JPH06152538A - Optical amplifier repeater - Google Patents

Abstract

PURPOSE:To hold the change of an ASK modulation degree at a constant value by correcting the change of a response level accompanying the fluctuation of the quantizing efficiency of an exciting light source by a simple circuit constitution, and to make a circuit scale compact. CONSTITUTION:This device is equipped with an exciting light source 9 which outputs an exciting light, light source driving circuit 10 which drives the exciting light source 9, oscillator 16 which generates a response frequency for ASK- modulating the exciting light, WDM coupler 5 which multiplexes the exciting light and an optical signal, rare earth dope fiber 3 which amplifies the optical signal by the exciting light, optical branching circuit 8 which branches the optical signal and a frequency for monitor transmitted from an optical terminal station device, direct current amplifier 12 which direct current-amplifies the optical signal, and outputs a control voltage, and and BPF 19 which extracts the frequency for monitor. The device is equipped with a superimposing circuit 15 which PWM-modulates a response frequency by in-repeater information (x) according to the frequency for monitor, and a gain variable multiplier 13 which amplitude-controls the PWM modulated signal by the control voltage outputted from the direct current amplifier 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplification repeater, and more particularly to an optical amplification repeater using a rare earth-doped fiber.

[0002]

2. Description of the Related Art Referring to FIG. 3, a conventional optical amplification repeater is designed so that a pumping light source 9 drives a WDM (Wavelength D).
ivision Multiplex; wavelength division multiplexing)
A backward pumping basic configuration for amplifying an optical signal input through the input fiber 1 by introducing pumping light into the rare earth-doped fiber 3 through the coupler 5, and a WDM coupler 5 and a rare earth-doped fiber for stabilizing the amplification operation. An isolator 4 and an isolator 6 are formed on both sides of 3. These pumping light source 9, coupler 5 and isolator 6, a band pass filter (BPF) 7 for removing unnecessary optical noise other than optical signals, and a part of the output power of the optical amplification repeater at the output of BPF 7. Optical branch circuit 8 for branching
A photodetector 11 that receives the branched output from the optical branching circuit 8 and detects an optical signal; and a direct current amplifier 12 that amplifies the optical detection signal from the optical detector 11 and outputs a control voltage.
The pump light source 9 is controlled by the control voltage of the output of the DC amplifier 12.
A feedback circuit is constituted by the light source drive circuit 10 for driving the optical amplifier, and the output power of the optical amplification repeater transmitted through the output fiber 2 is controlled to be constant.

The above is the configuration and function of amplifying the optical signal of the optical amplification repeater. Next, in order to monitor the information x inside the repeater of the optical amplification repeater by an external optical terminal device, A configuration and a function for transmitting the information x to the optical terminal device will be described.

In the optical amplification repeater system, when the supervisory frequency f _SV is superimposed on the optical signal and transmitted, the supervisory frequency f _{SV is applied} to the ASK (Amplitude Shift K).
A modulation method is used. The monitoring frequency f _SV which is ASK-modulated by this method and superposed on the optical signal and sent from the optical terminal device is inputted through the input fiber 1, and isolators 4, rare earth-doped fibers 3, W
The light is branched by the optical branching circuit 8 through the DM coupler 5, the isolator 6 and the BPF 7. Branched monitoring frequency f _SV
Is input to the BPF 19 (f ₀ = f _SV ) through the photodetector 11 and the monitoring frequency f _SV is extracted. The monitoring frequency f _SV extracted by the BPF 19 is demodulated and decoded by the control signal receiving circuit 18 to output the first, second and third control signals, and the A / D converter 20 is controlled by the first control signal. Then second
Control signal controls the P / S converter 17, and the third control signal controls the buffer circuit 23. The A / D converter 20 is controlled by the first control signal from the control signal receiving circuit 18, converts the repeater internal information x of the analog signal into a digital signal, and supplies the digital signal to the P / S converter 17. P /
The S converter 17 converts the in-repeater information x of the parallel signal from the A / D converter 20 into serial data by the second control signal from the control signal receiving circuit 18, and supplies the serial data to the superimposing circuit 15. The repeater internal information x converted into serial data is subjected to PWM modulation of the response frequency f _RES from the oscillator 16 in the superimposing circuit 15 and both are superimposed on the control voltage from the DC amplifier 12 through the variable gain amplifier 13 and the capacitor 24. The light source drive circuit 10 is controlled. As a result, the light source drive circuit 10 drives the excitation light source 9 to drive the excitation light source 9
ASK output power is modulated. That is, the response frequency f _RES
Then, the output power of the pumping light source 9 is ASK-modulated to send the repeater internal information x through the output fiber 2 and transmit it to the optical terminal device.

