JPH10150414A - Optical amplification device for wavelength multiplex transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold light intensity per wave in remaining signal light even if arbitrary signal light extincts by individually detecting light and setting light intensity becoming maximum to be a prescribed level. SOLUTION: The outputs of respective pilot tone detectors 33-1 to 33-n are amplified in invertible amplifiers 51-1 to 51-n and are outputted as negative voltage values. Then, they are inputted to an invertible amplifier 53 through the diodes 51-1 to 51-n of inverted connection. Only a diode connected to the amplifier whose negative voltage value is the largest becomes a forward direction and it is turned on. The other diodes become the voltage state of an inverted direction and they are turned off. Since the input voltage value of the invertible amplifier 53 is matched with the largest absolute value among the negative voltage values which the invertible amplifiers 51-1 to 51-n output, the invertible amplifier 53 selects and outputs the largest value in detected signal light intensity. A differential amplifier 71 detects a difference between the value and reference voltage, inputs it to a controller 73 and negatively feeds back/controls an exciting laser 14. Thus, the largest light intensity of signal light is kept to the prescribed level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength division multiplexing transmission optical amplifying apparatus for amplifying a plurality of multiplexed signal lights at a time. In particular, the present invention relates to an optical amplifying apparatus for wavelength division multiplexing transmission which can compensate for fluctuations in the number of wavelengths and fluctuations in fiber loss in an optical fiber transmission line, and can always maintain the output light intensity per signal light at a predetermined level.

[0002]

2. Description of the Related Art Multiplexed signal lights of a plurality of wavelengths can be collectively amplified by using an optical fiber amplifier or a semiconductor optical amplifier. Here, it is necessary to keep the output signal light intensity of the optical amplifier large in order to prevent a decrease in the signal-to-noise ratio (S / N). On the other hand, when the signal light intensity per one wave input to the optical fiber exceeds a predetermined level,
Non-linear phenomena such as four-wave mixing and self-phase modulation occur, and the transmission characteristics deteriorate rapidly. Therefore, in the wavelength division multiplexing transmission optical amplifying device, even if the sum of the input signal light intensities (total light intensity) changes due to the change in the number of wavelengths or the change in the fiber loss, the signals are collectively amplified and output. It is necessary to control such that the light intensity per one wave of the signal light is always kept at a predetermined level. Hereinafter, a conventional optical amplifying apparatus for wavelength multiplex transmission having such a function will be described.

(First Conventional Apparatus) A first conventional apparatus determines the sum of the intensities of a plurality of signal lights output from an optical amplifier (total light intensity Psum) and the number of signal lights (the number of wavelengths n). Detected and light intensity per signal light wave (Psum / n)
In this configuration, the gain of the optical amplifier is feedback-controlled so that the level becomes a predetermined level. (Reference: Yoshida et al., "WDM optical amplifier output level control method", 1996 IEICE Communications Society Conference, Lecture No. B1096).

FIG. 5 shows a configuration example of a first conventional apparatus.
In the figure, an optical fiber amplifier 10 includes an optical isolator 11, an erbium-doped optical fiber 12, an optical multiplexer 13,
The optical isolator 15 is connected in order, and the pump light output from the pump laser 14 is input to the erbium-doped optical fiber 12 via the optical multiplexer 13 to be pumped. Erbium-doped optical fiber 12 via optical isolator 11
, Λn) are collectively amplified by the erbium-doped optical fiber 12 in the excited state, and output via the optical multiplexer 13 and the optical isolator 15. Here, when the drive current of the pump laser 14 is controlled to change the pump light intensity, the pump state in the erbium-doped optical fiber 12 changes, and the gain of the optical fiber amplifier 10 changes.

The output of the optical fiber amplifier 10 is partially branched by the optical couplers 21 and 22, respectively, and input to the photodetector 41 and the wavelength number detection circuit 91, where the total light intensity Psum and the number of wavelengths n are detected. The divider 92 receives the total light intensity Psum and the number of wavelengths n, and detects the light intensity Psum / n per signal light wave at the output of the optical fiber amplifier 10. The differential amplifier 71 detects a difference between the light intensity Psum / n per one signal light and the reference voltage output from the reference voltage generation circuit 72, and inputs the difference to the controller 73 as an error signal. 14 is subjected to negative feedback control.

