Optical amplifier and optical amplifier monitoring method

Abstract

To improve abnormality detection precision of an optical amplifier.SOLUTION: An optical amplifier has an amplification part, a control part and a detection part. The amplification part amplifiers a light signal. The control part controls the amplification on the light signal by the amplification part based upon the light power of the light signal amplified by the amplification part. The detection part detects abnormality based upon the amount of noise included in the light signal amplified by the amplification part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical amplifier and an optical amplifier monitoring method. [Background technology]

[0002] Optical amplification is one of the technologies essential to optical communications. There are two types of optical amplifiers: optical fiber amplifiers (OFA) and semiconductor optical amplifiers (SOA). There are further two types of optical fiber amplifiers: rare-earth doped fiber amplifiers and fiber Raman amplifiers.

[0003] FIG. 6 is a diagram showing an example of the configuration of an optical amplifier 910 incorporating the above-described optical amplification technology. The optical amplifier 911 of the optical amplifier 910 amplifies an optical input signal to the optical amplifier 910 using optical amplification technology, utilizing a drive current supplied from a drive current supply 912, and outputs the amplified signal. An optical splitter 913 is disposed on the output side of the optical amplifier 911. One of the two signals split by the optical splitter 913 becomes an optical output signal from the optical amplifier 910, and the other signal is output to an optical receiver 914 disposed after the optical splitter 913. The optical receiver 914 detects the optical output signal input from the optical splitter 913 and feeds back the obtained optical output signal intensity information to the drive current supply 912. This generally performs control such as maintaining a constant power of the output optical signal (APC: Auto Power Control). Meanwhile, the monitor / detector 915 monitors the amount of drive current in the drive current supply 912, and if an abnormal value is detected, transmits abnormality information to a monitoring system via an alarm issuing unit 916. Here, based on the abnormality information, control such as stopping the operation of the optical amplifier 910 may be performed.

[0004] As described above, in optical amplifiers, it is common to monitor the drive current value supplied from a drive current supply unit and monitor the optical amplifier for abnormalities based on fluctuations in the drive current value. However, the drive current value in these optical amplifiers can also fluctuate due to temperature. Therefore, with conventional techniques for monitoring the drive current value, it is difficult to accurately set a threshold value used to determine whether the drive current value is normal or abnormal, resulting in a problem of reduced accuracy in abnormality detection.

[0005] Furthermore, a typical example of a rare-earth doped fiber amplifier is the EDFA (erbium-doped fiber amplifier). EDFA is a type of OFA. EDFA is an optical amplifier that amplifies signal light by utilizing stimulated emission of pump light when signal light and pump light are input into an optical fiber (EDFA coil) whose core is doped with erbium. This technology has been widely used in the field of optical transmission to date, due to its characteristics of high gain, low noise, and polarization independence. A type in which the input direction of the pump light source is the same as the signal light is called forward pumping, and a type in which the input direction is opposite is called backward pumping. A combination of both is called bidirectional pumping.

[0006] In recent years, EDFAs with cooler-less pump lasers that do not have temperature management or control functions have been developed and introduced (see, for example, Non-Patent Document 1). Because these pump lasers do not have temperature monitoring or control functions, they are easier to reduce cost and size compared to conventional products, and their introduction is progressing. Furthermore, such EDFAs generally have one or all of the following functions: APC (Automatic Power Control), which keeps the output optical signal power constant even when the power of the optical signal input to the EDFA fluctuates; AGC (Auto Gain Control), which keeps the amplification gain of the EDFA constant even when such fluctuations occur; and ACC (Auto Current Control), which keeps the drive current of the pump laser within the EDFA constant, and operate according to the system to which they are applied.

