JPH11317709A - Optical fiber amplification device, and optical transmission device and optical reception device equipped with same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation in reception sensitivity and misalarming by precisely matching the wavelength of an optical filter which removes naturally emitted light from amplified signal light with the wavelength of the signal light. SOLUTION: In addition to an optical fiber amplifier including an optical fiber 1 for amplification, an exciting light source 2 which outputs excited light, and an optical multiplexer 3 which inputs the excited light to the optical fiber amplifier and a variable wavelength optical filter 7 which outputs passing amplified signal light by selectively transmitting light of specific wavelength of the amplified signal light with a wavelength control signal, a signal light output level control part 6 which detects the signal light output level of the passing amplified signal light and controls the excited light output level to hold the passing amplified signal light output level constant and a wavelength control part which outputs a wavelength selects signal to the variable wavelength optical filter 7 so that the excited light output level becomes minimum are provided. The signal light output level control part 6 controls the excited light source to vary the transmission wavelength of the variable wavelength optical filter 7 while holding the level of the amplified signal light constant, thereby setting the optical filter to the wavelength at which the output of the excited light becomes minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber amplifier provided with a wavelength tunable optical filter, and more particularly, to a post-stage (booster) optical fiber amplifier arranged downstream of an optical transmitter and a stage upstream of an optical receiver. And a front (pre) optical fiber amplifying device arranged at

[0002]

2. Description of the Related Art Optical fiber amplifiers are widely used as means for directly amplifying signal light propagating through a transmission line.
The optical fiber amplifier includes an amplification optical fiber that amplifies input signal light, a pump light source that outputs pump light, and an optical multiplexer that causes the pump light to enter the amplification optical fiber.

In an optical fiber amplifier, an optical multiplexer is arranged in front of an amplification optical fiber and pumping light is incident from the front of the amplification optical fiber. There is a backward excitation type in which light is incident from behind. In any of the configurations, the optical fiber amplifier is feedback-controlled to keep the output level of the signal light amplified by the optical fiber amplifier at a predetermined value.

In an optical fiber amplifier, since the amplified signal light contains spontaneous emission light, the spontaneous emission light component becomes noise when received by a receiving circuit arranged at a subsequent stage, and the S / S signal becomes noise. The N ratio deteriorates. In order to prevent this, an optical filter is arranged at the subsequent stage of the optical fiber amplifier so as to remove the spontaneous emission light component and output only the signal light component. As this optical filter, a band-pass optical filter that transmits only the wavelength of the signal light to be used and light near the wavelength is used.

FIG. 11 is a diagram showing a configuration of an example of an optical fiber amplifier having a conventional optical filter. In front of the amplification optical fiber 21, an optical multiplexer 23 for multiplexing the excitation light output from the excitation light source 22 with the signal light and causing the multiplexed light to enter the amplification optical fiber is arranged. On the other hand, an optical splitter 25 for splitting a part of the amplified signal light and a light receiving element 26 for receiving the split amplified signal light and detecting the output level thereof are arranged downstream of the amplification optical fiber 21. ing. The signal light output level control circuit (ALC circuit) 27 controls the pump light source based on the level of the electric signal output from the light receiving element 26, and controls the output of the pump light so that the signal light output level becomes constant. .

Here, an optical filter 24 that removes spontaneous emission light contained in the amplified signal light and passes only the signal light is provided between the amplification optical fiber 17 and the optical splitter 25.
Is arranged. The pass wavelength band of the optical filter 24 is set in advance to the wavelength of the signal light.

FIG. 12A is a diagram showing the spectrum of the amplified signal light output from the conventional optical fiber amplifier and the transmission wavelength characteristic of the optical filter 24. FIG. 2 shows an optical spectrum of the amplified signal light.

As can be seen from the drawing, if the passing wavelength band of the optical filter 24 set with respect to the wavelength of the signal light is shifted, not only the original signal light is output,
Since a part of the signal light is cut off and the spontaneous emission light remains, as a result, noise is increased and the S / N ratio is deteriorated. In particular, in wavelength division multiplexing transmission in which signal light having wavelengths close to each other and having a narrow spectrum is wavelength-multiplexed, if the wavelength of the signal light deviates even slightly from the pass wavelength band of the optical filter 24, the S / N ratio increases. affect.

Even if the light output from the optical filter 24 is only a noise component, the ALC circuit 27 controls the signal light level output from the optical fiber amplifier to be constant. If such light is directly input to a receiving circuit arranged at a subsequent stage, there is a possibility that the receiving sensitivity may be degraded or a clock-cut alarm may be erroneously issued.