With such a configuration, even if the fiber loss changes and the intensity of the wavelength-division multiplexed signal light input to the optical fiber amplifier 10 changes, or if the number of wavelengths of the wavelength-division multiplexed signal light changes, the optical loss can be reduced. The light intensity per signal light output from the fiber amplifier 10 is controlled to be constant. (Second Conventional Apparatus) A second conventional apparatus detects the light intensity of one specific signal light among a plurality of multiplexed signal lights output from an optical amplifier, and detects the intensity of the signal light at a predetermined level. In this configuration, the gain of the optical amplifier is controlled as follows (see AKSrivastava et al., "Fast Gaincontrol in an Erb"
ium-Doped Fiber Amplifier ", ECOC'96, Postdeadline
PaperNo.PDP4).

FIG. 6 shows a configuration example of a second conventional apparatus.
In the figure, an optical fiber amplifier 10, an optical coupler 21, a light receiver 41, a differential amplifier 71, a reference voltage generating circuit 72, and a controller 73 are the same as those in the first conventional configuration. First
The difference between the conventional configuration and the present configuration is that the wavelength division multiplexed signal light split by the optical coupler 21 is input to the optical receiver 41 via the optical bandpass filter 32.

[0008] The optical bandpass filter 32 allows only a specific signal light (here, wavelength λ1) to pass therethrough from the wavelength multiplexed signal light. The light receiver 41 detects the light intensity of the signal light,
Negative feedback control of the excitation laser 14 is performed so that the detected value becomes equal to the reference voltage output from the reference voltage generation circuit 72.

[0009]

[Problems to be solved by the invention]

(Problems of the first conventional device) The first conventional device has a problem that only slow fiber loss fluctuation can be compensated. Hereinafter, the reason will be described with reference to FIGS. FIG. 7 shows the time change of the input light intensity when the number of wavelengths input to the first conventional device changes from one wave (λ1) to eight waves (λ1, λ2,..., Λ8).

[0010] indicates the light intensity of the signal light λ1, and indicates the total light intensity. At time ts, the number of wavelengths changes from one wave (λ1) to eight waves (λ1, λ2,..., Λ8). However, the total light intensity is such that the signal light intensity of seven waves (λ2, λ3,..., Λ8) starts to increase at time ts and time te (= ts +
At t), the light intensity change accompanying the change in the number of wavelengths ends. on the other hand,
Since the detection threshold value is set sufficiently low to avoid malfunction, the wavelength number detection circuit 91 detects a change in the number of wavelengths (1 wave → 8 waves) immediately after time ts. However, since the total light intensity immediately after the time ts is almost one wave, the light intensity of about one wave is divided by eight waves by the divider 92, and the state where the input light intensity temporarily decreases is obtained. Is determined. And
Negative feedback control works to increase the number to eight waves, and the gain of the optical fiber amplifier 10 is increased.

FIG. 8 shows a calculation example of a time change of the output signal light intensity of the optical fiber amplifier 10 which is negatively feedback-controlled with respect to the fluctuation of the number of wavelengths. t is the continuation time (te-ts) of the light intensity change accompanying the change in the number of wavelengths. T is a response time constant of the feedback-controlled optical fiber amplifier 10. When the response time constant T is short, that is, when T / t is small, the light intensity of the signal light λ1 temporarily increases greatly. Therefore, in order to control the output light intensity of the signal light (λ1 here) originally present when the number of wavelengths changes, T is sufficiently longer than t, for example, T / t ≧ 10. It is necessary to design.

FIG. 9 shows the temporal change of the input light intensity when the wavelength-division multiplexed signal light (λ1, λ2,..., Λ8) input to the first conventional device is temporarily reduced due to the fluctuation of the fiber loss. Is the light intensity of the signal light λ1, and is the wavelength multiplexed signal light (λ
1, λ2, ..., λ8). here,
The fiber loss increases from time ts to time tc (= ts + τ), and decreases from time tc to time te (= tc + τ). Such fiber loss fluctuations occur, for example, when the optical fiber transmission line is accidentally contacted during maintenance work. When the input light intensity changes due to the fiber loss fluctuation, negative feedback control is applied to the optical fiber amplifier 10.

