JPH06326383A - Optical fiber amplifier - Google Patents

Abstract

PURPOSE:To obtain an optical fiber amplifier provided with a redundancy constitution for maintaining a stable amplifying action by a method wherein signal light and excitation light are entered into an optical fiber for amplification, which is doped with an active substance for light amplification. CONSTITUTION:An optical fiber amplifier 16 is formed into a constitution wherein an Er-doped quartz optical fiber, which is doped with a trace element, Er, as active ions, is used for the core part of an optical fiber 16 for amplification and at the time of reference operation of the optical fiber 16, an excitation light source LDa is used as an active excitation light source and an excitation light source LDb is used as an excitation light source for stand-by and moreover, during the period when the light source LDa is actuated, the light source LDb is feebly made to emit to monitor the relative ratio of the luminous intensity of the light source LDb to feeding power and when an abnormality is generated in the light source LDa, the respective luminous intensities of the light sources LDa and LDb are adjusted so as to gradually decrease or increase, the sum of these light intensities is maintained in such a way that it is always kept in a prescribed intensity and an operation change-over control 22 of the light source LDa and the light source LDb is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional pumping type optical fiber amplifier, and more particularly to an optical fiber amplifier having a redundant structure for maintaining a stable amplifying action.

[0002]

2. Description of the Related Art A conventional bidirectional pumping type optical fiber amplifier has a structure as shown in FIG. That is, the first optical isolator 2, the first optical multiplexer 3, the amplification optical fiber 4, the second optical multiplexer 5, and the second isolator 6 are provided in the input optical fiber 1 into which the signal light is input. An amplification path formed by being serially connected in order is provided, and light (that is, amplified signal light) that has passed through the second optical isolator 6 is output to the output optical fiber 7.

Further, a pair of pumping light sources 9 and 10 for generating laser light by the power supplied from the pumping light source driving device 8 is provided, and the laser light (referred to as forward pumping light) generated by the pumping light source 9 is transmitted through the optical fiber 11. To the first optical multiplexer 3 via
Laser light generated by the excitation light source 10 (referred to as backward excitation light)
Are input to the second optical multiplexer 5 via the optical fiber 12, respectively.

Then, the first optical multiplexer 3 multiplexes the signal light having passed through the first optical isolator 2 and the forward pumping light and supplies the multiplexed light to the input side of the amplification optical fiber 4, and the second optical multiplexer 3 The optical multiplexer 5 supplies the backward pumping light to the output side of the amplification optical fiber 4 and guides the signal light amplified by the amplification optical fiber 4 to the second optical isolator 6.

As described above, the forward pumping light and the backward pumping light are simultaneously supplied to the amplifying optical fiber 4 to excite the rare earth element added to the core portion of the amplifying optical fiber 4 to generate the signal light. It is designed to be amplified.

[0006]

However, in such a conventional optical fiber amplifier, since the respective pumping light sources 9 and 10 are configured to separately generate the forward pumping light and the backward pumping light. When one of the pumping light sources is deteriorated, the sum of the forward pumping light and the backward pumping light supplied to the amplification optical fiber 4 is changed in intensity, and the amplification factor is changed. Invite. Therefore, a stable amplification factor cannot always be set, and these pumping light sources 9 and 1 cannot be set.
However, there is a problem that amplification accuracy and reliability are low because the characteristics are deteriorated only by the occurrence of an abnormality on one side.

The present invention has been made in view of the above problems, and an object thereof is to provide an optical fiber amplifier having a redundant configuration for maintaining a stable amplification action.