Therefore, in order to solve such a problem, for example, a configuration using a wavelength tunable optical filter capable of changing a pass wavelength band of an optical filter as disclosed in Japanese Patent Application No. 9-326557 has been proposed. ing. According to such a configuration, the pass wavelength band of the optical filter can be arbitrarily set, and the above problem can be solved by controlling the pass wavelength band so that it matches the wavelength of the signal light.

[0011]

However, according to the configuration described in the above publication, for example, the control of the pass wavelength band of the optical filter controls the output of the signal light amplified by the optical branching element disposed downstream of the optical filter. Since the level is directly monitored, a new problem arises in that the signal light output level greatly fluctuates in the process of controlling the wavelength.

The present invention solves the above-described problems of the conventional configuration and maintains the level of the amplified signal light output from the optical fiber amplifying device constant while maintaining the level of the pass wavelength band of the optical filter. The purpose of the present invention is to realize optical transmission with less noise by matching the signal with the signal light.

[0013]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned drawbacks, an optical fiber amplifier according to the present invention has an amplifying optical fiber, a pumping light source for outputting pumping light, and a pumping light input to the amplifying optical fiber. An optical fiber amplifier that includes an optical multiplexer that amplifies the input signal light and outputs an amplified signal light,
A wavelength tunable optical filter for setting a specific wavelength by a wavelength control signal, selectively transmitting light of a specific wavelength from the amplified signal light, and outputting a passing amplified signal light. A signal light output level control unit that detects a signal light output level of the passing amplified signal light, controls the pumping light output level of the pump light, and holds the passed amplified signal light output level at a predetermined value; A wavelength control unit that outputs a wavelength selection signal to the wavelength tunable optical filter so that the output level is minimized.

Here, the pumping light source is a semiconductor laser diode, and the light output level control section includes an injection current control circuit for controlling a bias current to the semiconductor laser diode to control a pumping light output level. The wavelength controller is
A wavelength control signal setting circuit for setting a wavelength control signal by a bias current is provided. This wavelength control signal setting circuit converts a bias current into an analog voltage signal.
A voltage conversion circuit, an analog / digital conversion circuit for converting an analog voltage signal into a digital voltage signal, and a wavelength setting circuit for determining a magnitude of a bias current based on the digital voltage signal and setting a wavelength control signal.

Further, the wavelength control section may be provided with an excitation light monitor section for detecting an excitation light output level instead of using the bias current, and set the wavelength control signal based on the excitation light output level. For example, as the configuration of the pumping light monitoring section, a light receiving element may be provided to receive the rear output light of the semiconductor laser diode, convert the light into an electric signal, and monitor the pumping light output level, or a part of the pumping light. May be provided with an optical splitter for monitoring the excitation light, which outputs the monitor excitation light by monitoring the excitation light output level by receiving the monitor excitation light and converting it into an electric signal. Also in such a configuration, similarly to the above, the wavelength control signal setting circuit includes a current / voltage conversion circuit that converts a current indicating an excitation light output level into an analog voltage signal, and an analog / voltage conversion circuit that converts an analog voltage signal into a digital voltage signal. A digital conversion circuit;
A wavelength setting circuit that sets the wavelength control signal by determining the magnitude of the pump light output level based on the digital voltage signal.

The signal light output level control section is configured to split a part of the passing amplified signal light to output a branched signal light, and to convert the branched signal light into an electric signal to output the passed amplified signal light. And a light receiving circuit that outputs an output level.

In the optical fiber amplifier of the present invention, the optical multiplexer may be of a forward pump type in which an optical fiber is arranged on the side of the amplification optical fiber to which the signal light is inputted, or the optical multiplexer may be an amplification optical fiber. It is also possible to use a backward pumping type disposed between the optical filter and the variable wavelength optical filter.

The optical fiber amplifying device of the present invention is not limited to the above-mentioned basic configuration, that is, instead of controlling the output level of the amplified signal light to be constant, the input signal light and the amplification are controlled. It is also possible to detect both output levels of the obtained signal light and perform feedback control so as to make the gain of the optical fiber amplifier constant, and control so that the pass wavelength bands of the optical filters are made to match.

In order to realize such control, a specific wavelength is set by an optical fiber amplifier and a wavelength control signal as described above, and light of a specific wavelength is selectively transmitted from the amplified signal light and passed therethrough. A wavelength tunable optical filter for outputting an amplified signal light as a basic configuration, further detecting an input signal light output level of the signal light and a pass amplified signal light output level of the passed amplified signal light, respectively, and outputting the pump light of the pump light. A gain control unit that controls the level to maintain the gain of the optical amplifier at a predetermined value; and a wavelength control unit that outputs a wavelength control signal to the wavelength tunable optical filter so that the pump light output level is minimized. It is characterized by having.

