JP2004014760A - Optical amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical amplifier which is equipped with a simple control circuit and operates very stably and components which can be increased in degree of integration. <P>SOLUTION: The optical amplifier is equipped with a feedback control unit 8 which carries out feedback control to keep all the outputs of pumping light sources 1a and 1b constant through feedback signals 11ab on electrical signals outputted from a PD 7, and a shutdown control unit 9 which constantly monitors warning signals 12a and 12b indicating faults in the pumping light sources 1a and 1b and outputs shutdown signals 13a or 13b to the pumping light sources 1a and 1b independently of the feedback signals 11ab when receiving the warning signals 12a and 12b. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical amplifier, and more particularly, to an optical amplifier having a plurality of pump light sources.
[0002]
[Prior art]
FIG. 3 is a diagram schematically illustrating an example of a conventional optical amplifier.
[0003]
In the conventional optical amplifier shown in FIG. 3, the pump light source 1A is on the substrate 10A, the pump light source 1B is on the substrate 10B, the optical isolators 3-1 and 3-2, the multiplexer 4, the amplification optical fiber (for example, Erbium). -Doped Fiber (hereinafter, EDF) 5 and optical switch 20 are mounted on substrate 10C, respectively.
[0004]
The pumping light output from the pumping light source 1A or 1B is transmitted from the multiplexer 4 to the EDF 5 through the optical switch 20. The optical switch 20 normally selects the excitation light source 1A, which is the active excitation light source, and switches to the excitation light source 1B, which is the standby excitation light source, when a failure occurs in the excitation light source 1A.
[0005]
The input signal light (main signal) input from the main signal input port of the substrate 10C passes through the optical isolator 3-1 and is then amplified in the EDF 5 by the excitation light from the multiplexer 4. The amplified input signal light is output from the main signal output port through the multiplexer 4 and the optical isolator 3-2.
[0006]
In the conventional optical amplifier shown in FIG. 3, three substrates, namely, a substrate 10A on which the excitation light source 1A is mounted, a substrate 10B on which the excitation light source 1B is mounted, and a substrate 10C on which the EDF 5 and the like are mounted are completely independent. By making the three substrates independent in this way, for example, when a failure occurs in the pump light source, the substrate having the failed pump light source can be replaced without replacing the entire optical amplifier.
[0007]
On the other hand, JP-A-6-326383 discloses another example (optical fiber amplifier) of a conventional optical amplifier.
[0008]
In the optical fiber amplifier disclosed in Japanese Patent Application Laid-Open No. 6-326383, the optical switch 20 of the conventional optical amplifier shown in FIG. 3 is replaced with an optical multiplexer / demultiplexer, and an automatic power control circuit, an automatic temperature control circuit, a photoelectric conversion element, The configuration is such that a central control unit and the like are added.
[0009]
The central control unit collectively controls the excitation light source based on various control signals exchanged with the excitation light source, the automatic power control circuit, the automatic temperature control circuit, and the photoelectric conversion element. In addition, when an abnormality occurs in the active excitation light source, the output of the standby excitation light source, which is always weakly illuminated, is gradually increased while gradually shutting off the active excitation light source, so that the overall light output is increased. Keep constant.
[0010]
[Problems to be solved by the invention]
In the conventional optical amplifier shown in FIG. 3, since the pumping light from the pumping light sources 1A and 1B is switched by the optical switch 20, the main signal is momentarily interrupted when the pumping light source is switched, and the optical output becomes temporarily unstable. was there. In addition, since the substrate is separated into three parts, and the optical switch 20 generally occupies a large volume capacity, components cannot be sufficiently integrated, and the mounting capacity increases.
[0011]
On the other hand, in an optical fiber amplifier disclosed in Japanese Patent Application Laid-Open No. 6-326383, a central control unit transmits various control signals exchanged between an excitation light source, an automatic power control circuit, an automatic temperature control circuit, and a photoelectric conversion element. Since they are handled collectively, there is a problem that software control such as switching of the excitation light source becomes complicated.
[0012]
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical amplifier which has a simple control circuit, high stability, and can be highly integrated.
[0013]
[Means for Solving the Problems]
The present invention relates to an optical amplifier for amplifying an input signal light, comprising: a plurality of pumping light sources that are independently pumped; And a plurality of pump light sources using an optical fiber, at least one amplifying optical fiber for amplifying the input signal light by the pump light, and a part of the output light from the amplifying optical fiber so that the output light level is constant. A feedback control unit that outputs a control signal, and an excitation light source monitor that stops power supply to an abnormal excitation light source when an abnormality is detected in any of the plurality of excitation light sources, regardless of the control signal of the feedback control unit. A control unit.