[0008]

In order to achieve such an object, the present invention provides a signal light and a pump light which are incident on an amplification optical fiber to which an active material for light amplification is added. An optical fiber amplifier for amplifying signal light, a plurality of pumping light sources for generating coherent light of a predetermined wavelength, and coherent light generated from these pumping light sources are combined, and the combined light is An optical multiplexer / demultiplexer for branching and outputting the forward pumping light and the backward pumping light having predetermined light intensities, respectively, and the input signal light and the forward pumping light are combined to the amplification optical fiber from its input side. A first optical multiplexer for supplying and a second optical waveguide for supplying the backward pumping light to the amplification optical fiber from its output side and guiding the signal light amplified by the amplification optical fiber to the output side. Optical multiplexer and husband of each of the excitation light sources A plurality of automatic power control circuits provided for each of the excitation light sources, and a light emission of each of the plurality of automatic power control circuits, each of which supplies electric power for keeping the emission intensity of each of them constant based on each emission reference value. A reference value and a central control unit for controlling respective operations, wherein the central control unit defines one set of the plurality of pump light sources and the automatic power control circuit as a working pump light source and a working automatic power control circuit. By setting a light emission reference value accordingly, light emission corresponding to a predetermined amplification factor of the amplification optical fiber is performed, and the remaining set of pump light sources and automatic power control circuits are used as standby pump light sources and standby automatic power control circuits. By setting a light emission reference value so that weak light emission is performed, the emission intensity and the supply power of each of the active excitation light source and the standby excitation light source are sequentially monitored, and the respective supply power is When departing from the scope of the relative ratio of the emission intensity of each are predetermined against,
It was decided that an abnormality occurred.

If the relative ratio of the emission intensity to the power supplied to the working pumping light source deviates from a predetermined range, it is determined that an abnormality has occurred in the working pumping light source or the standby pumping light source, and the remaining amount Switching the standby pumping light source and the standby automatic power control circuit of any one of the above groups to the working pumping light source and the working automatic power control circuit, and switching the operation of the working pumping light source and the automatic power control circuit It was made to control.

Further, when it is determined that the abnormality has occurred and the switching control is performed, the emission intensity of the pumping light source that is currently in use is gradually decreased, and the emission intensity of the excitation light source that is in standby is gradually increased. The switching control is carried out while keeping the sum of the respective light emission intensities constant.

Further, the alarm information is generated when it is judged that the abnormality has occurred or the switching control is performed.

[0012]

According to this structure, the standby pumping light source is also monitored for abnormality, so that the standby pumping light source is prevented from malfunctioning even while the active pumping light source is operating. be able to. Therefore, it is possible to prevent the occurrence of a serious abnormality such as an abnormality also occurring in the standby excitation light source when the switching control between the active excitation light source and the standby excitation light source is performed. Further, rather than simply switching the operation of the active and standby pumping light sources, the emission intensity of each is gradually decreased or increased so that the sum of these light intensities is always maintained at a predetermined intensity. Since the processing is performed, an abnormality such as a momentary interruption of the amplification optical fiber amplification does not occur, and a predetermined amplification factor can always be obtained. Further, it is possible to prevent an accident from occurring in advance according to the alarm information.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical fiber amplifier according to the present invention will be described below with reference to the drawings. First, the configuration will be described with reference to FIG. 1. A first optical multiplexer 14, a first optical isolator 15, an amplification optical fiber 16, and an input optical fiber 13 into which a signal light to be amplified is input. An amplification path is provided in which the second optical multiplexer 17, the second optical isolator 18, and the optical directional coupler 19 are sequentially connected in series,
It is configured to output the light (that is, the amplified signal light) that has passed through the optical directional coupler 19 to the output optical fiber 20.

Here, the amplification optical fiber 16 is an Er-doped silica optical fiber in which a trace amount of Er element is added as an active ion to the core portion, or a Pr-doped fluoride optical fiber in which Pr element is similarly added. A rare-earth-doped amplification optical fiber such as the above is applied. When the Er-doped silica optical fiber is applied, the signal light in the 1.55 μm band is amplified by supplying the excitation light having the wavelength of 1.48 μm, and when the Pr-doped fluoride optical fiber is applied, Signal light in the 1.55 μm band is amplified by supplying pumping light having a wavelength of 1.3 μm. Note that which type of amplification optical fiber 16 is applied is a matter of choice determined in accordance with design specifications and the like, and since the principle and configuration are the same in both cases, in this embodiment,
The case of applying an Er-doped silica optical fiber will be described.