Here, since the pumping light source 9 changes in quantum efficiency due to temperature fluctuations, aging changes, etc., the ASK modulation degree also changes. To correct this change, the repeater internal information x
After the response frequency f _RES PWM-modulated by the WDM coupler 5 and multiplexed with the optical signal is branched by the optical branching circuit 8, B
It is extracted by the PF 21 (f ₀ = f _RES ) and the level fluctuation of the extracted response frequency f _RES is detected by the detection circuit 22 and supplied to the buffer circuit 23. The buffer circuit 23 drives the light source drive circuit 10 by controlling the variable gain amplifier 13 with the level variation of the response frequency f _RES from the detection circuit 22 in response to the third control signal from the control signal reception circuit 18 to drive and excite the light source drive circuit 10. The response level of the light source 9, that is, the output power is corrected and kept constant. Here, since the response frequency f _RES is not always transmitted, the buffer circuit 23 is controlled by the third control signal from the control signal receiving circuit 18 so that the above correction functions only when the response frequency f _RES is transmitted. .

[0006]

In this conventional optical amplification repeater, the circuit is complicated, the scale is large, and miniaturization is difficult.

[0007]

In the optical amplification repeater according to the present invention, a monitoring frequency is sent from the optical terminal equipment to the optical amplification repeater, and the internal information of the repeater is returned from the optical amplification repeater. In an optical amplification repeater system for monitoring information in a repeater, a pumping light source that outputs a pumping light that is ASK-modulated by being controlled by a first control signal, and a first control signal that is controlled by a second control signal A light source driving means for driving the pumping light source to ASK-modulate the pumping light; a frequency generating means for generating a modulation frequency for ASK-modulating the pumping light output from the pumping light source; A WDM coupler for multiplexing the pumping light and an optical signal;
A rare-earth-doped fiber for introducing the pumping light through a coupler to amplify the optical signal, a multiplexed signal of the optical signal amplified by the rare-earth-doped fiber from the WDM coupler and the pumping light, and the rare-earth-doped fiber, A signal branching unit for branching a monitoring frequency that is ASK-modulated and transmitted from the optical terminal device through the WDM coupler, and light for detecting the optical signal from the output of the signal branching unit, amplifying the DC signal, and outputting a control voltage. Detection means,
A frequency extracting means for extracting the monitoring frequency from the output of the signal branching means, and a PWM control of the modulating frequency from the frequency generating means by the in-repeater information controlled by the monitoring frequency of the output of the frequency extracting means. Modulate and P
A modulation means for outputting a WM modulation signal, an amplitude control means for controlling the amplitude of the PWM modulation signal from the modulation means by a control voltage for the output of the light detection means, and an amplitude control for the control voltage for the output of the light detection means. Signal superimposing means for superimposing the PWM modulation signal output from the means to output the second control signal.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. Referring to FIG. 1 showing an embodiment of the present invention, the basic of backward pumping for amplifying an optical signal input through an input fiber 1 by introducing pumping light from a pumping light source 9 through a WDM coupler 5 into a rare earth-doped fiber 3. Configuration and
In order to stabilize the amplification operation, an isolator 4 and an isolator 6 are formed on both sides of the WDM coupler 5 and the rare earth-doped fiber 3. These pumping light source 9, coupler 5 and isolator 6, BPF 7 for removing unnecessary optical noise other than optical signals, and optical branching circuit 8 for branching a part of the output power of the optical amplification repeater by the output of BPF 7. ,
Photodetector 11 that receives the branch output from the optical branch circuit 8 and detects an optical signal, DC amplifier 12 that amplifies the photodetection signal from the photodetector 11 by DC, and outputs a control voltage, and DC amplifier 12 output A feedback circuit is configured with a light source drive circuit 10 that drives the pumping light source 9 under the control voltage of 1 to control the output power of the optical amplification repeater sent through the output fiber 2 to be constant.

The above is the configuration and function of amplifying the optical signal of the optical amplifying repeater. Next, in order to monitor the information x inside the repeater of the optical amplifying repeater by an external optical terminal device, A configuration and a function for transmitting the information x to the optical terminal device will be described.

In the optical amplification repeater system, a method of ASK-modulating the monitoring frequency f _SV is used when the monitoring frequency f _SV is superimposed on the optical signal and transmitted. The monitoring frequency f _SV which is ASK-modulated by this method and superposed on the optical signal and sent from the optical terminal device is input through the input fiber 1, and isolators 4, rare earth-doped fibers 3,
The light is branched by the optical branching circuit 8 through the WDM coupler 5, the isolator 6 and the BPF 7. Branched monitoring frequency f
_{The SV} is input to the BPF 19 (f ₀ = f _SV ) through the photodetector 11 and the monitoring frequency f _SV is extracted. The monitoring frequency f _SV extracted by the BPF 19 is demodulated and decoded by the control signal receiving circuit 18 to output the first, second and third control signals, and the A / D converter 20 is controlled by the first control signal. Then, the P / S converter 17 is controlled by the second control signal and the buffer circuit 23 is controlled by the third control signal. A / D
The converter 20 is controlled by the first control signal from the control signal receiving circuit 18 to convert the repeater internal information x of an analog signal into a digital signal and supply it to the P / S converter 17. P
The / S converter 17 converts the in-relay information x of the parallel signal from the A / D converter 20 into serial data by the second control signal from the control signal receiving circuit 18 and superimposes it on the superimposing circuit 15.
Supply to. The repeater internal information x converted into serial data is subjected to PWM modulation of the response frequency f _RES from the oscillator 16 in the superimposing circuit 15 and both are superimposed on the control voltage from the DC amplifier 12 through the variable gain amplifier 13 and the capacitor 24. The light source drive circuit 10 is controlled. As a result, the light source drive circuit 10 drives the pumping light source 9 and ASK-modulates the output power of the pumping light source 9. That is, the response frequency f
By SK modulating the output power of the pumping light source 9 with _RES , the repeater internal information x is sent out through the output fiber 2 and transmitted to the optical terminal device.