[0007] 7 is a diagram showing the configuration of an EDFA 920 that incorporates a cooler-less pump laser and performs APC operation. The transmission optical signal input to the EDFA 920 passes through an optical isolator 921, then is multiplexed in an optical multiplexer 922 with a pump optical signal from a cooler-less pump laser 923, and then is input to an EDF coil 924. In the EDF coil 924, the transmission optical signal is amplified using stimulated emission of light. The transmission optical signal output from the EDF coil 924 passes through a filter 925 for suppressing pump light and an optical isolator 926 for blocking return light, and then the optical power is split into two by an optical splitter 927. One of the split signals by the optical splitter 927 is output from the EDFA 920. The other split transmission optical signal is optical-electrically converted in an optical receiver 928 located downstream, and the resulting current information is sent to an APC control unit 929. Based on the received current information, the APC control unit 929 determines the drive current value required for the cooler-less pump laser 923, and the cooler-less pump laser 923 emits light at the determined current value. The current monitoring and detection unit 930 monitors the drive current value to the cooler-less pump laser 923 to determine whether it is normal or abnormal, and if an abnormality is detected, sends alarm information to an alarm issuing unit 931. The alarm issuing unit 931 issues the received alarm information to an external monitoring system. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] "Compact Coolerless Pump Laser Module for Optical Amplifier Excitation (Mini Pump, FOL0903m Series)", Furukawa Electric Co., Ltd., Furukawa Electric Review, No. 109, pp. 73-74, January 2002. Summary of the Invention [Problem to be solved by the invention]

[0009] In the optical amplifier described above, there exists a failure mode in which the optical amplifier output optical power is normal, but noise characteristics deteriorate. Such deterioration of noise characteristics occurs when the input optical power to the optical amplifier (EDFA 920) is lower than expected. Alternatively, the deterioration of noise characteristics occurs when the input optical power to the optical amplifier (EDF coil 924) is lower than expected due to a failure of an optical device, such as an optical connector typically inserted at the input of the optical amplifier section (EDF coil 924) in the optical amplifier, an optical isolator 921 for suppressing feedback light, or an optical multiplexer 922 for multiplexing with the pumping optical signal, resulting in a relative increase in the amount of noise light relative to the signal light.

[0010] Regarding the former case of "when the input optical power to the optical amplifier (EDFA920) is lower than expected," this drop can be detected as an abnormality by branching off a portion of the optical power of the input optical signal at the input section that inputs the optical signal to EDFA920, and having the monitoring section monitor the power of that branched light.

[0011] On the other hand, optical devices such as an optical isolator 921 that is generally inserted in the optical amplification circuit of an EDFA and an optical multiplexer 922 for multiplexing with an excitation optical signal are arranged in a stage subsequent to the optical branching unit for monitoring a decrease in input optical power that branches the optical signal to be input to the monitoring unit. Therefore, if a decrease in the input optical power to the optical amplification unit (EDF coil 924) occurs due to a failure of these optical devices, the abnormality cannot be detected by the monitoring unit monitoring the optical power as described above.

[0012] In addition, in such a situation, the input optical power to the optical receiver decreases, causing the APC operation of the optical amplifier to increase the drive current of the pump laser more than expected, resulting in an increase in the amount of noise light relative to the signal light, and degrading the noise characteristics of the output optical signal.

[0013] Conventionally, abnormal operation such as that described above has generally been detected by monitoring the drive current of the pump laser. However, the drive current value of a cooler-less pump laser also fluctuates depending on the temperature of the pump laser itself. Therefore, in the conventional technology for monitoring the drive current value of a cooler-less pump laser, it is difficult to accurately set a threshold value used to determine whether the drive current value is normal or abnormal, resulting in a problem of reduced accuracy in abnormality detection.

[0014] In view of the above circumstances, an object of the present invention is to provide an optical amplifier and an optical amplifier monitoring method that can improve the accuracy of abnormality detection. [Means for solving the problem]

[0015] An optical amplifier according to one embodiment of the present invention comprises an amplifier unit that amplifies an optical signal, a controller that controls the amplification of the optical signal by the amplifier unit based on the optical power of the optical signal amplified by the amplifier unit, and a detector that detects an abnormality based on the amount of noise contained in the optical signal amplified by the amplifier unit.