According to the present invention, a semiconductor laser diode is used as an excitation light source in the same manner as described above.
It is possible to adopt a configuration in which the gain control unit controls the bias current to the semiconductor laser diode to control the pump light output level. In addition, the wavelength control unit may include a wavelength control signal setting circuit that sets a wavelength control signal using a bias current. Further, the wavelength control signal setting circuit includes a current / voltage conversion circuit for converting a bias current into an analog voltage signal, an analog / digital conversion circuit for converting an analog voltage signal into a digital voltage signal, and a magnitude of the bias current based on the digital voltage signal. And a wavelength setting circuit that sets the wavelength control signal by determining the wavelength control signal.

Further, the wavelength control section may be provided with a pump light monitor section for detecting the pump light output level and a wavelength control signal setting circuit for setting a wavelength control signal based on the pump light output level. The pumping light monitoring unit includes a light receiving element that receives the rear output light of the semiconductor laser diode, converts the output light into an electric signal, and outputs a pumping light output level, or the pumping light monitoring unit includes a part of the pumping light. And a light receiving element that receives the monitor pump light and converts the monitor pump light into an electric signal to output the pump light output level. .

The gain control means includes: a first optical splitter for splitting a part of the signal light to output a first split signal light;
A first light receiving circuit that converts the first branched signal light into an electric signal and outputs the first electric signal, and a second light receiving circuit that branches a part of the passing amplified signal light and outputs a second branched signal light And a second light receiving circuit that converts the second branched signal light into an electric signal and outputs a second electric signal.

It should be noted that also in the above configuration, the forward excitation type,
Any of the backward-pumped optical fiber amplifiers can be used.

The optical fiber amplifier of the present invention can be applied to an optical transmitter or an optical receiver to constitute an optical transmitter or an optical receiver in which the S / N ratio is prevented from deteriorating. That is, an optical receiver characterized by comprising an optical receiver for receiving the pass-amplified signal light output from the optical fiber amplifier, the optical fiber amplifier, and the output from the optical fiber amplifier An optical receiving device including an optical receiver for receiving the pass amplification signal light can be configured.

Further, in the optical receiving apparatus, a wavelength-division multiplexed signal light obtained by wavelength-multiplexing a plurality of signal lights having different wavelengths from each other is input as the signal light, and the wavelength of an arbitrary signal light is selected from the plurality of signal lights. And a signal light selection circuit for adjusting the pass wavelength band of the wavelength tunable optical filter to the wavelength of the above-mentioned arbitrary signal light is provided, so that the present invention can be applied to an optical receiver of a wavelength division multiplexing optical transmission device.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical fiber amplifier according to the present invention comprises:
In an optical transmitter, an optical repeater, or an optical receiver used for wavelength division multiplexing (WDM) transmission or the like, a pass wavelength band of a wavelength tunable optical filter arranged on an output side of a booster or a pre-optical fiber amplifier is changed to a signal light It is intended to provide a configuration for performing control so as to match the wavelength.

Hereinafter, an optical fiber amplifier according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a block diagram showing the configuration of the first embodiment of the optical fiber amplifier of the present invention. In FIG. 1, an input signal light (input from the left side in the figure) is amplified by an optical fiber amplifier and output (output rightward in the figure). The optical fiber amplifier includes an amplification optical fiber 1, an excitation light source 2 for outputting excitation light, and an optical multiplexer 3 for multiplexing the excitation light with the signal light and inputting the signal light to the amplification optical fiber 1.

A tunable optical filter 7 is arranged on the output side of the amplifying optical fiber 1 of the optical fiber amplifier.
The tunable optical filter includes a tunable optical filter control circuit 1
A function of selectively passing only light of a specific wavelength band (pass wavelength band) out of signal light amplified by an optical fiber amplifier by a wavelength control signal input from 1 and blocking light of other wavelengths. Have. In the amplified signal light,
Since light that causes noise such as spontaneous emission light is included in addition to the original signal light, the light is removed by the wavelength variable optical filter 7 and output. Here, it is necessary to match the wavelength of the signal light with the specific wavelength to be passed. Note that an acousto-optic optical filter and an electro-optic optical filter are known as optical filters having the above-described wavelength variable function.

On the output side of the tunable optical filter 7, an optical splitter 4 for splitting a part of the amplified signal light selectively transmitted by the tunable optical filter 7 and outputting a split signal light is arranged. I have. The signal light branched here is received by the light receiving element 5 and converted into an electric signal, and the signal light output level is output to the signal light output level control (ALC: automatic level control) circuit 6.

The ALC circuit 6 controls the output level of the pumping light output from the pumping light source in accordance with the detected signal light output level so that the signal light output level is kept constant. When a semiconductor laser diode is used as the pump light source, the output level of the pump light is controlled by a bias current to the semiconductor laser diode.