Further, in FIG. 1, a pair of pumping light sources for generating a laser beam having a wavelength of 1.48 μm (a semiconductor laser light source having uniform characteristics is applied in this embodiment).
The pump light source LDa is provided with LDa and LDb, and the pump light source LDa performs feedback control of the automatic power control circuit APCa and the automatic temperature control circuit ATCa to control the light intensity of the laser light and the pump light source LD.
The temperature of a itself is automatically controlled, while the excitation light source LDb
Is an automatic power control circuit APCb and an automatic temperature control circuit AT
By the feedback control with Cb, the light intensity of the laser light and the temperature of the pumping light source LDb itself are automatically controlled.

That is, the excitation light source LDa has a built-in photoelectric conversion element such as a photodiode for detecting a part of the emitted laser light, and the automatic power control circuit APCa is
Emission reference value (voltage or current value) T set internally
Excitation is performed so that the difference between h _La and the level (voltage or current value) of the photoelectric conversion output signal S _La of this photoelectric conversion element is zero.
The light intensity of the laser light is made constant by feedback-controlling the power supplied to the source LDa at high speed. Also, the excitation light source L
Da has a built-in temperature detection sensor such as a thermistor for detecting the temperature of itself and a temperature control element such as a Peltier element, and the automatic temperature control circuit ATCa has a temperature reference value (voltage or voltage) set therein. (Current value) Th _Ta and the level (voltage or current value) of the temperature measurement output signal S _Ta of the temperature detection sensor is controlled to be zero at high speed so that the power supplied to the temperature control element is fed back. As a result, the temperature of the excitation light source LDa itself is kept constant.

The pumping light source LDa is also used as one pumping light source LDb.
Similarly, the photoelectric conversion element, the temperature detection sensor, and the temperature control element are provided, and the automatic power control circuit APCb is
Emission reference value (voltage or current value) T set internally
The power supply to the excitation light source LDb is feedback-controlled at high speed so that the difference between the level of h _Lb and the level (voltage or current value) of the photoelectric conversion output signal S _Lb of this photoelectric conversion element becomes zero, and an automatic temperature control circuit is provided. The ATCb sets the difference between the temperature reference value (voltage or current value) Th _Tb set internally and the level (voltage or current value) of the temperature measurement output signal S _Tb of this temperature detection sensor to zero. The light intensity of the laser light and the temperature of the excitation light source LDa itself are made constant by fast feedback control of the power supplied to the temperature control element.

Further, an optical multiplexer / demultiplexer 2 for multiplexing the laser beams emitted from the pumping light sources LDa and LDb and at the same time branching and outputting to the forward pumping light and the backward pumping light having the same light intensity.
1 is provided to supply the forward pumping light to the first optical multiplexer 14 and the backward pumping light to the second optical multiplexer 17. In addition, if necessary, between the pumping light sources LDa and LDb or the optical multiplexer / demultiplexer 21, and between the optical multiplexer / demultiplexer 21 or the first and second optical sources.
By connecting the second optical multiplexers 14 and 17 with an optical fiber, the laser light and the forward pumping light and the backward pumping light are guided. In addition, the optical coupler 2
1 is a 2-to-2 branch coupler such as a melt-stretched fiber coupler.

Then, the first optical multiplexer 14 multiplexes the signal light and the forward pumping light and supplies it to the amplification optical fiber 16 from the front side through the first optical isolator 15, while The optical multiplexer 17 of 2 supplies the backward pumping light to the amplification optical fiber 16 from the rear side thereof, and also supplies the signal light amplified by the amplification optical fiber 16 to the second optical isolator 1
Transmit to 8 side. Incidentally, the first and second optical isolators 1
Reference numerals 5 and 18 are both polarization independent optical isolators.

Further, the optical directional coupler 19 supplies a part (about -13 dB) of the amplified signal light which has passed through the optical isolator 18 to a photoelectric conversion element PD such as a photodiode for photoelectric conversion. The element PD transmits to the central control unit 22 a photoelectric conversion output signal _SPD of a voltage or current proportional to the light intensity of the signal light.

