JPH06164515A - Optical amplifying repeater - Google Patents

Abstract

PURPOSE:To branch/synthesize another signal which is waveform-multiplexed with a main signal so that a high S/N rate can be obtained without being affected by the main signal by simultaneously branching the optical signal which is waveform- multiplexed and synthesizing exciting light to branching light. CONSTITUTION:The main signal is loaded on a 1.55mum-band and a monitor control signal on the optical signal of a 1.347m-band, for example, so as to transmit them on an optical fiber transmission line 8. When the both optical signals are inputted from the transmission line 8 to the terminal (1) of a WDM coupler 1, the main signal is branched to the optical amplifier fiber 2 of a terminal (2)-side and a control signal to the light-receiving element 5 of a terminal (3)-side. The main signal is light-amplified by excitation by inputting the exciting light of the 1.48mum-band to the terminal (4) of the coupler 1. On the other hand, the control signal is converted into an electric signal in the element 5, is monitor-controlled and amplified in an electric circuit 6 and is electrically/optically converted into the original wavelength band in a light- emitting element 7. Furthermore, the main signal which is inputted to the terminal (4) of a WDM coupler 3 and is amplified in an amplifier 2 is synthesized with the control signal in the terminal (2) so as to output it again to an optical fiber 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier repeater used in an optical communication system or the like. The optical amplifier that amplifies the signal light as it is does not require a high-speed electronic circuit, and has excellent characteristics such as high gain, high output, and no dependence on the signal speed, and is applicable to various systems. Is possible. When using an optical amplifier as a repeater, it is important to perform supervisory control in order to grasp the state of each repeater. Therefore, the main signal and supervisory control signal are multiplexed and transmitted. It is necessary to be able to efficiently multiplex / separate from the signal.

[0002]

2. Description of the Related Art In an optical amplification repeater system, in order to monitor and control each repeater, the same optical wavelength is used to superimpose a supervisory control signal on a main signal for transmission, or the optical wavelength of the main signal (usually , 1.55 μm band) and several nm to several tens of n
A method is being studied in which a supervisory control signal is placed on optical wavelengths distant from each other by m, and the signals are multiplexed and transmitted in the state of optical signals.

[0003]

In the case of the method of superimposing the supervisory control signal on the main signal for performing supervisory control of each repeater, the main signal is intensity modulation and the supervisory control signal is also amplitude modulation.
The component of the main signal leaks depending on the frequency of the supervisory control signal, the characteristics of the supervisory control signal depend on the mark ratio of the main signal, and the S / N ratio of the supervisory control signal is poor because of minute modulation. There is a problem such as the deterioration of the amplitude of.

In the latter case of the wavelength division multiplexing method,
In order to process the main signal light and the supervisory control signal light separately in each repeater, a demultiplexer for demultiplexing the supervisory control signal light from the multiplexed main signal light and a demultiplexer A multiplexer for multiplexing the supervisory control signal light with the main signal light again and sending it to the transmission line is required, and the number of optical components increases, which is disadvantageous in terms of price and reliability. Also, the main signal suffers loss,
There are problems that the gain is lowered and the noise figure of the repeater is deteriorated.

The present invention has been made in view of the above problems, and it is an object of the present invention to determine what kind of modulation the other signals such as the wavelength-multiplexed supervisory control signals are not affected by the main signal at all. The method is also applicable, and is to enable efficient demultiplexing and multiplexing with the main signal so that a high S / N ratio can be obtained.

[0006]

FIG. 1 is a diagram illustrating the principle of the present invention. The optical amplification repeater of the present invention is an optical amplification repeater that repeats wavelength-multiplexed optical signals in the first and second optical wavelength bands, and is wavelength-multiplexed with a pumping light source 31 that generates pumping light. An optical signal is input and demultiplexed into optical signals in the first and second optical wavelength bands, and the pumping light from the pumping light source 31 is input to the remaining input terminal and demultiplexed. First WDM coupler 3 for multiplexing optical signals in the optical wavelength band of
2 and an optical amplifier 33 for optically amplifying the optical signal of the first wavelength band demultiplexed by the first WDM coupler 32 by using the pump light.
And a regenerative repeater circuit 34 for regeneratively repeating the optical signal of the second wavelength band demultiplexed by the first WDM coupler 32, an optical signal output from the optical amplifier 33, and an optical signal output from the regenerative repeater circuit 34. And a second WDM coupler 35 that multiplexes the signals.

The above-described optical amplification repeater is based on the regeneration repeater circuit 34.
Instead of the above, a second optical amplifier that optically amplifies an optical signal in the second wavelength band as an optical signal can be provided.