A signal indicating an increase or decrease of the bias current to the pump light source is input to the wavelength tunable optical filter 11, and this signal becomes a wavelength control signal to control the pass wavelength band of the wavelength tunable optical filter 7. In this embodiment, the bias current is
The voltage is converted into a voltage signal by the voltage converter 8, further converted into a digital signal by the analog / digital converter 9, and the CPU 10 determines whether the value of the original bias current is increased or decreased. Is determined in the direction of the arrow.

The tunable optical filter control circuit 11 changes the passing wavelength band wavelength of the tunable optical filter 7 to cause a change in the signal light output level of the amplified signal light passing through the optical filter 7. The optical fiber amplifier of the present invention detects the change in the injection current to the pump light source, thereby eliminating the shift between the signal light and the pass wavelength band of the wavelength tunable optical filter 7 and matching the signal light output. The wavelength control is also dynamically performed while performing the feedback control for maintaining the level.

That is, control is performed so that the output level of the amplified signal light passed by the ALC circuit 6 becomes constant.
The closer the center wavelength of the pass wavelength band of the wavelength tunable optical filter 7 to the wavelength of the signal light, the smaller the gain of the optical fiber amplifier required to keep the level constant, so that the bias current to the pump light source 2 is smaller. Become.

The magnitude of the bias current to the excitation light source 2 is represented by CP
Determined by U10, the wavelength tunable optical filter control circuit 11 controls the wavelength tunable optical filter 7 so that the injection current to the excitation light source 2 is minimized, that is, the pass wavelength band of the wavelength tunable optical filter 7 is closest to the wavelength of the signal light. The pass wavelength band of the tunable optical filter 7 is controlled.

FIG. 2 illustrates the above-described wavelength control, and shows the spectrum of the amplified signal light output from the optical fiber amplifier of the present invention and the transmission wavelength characteristics of the wavelength variable optical filter. In the figure, (a) and (b)
Are the amplified signal light before (FIG. 2A) and after (FIG. 2B) the optical filter 7 when the spectrum of the amplified signal light and the passing wavelength band of the tunable optical filter match. (C) and (d) show the state of the optical spectrum before passing through the optical filter 7 when both do not match (FIG. 2).
(C)) and the state after passing (FIG. 2 (d)). As shown in FIG. 2, even though the pass wavelength band of the optical filter 7 is initially shifted from the wavelength of the amplified signal light (see (c)), the S / N ratio of the amplified signal light is deteriorated ((d) )
Reference), the wavelength control of the optical filter 7 is performed by the optical fiber amplifier of the present invention (see (a)), the two become coincident, and the S / N ratio is improved and output ((b)).
reference).

As a result, the signal whose S / N ratio (the ratio of the main signal component to the noise component) is degraded by the shift of the pass wavelength band of the wavelength tunable optical filter 7 from the wavelength of the signal light is shifted to the subsequent stage.
For example, when an optical fiber amplifying device is used as a pre-amplifier of a receiving device, it can be prevented that the signal is input to the receiving device and the receiving sensitivity is degraded.

In addition, a rare earth element-doped optical fiber is generally used as the amplification optical fiber 1. For example, erbium-doped optical fiber is widely used for optical communication in which the wavelength of signal light is in the 1.55 μm band. ing. In this case, the wavelength of the excitation light used is in the band of 1.48 μm or 0.98 μm.

In this embodiment, the pumping light is a forward pumping type in which the pumping light is multiplexed with the signal light on the input side of the amplifying optical fiber 1 and input. , And may be of the backward excitation type. In the case of the backward pumping type, the optical multiplexer 3 is disposed between the amplification optical fiber 1 and the wavelength tunable optical filter 7 so that the pumping light enters the amplification optical fiber 1. If the wavelength of the pump light and the wavelength of the signal light are different after the optical fiber 7 is disposed,
This is because the pump light does not enter the amplification optical fiber 1.

Next, the second embodiment of the optical fiber amplifier of the present invention will be described.
The third embodiment and the third embodiment will be described.

FIG. 3 is a block diagram showing a configuration of a second embodiment of the optical fiber amplifier according to the present invention. A basic configuration of an optical fiber amplifier, a configuration in which a wavelength tunable optical filter 7 is arranged on the output side of an amplification optical fiber, a part of an amplified signal light passing through the optical filter 7 is branched and monitored, and an ALC circuit 6 is provided.
Is the same as that of the first embodiment.