A microcomputer system or the like is applied to the central control unit 22, and the photoelectric conversion output signal SPD from the photoelectric conversion element PD and the excitation light source LDa,
The photoelectric conversion output signals S _La and S _{Lb from the LDb} and the temperature measurement output signals S _Ta and S _Tb are input, and a predetermined analysis process based on these signals is performed, and a control signal C _Ta corresponding to the analysis result, By outputting C _La , C _Tb and C _Lb , reference values Th _Ta , Th _La and T of the automatic temperature control circuits ATCa and ATCb and the automatic power control circuits APCa and APCb are output.
Processing such as automatically changing h _Tb and Th _Lb , stopping the operation of the excitation light sources LDa and LDb when an abnormality occurs, and generating alarm information is performed.

Next, the operation of the embodiment having such a configuration will be described with reference to the flow charts of FIGS. 2 to 4 and the explanatory view of FIG.

First, when the power is turned on, the central control unit 22 controls the control signal C in step 100 of FIG.
_Ta , C _Tb and C _La , C _Lb are automatic temperature control circuits ATCa, A
By inputting TCb and the automatic power control circuits APCa and APCb, the temperature reference values Th _Ta and Th _Tb and the light emission reference values Th _La and Th _Lb are respectively standard temperature reference values Th _Ta1 and T _Ta .
Set h _Tb1 and light emission reference values Th _La1 and Th _Lb1 .
Here, the temperature reference values Th _Ta1 and Th _Tb1 are both set to 25 ° C. or the like at which the pumping light sources LDa and LDb can be optimally operated.

On the other hand, automatic power control circuits APCa, APC
The standard light emission reference values Th _La1 and Th _Lb1 of b have a relationship of Th _La1 >> Th _Lb1 as shown in FIG.
The emission reference value Th _Lb1 causes the excitation light source LDb to emit laser light with a weak intensity that hardly contributes to the amplification action, and the emission reference value Th _La1 indicates the excitation light source LDa with a predetermined amplification factor of the amplification optical fiber 16. Is a value for causing laser light emission with a light intensity that almost determines. Therefore,
During the standard operation, the pumping light source LDa is used as the working pumping light source, and the pumping light source LDb is used as the standby pumping light source. It should be noted that the reason why the standby pumping light source LDb emits weak light even though it hardly contributes to the amplifying action is that the central control unit 22 sequentially monitors the operation of the pumping light source LDb based on the photoelectric conversion output signal S _Lb , This is to detect the presence or absence of the abnormality.

When the standard setting is made in this way, the automatic temperature control circuits ATCa and ATCb are set in step 3 shown in FIG.
00 to 340, the automatic power control circuit APC
a, APCb are steps 400 to 440 shown in FIG.
The above process is repeated at high speed.

That is, each automatic temperature control circuit ATCa,
The ATCb detects the respective temperatures of the pumping light sources LDa and LDb by inputting the temperature measurement output signals S _Ta and S _Tb from the pumping light sources LDa and LDb in step 300 of FIG. 3, and then in step 310, temperature measurement output signal S _Ta, the difference between the level of S _Tb and respectively corresponding standard reference temperature Th _Ta1, Th _Tb1 Δ _Ta, detects the delta _Tb. Then fed in step 320, the difference delta _Ta, the electric power supplied to the zero delta _Tb each excitation light source LDa, the temperature control element LDb. Then, in step 330,
When there is an instruction to change the temperature reference values Th _Ta and ThTb from the central control unit 22, the respective automatic temperature control circuits ATCa and ATCb change the temperature reference values ThTa and Th _Tb in step 340 and then execute step 300. When there is no change instruction, the temperature feedback control is performed based on the original temperature reference values Th _Ta and Th _Tb . Therefore, the standard setting is made and the temperature reference value T
Until the instruction to change h _Ta , Th _Tb , the temperature reference values Th _Ta , Th _Tb are the standard temperature reference values Th _Ta1 , Th.
_Since it becomes _Tb1 , the excitation light sources LDa and LDb are maintained at, for example, 25 ° C. described above.