[0016] An optical amplifier monitoring method according to one aspect of the present invention includes an amplification step of amplifying an optical signal, a control step of controlling the amplification of the optical signal in the amplification step based on the optical power of the optical signal amplified in the amplification step, and a detection step of detecting an abnormality based on the amount of noise contained in the optical signal amplified in the amplification step. [Effects of the Invention]

[0017] According to the present invention, it is possible to improve the accuracy of detecting abnormalities in an optical amplifier. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an optical amplifier according to a first embodiment. [Figure 2] FIG. 10 is a diagram illustrating a configuration of an EDFA according to a second embodiment. [Figure 3]FIG. 10 is a diagram illustrating a configuration of an EDFA according to a second embodiment. [Figure 4] FIG. 10 is a diagram illustrating a configuration of an EDFA according to a third embodiment. [Figure 5] FIG. 10 is a diagram illustrating a configuration of an EDFA according to a third embodiment. [Figure 6] FIG. 1 is a diagram showing the configuration of an optical amplifier according to the prior art; [Figure 7] FIG. 1 is a diagram illustrating the configuration of an EDFA according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. This embodiment relates to an optical amplifier and an optical amplifier monitoring method for determining an abnormality in an optical amplifier section based on the amount of spontaneous emission light from the optical amplifier section. In the optical amplifier monitoring method of this embodiment, the amount of ASE (amplified spontaneous emission) in the optical amplifier output light is directly monitored to monitor deterioration in the noise characteristics of the optical amplifier output light. Compared to conventional techniques that monitor the drive current value of the optical amplifier, this embodiment can directly monitor the amount of noise, making it easy to set normal and abnormal ranges regardless of temperature fluctuations in the drive current, and achieving highly accurate monitoring.

[0020] (First embodiment) The optical amplifier of the first embodiment splits the output optical signal of the optical amplifier section and directly measures the noise level (ASE) of the split output optical signal. The first embodiment is applied to, for example, a conventional optical amplifier 910 shown in FIG.

[0021] 1 is a diagram showing an example of the configuration of an optical amplifier 100 according to the first embodiment. The optical amplifier 100 includes an optical amplifying unit 101, a drive current supplying unit 102, an optical branching unit 103, an optical branching unit 104, an optical receiving unit 105, a filtering unit 106, an optical receiving unit 107, an ASE monitoring and detecting unit 108, and an alarm issuing unit 109. The optical amplifying unit 101, the drive current supplying unit 912, the optical branching unit 103, the optical receiving unit 105, and the alarm issuing unit 109 can be the optical amplifying unit 911, the drive current supplying unit 912, the optical branching unit 913, the optical receiving unit 914, and the alarm issuing unit 916 of the optical amplifier 910 shown in FIG. 6.

[0022] The optical amplifying unit 101 amplifies an optical input signal to the optical amplifier 100 using optical amplification technology, utilizing a drive current supplied from the drive current supplying unit 102, and outputs the amplified signal. The optical branching unit 103 branches the optical input signal output from the optical amplifying unit 101 into two. One of the two branches by the optical branching unit 103 becomes an optical output signal from the optical amplifier 100, and the other is output to the optical branching unit 104. The optical branching unit 104 branches the optical input signal output from the optical branching unit 103 into two, and one of the branches is output to the optical receiving unit 105 as in the conventional technology shown in FIG. 6, while the other branch is output to the filtering unit 106.

[0023] The optical receiving unit 105 detects the optical output signal input from the optical branching unit 104, and feeds back intensity information of the detected optical output signal to the drive current supplying unit 102. The drive current supplying unit 102 supplies a drive current to the optical amplifying unit 101 based on the intensity information input from the optical receiving unit 105.