While the first embodiment sets the wavelength control signal based on the bias current to the pump light source, in the present embodiment, the pump light output from the back of the semiconductor laser diode of the pump light source 2 is used. The difference is that light is received by a light receiving element (not shown) and the wavelength control signal is set by the monitor current of the excitation light. Subsequent processing such as conversion of the monitor current output from the light receiving element by the current / voltage converter 8 is the same as in the first embodiment.

FIG. 4 is a block diagram showing the configuration of a third embodiment of the optical fiber amplifier according to the present invention, which is similar to the configuration of the second embodiment. In the present embodiment, a part of the output light from the front is branched by the optical splitter 13 and received by the light receiving element 12 to monitor the monitor current. The difference is that a wavelength control signal is output to the current / voltage converter 8 to set the wavelength control signal.

Next, the fourth embodiment of the optical fiber amplifier of the present invention will be described.
Next, the sixth to sixth embodiments will be described.

FIG. 5 is a block diagram showing the configuration of a fourth embodiment of the optical fiber amplifier according to the present invention. In contrast to the first embodiment shown in FIG. 1, in the first embodiment, the amplified signal light that has passed through the wavelength tunable optical filter 7 is monitored and A
The output level of the pump light is controlled by the LC circuit so that the output level of the amplified signal light becomes constant. On the other hand, in the present embodiment, not only the amplified signal light passing through the optical filter 7 but also the optical splitter 14
And a part of the input signal light is branched and monitored by the light receiving element 15. Then, a gain control (AGC: automatic gain control) circuit 16 calculates the gain of the optical fiber amplifier from the amplified signal light and the input signal light, and controls the output level of the pump light so that the gain becomes constant. The points are different. Other configurations are the same as those of the first embodiment.

FIG. 6 is a block diagram showing the configuration of a fifth embodiment of the optical fiber amplifier according to the present invention. In contrast to the second embodiment shown in FIG. 3, in the present embodiment, not only the amplified signal light passing through the optical filter 7 but also the optical splitter 14 is arranged in front of the optical fiber amplifier, as described above. A part of the input signal light is branched and monitored by the light receiving element 15. Then, a gain control (AGC: automatic gain control) circuit 6
Is that the gain of the optical fiber amplifier is calculated from the amplified signal light and the input signal light, and the output level of the pump light is controlled so that the gain is constant. Other configurations are the same as those of the second embodiment.

FIG. 7 is a block diagram showing the configuration of a fifth embodiment of the optical fiber amplifier according to the present invention. In contrast to the second embodiment shown in FIG. 4, in the present embodiment, as in the above, not only the amplified signal light that has passed through the optical filter 7 but also the optical splitter 14 is arranged in front of the optical fiber amplifier. A part of the input signal light is branched and monitored by the light receiving element 15. Then, a gain control (AGC: automatic gain control) circuit 6
Is that the gain of the optical fiber amplifier is calculated from the amplified signal light and the input signal light, and the output level of the pump light is controlled so that the gain is constant. Other configurations are the same as those of the third embodiment. The optical fiber amplifier described above can also be applied as a booster amplifier in an optical transmission device, as shown in FIG. The optical transmitter shown in FIG. 8 includes an optical transmitter 18 that converts an electric signal into an optical signal and sends out the signal light, an optical fiber amplifier that amplifies the signal light and sends out the amplified signal light to the optical transmission line, and It is composed of The optical fiber amplifier of the present invention is applied to the optical fiber amplifier 17. Since the amplified signal light contains spontaneous emission light, which causes noise, an optical filter is disposed downstream of the optical fiber amplifier in order to remove the light. Here, if the pass band of the optical filter does not coincide with the wavelength of the amplified signal light, the level of the transmitted signal light is reduced. However, according to the present invention, the pass band and the wavelength of the signal light coincide with each other. The signal light is transmitted in an optimal state without such a situation. FIG. 9 is a diagram showing an optical receiving apparatus of the present invention, which comprises an optical receiver 19 for converting an optical signal into an electric signal, and an optical fiber amplifying apparatus 17 arranged at the preceding stage for amplifying the signal light. You. Also in this case, an optical filter that blocks spontaneous emission light is disposed downstream of the optical fiber amplifier disposed as a preamplifier. Here, by applying the optical fiber amplifying device of the present invention, the signal light is received in a state where the pass band and the wavelength of the signal light coincide with each other, so that problems such as deterioration of the S / N ratio hardly occur. Further, as shown in FIG. 10, the present invention can be applied to an optical receiver for wavelength-division multiplexed signal light in which signal lights (channels) having a plurality of different wavelengths are multiplexed. In this case, for example, a channel selection signal is transmitted from the optical receiver to the wavelength tunable optical filter of the optical fiber amplifier,
It is possible to select the signal light of an arbitrary channel by accurately adjusting the wavelength.