FIG. 10 shows a calculation example of a time change of the output signal light intensity of the optical fiber amplifier 10 which is negatively feedback-controlled with respect to the fiber loss fluctuation. τ is the continuation time (tc−ts = te−tc) of the light intensity change due to the fiber loss fluctuation. T is a response time constant of the feedback-controlled optical fiber amplifier 10. When the speed of the fiber loss fluctuation is high, that is, when τ / T is small, the negative feedback control cannot be performed in time and all the signal light intensities decrease in accordance with the increase in the fiber loss. Therefore, in order to control the output light intensity per signal light to be kept constant when the fiber loss fluctuates, τ is sufficiently longer than T, for example, τ /
It is necessary to design so that T ≧ 10.

As described above, the first conventional apparatus shown in FIG. 5 needs to be designed so that T / t ≧ 10 and τ / T ≧ 10. This satisfies τ / t ≧ 100,
In other words, it indicates that only a fiber loss variation (τ) that is much slower than a light intensity variation (t) accompanying a wavelength number variation can be compensated. For example, when an optical signal is intermittently switched using a quartz waveguide optical switch utilizing the thermo-optic effect, t is several milliseconds. Therefore, the response time constant T of the optical fiber amplifier 10 needs to be set to several tens milliseconds or more. The fiber loss fluctuation that can be compensated is limited to a slow fluctuation in which τ is several hundred ms or more.

(Problem of Second Conventional Apparatus) In the second conventional apparatus, the intensity of a specific signal light is monitored and controlled.
Even if the total output light intensity changes with a change in the number of wavelengths, a transient response as shown in FIG. 8 does not occur in principle. For this reason, the response time constant T of the optical fiber amplifier 10 controlled by the negative feedback is equal to the duration t of the light intensity change due to the change in the number of wavelengths.
Irrespective of the time, it can be set to, for example, 1 ms or less. In this case, it is possible to compensate for a fast fiber loss fluctuation in which τ is 10 ms or less.

However, in the configuration shown in FIG. 6, the negative feedback control of the optical fiber amplifier 10 is controlled by a specific signal light (here, λ
1) will depend on the existence. Therefore, if the signal light λ1 disappears or attenuates due to a failure, the amplification gain cannot be controlled correctly even if the remaining signal light arrives normally, and all communications may be interrupted. is there. That is, the influence of the failure of the signal light λ1 affects all other signal lights.

According to the present invention, a wavelength that can be controlled so as to always compensate for a fast fiber loss fluctuation and to keep the output light intensity per signal light constant without depending on the presence or absence of a specific signal light. It is an object to provide an optical amplifier for multiplex transmission.

[0018]

An optical amplifying apparatus for wavelength division multiplexing transmission according to the present invention uses the output of an optical amplifying means for collectively amplifying multiplexed signal lights of a plurality of wavelengths to obtain an optical intensity detecting means. The light intensity of the signal light of the wavelength is individually detected, and further, the maximum value of each light intensity is selected by the maximum value detecting means, and the optical amplifier means is controlled by the feedback control means so that the light intensity of the maximum value becomes a predetermined level. This is a configuration for controlling the gain of.

Thus, the light intensity of the strongest signal light among the plurality of signal lights amplified by the optical amplifying means is always maintained at a predetermined level. Therefore, even if an arbitrary signal light out of the plurality of signal lights disappears, the light intensity per wave of the remaining signal light is kept at a predetermined level. Further, when the number of wavelengths changes, the light intensity per one wave of the signal light not involved in the change is controlled to be maintained at a predetermined level. Instead, the response time constant T of the feedback control can be set short. Therefore, it is possible to compensate for a rapid fiber loss variation without depending on the presence or absence of a specific signal light.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 shows a first embodiment of an optical amplifying device for wavelength division multiplexing transmission according to the present invention. In the figure, an optical amplifier (optical fiber amplifier 10: optical isolator 11, erbium-doped optical fiber 12, optical multiplexer 13, pump laser 14, optical isolator 15) for collectively amplifying multiplexed signal lights of a plurality of wavelengths. The feedback control means (differential amplifier 71, reference voltage generation circuit 72, controller 73) for controlling the gain of the optical fiber amplifier 10 is the same as that of the conventional device shown in FIG. Furthermore, as light intensity detection means,
The optical coupler 21, the light receiver 42, and the pilot tone detectors 33-1 to 3-3 which branch a part of the output of the optical fiber amplifier 10.
33-n, and inverting amplifiers 51-1 to 51-n, diodes 52-1 to 52-n as maximum value detecting means.
n, an inverting amplifier 53 is provided.