Further, the above-mentioned optical amplification repeater has a second WDM
The pump light may be configured to be input to the remaining output terminals of the coupler, and the pump light may be configured to be input to the optical amplifier from the opposite direction and to be backward pumped.

The above-mentioned first and second WDM couplers can be constructed by fiber fusion type WDM couplers capable of selecting the wavelength period of the loss of the passing signal light by appropriately selecting the fusion length and the fusion interval. .

[0010]

[Function] WDM (Wavelenght Divis) such as fiber fusion type
Ion Multiplex: A coupler has a wavelength dependence in the loss of the passing signal light depending on the signal light passing path, and repeats the characteristics of attenuation and transmission at a certain wavelength cycle. The wavelength period and the like can be selected by appropriately selecting the landing interval. By utilizing this property, the demultiplexing of the wavelength-multiplexed optical signal and the multiplexing of the pumping light into the demultiplexed light are performed at the same time.

For example, the first wavelength is 1.55 μm
Band, using the 1.34 μm band as the second light wavelength, 1.
When a main signal is put on 55 μm and another signal such as a monitor control signal is put on the 1.34 μm band, the fiber fusion type WD
When the wavelength-multiplexed optical signal in the 1.55 μm band and 1.3 μm band is input to the M coupler terminal, 1.55 μm is input to the terminal.
An optical signal in the μm band and an optical signal in the 1.34 μm band can be demultiplexed and output to the terminal.

At the same time, when an optical signal in the 1.48 μm band, which is the excitation wavelength in the optical fiber doped with a rare earth element for amplifying the optical signal in the 1.55 μm band, is input from the terminal,
The optical signal in the 1.48 μm band is output to the terminal (not output to the terminal) and can be combined with the optical signal in the 1.55 μm band at the terminal. By connecting a rare earth element-doped optical fiber amplifier to the end of the output of this terminal, a forward pumping type optical amplifier for amplifying an optical signal in the 1.55 μm band can be constructed.

In the second WDM coupler, an optical signal in the 1.55 μm band from the terminal and 1.34 from the terminal
When an optical signal in the μm band is input, the optical signals of both wavelengths are combined and output to the terminal. In this case, if the 1.48 μm band optical signal is input from the vacant terminal, the
The optical signal in the 8 μm band is output to the terminal, whereby the optical fiber amplifier 2 can be backward pumped.

As a result, conventionally, when the WDM coupler is used, it is used separately for the purpose of multiplexing and demultiplexing two wavelengths, and one port is wasted. However, the wavelength to be used can be selected as described above. For example, it is possible to combine and demultiplex optical signals of three wavelengths at the same time, and it is possible to increase the functions without increasing the number of optical components.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an optical amplification repeater as an embodiment of the present invention. In the figure, 1 is a fiber fusion type WDM
(Wavelenght Division Multiplex) A coupler with an optical fiber transmission line 8 at its terminal.
From the laser diode 4 for pumping is input to its terminal, and the optical fiber amplifier 2 is connected to the subsequent stage of the terminal, and the optical fiber amplifier 2 is connected to the subsequent stage of the terminal. A light receiving element 5 formed of a photodiode that senses an optical signal in the 1.34 μm band is connected.

3A and 3B show the structure and characteristics of the WDM coupler 1 of this embodiment. In the fiber-fusion type WDM coupler, the loss of the passing optical signal has wavelength dependence in the path from terminal to terminal and from terminal to terminal, or from terminal to terminal and terminal to terminal. FIG. 3B shows this wavelength dependence. As shown in the figure, the WDM coupler 1 repeats the characteristics of attenuation and transmission at a certain wavelength cycle,
The wavelength period and the like can be selected by appropriately selecting the fusion length L and the fusion interval D.

Utilizing this property, the values of the interval and the wavelength are set so as to have the characteristics shown in FIG. 3B in this embodiment. That is, in the → route, the optical signal input from the terminal and output to the terminal has a wavelength of 1.34
The wavelengths of 1.4 μm and 1.48 μm are attenuated and the wavelength is 1.4.
The 1 μm band and the 1.55 μm band are transmitted. In the path of →, optical signals input from the terminal and output to the terminal are attenuated at wavelengths of 1.41 μm band and 1.55 μm band, and wavelengths of 1.34 μm band and 1.48 μm band are attenuated.
The band is transmitted. The same applies to the → route and → route. In the → route, the optical signal input from the terminal and output to the terminal has a wavelength of 1.34 μm.
The wavelengths of 1.41 μm and 1.48 μm are transmitted.
Those in the μm band and the 1.55 μm band are attenuated. Also →
In the path of, the optical signals input from the terminal and output to the terminal are transmitted at wavelengths of 1.41 μm band and 1.55 μm band, and attenuated at wavelengths of 1.34 μm band and 1.48 μm band. It

The optical fiber amplifier 2 is a rare-earth element-doped optical fiber, and uses a pumping light in the 1.48 μm band for 1.5.
It is an optical amplifier that amplifies an optical signal in the 5 μm band. The output signal of the optical fiber amplifier 2 is input to the terminal of a WDM coupler 3 having the same configuration as the WDM coupler 1.