[0048]

As described above, according to the optical fiber amplifier of the present invention, the pass wavelength band of the wavelength tunable optical filter is controlled to match the wavelength of the signal light.
It is possible to prevent the deterioration of the S / N ratio of the signal light input to the receiving circuit due to the shift of the pass wavelength band of the optical filter from the wavelength of the signal light (main signal). Also, a large deviation occurs between the wavelength band of the signal light and the passing wavelength band of the optical filter, and the signal passes through the optical filter. Therefore, even if only the noise component is present, the ALC circuit operates according to the level of the noise component, and an alarm is generated. It is also possible to prevent a misfire from occurring. Then, the current injected into the pump light source is monitored, and at the same time as the wavelength is controlled, the pump light is also controlled so as to keep the level of the amplified signal light passed through the wavelength tunable optical filter constant. The output level of the signal light output to the subsequent stage can be stably maintained.

[Brief description of the drawings]

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

FIGS. 2A and 2B are diagrams illustrating a spectrum of an amplified signal light output from an optical fiber amplifier of the present invention and a transmission wavelength characteristic of a wavelength tunable optical filter, wherein FIGS. Before passing through the optical filter 7 when the passing wavelength bands of the tunable optical filter match (FIG.
(A)) and the state of the optical spectrum of the amplified signal light after passing (FIG. 2 (b)), and (c) and (d) before passing through the optical filter 7 when both do not match (FIG. (C)) and the state of the optical spectrum of the amplified signal light after passing (FIG. 2 (d)), respectively.

FIG. 3 is a block diagram showing the configuration of a second embodiment of the optical fiber amplifier according to the present invention.

FIG. 4 is a block diagram showing a configuration of a third embodiment of the optical fiber amplifier according to the present invention.

FIG. 5 is a block diagram showing the configuration of a fourth embodiment of the optical fiber amplifier according to the present invention.

FIG. 6 is a block diagram showing the configuration of a fifth embodiment of the optical fiber amplifier according to the present invention.

FIG. 7 is a block diagram showing a configuration of a sixth embodiment of the optical fiber amplifier according to the present invention.

FIG. 8 is a block diagram illustrating a configuration of an embodiment of an optical transmission device including the optical fiber amplifier according to the present invention.

FIG. 9 is a block diagram illustrating a configuration of an embodiment of an optical receiver including an optical fiber amplifier according to the present invention.

FIG. 10 is a block diagram showing a configuration of an embodiment of an optical receiving device provided with the optical fiber amplifying device of the present invention, which is used for wavelength division multiplexed optical transmission.

FIG. 11 is a block diagram showing a configuration of a conventional optical fiber amplifier.

12A and 12B are block diagrams illustrating a spectrum of signal light amplified by a conventional optical fiber amplifier and a wavelength characteristic of an optical filter, and FIG. 12A illustrates an optical spectrum of an amplified signal light before passing through an optical filter 20; (B) shows the optical spectrum after passing through.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Amplification optical fiber 2 Pump light source 3 Optical multiplexer 4 Optical splitter 5 Light receiving element 6 Signal light output level control circuit (ALC circuit) 7 Wavelength variable optical filter 8 Current / voltage conversion circuit (IV conversion part) 9 Analog / Digital Conversion circuit (AD conversion unit) 10 Injection current discrimination circuit (CPU) 11 Variable wavelength optical filter control circuit 12 Light receiving element 13 Optical splitter 14 Optical splitter 15 Light receiving element 16 Gain control circuit (AGC circuit) 17 Optical fiber amplifier 18 Optical transmitter 19 Optical receiver 20 Wavelength selection circuit 21 Amplifying optical fiber 22 Pump light source 23 Optical multiplexer 24 Optical filter 25 Optical splitter 26 Light receiving element 27 Signal light output level control circuit

Claims (31)