[0024] Meanwhile, the filtering unit 106 suppresses the main signal component of the optical output signal branched by the optical branching unit 104, filters out the ASE component, and outputs it to the optical receiving unit 107. The optical receiving unit 107 detects the amount of ASE component input from the filtering unit 106. The ASE monitoring and detection unit 108 monitors the amount of ASE component detected by the optical receiving unit 107. For example, the ASE monitoring and detection unit 108 determines whether the amount of ASE component falls within a normal range or an abnormal range. If the ASE monitoring and detection unit 108 detects an abnormality, it outputs abnormality information to the alarm issuing unit 109. The alarm issuing unit 109 transmits the abnormality information to an external monitoring system. The ASE monitoring and detection unit 108 may perform control such as stopping the operation of the optical amplifier 100 based on the abnormality information.

[0025] According to this embodiment, the ASE monitoring and detecting unit 108 of the optical amplifier 100 directly monitors the amount of noise, making it easy to set normal and abnormal ranges, and achieving highly accurate monitoring.

[0026] (Second embodiment) The amplifier of the second embodiment is a forward pumped EDFA with an APC control function for a cooler-less pump light source. The second embodiment is applied, for example, to the conventional EDFA shown in FIG. 7. As mentioned above, if the input optical power to the optical amplifier section (EDF coil) of the EDFA drops more than expected due to a failure of an optical device such as an optical isolator or optical multiplexer that is generally inserted in the front stage of the optical amplifier section of the EDFA, the APC control will increase the output of the pump laser more than expected, and the ASE will also increase. Therefore, in the second embodiment, the EDFA is equipped with a configuration for monitoring ASE.

[0027] 2 is a diagram showing an example of the configuration of an EDFA 200 according to the second embodiment. The EDFA 200 includes an optical isolator 201, an optical multiplexer 202, a cooler-less pump laser 203, an EDF coil 204, a filtering unit 205, an optical isolator 206, an optical branching unit 207, an optical branching unit 208, an optical receiver 209, an APC control unit 210, a filtering unit 211, an optical receiver 212, an ASE detection unit 213, and an alarm detection and generation unit 214. The optical isolator 201, optical multiplexer 202, cooler-less pump laser 203, EDF coil 204, filtering section 205, optical isolator 206, optical branching section 207, optical receiver 209 and APC control section 210 can be replaced by the optical isolator 921, optical multiplexer 922, cooler-less pump laser 923, EDF coil 924, filtering section 925, optical isolator 926, optical branching section 927, optical receiver 928 and APC control section 929 of the EDFA 920 shown in Figure 7.

[0028] Comparing EDFA200 with EDFA920 shown in FIG. 7, the difference is that instead of current monitoring and detection unit 930 that monitors the drive current of cooler-less pump laser 923, optical branching unit 208 for branching optical signal power is placed before optical receiver 209 for APC control, and the main component of the light branched by optical branching unit 208 is cut by filtering unit 211, and only the ASE component is extracted, which is then received by optical receiver 212.

[0029] Specifically, optical isolator 201 transmits an optical input signal to EDFA 200 and outputs it to optical multiplexer 202. Optical multiplexer 202 multiplexes the optical input signal transmitted by optical isolator 201 with an excitation light signal from cooler-less excitation laser 203, and inputs the multiplexed signal to EDF coil 204. In EDF coil 204, the input optical signal is amplified using stimulated emission of light. Filtering unit 205 outputs a transmission optical signal obtained by suppressing the excitation light contained in the optical output signal from EDF coil 204 to optical isolator 206. Optical isolator 206 blocks returning light and passes the transmission optical signal, which is output to optical splitter 207. Optical splitter 207 splits the transmission optical signal output from optical isolator 206 into two. One of the two signals split by the optical splitter 207 becomes an optical output signal from the EDFA 200 , and the other becomes an optical output signal to the optical splitter 208 .

[0030] The optical branching device 208 branches the optical output signal output from the optical branching device 207 into two, one of which is output to the optical receiver 209 as in the conventional technology shown in Figure 7, while the other of which is output to the filtering unit 211.

[0031] The optical receiver 209 converts the optical output signal branched by the optical brancher 208 into an electrical signal, and outputs power information of the converted electrical signal to the APC control unit 210. The APC control unit 210 determines the drive current value of the cooler-less pump laser 203 based on the received current information, and causes the cooler-less pump laser 203 to emit light with a current of the determined current value.