The monitor / control signal optically / electrically converted by the light receiving element 5 is inputted to the electronic circuit 6 and processed, and then is again electrically / optically converted into an optical signal in the 1.34 μm band by the light emitting element 7 which is a laser diode. It is then input to the terminal of the WDM coupler 3. Also, from the terminal of the WDM coupler 3, 1.
The excitation light in the 48 μm band can be input.

The operation of the apparatus of this embodiment will be described below.
In an optical communication system to which the optical amplification repeater of this embodiment is applied, an optical fiber transmission line 8 is prepared by adding a main signal to an optical signal in the 1.55 μm band and a supervisory control signal to an optical signal in the 1.34 μm band. To transmit. Now, the optical signals of the 1.55 μm band and the 1.34 μm band are transmitted from the optical fiber transmission line 8 to WD.
When input to the terminal of the M coupler 1, the WDM coupler 1 outputs the optical signal in the 1.55 μm band (main signal) to the optical amplification fiber 2 on the terminal side, and the optical signal in the 1.3 μm band (monitoring control signal) into the terminal. It is demultiplexed to the light receiving element 5 on the side.

Further, by inputting the 1.48 μm band pumping light generated by the laser diode 4 to the terminal of the WDM coupler 1, the 1.48 μm band pumping light is combined with the 1.55 μm band optical signal at the terminal. Then, the light signal can be input to the optical amplification fiber 2, whereby an optical signal in the 1.55 μm band can be optically amplified by forward pumping.

On the other hand, the optical signal (monitoring control signal) in the 1.34 μm band is converted into an electric signal by the light receiving element 5, and the electronic circuit 6
Then, after performing monitoring control or amplification based on this monitoring control signal, the light emitting element 7 again performs electrical / optical conversion into an optical signal in the 1.34 μm band. Furthermore, input to the terminal of the WDM coupler 3, and thereby 1.34 μm at the terminal.
The optical signal of the band and the optical signal amplified by the optical fiber amplifier 2 is 1.5.
The optical signal in the 5 μm band is recombined and the optical fiber transmission line 9
Output to.

When pumping light in the 1.48 μm band is input from the terminal of the WDM coupler 3, this pumping light is output to the terminal side and the optical fiber amplifier 2 can be pumped backward.

Various modifications are possible in carrying out the present invention. For example, in the above-described embodiment, the optical signal in the 1.34 μm band demultiplexed by the WDM coupler 1 is optically / electrically converted, and then processed by the electronic circuit 6 to be electrically / optically converted again to generate an optical signal in the 1.55 μm band. Although the signal is multiplexed, the present invention is not limited to this, and these light receiving elements 5,
An optical amplifier is used instead of the electronic circuit 6 and the light emitting element 7, and the demultiplexed 1.34 μm band optical signal is optically amplified by the optical amplifier as it is and recombined with the 1.55 μm band optical signal. You may do it.

The signal to be put on the optical signal in the 1.34 μm band is not limited to the supervisory control signal.
The transmission signal may be wavelength-multiplexed by placing the main signal in the μm band.

FIG. 4 shows an example of a relay station constructed by using the optical amplification repeater of the present invention. In the figure, 11 and 15 are the optical amplification repeaters of the present invention described in the above embodiments, the optical amplifier repeater 11 is for the upstream line, and the optical amplification repeater 15 is for the downlink line. Further, reference numerals 12, 13, and 14 are WDM couplers having the same configuration as that of the WDM coupler 1, and reference numerals 16 and 17 are light emitting elements formed of photodiodes.

In the upstream line, the optical fiber transmission line 1
The optical signal input from 8 is optically amplified by the optical amplification repeater 11 and then transmitted to the optical fiber transmission line 19 via the WDM coupler 12. The output signal of the optical amplification repeater 11 contains a small amount of pumping light in the 1.48 μm band, but this pumping light is demultiplexed to the terminal of the WDM coupler 12 and then the WDM
It is input to the terminal of the coupler 13. Similarly, in the downlink, the optical signal output from the optical amplification repeater 15 is transmitted to the optical fiber transmission line 21 via the coupler 14 and
The 1.48 μm band pump light demultiplexed by the M coupler 14 is W
It is input to the terminal of the DM coupler 13.