[Claims] An amplification optical fiber, an excitation light source for outputting an excitation light, and an optical multiplexer for inputting the excitation light to the amplification optical fiber, wherein the input signal light is amplified and an amplified signal is amplified. An optical fiber amplifier that outputs light, a wavelength tunable optical filter that sets a specific wavelength by a wavelength control signal, selectively transmits light of the specific wavelength from the amplified signal light, and outputs a passing amplified signal light. A signal light output level control means for monitoring the passing amplified signal light, controlling a bias current to the pump light source, and maintaining the passed amplified signal light constant, and An optical fiber amplifier, comprising: a wavelength control unit that controls the specific wavelength so as to minimize the bias current. 2. An amplification optical fiber, an excitation light source for outputting excitation light, and an optical multiplexer for inputting the excitation light to the amplification optical fiber, wherein the input signal light is amplified and an amplified signal is amplified. An optical fiber amplifier that outputs light, a wavelength tunable optical filter that sets a specific wavelength by a wavelength control signal, selectively transmits light of the specific wavelength from the amplified signal light, and outputs a passing amplified signal light. A signal light output level control means for detecting a signal light output level of the passing amplified signal light, controlling a pumping light output level of the pump light, and holding the passed amplified signal light output level at a predetermined value; An optical fiber amplifier, comprising: a wavelength control unit that outputs the wavelength selection signal to the tunable optical filter so that the pump light output level is minimized. 3. The pump light source is a semiconductor laser diode, and the light output level control means includes a bias current control circuit for controlling a bias current to the semiconductor laser diode to control the pump light output level. 3. The optical fiber amplifier according to claim 2, wherein: 4. The optical fiber amplifier according to claim 3, wherein said wavelength control means includes a wavelength control signal setting circuit for setting said wavelength control signal by said bias current. 5. The current control circuit according to claim 1, wherein the wavelength control signal setting circuit converts the bias current into an analog voltage signal.
A voltage conversion circuit; an analog / digital conversion circuit that converts the analog voltage signal into a digital voltage signal; and a wavelength setting circuit that determines the magnitude of the injection current based on the digital voltage signal and sets the wavelength control signal. The optical fiber amplifier according to claim 4, wherein: 6. The optical fiber amplifier according to claim 3, wherein said wavelength control means comprises a wavelength control signal setting circuit for setting said wavelength control signal by said bias current. 7. The control circuit according to claim 1, wherein the wavelength control signal setting circuit includes a current / current converter for converting the bias current into an analog voltage signal.
A voltage conversion circuit; an analog / digital conversion circuit that converts the analog voltage signal into a digital voltage signal; and a wavelength setting circuit that determines the magnitude of the bias current based on the digital voltage signal and sets the wavelength control signal. 7. The optical fiber amplifier according to claim 6, wherein: 8. The wavelength control means includes: an excitation light monitoring means for detecting an excitation light output level; and a wavelength control signal setting circuit for setting the wavelength control signal based on the excitation light output level. The optical fiber amplifier according to claim 3. 9. The pump light monitoring means includes a light receiving element that receives the rear output light from the semiconductor laser diode, converts the output light into an electric signal, and outputs the pump light output level. Item 10. An optical fiber amplifier according to Item 8. 10. An excitation light monitoring optical splitter that outputs a monitor excitation light by branching a part of the excitation light, and receives the monitor excitation light and converts the monitor excitation light into an electric signal. 9. The optical fiber amplifier according to claim 8, further comprising: a light receiving element that outputs the pump light output level. 11. A wavelength control signal setting circuit, comprising: a current / voltage conversion circuit for converting a current indicating the pumping light output level into an analog voltage signal; and an analog / digital conversion for converting the analog voltage signal into a digital voltage signal. The optical fiber according to claim 9, further comprising: a circuit; and a wavelength setting circuit that determines the magnitude of the pumping light output level based on the digital voltage signal and sets the wavelength control signal. Amplifying device. 12. The signal light output level control means, comprising: an optical splitter that splits a part of the passing amplified signal light to output a split signal light; and converts the split signal light into an electric signal and outputs the split signal light. The optical fiber amplifier according to any one of claims 2 to 11, further comprising a light receiving circuit that outputs an output level of the amplified signal light. 13. The optical multiplexer according to claim 1, wherein the optical multiplexer is arranged on a side of the amplification optical fiber to which the signal light is input.
An optical fiber amplifier according to claim 1. 14. The optical multiplexer according to claim 1, wherein the optical multiplexer is disposed between the amplification optical fiber and the variable wavelength optical filter.