In this embodiment, the signal lights λ1, λ2,..., Λn input to the optical fiber amplifier 10 are low-frequency signals (pilot tones) f1, f2,.
It is assumed that weak intensity modulation is applied at fn. The signal light branched by the optical coupler 21 is converted into an electric signal by the light receiver 42. A plurality of pilot tones f1, f2,..., Fn are multiplexed on this electric signal, and the pilot tone detectors 33-1 to 33-n respectively intensify the corresponding pilot tones f1, f2,. Is detected. The intensity of each pilot tone individually corresponds to the light intensity of each signal light. The pilot tone detector can be realized by, for example, an electric synchronous detection circuit.

Each pilot tone detector 33-1 to 33-33
The output of -n is input to the inverting amplifiers 51-1 to 51-n, amplified at appropriate magnifications, and output as negative voltage values. The outputs of the inverting amplifiers 51-1 to 51-n are
Each is connected to the input of the inverting amplifier 53 via the reverse-connected diodes 52-1 to 52-n. Here, among the outputs of the inverting amplifiers 51-1 to 51-n, only the diode connected to the one having the largest negative voltage value becomes forward and turns on. At this time, the other diodes are in a reverse voltage state and are turned off. For this reason, the input voltage value of the inverting amplifier 53 is a
Among the negative voltage values output by 1-n, the absolute value coincides with the largest absolute value. Therefore, the inverting amplifier 53
The largest value among the detected signal light intensities is selected and output.

The differential amplifier 71 detects the difference between this value and the reference voltage output from the reference voltage generation circuit 72,
This is input to the controller 73 as an error signal, and the pump laser 14 is subjected to negative feedback control. Thereby, the light intensity of the strongest signal light among the plurality of amplified signal lights is maintained at a predetermined level. Note that the polarity of the diode and the presence or absence of the inverting amplifier are appropriately changed depending on the sign of the output voltage of the light receiver 42 and the direction of control by the controller 73. This is the same in other embodiments described below.

The maximum value detecting means is not limited to the configuration using the inverting amplifier and the diode. For example, the output of each of the pilot tone detectors 33-1 to 33-n is converted into a digital signal, and the digital signal is converted using a microprocessor. The maximum value may be detected, the maximum value may be converted into an analog signal and output to the differential amplifier 71. The same applies to other embodiments described below.

Next, a description will be given of how the present embodiment solves the problem of the first conventional device described with reference to FIGS. It is assumed that the input light intensity of the device of the present embodiment has changed as shown in FIG. In this embodiment, since the strongest signal light intensity is detected, control is performed here so that the light intensity of the signal light λ1 is kept constant. Further, the total light intensity is not detected. Therefore, the duration t of the total light intensity change
Even if the response time constant T of the optical fiber amplifier 10 subjected to the negative feedback control is set to be shorter, the output light intensity does not change as shown in FIG. 8 and the output light intensity of the signal light λ1 is always constant. Can be kept. Therefore, for example, t is several ms.
In this case, T can be designed to be, for example, several hundred μs.

On the other hand, when the input light intensity of the device of this embodiment changes as shown in FIG. 9, the response is exactly the same as that of the first conventional device. This is because, when the fiber loss changes, the change in the total light intensity and the change in the strongest signal light intensity are the same. Therefore, if T is designed to be several hundred μs, it is possible to compensate for a fiber loss variation in which τ is several ms.

