JPH06347841A - Optical amplifying repeater - Google Patents

Abstract

PURPOSE:To provide an optical amplifying repeater capable of reducing the optical loss and improving the noise figure. CONSTITUTION:In this optical amplifying repeater 1b, a light wavelength multiplexer/demultiplexer coupler (WDM) 3 extracting and branching a remaining exciting beam from a signal beam transmitted from the optical amplifying repeater 1a connected to an input initial stage as a prestage is arranged. By noninput detection circuit (DET) 12, a noninput state of the remaining exciting beam is detected, and a noninput detection signal is sent to a repeater output control circuit (CONT) 10. In the repeater output control circuit (CONT) 10, when the remaining exciting beam is in the noninput state, the optical amplifying repeater 1b is made to be in a stand-by state by suppressing the exciting beam generated by a laser diode(LD) 7 for exciting. When the optical remaining repeater 1b comes in the stand-by state, since the remaining exciting beam outputted from an optical coupler (CPL) is reduced, the optical amplifying repeaters after next stage become the stand-by state also by detecting the reduced exciting beam.

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 having a function of suppressing a pumping state of pumping light which is a combination of internally generated signal light when input signal light is in a non-input state. Regarding vessels.

[0002]

2. Description of the Related Art Conventionally, an optical amplifier is disclosed in, for example, Japanese Patent Laid-Open No. 4-14.
As disclosed in Japanese Patent No. 7226, it is incorporated in an optical fiber transmission system or the like, and is used to amplify the signal light transmitted through the optical fiber as it is.
However, when performing long-distance optical communication, the signal light transmitted through the optical fiber is attenuated, so a plurality of optical amplification repeaters including an optical amplifier that electrically amplifies the signal light are sequentially connected and the signal light is transmitted. By avoiding the attenuation of, the optical communication over a long distance is enabled.

FIG. 2 is a block diagram showing an example of a conventional optical amplification repeater. In this optical amplification repeater 1, when the signal light is input from the transmission line fiber 2 which is the input port of the optical coupler (CPL) 6a, it is branched to the first and second output ports of the optical coupler (CPL) 6a. ,
It is output to the optical wavelength combining / branching coupler (WDM) 3 and the photodiode (PD) 8a, respectively. The excitation laser diode (LD) 7 is a rare earth-doped optical fiber (ED
F) The pumping light of the wavelength λ2 necessary for pumping and amplifying 4 is emitted, and this pumping light is output to the first output port of the optical coupler (CPL) 6a in the optical wavelength combining / branching coupler (WDM) 3. It is multiplexed with the output signal light of wavelength λ1.

The rare earth-doped optical fiber (EDF) 4 absorbs the excitation light and amplifies the signal light by stimulated emission by the signal light. The output of the rare earth-doped optical fiber (EDF) 4 is an optical isolator (ISO) 5 for suppressing oscillation due to reflection of light, residual excitation light, and spontaneous emission light generated in the rare earth-doped optical fiber (EDF) 4. To the optical filter (FIL) 9 in order to prevent The signal light that has passed through these is branched by the optical coupler (CPL) 6b so that one becomes the output of the optical amplification repeater 1 and the other is transmitted to the photodiode (PD) 8b.

The repeater output control circuit (CONT) 10 is
An LD drive circuit (LDD) that monitors the output of the signal light detected by the photodiode (PD) 8b and supplies a current to the pumping laser diode (LD) 7 so that the output of the optical amplification repeater 1 becomes constant. ) 11 is controlled. The signal light output from the second output port of the optical coupler (CPL) 6a is converted from light to current by the photodiode (PD) 8a and detected by the no-input detection circuit (DET) 12.
The no-input detection circuit (DET) 12 outputs a no-input detection signal to the repeater output control circuit (CONT) 10 when detecting no-input of the signal light, and the repeater output circuit 10 is based on this no-input detection signal. LD to limit the LD current for excitation
The drive circuit (LDD) 11 is controlled.