On the other hand, each automatic power control circuit APCa,
The APCb is the pump light source L in step 400 of FIG.
The light intensity of each laser beam is detected by inputting the photoelectric conversion output signals S _La and S _Lb from Da and LDb. Next, in step 410, the photoelectric conversion output signals S _La and
Standard emission reference value T corresponding to the level of S _Lb
The differences Δ _La and Δ _Lb from h _La1 and Th _Lb1 are detected. next,
In step 420, each automatic power control circuit AP
Ca, APCb is, the difference delta _La, delta _Lb source excitation power supplied to zero each of LDa, the feedback control supplied to LDb performed. Next, in step 430, when there is an instruction to change the light emission reference values Th _La and Th _Lb from the central control unit 22, after changing the set reference values Th _La and Th _Lb in step 440, the process _proceeds to step 400. When the process is repeated and there is no change instruction, feedback control is performed based on the original light emission reference values Th _La and Th _Lb. Therefore, the standard setting is performed and the light emission reference values Th _La and Th are set.
Until the instruction to change _Lb is issued, the emission reference value Th _La ,
Since Th _Lb becomes the standard emission reference values Th _La1 and Th _Lb1 , the laser light emitted from the excitation light source LDa is held at a constant light intensity that determines the amplification factor of the amplification optical fiber 16, and the excitation light source LDb emits weak light. Held in the state of. And
An optical multiplexer / demultiplexer 21 multiplexes these laser lights and splits them into a front pumping light and a rear pumping light having equal light intensities, and first and second
Of the optical fiber 16 for amplification
Amplifies the signal light with a predetermined amplification factor.

Thus, the automatic temperature control circuit ATCa,
The ATCb and the automatic power control circuits APCa and APCb independently perform automatic feedback control only by setting the temperature reference values ThTa and ThTb and the light emission reference values ThLa and ThLb. In this embodiment, high-speed feedback control is realized. In order to do so, it is composed of an analog circuit.

Referring again to FIG. 2, the central control unit 22 operates in parallel with the operations of the automatic power control circuits APCa and APCb and the automatic temperature control circuits ATCa and ATCb.
The excitation light sources LDa and LDb are monitored. First, step 1
At 10, the photoelectric conversion output signals S _La and S _PD and the value P _{La of the} supplied power which the automatic power control circuit APCa supplies to the excitation light source LDa are detected.

Next, in step 120, the fluctuation of the level (voltage or current) of the light emission component of the photoelectric conversion output signal SPD is checked, and if the deviation is from a predetermined level, the automatic power control circuit is set so that the deviation becomes zero. Emission reference value T of APCa
h Fine-tune _La1 . Therefore, when this fine adjustment is performed, the automatic power control circuit APCa controls the laser light intensity of the pumping light source LDa based on the light emission reference value Th _La after the fine adjustment, and thus is amplified by the amplification optical fiber 16. The level of the light emission component of the signal light (amplified signal light) output from the optical directional coupler 19 is always kept constant.

Next, at step 130, the relative ratio between the level of the photoelectric conversion output signal S _La and the supplied power value P _La is obtained. That is, when the supplied power value P _La is large enough to deviate from the predetermined range (safety range) as compared with the level of the photoelectric conversion output signal S _La , the pumping light source LDa has a predetermined value unless it is due to large power. It is determined that an abnormal state in which a laser beam having a light intensity of 1 cannot be generated, or an abnormality has occurred in the automatic power control circuit APCa, and the supplied power value P _La is compared with the level of the photoelectric conversion output signal S _La within this safe range. If inside,
It is determined that the excitation light source LDa and the automatic power control circuit APCa are in the normal state. Then, when such an abnormal state is detected, the process proceeds to step 1 through step 140.
If it is in the normal state, the process proceeds to step 150.

In step 150, the central control unit 22 controls the photoelectric conversion output signal S _Lb output from the pumping light source LDb and the automatic power control circuit APCb to drive the pumping light source LDb.
The value P _Lb of the power supplied to b is detected.

