are connected in multiple stages, when transmitting such alarm information, its digital signal is FSK (Fr (Fr) of a frequency common to all optical direct amplifiers in the communication system.
frequency shift keying). Then, the semiconductor laser for excitation is modulated with this FSK signal to superimpose warning information on the main signal light,
It was supposed to be transmitted downstream.

[0004]

As described above, in the conventional multi-stage relay alarm transfer system, the FSK signal of a predetermined frequency is supplied to the optical direct amplifier for amplifying the main signal light,
The alarm information is transferred to the downstream side by performing SK modulation. In such a multi-stage relay alarm transfer system, no problem arises when one optical direct amplifier superimposes and transfers alarm information, but two or more optical direct amplifiers cannot superimpose alarm information at the same time. It was

SUMMARY OF THE INVENTION An object of the present invention is to provide a multistage relay alarm transfer method or system capable of superposing alarm information on the main signal light by a plurality of optical direct amplifiers.

[0006]

According to the multistage relay alarm transfer method of the invention described in claim 1, optical direct amplifiers connected in series in multistage via optical fibers respectively successively transfer main signal light, and The optical direct amplifiers are assigned different frequencies for different frequency shift keying modulation, and the alarm information created by the repeater to which the optical direct amplifier belongs is modulated to the intensity of the excitation light at the assigned frequency to generate the alarm information. It is designed to be superimposed on the main signal light and to be transferred to the downstream side.

That is, according to the first aspect of the present invention, since the alarm information is superimposed on the main signal light at different frequencies, it is possible to transfer a plurality of alarm information.

In the multi-stage relay alarm transfer system according to the second aspect of the present invention, optical direct amplifiers connected in series in multiple stages via optical fibers are provided with rare earth-doped fibers for inputting signal light from their respective input terminals, and the signal light. Wavelength-division multiplexing coupler that injects pumping light into the input rare-earth-doped fiber and outputs the amplified signal light to the output terminal, pumping light source that outputs this pumping light, and this pumping light source with each optical direct amplifier And a light source drive circuit for inputting to the wavelength division multiplexing coupler as pumping light having different intensities, which is modulated by the alarm information at a frequency peculiar thereto.

That is, different carrier frequencies of frequency shift keying are assigned to the respective optical direct amplifiers, and the alarm information is frequency-multiplexed with the frequency shift keying signals of these frequencies and superposed on the main signal light. It becomes possible to transfer the alarm information of.

[0010]

EXAMPLES The present invention will be described in detail below with reference to examples.

FIG. 1 shows a configuration of a multistage relay alarm transfer system according to an embodiment of the present invention. This system has a configuration in which first to Nth optical direct amplifiers 11 _{1 to} 11 _N are connected in series by optical fiber transmission lines 12 _{1 to} 12 _N. The main signal light 13 is input to the first optical direct amplifier 11 ₁ . The respective optical direct amplifiers 11 _{1 to} 11 _N are adapted to receive injection of pumping lights 14 _{1 to} 14 _N from a pumping light source not shown in this figure. These excitation light is modulated by the alarm information of each different frequencies f ₁ ~f _N.

FIG. 2 shows the configuration of an optical direct amplifier which constitutes this multistage relay alarm transfer system. The optical direct amplifier 11 includes an erbium-doped fiber 22 which directly amplifies the main signal light input from the input terminal 21 or alarm information already superposed on the main signal light, and a semiconductor laser 23 for exciting the erbium-doped fiber 22. The excitation light 14 output from the semiconductor laser 23 is input to the wavelength division multiplexer 24. The wavelength division multiplexing coupler 24 receives the output light of the erbium-doped fiber 22 and the pumping light 14 and outputs the output light to the output terminal 25 of the optical direct amplifier 11.

On the other hand, the alarm information 26 created by a circuit (not shown) is input to the frequency modulation circuit 27. The frequency modulation circuit 27 creates the FSK modulation signal 28 based on the center frequency peculiar to the optical direct amplifier 11, and inputs this to the semiconductor laser drive circuit 29. The semiconductor laser drive circuit 29 modulates the intensity of the output light of the semiconductor laser 23 and sends it as the excitation light 14 to the wavelength division multiplexing coupler 24. As a result, the alarm information is superimposed on the main signal light 13 that passes through the erbium-doped fiber 22 and is amplified.

FIG. 3 shows the frequency characteristic of the modulation efficiency of the main signal light by pumping light modulation and the frequency characteristic of the gain between the input and the output of the optical direct amplifier of this embodiment.
In the figure, the horizontal axis represents frequency, and the vertical axis represents relative modulation efficiency and relative gain between input and output. In this example, the usable frequency range R is 0.7 KHz to 4 KH.
It is in the range of z. That is, by setting the frequencies f _{1 to} f _N at equal intervals, for example, N pieces of alarm information can be transmitted at the same time. In FIG. 1, the alarm information is superimposed on each of the optical direct amplifiers 11 _{1 to} 11 _N by frequency multiplexing at the frequencies f _{1 to} f _N.

On the receiving side of this multi-stage relay alarm transfer system, the main signal light is separated and the alarm information superposed by frequency multiplexing is selected at each frequency to reproduce each alarm information. it can.

In the embodiment, the erbium-doped fiber is used for the optical direct amplifier, but it is also possible to use other rare-earth-doped fiber.

[0017]

As described above, according to the present invention, the alarm information created by the repeaters having the respective optical direct amplifiers is frequency-multiplexed at different frequencies and superposed on the main signal light. There is an effect that a plurality of alarm information can be transferred to the downstream side at the same time without providing the transmission path, and the communication system can be configured at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a multistage relay alarm transfer system and a frequency characteristic of alarm information according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of an optical direct amplifier that realizes the multistage relay alarm transfer method or system of this embodiment.

FIG. 3 is a characteristic diagram showing frequency characteristics of modulation efficiency of main signal light by pumping light modulation and frequency characteristics of gain between input and output in the optical direct amplifier of the present embodiment.

[Explanation of symbols]

11 Optical Direct Amplifier 12 Optical Fiber 13 Main Signal Light 14 Pumping Light 21 Input Terminal 22 Erbium Doped Fiber 23 Semiconductor Laser 25 Output Terminal 26 Warning Information 27 Frequency Modulation Circuit 29 Semiconductor Laser Driving Circuit f _{1 to} f _N Frequency

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Claims (2)

[Claims] 1. Optical direct amplifiers connected in series in multiple stages via optical fibers sequentially transfer main signal light, and these optical direct amplifiers respectively assign different frequencies for frequency shift keying modulation. And modulating the alarm information created by the repeater to which the optical direct amplifier belongs at the assigned frequency into the intensity of the pumping light, superimposing the alarm information on the main signal light, and transferring it to the downstream side. Multi-stage relay alarm transfer method. 2. Optical direct amplifiers, which are connected in series in multiple stages via optical fibers, inject pumping light into a rare earth-doped fiber into which signal light is input from each input terminal and a rare earth-doped fiber into which this signal light is input. Then, the wavelength division multiplexing coupler that outputs the amplified signal light to the output terminal, the pumping light source that outputs this pumping light, and this pumping light source is modulated by the alarm information at the frequency unique to each optical direct amplifier and the intensity of A multistage relay alarm transfer system, comprising: a light source drive circuit for inputting different excitation lights to a wavelength division multiplexing coupler.