Further, in the configuration of the present embodiment, even if any one of the plurality of input signal lights disappears, there is no problem in the control operation. That is, since the operation can be performed regardless of the presence or absence of the specific signal light, the problem of the second conventional device is also solved. In the present embodiment, the optical coupler 21, the light receiver 42, and the pilot tone detectors 33-1 to 33-n have been described as the optical intensity detecting means for individually detecting the optical intensities of a plurality of signal lights. However, the present invention is not limited to this. Since the pilot tone detector uses a narrow band electric filter, the response when the light intensity changes may be limited depending on the band. In order to avoid this, it is preferable to adopt a configuration that can detect the light intensity of the signal light of each wavelength without superimposing a pilot tone on the signal light.

For example, the above-mentioned reference (Yoshida et al., “W
An acousto-optic band-pass filter used in the wavelength number detection circuit in "DM Optical Amplifier Output Level Control Method", 1996 IEICE Communications Society Conference, Lecture No. B1096). The signal light extracted at 21 is input to a tunable bandpass filter that is repeatedly swept, and the output is converted into an electric signal by a photodetector to periodically detect an optical spectrum.
If there are a plurality of signal lights, there are a plurality of peaks in the optical spectrum. Therefore, each peak value may be detected and output. Further, an optical demultiplexer and a plurality of light receivers may be used. Next, this embodiment will be described.

(Second Embodiment) FIG. 2 shows a second embodiment of the optical amplifying apparatus for wavelength division multiplexing transmission according to the present invention. In the figure, optical amplifying means (optical fiber amplifier 10: optical isolator 11, erbium-doped optical fiber 12, optical multiplexer 1)
3, pump laser 14, optical isolator 15), maximum value detecting means (inverting amplifiers 51-1 to 51-n, diode 5)
2-1 to 52-n, inverting amplifier 53) and feedback control means (differential amplifier 71, reference voltage generating circuit 72, controller 73) are the same as those in the first embodiment shown in FIG.
The feature of this embodiment lies in that an optical coupler 21, an optical demultiplexer 31, and light receivers 41-1 to 41-n are provided as light intensity detecting means.

The plurality of signal lights split by the optical coupler 21 are split by the optical splitter 31 for each wavelength. As the optical demultiplexer 31, for example, an arrayed waveguide diffraction grating optical filter is used. The intensity of the demultiplexed signal light of each wavelength is detected by the light receivers 41-1 to 41-n, respectively, and input to the inverting amplifiers 51-1 to 51-n. With such a configuration, the light intensities of the plurality of signal lights amplified by the optical fiber amplifier 10 are individually detected. The following operation is the same as that of the first embodiment, and does not depend on the presence or absence of a specific signal light.
In addition, fast fiber loss fluctuation can be compensated.

In the second embodiment, since the wavelength is identified and split by the optical splitter 31, unlike the first embodiment, it is not necessary to superimpose a pilot tone for identifying each signal light. It is. Further, the signal light intensity is changed to the light receivers 41-1 to 41-1.
Since the light intensity is directly detected at 41-n, the response when the light intensity changes is quick. For this reason, the response time constant T of the optical fiber amplifier 10 that is feedback-controlled can be set shorter, and faster fiber loss fluctuation can be compensated.

(Third Embodiment) FIG. 3 shows a third embodiment of the optical amplifying apparatus for wavelength division multiplexing transmission according to the present invention. In the figure, optical amplifying means (optical fiber amplifier 10: optical isolator 11, erbium-doped optical fiber 12, optical multiplexer 1)
3, pump laser 14, optical isolator 15), maximum value detecting means (inverting amplifiers 51-1 to 51-n, diode 5)
2-1 to 52-n, inverting amplifier 53) and feedback control means (differential amplifier 71, reference voltage generating circuit 72, controller 73) are the same as those in the first embodiment shown in FIG.
A feature of the present embodiment is that an optical demultiplexer 3 for demultiplexing signal lights of a plurality of wavelengths which are collectively amplified by an optical fiber amplifier 10 is provided.
1, as optical intensity detecting means, optical couplers 21-1 to 21-n for branching a part of the demultiplexed signal light of each wavelength;
It is provided with light receivers 41-1 to 41-n.