Next, at step 160, the relative ratio between the level of the photoelectric conversion output signal S _Lb and the supplied power value P _Lb is obtained. That is, when the supply power value P _Lb is large enough to deviate from the predetermined range (safety range) as compared with the level of the photoelectric conversion output signal S _Lb , the pumping light source LDb is weak unless it is due to the large power. It is determined that an abnormal state in which even intense laser light cannot occur or an abnormality has occurred in the automatic power control circuit APCb, and the supplied power value P _Lb is within this safe range compared to the level of the photoelectric conversion output signal S _Lb. If
It is determined that the excitation light source LDb and the automatic power control circuit APCb are in the normal state. If it is determined that an abnormality has occurred, the process proceeds to step 180 via step 170 to generate alarm information indicating that an abnormality has occurred in the excitation light source LDb, and then repeats the process from step 110 again. Move to. On the other hand, if it is judged to be normal,
The process directly moves from step 170 to step 110.

As described above, when it is determined in step 140 that an abnormality has occurred in the pumping light source LDa or the automatic power control circuit APCa, the process proceeds to step 190, and the standby pumping light source LDb is changed to the working pumping light source LDb. At the same time, the pumping light source LDa stops emitting light. That is, the central control unit 22 supplies the control signal C _Lb to the automatic power control circuit APCb, so that the amplification reference value Th _Lb (Th _Lb = Th _La1) that equalizes the amplification factor of the amplification optical fiber 16 to the standard setting. + Th _Lb1 ) and the automatic power control circuit APCa is cut off from the power supply to the pumping light source LDa to cause only the pumping light source LDb to emit light.

Further, in this switching process, as shown in FIG. 5, after the emission reference value Th _La is gradually decreased from the standard emission reference value Th _La1 to zero at a predetermined reduction rate, the power to the excitation light source LDa is reduced. The supply is stopped, and conversely, the emission reference value Th _Lb
Is gradually increased from the standard emission reference value Th _Lb1 to a value of Th _La1 + Th _Lb1 at a predetermined increase rate, so that the forward pumping light supplied to the amplification optical fiber 16 can be obtained even during this switching processing period. The light intensity of the sum of backward excitation light is always made equal to that in the standard setting. Therefore, the amplification factor of the amplification optical fiber 16 is maintained constant during the switching process period, and the amplification factor is maintained thereafter.

Next, in step 200, central control unit 22, after generating an alarm information indicating that performing switching process, in step 210, the photoelectric conversion output signal S _Lb, and S _PD, the automatic power control circuit The supply power P _Lb supplied by the APCb to the excitation light source LDb is detected.

Next, in step 220, the fluctuation of the level (voltage or current) of the light emission component of the photoelectric conversion output signal _SPD is checked, and if it deviates from a predetermined level, automatic power control is performed so that the deviation becomes zero. Light emission reference value T of circuit APCb
Fine-tune h _Lb. Therefore, when this fine adjustment is performed, the automatic power control circuit APCb controls the laser light intensity of the pumping light source LDb based on the light emission reference value Th _Lb after the fine adjustment, and therefore is amplified by the amplification optical fiber 16. The level of the light emission component of the signal light (amplified signal light) output from the optical directional coupler 19 is always kept constant.

Next, in step 230, the relative ratio between the level of the photoelectric conversion output signal S _Lb and the supplied power value P _Lb is obtained. That is, when the supplied power value P _Lb is large enough to deviate from the predetermined range (safety range) as compared with the level of the photoelectric conversion output signal S _Lb , the pumping light source LDb is set to the predetermined value unless it is due to the large power. It is determined that an abnormal state in which the laser light having the light intensity of 1 cannot be generated, or an abnormality has occurred in the automatic power control circuit APCb.

