JP2513151B2 - Optical amplification repeater - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifying repeater having a standby function of detecting a signal light non-input state and stopping an optical amplifying operation when a line is not used.

[0002]

2. Description of the Related Art As a conventional optical amplification repeater, for example, one having a structure as shown in FIG. In this optical amplification repeater, when the signal light enters the repeater input In, the optical coupler 24 splits the signal light and outputs one to the optical wavelength combining coupler (WDM) 25 and the other to the photodetector 34. Output to.

The optical wavelength synthesizing coupler (WDM) 25 multiplexes the signal light and the pumping light pumped from the pumping light source 33 and outputs the multiplexed light to the rare earth-doped optical fiber (EDF) 26. The rare earth-doped optical fiber (EDF) 26 absorbs the pumping light and directly amplifies the signal light to generate amplified output signal light. The optical isolator 27 prevents oscillation due to reflection from the outside during optical amplification, and the optical filter 28 removes residual excitation light and spontaneous emission light generated in the rare earth-doped optical fiber (EDF) 26. Here, an optical wavelength synthesizing coupler (WDM) 25, a rare earth-doped optical fiber (EDF) 26, an optical isolator 2
7, the optical filter 28, and the excitation light source 33 collectively function as an optical amplification means for forward excitation.

Further, the directly amplified amplified output signal light is branched by the optical coupler 29, one of which becomes the repeater output Out and the other of which is input to the photodetector 30. by this,
The photodetector 30 outputs an optical output monitor signal, which is an electric signal proportional to the optical power, to the output control circuit 31. The output control circuit 31 monitors the optical output monitor signal from the photodetector 30, and outputs a control signal to control the pumping light source drive circuit 32 so that the repeater output Out is always constant. The excitation light source drive circuit 32 outputs a drive signal to drive the excitation light source 33 according to the control signal, so that the excitation light source 33 excites the excitation light described above.

On the other hand, the photodetector 34 outputs an optical input monitor signal which is an electric signal proportional to the power of the signal light incident on the repeater input In. Since the signal input detection / standby control circuit 35 compares the optical input monitor signal with a predetermined threshold value and outputs the drive command control signal to the excitation light source drive circuit 32 in the normal time when the signal light is input, the excitation light source drive circuit 32 The reference numeral 32 outputs a drive signal after referring to the drive command control signal with respect to the above-mentioned control signal.

On the other hand, when the repeater input In is cut off and no signal light is input, the optical input monitor signal becomes less than a predetermined threshold value, so the signal input detection / standby control circuit 35.
Outputs an excitation light source stop control signal instead of the drive command control signal. When the pumping light source driving circuit 32 receives the pumping light source stop control signal, the pumping light source driving circuit 32 stops outputting the driving signal to the pumping light source 33 regardless of the control signal from the output control circuit 31, so that the repeater enters the standby state.

When signal light is input to the repeater input In again from this standby state and the optical input monitor signal becomes larger than the threshold value, the signal input detection / operation control circuit 35 releases the excitation light source stop control signal and drives again. Since the command control signal is output to the excitation light source drive circuit 32, the optical amplification operation by the optical amplification means is restarted.

That is, the output control circuit 31 functions as a signal light control means for outputting a control signal for controlling the driving of the pumping light source 33 according to the result of detecting the presence or absence of the signal light input, and detects the signal input. The standby control circuit 35 and the pumping light source drive circuit 32 function as a standby unit that stops the operation of the optical amplification unit and puts it in a standby state according to the result of detecting the presence or absence of the input of signal light.

Incidentally, a technique related to the optical amplifier used in such an optical amplification repeater is disclosed in Japanese Patent Laid-Open No. 2-27397.
No. 6 publication.