As described above, in the optical amplification repeater, the longer the current supplied to the laser diode, the shorter the life thereof. Therefore, the life of the pump LD is prevented from being deteriorated by limiting the pump LD when there is no signal. There is. That is, by suppressing the excited state when there is no signal, the occurrence of an optical surge at the rise of signal light is prevented.

[0007]

In the case of the above-mentioned optical amplifier repeater, since the optical coupler (CPL) 6a is used in the first stage of inputting the signal light, the optical loss in this optical coupler (CPL) 6a is large. As a result, there is a drawback that the noise figure, which is an important characteristic for optical amplification, becomes large.

The present invention has been made to solve the above problems, and its technical problem is to provide an optical amplifier repeater capable of reducing the optical loss and improving the noise figure. .

[0009]

According to the present invention, a light for suppressing the pumping state of pumping light as a combination of the internally generated signal light when the input signal light is in a non-input state. In an amplification repeater, an optical separation means for obtaining separated light separated from the signal light by utilizing the property of light, and a no-input detection for detecting a no-input state of the signal light according to the separated light and outputting a no-input detection signal An optical amplification repeater including means and suppression executing means for suppressing the excited state based on the no-input detection signal is obtained.

Further, according to the present invention, in the above-mentioned optical amplification repeater, as an optical separating means, an optical wavelength combining / demultiplexing coupler for separating the residual pumping light from the signal light by utilizing the wavelength of the light is used. An amplification repeater is obtained.

[0011]

The optical amplifier repeater of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the basic configuration of an optical amplification repeater according to an embodiment of the present invention.

In this optical amplification repeater, a plurality of devices having the same structure are sequentially connected for performing long-distance optical communication.
In the case of the one shown in the figure, the signal light is the optical repeater amplifier 1 in the previous stage.
It is input from a through the transmission line fiber 2 which is the first input port of the optical wavelength combining / branching coupler (WDM) 3 arranged at the input first stage in the optical amplification repeater 1b. Further, the optical wavelength synthesizing / branching coupler (WDM) 3 utilizes the wavelength of the light to output the residual pumping light from the signal light (here, the residual pumping light is separated from the signal light. It may also be called)) and also functions as a light separation means for extracting and branching.

That is, this optical wavelength combining / branching coupler (WD
M) 3 relates to the pumping light of wavelength λ2 input from the pumping laser diode (LD) 7 connected to the second input port and the signal light of wavelength λ1 input from the first input port. The wavelength light is combined with low loss, transmitted to the first output port connected to the rare earth-doped optical fiber (EDF) 4 and the oscillation preventing optical isolator (ISO) 5, and input from the first input port. Wavelength λ1
And the residual pumping light of wavelength λ2 ′ are wavelength-separated and output to the first output port and the second output port connected to the photodiode (PD) 8a, respectively.

As a result, the optical wavelength combining / branching coupler (W
DM) 3 receives the signal light of wavelength λ1 and the residual pumping light of wavelength λ2 ′ from the first input port, and the pumping light of wavelength λ2 from the second input port, respectively, and outputs the signal of wavelength λ1 from the first output port. The signal light, the pumping light of wavelength λ2, and the residual pumping light of wavelength λ2 'are output from the second output port, respectively. Optical wavelength synthesizing / branching coupler (W
As the DM) 3, a fused WDM coupler is known.

As the rare earth-doped optical fiber (EDF) 4, there is a fiber doped with erbium (Er). In this case, the wavelength λ1 of the signal light may be 1.55 μm and the wavelength λ2 of the pumping light may be about 1.48 μm.
The output of the optical isolator (ISO) 5 is an optical coupler (CP
L) 6 is connected to the input port. Optical coupler (CP
The first output port of L) 6 is delivered as a repeater output. At the output of this repeater, the amplified signal light of the wavelength λ1 and the residual pump light of the wavelength λ2 ′ that is not absorbed by the rare earth-doped optical fiber (EDF) 4 are output. The second output port of the optical coupler (CPL) 6 is connected to an optical filter (FIL) 9 for transmitting the signal light of the wavelength λ1 and blocking the spontaneous emission light and the residual excitation light. Photodiode (PD) 8 connected to optical filter (FIL) 9
An LD drive circuit (LDD) that converts the signal light into a current in b and supplies a current to the pumping laser diode (LD) 7 so that the output of the signal light is constant in the repeater output control circuit 10.
Control 11