The optical fiber amplifier according to claim 2. 15. An amplification optical fiber comprising: an amplification optical fiber; an excitation light source for outputting excitation light; and an optical multiplexer for inputting the excitation light to the amplification optical fiber, and amplifying the input signal light to obtain an amplified signal. An optical fiber amplifier that outputs light, a wavelength tunable optical filter that sets a specific wavelength by a wavelength control signal, selectively transmits light of the specific wavelength from the amplified signal light, and outputs a passing amplified signal light. An optical fiber amplifier comprising: a gain for monitoring the signal light and the passing amplified signal light, controlling a bias current to the pump light source, and maintaining a constant gain of the optical fiber amplifier. An optical fiber amplifier, comprising: control means; and wavelength control means for controlling the specific wavelength so as to minimize the bias current. 16. An amplification optical fiber, an excitation light source for outputting excitation light, and an optical multiplexer for inputting the excitation light to the amplification optical fiber, wherein the input signal light is amplified and an amplified signal is amplified. An optical fiber amplifier that outputs light, a wavelength tunable optical filter that sets a specific wavelength by a wavelength control signal, selectively transmits light of the specific wavelength from the amplified signal light, and outputs a passing amplified signal light. The input signal light output level of the signal light and the pass amplification signal light output level of the pass amplification signal light are detected respectively, and the pump light output level of the pump light is controlled to set the gain of the optical amplifier in advance. An optical fiber, comprising: a gain control means for holding the value at a value; and a wavelength control means for outputting the wavelength control signal to the tunable optical filter so that the pump light output level is minimized. Amplifying device. 17. The pumping light source is a semiconductor laser diode, and the gain control means includes an injection current control circuit that controls a bias current to the semiconductor laser diode to control the pumping light output laser. The optical fiber amplifier according to claim 16, wherein: 18. The optical fiber amplifier according to claim 17, wherein said wavelength control means comprises a wavelength control signal setting circuit for setting said wavelength control signal by said bias current. 19. The circuit according to claim 19, wherein the wavelength control signal setting circuit is configured to convert the bias current into an analog voltage signal.
A voltage conversion circuit; an analog / digital conversion circuit that converts the analog voltage signal into a digital voltage signal; and a wavelength setting circuit that determines the magnitude of the bias current based on the digital voltage signal and sets the wavelength control signal. 19. The optical fiber amplifier according to claim 18, wherein: 20. The optical fiber amplifier according to claim 17, wherein said wavelength control means includes a wavelength control signal setting circuit for setting said wavelength control signal by said bias current. 21. The wavelength control signal setting circuit, comprising: a current / current for converting the bias current into an analog voltage signal;
A voltage conversion circuit; an analog / digital conversion circuit that converts the analog voltage signal into a digital voltage signal; and a wavelength setting circuit that determines the magnitude of the bias current based on the digital voltage signal and sets the wavelength control signal. 21. The optical fiber amplifier according to claim 20, wherein: 22. The wavelength control means includes: an excitation light monitoring means for detecting an excitation light output level; and a wavelength control signal setting circuit for setting the wavelength control signal based on the excitation light output level. The optical fiber amplifier according to claim 17, wherein 23. The pump light monitoring means, further comprising: a light receiving element that receives the rear output light of the semiconductor laser diode, converts the output light into an electric signal, and outputs the pump light output level. Item 23. The optical fiber amplifier according to Item 22. 24. The pumping light monitoring means, comprising: a pumping light monitoring optical splitter for branching a part of the pumping light and outputting monitor pumping light; and receiving the monitor pumping light and converting it into an electric signal. 24. The optical fiber amplifier according to claim 23, further comprising: a light receiving element that outputs the pumping light output level. 25. A current / voltage conversion circuit for converting a current indicating the pumping light output level into an analog voltage signal, and an analog / digital conversion for converting the analog voltage signal into a digital voltage signal. 25. The optical fiber according to claim 23, further comprising: a circuit; and a wavelength setting circuit that determines the magnitude of the pumping light output level based on the digital voltage signal and sets the wavelength control signal. Amplifying device. 26. The gain control means, comprising: a first optical splitter that splits a part of the signal light to output a first split signal light; and converts the first split signal light into an electric signal. A first light receiving circuit for outputting a first electric signal; a second optical splitter for splitting a part of the passing amplified signal light to output a second split signal light; 26. A second light receiving circuit according to claim 16, further comprising: a second light receiving circuit that converts the branched signal light into an electric signal and outputs a second electric signal. Optical fiber amplifier. 27. The optical fiber amplifier according to claim 26, wherein the optical multiplexer is disposed between the first optical splitter and the amplification optical fiber. 28. The optical system according to claim 15, wherein the optical multiplexer is disposed between the amplification optical fiber and the variable wavelength optical filter. Optical fiber amplifier. 29. An optical fiber amplifier according to claim 1, further comprising: an optical transmitter for inputting the signal light to the optical fiber amplifier. An optical transmission device including an optical fiber amplification device. 30. The optical fiber amplifying device according to claim 1, and an optical receiver for receiving the passing amplified signal light output from the optical fiber amplifying device. An optical receiving device comprising an optical fiber amplifying device. 31. An optical fiber amplifying apparatus according to claim 1, comprising: an optical receiver for receiving the passing amplified signal light output from the optical fiber amplifying apparatus. An optical receiver comprising an optical fiber amplifying device, wherein the signal light is a wavelength-division multiplexed signal light obtained by wavelength-multiplexing a plurality of signal lights having different wavelengths from each other, and further, any one of the plurality of signal lights. Signal light selecting means for selecting the wavelength of the signal light and adjusting the pass wavelength band of the wavelength tunable optical filter to the wavelength of the arbitrary signal light. Receiver.