[0010]

In the case of the optical amplification repeater described above, an optical coupler is provided at the input first stage in order to detect the input state of the signal light incident on the input of the repeater. Since optical loss occurs and the input of signal light is reduced, there is a problem that the signal-to-noise ratio is deteriorated as a result. Further, since the incident signal light is branched and detected by the optical coupler, it becomes difficult to fundamentally detect the presence or absence of the signal light input when the signal light input is small. Since there is a risk of erroneous detection, there is a problem in that the optical amplification operation from the standby state to the normal optical amplification state tends to become unstable.

The present invention has been made to solve the above problems, and its technical problem is that the presence or absence of the input of signal light can be detected with high sensitivity even when the input of signal light is small. It is an object of the present invention to provide an optical amplification repeater with a small input loss, which can stably perform an optical amplification operation from the standby state to the normal optical amplification state.

[0012]

According to the present invention, after the incident signal light is multiplexed with the pump light excited by the pump light source, the pump light is removed to directly output the signal light. Optical amplification means for obtaining amplified amplified signal output light, and signal light control means for outputting a control signal for controlling drive to the pumping light source according to the result of detection of the presence or absence of input of signal light from the amplified signal output light A standby means for stopping the operation of the optical amplifying means according to the control signal to put it in a standby state, a pulse signal generating means for outputting a pulse signal for periodically putting the optical amplifying means in the standby state, a control signal and a pulse signal An optical amplification repeater including switching means for switching between and, and switching control means for generating a switching control signal for switching the switching means according to the result of detection of the presence or absence of input of signal light from the amplified signal output light. Obtained.

Further, according to the present invention, the optical amplification means for removing the pumping light after multiplexing the amplified signal light obtained by directly amplifying the incident signal light with the pumping light pumped from the pumping light source. And a signal light control means for outputting a control signal for controlling the drive to the pumping light source according to the result of detecting the presence or absence of the signal light input from the amplified signal output light, and the operation of the optical amplification means according to the control signal is stopped. Standby means for making the optical amplifier means stand by, pulse signal generating means for outputting a pulse signal for periodically putting the optical amplifier in the standby state, switching means for switching between the control signal and the pulse signal, and the amplified signal output light Thus, the optical amplification repeater including the switching control means for generating the switching control signal for switching the switching means in accordance with the result of detecting the presence or absence of the input of the signal light can be obtained.

[0014]

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 structure of an optical amplification repeater according to an embodiment of the present invention.

In this optical amplification repeater, when the signal light is input to the repeater input In, the signal light is input to the optical wavelength combining coupler (WDM) 1 provided in the input first stage. In the optical wavelength synthesizing coupler (WDM) 1, the signal light and the pumping light source 12
It is combined with the excitation light excited by the optical fiber and output to the rare earth-doped optical fiber (EDF) 2. Rare earth doped optical fiber (E
The DF) 2 absorbs the pumping light and directly amplifies the signal light to obtain amplified signal output light. The optical isolator 3 prevents oscillation due to external reflection during optical amplification, and the optical filter 4 removes residual excitation light and spontaneous emission light generated in the rare earth-doped optical fiber (EDF) 2.

Here, an optical wavelength synthesizing coupler (WDM) is used.
1, a rare earth-doped optical fiber (EDF) 2, an optical isolator 3, an optical filter 4, and a pumping light source 12 function as an optical amplifying means for forward pumping.

The amplified signal output light that has been directly amplified is branched by the optical coupler 5, one of which serves as a repeater output Out and the other of which is input to the photodetector 6. As a result, the photodetector 6 outputs an optical output monitor signal, which is an electric signal proportional to the optical power, to the signal light detection / standby control circuit 7 and the output control circuit 8. The output control circuit 8 monitors the output of the optical output monitor signal from the photodetector 6, and outputs a control signal via the switching circuit 10 to control the pump light source drive circuit 11 so that the repeater output Out is always constant. Output. This allows
In the pumping light source drive circuit 11, the pumping light source 1 is responsive to the control signal.
A drive signal is output to drive 2, and the excitation light described above is excited from the excitation light source 12. The signal light detection / standby control circuit 7 monitors the output of the light output monitor signal, and outputs a switching control signal to the switching circuit 10 according to the presence / absence of signal light input.