The operation in which the light intensities of a plurality of signal lights are individually detected by the light receivers 41-1 to 41-n is the same as in the second embodiment, and does not depend on the presence or absence of a specific signal light. In addition, fast fiber loss fluctuation can be compensated. When an optical receiver for receiving each signal light is connected to the subsequent stage of the optical demultiplexer 31, the light receiver of each optical receiver may be used as the light receivers 41-1 to 41-n. it can. In that case, the optical couplers 21-1 to 21-n are unnecessary.

(Fourth Embodiment) FIG. 4 shows a fourth embodiment of the optical amplifying apparatus for wavelength division multiplexing transmission according to the present invention. In the figure, light intensity detecting means (optical coupler 21, optical demultiplexer 31,
Photodetectors 41-1 to 41-n, maximum value detecting means (inverting amplifiers 51-1 to 51-n, diodes 52-1 to 52-)
n, inverting amplifier 53), feedback control means (differential amplifier 7).
1, the reference voltage generation circuit 72 and the controller 73) are the same as those in the second embodiment shown in FIG. The feature of this embodiment resides in that a constant gain optical amplifier (constant gain optical fiber amplifier 80) and an optical attenuator (variable optical attenuator 90) are used as optical amplifiers.

The constant gain optical fiber amplifier 80 includes an optical isolator 11, an erbium-doped optical fiber 12, an optical multiplexer 13, a pump laser 14, and an optical isolator 15.
Optical couplers 16 and 17 for branching a part of the input light and the output light,
The photodetectors 81 and 82 detect the light intensity, the gain detector 83 detects the amplifier gain from the input / output light intensity, and the drive current of the pump laser 14 so that the detected gain value becomes the reference voltage of the reference voltage generation circuit 85. Amplifier 84 for feedback control of
It consists of. This configuration is an example, and any configuration may be used as long as the gain is controlled to be constant.

On the other hand, the wavelength multiplexed signal light output via the optical coupler 17 is collectively attenuated by the variable optical attenuator 90. The attenuation factor of the variable optical attenuator 90 is feedback-controlled via the controller 73 by the output of the differential amplifier 71. In the present embodiment, an optical amplifying unit whose gain can be controlled by the constant gain optical fiber amplifier 80 and the variable optical attenuator 90 is configured, so that the same effect as in the second embodiment can be obtained. Further, in the present embodiment, since the constant gain optical fiber amplifier 80 always operates with a constant gain, there is an advantage that a gain deviation between a plurality of signal lights having different wavelengths can be suppressed.
The gain deviation in the constant gain optical fiber amplifier 80 and the method of suppressing the gain deviation are described in a reference (Y. Sugaya et al.,
"Novel configuration for low-noise and wide-dynami
c-range Er-doped fiberamplifier for WDM systems ",
OAA'95, FC3).

In the present embodiment, the variable optical attenuator 90 is provided at the subsequent stage of the constant gain optical fiber amplifier 80 to control the gain. However, the present invention is not limited to this configuration. For example, a constant gain optical fiber amplifier 80
May be prepared in two sets, and a variable optical attenuator 90 is inserted between them to connect in series, thereby improving the noise figure and expanding the dynamic range.

In the first to fourth embodiments described above, the backward-pumped optical fiber amplifier in which the pump light is input from the output side of the erbium-doped optical fiber 12 is shown as the optical amplifying means. An optical fiber amplifier that inputs pump light from forward pumping or from both directions may be used. In addition, the present invention is not limited to the optical fiber amplifier, but may be any as long as it can collectively amplify a plurality of signal lights having different wavelengths with substantially equal gain.

[0039]

As described above, the optical amplifying apparatus for wavelength division multiplexing transmission according to the first aspect of the present invention individually detects the light intensities of a plurality of signal lights and sets the maximum light intensity to a predetermined level. Since the control is performed, the light intensity per wave of the remaining signal light can be maintained at a predetermined level even if any signal light among the plurality of signal lights disappears. In addition, when the number of wavelengths changes, control is performed so that the light intensity of the signal light that does not fluctuate is maintained at a predetermined level. The time constant T can be set short, thereby compensating for fast fiber loss fluctuations.