The operation of this relay station will be described below. The 1.55 μm band optical signal from the upstream transmission line 18 is amplified by the optical amplification repeater 11, passes through the WDM coupler 12, and is output to the upstream transmission line 19. The 1.48 μm band pump light remaining without being used in the optical amplification repeater 11 is the WDM coupler 1
It is demultiplexed by 2 and further passes through the WDM coupler 13,
The signal is input to the WDM coupler 14 on the downlink side and then input to the optical amplification neutralizer 15 on the downlink side from the opposite direction (input to the terminal of the WDM coupler 3), whereby the optical amplification repeater 1
5 will be back-excited. In this case, the loss of the WDM couplers 12 and 13 14 is 2.1 dB assuming 0.7 dB per unit.

The residual pumping light from the downstream optical amplification repeater 15 also enters the upstream optical amplification repeater 11 through the same path. As described above, according to the configuration of FIG. 4, the pumping light remaining at the outputs of the optical amplifying repeaters 11 and 15 can be input to the optical amplifying repeaters of the other line from the opposite direction and be pumped backward. Therefore, the remaining excitation light can be effectively used without waste.

Further, since a part (about 20 dB down) of the 1.55 μm band optical signal output to the transmission line by the WDM couplers 12 and 14 is input to the WDM coupler 13, that part of the optical signal is received respectively. Light can be received by the elements 16 and 17 and used as a monitor of signal light.

[0031]

As described above, in the optical amplification repeater system, for example, the main signal is carried on the 1.55 μm band optical signal, and the supervisory control signal and other signals are carried on the 1.34 μm band optical signal for transmission. By doing so, the signal on the 1.34 μm band side is not affected by the main signal at all, any modulation method may be used, and a high S / N ratio can be obtained. As for the configuration of the repeater, it is possible to simplify the configuration by using a WDM coupler for pumping light without increasing loss or the like.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing an optical amplification repeater as an embodiment of the present invention.

FIG. 3 is a diagram showing an example of the configuration and characteristics of a fiber fusion-bonded WDM coupler in the apparatus of the embodiment.

FIG. 4 is a diagram showing a relay station configured using the optical amplification repeater of the present invention.

[Explanation of symbols]

1,3,12,13,14, WDM coupler 2 Optical fiber amplifier 4 Light emitting element composed of pump laser diode (1.48
μm band) 5 Photodetector consisting of photodiode 6 Electronic circuit 7 Light emitting device consisting of laser diode (1.34 μm
Band) 8, 9, 18, 19, 20, 21 Optical fiber transmission line 16, 17 Light receiving element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H04J 14/02 8220-5K H04B 9/00 E

Claims (4)

[Claims] 1. An optical amplification repeater for repeating an optical signal wavelength-multiplexed in first and second optical wavelength bands, comprising: a pumping light source (31) for generating pumping light; and the wavelength-multiplexed light. A signal is input and this is input to the first and second
While demultiplexing into the optical signal of the optical wavelength band of the first, the pumping light from the pumping light source is input to the remaining input terminal, and is multiplexed with the demultiplexed optical signal of the first optical wavelength band. WDM of 1
A coupler (32), an optical amplifier (33) for optically amplifying an optical signal of the first wavelength band demultiplexed by the first WDM coupler by using the pumping light, and a demultiplexer by the first WDM coupler. A regenerative repeater circuit (34) for regeneratively repeating the waved optical signal in the second wavelength band, and a second remultiplexer for multiplexing the optical signal output from the optical amplifier and the optical signal output from the regenerative repeater circuit. WDM coupler (3
5) An optical amplification repeater including 2. The optical device according to claim 1, further comprising a second optical amplifier which optically amplifies an optical signal in the second wavelength band as an optical signal, instead of the regenerative repeater circuit. Amplifying repeater. 3. A pump light is configured to be input to the remaining output terminal of the second WDM coupler, and the pump light is input to the optical amplifier from the opposite direction to pump the light backward. The optical amplification repeater according to claim 1 or 2. 4. The first and second WDM couplers are fused lengths,
The optical amplification repeater according to any one of claims 1 to 3, wherein the optical amplification repeater is a fiber fusion type WDM coupler which can select a wavelength period of loss of passing signal light by appropriately selecting a fusion interval.