The switching circuit 10 has one terminal on the input side connected to the output control circuit 8 and the other terminal connected to the pulse generation circuit 9 for generating a pulse signal for periodically operating the optical amplifying means. Then, either the control signal or the pulse signal is selected according to the above-mentioned switching control signal. The switching circuit 10 is connected to the output control circuit 8 side when the switching control signal when the signal light is input is input, and is pulsed when the switching control signal when the signal light is not input is input. It operates so as to be connected to the generation circuit 9 side.

That is, in this optical amplification repeater, a signal for outputting a control signal for controlling the driving of the pumping light source 12 in accordance with the result of the output control circuit 8 detecting the presence or absence of the input of signal light from the optical amplification means. It functions as an optical control unit, and generates a switching control signal for switching the switching circuit 10 as a switching unit in accordance with the result of the detection / presence of the input of signal light by the optical amplification unit by the signal light detection / standby control circuit 7. It functions as a switching control means. The pumping light source drive circuit 11 also functions as a standby unit that stops the operation of the optical amplification unit according to the control signal and puts it in a standby state.
However, in the case of this optical amplification repeater, in the standby state when no signal light is input, the switching circuit 10 is connected to the pulse generation circuit 9 side by the switching control signal from the signal light detection / standby control circuit 7 to generate a pulse. Since the pulse signal from the circuit 9 is output to the pumping light source drive circuit 11, the operation of the optical amplifying means is not completely stopped in the standby state, but operates periodically (the standby state is regularly performed. )
Will be.

In short, in the optical amplification operation of this optical amplification repeater, the pumping light source drive circuit 11 is connected to the output control circuit 8 side by the switching circuit 10 while the input of the signal light is continued, and the output of the repeater is It is controlled to be constant. Also, when the input of signal light is cut off, the repeater output O
ut becomes only spontaneous emission light, and the optical output power decreases,
This decrease in the output of the amplified signal output light is due to signal light detection
It is detected by the standby control circuit 7. Continued signal light detection
The standby control circuit 7 outputs a switching control signal to the switching circuit 10 to switch the connection of the switching circuit 10 to the pulse generation circuit 9 side. As a result, the excitation light source drive circuit 11
Since a periodic pulse signal is input from the pulse generation circuit 9 via the switching circuit 10, the optical amplification repeater regularly performs the optical amplification operation even in the standby state.

The pulse signal has a pulse width of several milliseconds and a pulse period of several seconds. The pumping light from the pumping light source 12 is pumped during this pulse width, and the optical amplification operates. At this time, if the signal light is input, the amplified signal output light that is optically amplified is output as the repeater output Out. Also, this repeater output Out will differ depending on whether or not the signal light is input.
Since the standby control circuit 7 constantly detects this difference, when the input of the signal light is restored, the switching circuit 10 is connected to the output control circuit 8 to automatically perform the normal optical amplification operation from the standby state. Return to the state.

FIG. 2 is a timing chart showing the relationship of the signals of the respective parts in the optical amplification operation by the optical amplification repeater from the standby state to the return to the normal optical amplification state. From FIG. 2, according to the optical amplification operation of this optical amplification repeater, the pulse generation circuit 9 outputs the periodic pulse signal p regardless of the presence or absence of the input of the signal light a from the repeater input In. Therefore, the amplified signal output light b from the repeater output Out becomes a rectangular wave having a relatively low level corresponding to the pulse period of the pulse signal p in the non-input state of the signal light a, and in the input recovery state of the signal light a. It can be seen that a relatively high level continuous amplified wave irrelevant to the pulse signal p is obtained.

FIG. 3 is a block diagram showing the basic structure of an optical amplification repeater according to another embodiment of the present invention. Compared to the optical amplification repeater of the previous embodiment, this optical amplification repeater does not use the optical filter 4 in that the rare earth-doped optical fiber (EDF) 2 is provided at the input first stage of the repeater input In. Except for the points, it has the same structure.