[0032] Meanwhile, the filtering unit 211 suppresses the main signal component of the other optical output signal branched by the optical branching unit 208, filters the ASE component, and outputs it to the optical receiver 212. The optical receiver 212 receives the optical signal containing the ASE component input from the filtering unit 211. The ASE detection unit 213 converts the power of the optical signal received by the optical receiver 212 into an ASE amount. The alarm detection and issuance unit 214 determines whether the ASE amount detected by the ASE detection unit 213 is normal or abnormal. For example, the alarm detection and issuance unit 214 determines whether the amount of the ASE component falls within a normal range or an abnormal range. If the alarm detection and issuance unit 214 determines an abnormality, it issues an alarm to an external monitoring system. Note that if the alarm detection and issuance unit 214 determines an abnormality, it may issue an alarm to the external monitoring system as described above, or may take an action such as stopping the output of the cooler-less pump laser 203 when it determines an abnormality.

[0033] 2, optical splitter 208 is provided between optical splitter 207 and optical receiver 209, but another optical splitter may be provided at the optical output port of optical splitter 207. Fig. 3 is a diagram showing an example of the configuration of EDFA 250 of the second embodiment. In EDFA 250 shown in Fig. 3, the same components as those in EDFA 200 shown in Fig. 2 are given the same reference numerals, and their description will be omitted. EDFA 250 shown in Fig. 3 differs from EDFA 200 shown in Fig. 2 in that, instead of optical splitter 208, optical splitter 251 is provided after the optical output port of optical splitter 207.

[0034] Optical branching device 207 branches the transmission optical signal output from optical isolator 206 into two, outputs one of the branches to optical branching device 251, and outputs the other branch to optical receiver 209. Optical branching device 251 branches the transmission optical signal input from optical branching device 207 into two. One of the two branches by optical branching device 251 becomes an optical output signal from EDFA 250, and the other becomes an optical output signal to filtering unit 211.

[0035] The EDFAs 200 and 250 of this embodiment directly monitor the amount of ASE contained in the optical amplifier output light, and therefore, compared to conventional technology that monitors the drive current of the amplifier device, it is easier to set normal and abnormal ranges regardless of the drive current value of the excitation laser, and highly accurate monitoring can be achieved.

[0036] (Third embodiment) In the third embodiment, in addition to monitoring the ASE, the main signal is also monitored. The third embodiment will be described, focusing on the differences from the second embodiment.

[0037] 4 is a diagram showing an example of the configuration of an EDFA 300 according to the third embodiment. In the EDFA 300 shown in FIG. 4, the same components as those in the EDFA 200 of the second embodiment shown in FIG. 2 are designated by the same reference numerals, and their description will be omitted. The EDFA 300 shown in FIG. 4 differs from the EDFA 200 shown in FIG. 2 in that it includes a three-port filtering unit 301 instead of the filtering unit 211, that it further includes a main signal monitoring unit 302, and that it includes an alarm detection and generation unit 303 instead of the alarm detection and generation unit 214. In this way, the EDFA 300 is configured to utilize transmitted light from the three-port filtering unit 301 and provide the main signal monitoring unit 302 downstream, thereby enabling main signal monitoring separate from ASE monitoring and detecting ASE using reflected light.

[0038] One of the optical input signals branched into two by optical brancher 208 is output to optical receiver 209, and the other is output to three-port filtering unit 301. Three-port filtering unit 301 has three ports: an input port, a transmission port, and a reflection port. Three-port filtering unit 301 receives the optical input signal branched by optical brancher 208 from the input port. Three-port filtering unit 301 transmits the main signal band of the input optical input signal using an optical filter and outputs it from the transmission port to main signal monitoring unit 302, and outputs reflected light, which is the optical input signal that is reflected but not transmitted by the optical filter, from the reflection port to optical receiver 212. The reflected light is an optical signal containing an ASE component.