Here, since the quantum efficiency of the pumping light source 9 changes due to temperature fluctuations, aging changes, etc., the ASK modulation degree also changes. To correct this change, a constant level reference voltage V _ref is supplied from the inside of the optical amplification repeater to the variable gain amplifier 14, and the reference voltage V _ref is supplied to the DC amplifier 12.
The response level of the pumping light source 9, that is, the output power is kept constant by controlling by the output control voltage and controlling the variable gain amplifier 13 by the changed output to control the signal amplitude of the response frequency f _RES . That is, when the quantum efficiency of the pumping light source 9 changes and the output power changes, the amplification factor of the optical signal in the rare earth-doped fiber changes in accordance with the change, and the level of the optical signal fluctuates. 11 is detected and the control voltage of the output of the DC amplifier 12 changes.
Therefore, by controlling the signal amplitude of the response frequency f _{RES by} changing the control voltage of the output of the DC amplifier 12, the response level of the pumping light source 9, that is, the output power can be kept constant.

Next, the characteristics of the pumping light source 9 will be described with reference to FIG. 2. When the light source characteristics in the initial stage are S ₁ and the deterioration characteristics are S ₂ , the optical signal output power is kept constant, that is, the pumping light source. Since the bias current is controlled so that the output power becomes constant, the bias current changes from I _B1 to I _B2 . Therefore, the control voltage of the light source drive circuit 10 changes from V _B1 to V _B2 , but when the modulation is constant with the amplitude V _PP1 , the change amount of the pump light source output P _P becomes small. Therefore, in order to keep the amount of change in the pump light source output P _P constant, V _PP1 is increased only by the amount of change in efficiency from S ₁ to S ₂ and V _PP2 is increased.
You can do it as Here, the change in efficiency in order to respond to changes in V _B, it is possible to correct the change in efficiency by performing the control of the V _PP to V _B as information. Strictly speaking, a change in I _B also includes a change in I _th , so a slight error occurs, but
There is no problem in practical use.

[0013]

As described above, according to the present invention, the change in the response level due to the change in the quantum efficiency of the pumping light source can be corrected by the simple circuit configuration to keep the change in the ASK modulation constant. The circuit scale can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an optical amplification repeater according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a pumping light source of the optical amplification repeater according to the embodiment.

FIG. 3 is a block diagram showing a conventional optical amplification repeater.

[Explanation of symbols]

 1 Input Fiber 2 Output Fiber 3 Rare Earth Doped Fiber 4,6 Isolator 5 WDM Coupler 7 Bandpass Filter (BPF) 8 Optical Branch Circuit 9 Excitation Light Source 10 Light Source Driving Circuit 11 Photodetector 12 DC Amplifier 13, 14 Gain Variable Amplifier 15 superposition circuit 16 oscillator 17 P / S converter 18 control signal receiving circuit 19 band pass filter (BPF) 20 A / D converter x repeater information

Claims (1)

[Claims] 1. An optical amplification repeater system in which a monitoring frequency is sent from an optical terminal device to an optical amplification repeater and information in the repeater is returned from the optical amplification repeater to monitor the information in the repeater, A pumping light source that outputs ASK-modulated pumping light controlled by a first control signal, and a second control signal that drives the pumping light source by the first control signal to drive the pumping light ASK Light source driving means for modulating, frequency generating means for generating a modulation frequency for ASK-modulating the pumping light of the pumping light source output, and WD for multiplexing the pumping light from the pumping light source and an optical signal
An M coupler, a rare earth-doped fiber for introducing the pumping light through the WDM coupler to amplify the optical signal, and a multiplexed signal of the optical signal amplified by the rare earth-doped fiber from the WDM coupler and the pumping light. And signal branching means for branching the ASK-modulated monitoring frequency transmitted from the optical terminal equipment through the rare earth-doped fiber and the WDM coupler, and detecting the optical signal from the output of the signal branching means and amplifying it with direct current. A photodetector that outputs a control voltage, a frequency extractor that extracts the monitoring frequency from the output of the signal branching unit, a frequency controlled by the monitoring frequency of the output of the frequency extractor, and the frequency according to the in-repeater information. Modulation means for PWM-modulating the modulation frequency from the generating means to output a PWM modulation signal; Amplitude control means for controlling the amplitude of the PWM modulation signal from the modulation means by the control voltage of the output means output; and the PWM modulation signal of the amplitude control means output superimposed on the control voltage of the light detection means output. An optical amplification repeater, comprising: a signal superimposing unit that outputs a second control signal.