However, the optical amplifying means here is a rare earth-doped optical fiber (EDF) 2, an optical wavelength combining coupler (WDM).
1, an optical isolator 3, and a pumping light source 12 for performing backward pumping optical amplification.

In this optical amplification means, the rare-earth doped optical fiber (EDF) 2 directly amplifies the incident signal light, and the resulting amplified signal output light is an optical wavelength synthesizing coupler (WD).
M) Output to 1. The optical wavelength synthesizing coupler (WDM) 1 combines the amplified signal output light with the pumping light pumped from the pumping light source 12, and then removes the pumping light. The subsequent optical amplification operation by the other components is performed in exactly the same way as in the previous embodiment. That is, also in this case, the optical amplifying means periodically performs optical amplifying operation by the pulse signal from the pulse generator 9 during standby without input, and when signal light is input again, normal optical amplifying operation by the output control circuit 8 is performed. Is performed, and it automatically returns from the standby state.

[0027]

As described above, according to the optical amplifier repeater of the present invention, the optical coupler used in the first stage of the input is unnecessary, and the pulse generation is performed according to the detection result of the presence or absence of the signal light input. Even if the input of the signal light is small, even if the input of the signal light is small, the light amplification operation by the optical amplifier is not stopped completely even in the standby state by the switching control using the means. The presence / absence of a signal can be detected with high sensitivity, and the optical amplification operation from the standby state to the return to the normal optical amplification state can be performed accurately and with good stability. The ratio will be significantly improved.

[Brief description of drawings]

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

FIG. 2 is a timing chart showing a relation of signals of respective parts in an optical amplification operation from a standby state by the optical amplification repeater shown in FIG. 1 to a return to a normal optical amplification state.

FIG. 3 is a block diagram showing a basic configuration of an optical amplification repeater according to another embodiment of the present invention.

FIG. 4 is a block diagram showing a basic configuration of a conventional optical amplification repeater.

[Explanation of symbols]

 1,25 Optical wavelength synthesizing coupler (WDM) 2,26 Rare earth doped optical fiber (EDF) 3,27 Optical isolator 4,28 Optical filter 5,24,29 Optical coupler 6,30,34 Photodetector 7 Signal light detection / Standby control circuit 8,31 Output control circuit 9 Pulse generation circuit 10 Switching circuit 11,32 Excitation light source drive circuit 12,33 Excitation light source 35 Signal input detection / standby control circuit

Claims (2)

(57) [Claims] 1. An optical amplifier for obtaining an amplified signal output light obtained by multiplexing incident signal light with pumping light pumped from a pumping light source, removing the pumping light, and directly amplifying the signal light. Means, signal light control means for outputting a control signal for controlling the drive to the pumping light source according to the result of detecting the presence or absence of the input of the signal light from the amplified signal output light, and the light according to the control signal Standby means for stopping the operation of the amplifying means to put it in a standby state, pulse signal generating means for outputting a pulse signal for periodically putting the optical amplifying means into the standby state, the control signal and the pulse signal Switching means for switching the switching means and switching control means for generating a switching control signal for switching the switching means according to the result of detection of the presence or absence of the input of the signal light from the amplified signal output light. An optical amplifier repeater characterized by including. 2. Optical amplification means for removing the pumping light after multiplexing the amplified signal light obtained by directly amplifying the incident signal light with the pumping light pumped from the pumping light source, and the amplified signal output. Signal light control means for outputting a control signal for controlling the drive to the pumping light source according to the result of detecting the presence or absence of the input of the signal light from the light, and stopping the operation of the optical amplification means according to the control signal. Standby means for bringing the optical amplifier into a standby state, a pulse signal generating means for outputting a pulse signal for periodically bringing the optical amplifier into the standby state, a switching means for switching between the control signal and the pulse signal, Switching control means for generating a switching control signal for switching the switching means according to a result of detection of the presence or absence of the input of the signal light from the amplified signal output light. Optical amplifier repeater.