[0039] Main signal monitoring unit 302 monitors the main signal output from the transmission port by three-port filtering unit 301, determines whether the signal is normal or abnormal, and if it determines that the signal is abnormal, notifies alarm detection and issuance unit 303 of the abnormality. Optical receiver 212 also receives the optical signal containing the ASE component output from the reflection port by three-port filtering unit 301, and converts the power of the received optical signal into an ASE amount. Similar to alarm detection and issuance unit 214 in the second embodiment, alarm detection and issuance unit 303 determines whether the signal is normal or abnormal based on the ASE amount detected by ASE detection unit 213. If main signal monitoring unit 302 or ASE detection unit 213 determines that the signal is abnormal, alarm detection and issuance unit 303 issues an alarm to an external monitoring system.

[0040] Another example of main signal monitoring is monitoring the normality of the signal wavelength using the transmission characteristics of three-port filter unit 301. If the signal light wavelength deviates to a point outside the transmission characteristics of three-port filter unit 301, the power of the received light transmitted to the transmission port decreases, and the power of the light reflected to the reflection port increases. Therefore, main signal monitoring unit 302 on the transmission side detects the optical power of the received signal light, and ASE detection unit 213 on the reflection side detects the optical power of the reflected light. Alarm detection and issuance unit 303 can detect wavelength deviation by comparing the optical power detected by main signal monitoring unit 302 with the optical power detected by ASE detection unit 213.

[0041] In FIG. 4, optical splitter 208 is provided between optical splitter 207 and optical receiver 209, but similar to EDFA 250 of the second embodiment shown in FIG. 3, another optical splitter may be provided at the optical output port of optical splitter 207.

[0042] 5 is a diagram showing an example of the configuration of an EDFA 350 according to the third embodiment. In the EDFA 350 shown in FIG. 5, the same components as those in the EDFA 250 shown in FIG. 3 and the EDFA 300 shown in FIG. 4 are designated by the same reference numerals, and their description will be omitted. The EDFA 350 shown in FIG. 5 differs from the EDFA 300 shown in FIG. 4 in that, instead of the optical splitter 208, an optical splitter 251 is disposed after the optical output port of the optical splitter 207. The optical splitter 207 splits the transmission optical signal output from the optical isolator 206 into two signals, outputs one of the split signals to the optical splitter 251, and outputs the other of the split signals to the optical receiver 209. The optical splitter 251 splits the transmission optical signal input from the optical splitter 207 into two signals, and outputs one of the split signals as an optical output signal from the EDFA 350 and the other of the split signals as an optical output signal to the filtering unit 211.

[0043] As in the second embodiment, the EDFAs 300 and 350 of this embodiment directly monitor the amount of ASE contained in the optical amplifier output light, and therefore, compared to conventional techniques that monitor the drive current of the amplifier device, it is easy to set normal and abnormal ranges regardless of the drive current value of the pump laser, and highly accurate monitoring can be achieved. Furthermore, the EDFAs 300 and 350 can monitor the main signal.

[0044] 2 to 5 show an example in which the EDFA is forward pumped, but the same method as above can also be applied to the cases of backward pumping and bidirectional pumping. In the case of backward pumping, an optical coupler is provided between the EDF coil 204 and the filter unit 205, which inputs the pumping light signal output from the backward pumping laser to the EDF coil 204. In this case, APC control for bidirectional pumping may be controlled by the forward pumping laser (cooler-less pumping laser 203), or by the backward pumping laser, or both may be used.

[0045] In the embodiment described above, the amplifier determines whether an abnormality exists in the optical amplifier unit based on the amount of noise (ASE) in the output optical signal from the optical amplifier unit, rather than the drive current value of the pump laser as in the conventional case. According to this embodiment, even when the drive current value of the pump laser varies with temperature, an abnormality can be detected with high accuracy, and a cooler-less pump laser can also be applied.