If it is determined that an abnormality has occurred, the process proceeds from step 240 to step 250 to generate alarm information indicating that both pump light sources LDa and LDb are abnormal, and then step If there is no abnormality, the process proceeds to the repeating processing from 210 and step 240 is performed.
Directly to the processing of step 210. Therefore, even if the alarm information is issued in step 250, the operation of the excitation light source LDb is not immediately stopped, but the amplification is performed until the maintenance staff finally cuts off the power according to the alarm information. Since the amplification operation by the optical fiber 16 is continued, the amplification processing of the signal light is not inadvertently stopped.

As described above, according to this embodiment, in the standard operation period in which the processes of Steps 110 to 180 are repeated, the pumping light source LDa operates as the active and the pumping light source LDb operates as the standby, and in Steps 130 and 140. When an abnormality of the excitation light source LDa is detected, steps 190 to
By repeating the processing of 250, the excitation light source L
Only Db operates as a working pump light source. The presence or absence of abnormality of the standby pumping light source LDb is monitored even during the processing period of steps 110 to 180.
Even during the period when Da is operating as it is, it is possible to prevent the abnormality of the pumping light source LDb. Therefore, in accordance with the occurrence of an abnormality in the excitation light source LDa, step 190
It is possible to prevent the occurrence of a serious abnormality such as an abnormality also occurring in the pumping light source LDb when the switching process is performed in step.

Further, in the switching processing of step 190, the operation of the pumping light sources LDa and LDb is not simply switched, but the light intensities of the respective laser lights are gradually decreased or increased so that the light intensities of these laser lights are changed. Since the sum is processed so as to be always maintained at a predetermined intensity, the amplification optical fiber 16
It exhibits an excellent effect that a predetermined amplification factor can always be obtained without causing an abnormality such as a momentary interruption of the amplification.

In this embodiment, the optical directional coupler 19 is used.
A case has been described in which the photoelectric conversion element PD is provided and feedback control is performed to make the optical intensity of the amplified signal light constant based on the photoelectric conversion output signal _SPD . However, if such feedback control is not necessary, it is omitted. be able to. In this case, the processes of steps 120 and 220 in FIG. 2 are omitted.

[0043]

As described above, according to the present invention, the presence or absence of an abnormality in the standby pumping light source is also monitored, so that the standby pumping light can be used even before the working pumping light source is operating. It is possible to prevent the abnormality of the light source. Therefore, it is possible to prevent the occurrence of a serious abnormality such as an abnormality also occurring in the standby excitation light source when the switching control between the active excitation light source and the standby excitation light source is performed. Further, rather than simply switching the operation of the active and standby pumping light sources, the emission intensity of each is gradually decreased or increased so that the sum of these light intensities is always maintained at a predetermined intensity. Since the processing is performed, an abnormality such as a momentary interruption of the amplification optical fiber amplification does not occur, and a predetermined amplification factor can always be obtained. Further, it is possible to prevent an accident from occurring in advance according to the alarm information. As described above, since it has an excellent redundant configuration, a highly reliable optical fiber amplifier can be applied.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an optical fiber amplifier according to the present invention.

FIG. 2 is a flowchart for explaining the operation of one embodiment.

FIG. 3 is a flowchart for further explaining the operation of the embodiment.

FIG. 4 is a flowchart for further explaining the operation of the embodiment.

FIG. 5 is an explanatory diagram illustrating a switching control operation according to an embodiment.

FIG. 6 is a block diagram showing a configuration of an example of a conventional optical fiber amplifier.

[Explanation of symbols]

13, 20 ... Optical fiber, 14 ... First optical multiplexer, 1
5, 18 ... Optical isolator, 16 ... Optical fiber for amplification,
17 ... Second optical multiplexer, 19 ... Optical directional coupler, 21 ...
Optical combiner, LDA, LDb ... Excitation light source, APCa, A
PCb ... Automatic power control circuit, ATCa, ATCb ... Automatic temperature control circuit, 22 ... Central control unit, PD ... Photoelectric conversion element.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01S 3/10 Z 8934-4M

Claims (5)