[0014]
Preferably, when an abnormality is detected in any one of the plurality of excitation light sources, the excitation light source monitoring and control unit stops supplying power to the abnormal excitation light source at a moderate speed such that the output light level becomes substantially constant. Let it.
[0015]
More preferably, the plurality of pumping light sources are mounted on the same substrate as other components of the optical amplifier, and can be detached and attached independently from the substrate.
[0016]
Therefore, according to the present invention, since the feedback control unit and the excitation light source monitoring control unit are made independent, complicated control by software is not required, and the control circuit is simplified. Further, by shutting off the power supply to the abnormal excitation light source at a moderate speed such that the change in the output light of the amplification optical fiber becomes substantially constant, high stability of the output light is ensured. Further, by mounting all the components of the optical amplifier on the same substrate, high integration of the optical amplifier is possible.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions have the same reference characters allotted, and description thereof will not be repeated.
[0018]
FIG. 1 is a diagram schematically showing an example of the optical amplifier of the present invention.
The optical amplifier of the present invention shown in FIG. 1 includes pump light sources 1a and 1b, a multiplexer / demultiplexer 2, optical isolators 3-1 and 3-2, multiplexers 4-1 and 4-2, an EDF 5, a coupler 6, and a photoelectric converter. A conversion element (for example, Photo Detector: hereinafter, PD) 7, a feedback control device 8, and a shutdown control device 9 are mounted on one substrate 10. Note that the excitation light sources 1a and 1b can be detached and attached independently from the substrate 10, respectively.
[0019]
Therefore, even if the entire optical amplifier is mounted on one substrate for high integration, for example, if a failure occurs in the pump light source, the failed pump light source can be individually replaced without replacing the entire optical amplifier. can do. Further, by using other components such as the multiplexer / demultiplexer 2 in FIG. 1 in place of the optical switch 20 which occupies a large volume capacity in the conventional optical amplifier in FIG. 3, further high integration of the optical amplifier is achieved. Becomes possible.
[0020]
Next, the detailed operation will be described. The excitation light sources 1a and 1b are equivalent without regard to the working system and the standby system, and both emit light at all times. The pumping lights output from the pumping light sources 1a and 1b are multiplexed once by the multiplexer / demultiplexer 2, and then demultiplexed to the multiplexers 4-1 and 4-2.
[0021]
On the other hand, the input signal light (main signal) input from the main signal input port passes through the optical isolator 3-1 and then is combined with the pump light (forward pump light) branched to the multiplexer 4-1. Is output to the EDF5. The pump light (rear pump light) split into the multiplexer 4-2 is also output to the EDF 5, and the input signal light is amplified in the EDF 5 by the forward pump light and the rear pump light. The amplified input signal light passes through the multiplexer 4-2, the optical isolator 3-2, and the coupler 6, and is output from the main signal output port.
[0022]
When the input signal light passes through the coupler 6, a part of the power in proportion to the power of the input signal light is branched and sent to the PD 7. The input signal light sent to the PD 7 is photoelectrically converted and sent to the feedback control device 8. The feedback control device 8 performs a feedback control based on the electric signal from the PD 7 to keep the total output including the excitation light sources 1a and 1b constant. This feedback control is performed by branching and outputting one type of analog feedback signal 11ab that commonly controls the excitation light sources 1a and 1b to the excitation light sources 1a and 1b.
[0023]
When the excitation light sources 1a and 1b detect their own abnormalities, they output alarm signals 12a and 12b to the shutdown control device 9, respectively. The shutdown control device 9 constantly monitors the alarm signals 12a and 12b, and when receiving the alarm signal, outputs a shutdown signal 13a or 13b to the excitation light source.
[0024]
FIG. 2 is a diagram showing various output changes before and after the occurrence of an abnormal excitation light source.
The upper part of FIG. 2 shows the output of the optical amplifier before and after the occurrence of the abnormal pump light source. The output of the optical amplifier is kept constant by the feedback signal so as not to fluctuate even when the pump light source is abnormal.
[0025]
The middle part of FIG. 2 shows the transition of the feedback signal before and after the occurrence of the abnormal excitation light source. When an abnormal pumping light source is generated, the abnormal pumping light source is shut down. At this time, the output of the feedback signal increases so that the output of the optical amplifier does not fluctuate. As a result, the output of the normal pumping light source increases.