[0046] According to the above-described embodiment, the optical amplifier includes an amplifier unit, a controller, and a detector unit. For example, the optical amplifier corresponds to the optical amplifier 100, EDFA 200, 250, 300, and 350 of the embodiments. The amplifier unit amplifies an optical signal. For example, the amplifier unit corresponds to the optical amplifier unit 101, drive current supply unit 102, cooler-less pump laser 203 (forward pumping laser), optical multiplexer 202, EDF coil 204, backward pumping laser, and optical coupler of the embodiments. The controller controls the amplification of the optical signal by the amplifier unit based on the optical power of the optical signal amplified by the amplifier unit. For example, the controller corresponds to the drive current supply unit 102, optical receiving unit 105, optical receiver 209, and APC controller 210 of the embodiments. The detector detects an abnormality based on the amount of noise contained in the optical signal amplified by the amplifier unit. The detection unit corresponds to, for example, the filtering unit 106, optical receiving unit 107, ASE monitoring and detecting unit 108, filtering unit 211, three-port filtering unit 301, optical receiver 212, ASE detecting unit 213, and alarm detecting and issuing unit 214 in the embodiment.

[0047] The optical amplifier may be, for example, an erbium-doped optical fiber amplifier.

[0048] The optical amplifier may further include a filtering unit. For example, the filtering unit corresponds to the three-port filtering unit 301 of the embodiment. The filtering unit separates the optical signal amplified by the amplifying unit into a main signal component optical signal in the main signal band and a noise component optical signal excluding the main signal band. The detecting unit monitors each of the main signal component optical signal and the noise component optical signal to detect an abnormality. The detecting unit may also detect a wavelength shift of the optical signal based on the ratio between the optical power of the main signal component optical signal and the optical power of the noise component optical signal.

[0049] Although the embodiments of the present invention have been described above with reference to the drawings, it is clear that the above embodiments are merely examples of the present invention and that the present invention is not limited to the above embodiments. Therefore, additions, omissions, substitutions, and other modifications of components may be made without departing from the technical spirit and scope of the present invention. [Explanation of symbols]

[0050] 100, 910...Optical amplifier 101, 911...Optical amplifier 102, 912...Drive current supply unit 103, 104, 207, 208, 251, 913, 927...Optical splitters 105, 107, 914...Optical receiving unit 106, 205, 211, 925...Filtering section 108...ASE monitoring and detection unit 109, 916, 931...Alarm issuing department 200, 250, 300, 350, 920…EDFA 201, 206, 921, 926... Optical isolators 202, 922...Optical multiplexer 203, 923... Cooler-less pump laser 204, 924...EDF coil 209, 212, 928...Optical receiver 210, 929...APC control unit 213...ASE detection section 214...Alarm detection and issuing unit 301...3-port filter section 302...Main signal monitoring unit 303...Alarm detection and issuing unit 915…Monitoring and detection unit 930...Current monitoring and detection unit

Claims

1. an amplifier unit that amplifies an optical signal; a control unit that controls the amplification of the optical signal by the amplifier unit based on the optical power of the optical signal amplified by the amplifier unit; a detection unit that detects an abnormality based on the amount of noise contained in the optical signal amplified by the amplification unit; An optical amplifier comprising:

2. the optical amplifier is an erbium-doped optical fiber amplifier; 2. The optical amplifier according to claim 1.

3. a filter unit that separates the optical signal amplified by the amplifier unit into a main signal component optical signal in a main signal band and a noise component optical signal excluding the main signal band, the detection unit monitors each of the main signal component optical signal and the noise component optical signal to detect an abnormality.

3. The optical amplifier according to claim 2.

4. the detector detects the wavelength shift of the optical signal based on a ratio between the optical power of the main signal component optical signal and the optical power of the noise component optical signal.

4. The optical amplifier according to claim 3.

5. an amplifying step of amplifying an optical signal; a control step of controlling the amplification of the optical signal in the amplifying step based on the optical power of the optical signal amplified in the amplifying step; a detection step of detecting an abnormality based on the amount of noise contained in the optical signal amplified in the amplification step; An optical amplifier monitoring method comprising:

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