[Claims] 1. A signal light and a pumping light are incident on an amplification optical fiber to which an active substance for light amplification is added,
An optical fiber amplifier for amplifying the signal light, wherein a plurality of pumping light sources for generating coherent light of a predetermined wavelength are combined with coherent light generated from these pumping light sources, and the combined light is combined. And an optical multiplexer / demultiplexer for branching and outputting the forward pumping light and the backward pumping light having predetermined light intensities, respectively, and the input signal light and the forward pumping light are combined and input to the amplification optical fiber. And a second optical multiplexer that supplies the backward pumping light to the amplification optical fiber from its output side and guides the signal light amplified by the amplification optical fiber to the output side. An optical multiplexer, and a plurality of automatic power control circuits provided for each of the excitation light sources, which supplies electric power for keeping the emission intensity of each of the excitation light sources constant based on each emission reference value, , The plurality of automatic power control times A central control unit for controlling respective emission reference values and respective operations of the central control unit, wherein the central control unit includes one set of the plurality of pumping light sources and an automatic power control circuit as a working pumping light source and a working automatic power supply. By setting a light emission reference value to serve as a control circuit, light emission corresponding to a predetermined amplification factor of the amplification optical fiber is performed, and the remaining set of pumping light sources and automatic power control circuits are set as standby pumping light sources and standby Weak emission is performed by setting a light emission reference value to be an automatic power control circuit, and the emission intensity of each of the active excitation light source and the standby excitation light source and the supply power are sequentially monitored, and the supply power is reduced. An optical fiber amplifier, characterized in that when the relative ratio of the respective emission intensities deviates from a predetermined range, it is judged that an abnormality has occurred. 2. A signal light and a pumping light are incident on an amplification optical fiber to which an active substance for light amplification is added,
An optical fiber amplifier for amplifying the signal light, wherein a plurality of pumping light sources for generating coherent light of a predetermined wavelength are combined with coherent light generated from these pumping light sources, and the combined light is combined. And an optical multiplexer / demultiplexer for branching and outputting the forward pumping light and the backward pumping light having predetermined light intensities, respectively, and the input signal light and the forward pumping light are combined and input to the amplification optical fiber. And a second optical multiplexer that supplies the backward pumping light to the amplification optical fiber from its output side and guides the signal light amplified by the amplification optical fiber to the output side. An optical multiplexer, and a plurality of automatic power control circuits provided for each of the excitation light sources, which supplies electric power for keeping the emission intensity of each of the excitation light sources constant based on each emission reference value. And the plurality of automatic power controls A central control unit for controlling respective light emission reference values and respective operations of the optical path, wherein the central control unit includes a set of the plurality of pump light sources and an automatic power control circuit as a working pump light source and a working auto source. By setting a light emission reference value to be a power control circuit, light emission corresponding to a predetermined amplification factor of the amplification optical fiber is performed, and the remaining set of pump light sources and the automatic power control circuit are set as standby pump light sources and standby. A weak emission is performed by setting a light emission reference value so as to be an automatic power control circuit for use, and the emission intensity of each of the active excitation light source and the standby excitation light source and the supplied power are sequentially monitored, and the active excitation light source is When the relative ratio of the emission intensity to the supply power of the power source deviates from a predetermined range, it is determined that an abnormality has occurred in the working pumping light source or the standby pumping light source, and the remaining group Switch any one set of the standby pumping light source and the standby automatic power control circuit to the working pumping light source and the working automatic power control circuit, and perform switching control to cut off the operation of the working pumping light source and the automatic power control circuit. An optical fiber amplifier characterized by the above. 3. The central control unit gradually reduces the light emission intensity of the currently used excitation light source when determining that the abnormality has occurred and performing the switching control, and the excitation light for standby has been used. 3. The optical fiber amplifier according to claim 2, wherein the light emission intensity of the light source is gradually increased to perform the switching control while keeping the sum of the emission intensity of each light source constant. 4. The optical fiber amplifier according to claim 1, wherein the central control unit generates alarm information when determining that the abnormality has occurred. 5. The optical fiber amplifier according to claim 2, wherein the central control unit generates alarm information in accordance with the switching control.