[0026]
The lower part of FIG. 2 shows the output transition of the abnormal excitation light source before and after the occurrence of the abnormal excitation light source. When an abnormality occurs in the excitation light source, the output of the abnormal excitation light source is shut down by a shutdown signal from the shutdown control device 9.
[0027]
Next, the detailed operation will be described. In the normal state of FIG. 2, in a state where all of the plurality of pumping light sources are operating normally, all pumping light sources are operated at a constant output by the pumping light source output control feedback signal so that the optical amplifier output is constant. I have.
[0028]
When an abnormality occurs in any of the plurality of excitation light sources, the abnormal excitation light source outputs an alarm signal to the shutdown control device 9, and the shutdown control device 9 outputs a shutdown signal to the abnormal excitation light source. The output of the abnormal excitation light source changes to the output cutoff level after the abnormal excitation light source output cutoff period due to the shutdown signal.
[0029]
Each signal operation during transition will be described. When the shutdown signal is input to the abnormal excitation light source, the output of the abnormal excitation light source starts decreasing at a predetermined time constant. The output of the optical amplifier also decreases due to the decrease in the output of the abnormal pump light source. The PD 7 detects this decrease and sends it to the feedback control device 8. The feedback control device 8 controls the pump light source output control feedback signal so that the output of the pump light source increases to compensate for the decrease in the output of the optical amplifier. The output of the normal pumping light source is increased by the feedback signal, and the output of the optical amplifier is restored to the output at the time of normal. Since the abnormal excitation light source receives the shutdown signal, it transitions to the output cutoff level regardless of the feedback signal.
[0030]
By reducing the output of the extraordinary pumping light source with a time constant that does not affect the transmission quality, the output of the optical amplifier can be made substantially unchanged during the period of shutting off the output of the extraordinary pumping light source, as shown in FIG. The power supply to the abnormally pumped light source may be cut off at a slow speed so as not to cause a temporary change in the output of the optical amplifier. The shutdown speed here is, for example, the relaxation time constant of erbium ions of the EDF 5 (maximum 10 ms). Degree) longer speed.
[0031]
In the above description of the embodiments, two pump light sources, two output ports of the multiplexer / demultiplexer, and one EDF are used. However, the configuration of the present invention is not limited to this example. Absent.
[0032]
The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0033]
【The invention's effect】
As described above, according to the present invention, since the feedback control device and the shutdown control device are made independent, complicated control by software is not required, and thus the control circuit is simplified. Further, since the power supply cutoff speed to the abnormally pumped light source is slow enough to prevent a temporary change in the output of the optical amplifier, high stability of the output light is ensured. Further, by mounting all the components of the optical amplifier on the same substrate, high integration of the optical amplifier is possible.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating an example of an optical amplifier of the present invention.
FIG. 2 is a diagram showing various output changes before and after generation of an abnormal excitation light source.
FIG. 3 is a diagram schematically illustrating an example of a conventional optical amplifier.
[Explanation of symbols]
1a, 1b, 1A, 1B Excitation light source, 2 multiplexer / demultiplexer, 3-1, 3-2 optical isolator, 4, 4-1, 4-2 multiplexer, 5 EDF, 6 coupler, 7 PD, 8 feedback Control device, 9 Shutdown control device, 10, 10A, 10B, 10C Substrate.

Claims (3)

An optical amplifier for amplifying an input signal light,
A plurality of excitation light sources that independently excite,
A multiplexer / demultiplexer that once multiplexes the excitation lights from the plurality of excitation light sources, and outputs the multiplexed light to at least one port;
At least one amplification optical fiber for amplifying the input signal light by the pump light,
Using a part of the output light from the amplification optical fiber, a feedback control unit that outputs a control signal to the plurality of pump light sources so that the output light level is constant,
When detecting an abnormality in any of the plurality of excitation light sources, regardless of the control signal of the feedback control unit, comprising an excitation light source monitoring and control unit that stops power supply to the abnormal excitation light source, Optical amplifier. The pumping light source monitoring and control unit, when detecting an abnormality in any of the plurality of pumping light sources, supplies power to the abnormal pumping light source at a moderate speed such that the output light level becomes substantially constant. The optical amplifier according to claim 1, wherein the optical amplifier is stopped. The optical amplifier according to claim 1, wherein the plurality of pumping light sources are mounted on the same substrate as other components of the optical amplifier, and each of the plurality of pumping light sources can be independently attached to and detached from the substrate.

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