On the other hand, an optical wavelength combining / branching coupler (WDM)
The second output port of 3 has a photodiode (PD)
8a is connected, and the residual excitation light of wavelength λ2 ′ is photoelectrically converted by the photodiode (PD) 8a and sent to the no-input detection circuit (DET) 12. No input detection circuit (D
When the ET) 12 detects the non-input state of the residual pumping light of the wavelength λ2 ', it outputs a no-input detection signal to the repeater output control circuit (CONT) 10. Repeater output control circuit (CO
The NT) 10 limits the current of the pumping laser diode (LD) 7 on the basis of the no-input detection signal and suppresses the pumping light of the wavelength λ2 to put the optical amplification repeater 1b in the standby state.

As a standby method for the optical amplifying repeater 1b, means for limiting the current of the pumping LD, limiting the output of the pumping LD, limiting the optical output of the optical repeater amplifier 1a, and the like are used. Can be taken.

Next, the circuit operation of the optical amplification repeater 1b will be briefly described. Optical amplification repeater 1a in the previous stage
The signal light having the wavelength λ1 and the residual pumping light having the wavelength λ2 ′ output from the optical fiber are propagated to the transmission line optical fiber 2 and input from the first input port of the optical wavelength combining / branching coupler (WDM) 3. Here, when the optical amplification repeater 1a in the preceding stage is in the standby state, the optical amplification repeater 1b detects the non-input state of the residual pump light and enters the standby state. Optical amplifier repeater 1 in standby state
In b, since the residual pumping light is significantly reduced, the optical amplification repeater in the next stage, which relays the residual pumping light, also detects the non-input state of the residual pumping light and enters the standby state.

That is, when the optical amplification repeater in the first stage is in the standby state, the optical amplification repeaters in the subsequent stages are automatically in the standby state, and automatically when the standby state of the optical amplification repeater in the first stage is released. Therefore, the optical amplification repeaters in the subsequent stages also detect the residual pumping light and are restored to the line.

[0020]

As described above, according to the optical amplification repeater of the present invention, the optical signal for extracting and branching the residual pumping light from the signal light output from the previous stage without using the optical coupler in the first stage of input is provided. Separation means is arranged, the no-input state of the residual excitation light is detected by the no-input detection means, and the excitation state of the internally generated excitation light is suppressed by the suppression execution means based on the no-input detection signal. Therefore, even if a plurality of relay connections are made for long-distance optical communication, the optical loss is reduced and the noise figure is improved.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing the basic configuration of a conventional optical amplification repeater.

[Explanation of symbols]

 1, 1a, 1b Optical amplification repeater 2 Transmission line optical fiber 3 Optical wavelength combining / demultiplexing coupler (WDM) 4 Rare earth doped optical fiber (EDF) 5 Optical isolator (ISO) 6, 6a, 6b Optical coupler (CPL) 7 Excitation laser diode (LD) 8a, 8b Photodiode (PD) 9 Optical filter (FIL) 10 Repeater output control circuit (CONT) 11 LD drive circuit (LDD) 12 No input detection circuit (DET)

Claims (2)

[Claims] 1. An optical amplification repeater for suppressing a pumping state of pumping light as a multiplexed light with respect to the signal light generated internally when the input signal light is in a non-input state, And a non-input detecting means for detecting a no-input state of the signal light according to the separated light and outputting a no-input detection signal, and the no-input detection. Suppression executing means for executing suppression of the excited state based on a signal. 2. The optical amplification repeater according to claim 1,
An optical amplification repeater characterized in that an optical wavelength synthesizing / demultiplexing coupler for separating the residual pumping light from the signal light by using the wavelength of light is used as the light separating means.