According to a second aspect of the present invention, there is provided an optical amplifying apparatus for wavelength division multiplexing transmission.
By using the constant gain optical amplifying means and the optical attenuating means as the optical amplifying means, it is possible to suppress the gain deviation between a plurality of signal lights having different wavelengths. The optical amplifier for wavelength division multiplexing transmission according to the third aspect uses the optical demultiplexing means and the plurality of photoelectric conversion means as the light intensity detecting means, so that a change in signal light intensity can be detected quickly, and a faster fiber loss can be achieved. Fluctuations can be compensated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an optical amplifier for wavelength division multiplexing transmission according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the optical amplifying device for wavelength division multiplexing transmission of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the optical amplifying device for wavelength division multiplexing transmission of the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the optical amplifying apparatus for wavelength division multiplexing transmission of the present invention.

FIG. 5 is a block diagram showing a configuration example of a first conventional device.

FIG. 6 is a block diagram showing a configuration example of a second conventional device.

FIG. 7 is a diagram showing a time change of the input light intensity of the first conventional device when the number of wavelengths changes from one wave to eight waves.

FIG. 8 is a diagram illustrating a calculation example of a temporal change in the output signal light intensity of the optical fiber amplifier 10 that is negatively feedback-controlled with respect to a change in the number of wavelengths.

FIG. 9 is a diagram showing a change over time of the input light intensity of the first conventional device when a change in fiber loss occurs.

FIG. 10 is a diagram showing a calculation example of a time change of the output signal light intensity of the optical fiber amplifier 10 that is negatively feedback-controlled with respect to the fiber loss fluctuation.

[Explanation of symbols]

 Reference Signs List 10 optical fiber amplifier 11, 15 optical isolator 12 erbium-doped optical fiber 13 optical multiplexer 14 pumping laser 16, 17, 21, 22 optical coupler 31 optical demultiplexer 32 optical bandpass filter 33 pilot tone detector 41, 42, 81 , 82 Receiver 51, 53 Inverting amplifier 52 Diode 71, 84 Differential amplifier 72, 85 Reference voltage generating circuit 73 Controller 80 Constant gain optical fiber amplifier 83 Gain detector 90 Variable optical attenuator 91 Wavelength number detecting circuit 92 Divider

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/28 10/26 10/14 10/04 10/06

Claims (3)

[Claims] 1. An optical amplifying means for collectively amplifying a plurality of multiplexed signal lights of a plurality of wavelengths, and individually adjusting the light intensities of the multiplexed signal lights of a plurality of wavelengths output from the optical amplifying means. Light intensity detection means for detecting, maximum value selection means for selecting the maximum value of the light intensity of the signal light of each wavelength detected by the light intensity detection means, and light of the maximum value selected by the maximum value selection means Feedback control means for controlling the gain of the optical amplifying means so that the intensity is at a predetermined level. 2. An optical amplifying means having a constant gain optical amplifying means and an optical attenuating means whose gain is controlled to be constant, amplifying the multiplexed signal light of a plurality of wavelengths collectively, and said optical amplifying means. Light intensity detecting means for individually detecting the light intensities of the multiplexed signal lights of a plurality of wavelengths output from the apparatus, and selecting the maximum value of the light intensity of the signal light of each wavelength detected by the light intensity detecting means. And a feedback control unit that controls an attenuation rate of an optical attenuating unit of the optical amplifying unit so that the light intensity of the maximum value selected by the maximum value selecting unit becomes a predetermined level. An optical amplifier for wavelength division multiplexing transmission. 3. The optical amplifying device for wavelength division multiplexing transmission according to claim 1, wherein the optical intensity detecting means converts the multiplexed signal light of a plurality of wavelengths output from the optical amplifying means into each wavelength. Wavelength division multiplexing transmission, comprising: a light demultiplexing means for demultiplexing every wavelength; and a plurality of photoelectric conversion means for detecting the light intensity of the signal light of each wavelength demultiplexed by the light demultiplexing means. Optical amplifying device.