JP2010177221A - Semiconductor optical amplification system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformize outputs of signal light of all wavelength components, with no attenuation of light. <P>SOLUTION: Each of the signal lights (separated light) separated by AWG enters a semiconductor optical amplifier array 14. The current corresponding to the volume of received light of reference light for each wavelength component outgoing from a rear end face, being not reflected, of the semiconductor optical amplifier array 14, is outputted from a photodiode array 15 and enters a control circuit 2. The gain for each of separated light (wavelength component) at the semiconductor optical amplifier array 14 is separately controlled by the control circuit 2 so that the separated light for each of all wavelength components reaches a predetermined output. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor optical amplification system.

  In a wavelength division multiplexing (WDM) optical amplifier, when signal light having each wavelength component is amplified, if there is a difference in output (power) for each wavelength component, the S / N ratio deteriorates and is transmitted. Deterioration of characteristics occurs. In Patent Document 1, after amplifying signal light, the light intensity is attenuated by using a variable optical attenuator (VOA), so that the light intensity of all wavelength components is changed to the light intensity of all wavelength components. Among them, it is described that the light intensity is adjusted to the minimum light intensity.

Japanese Patent No. 3298404

  However, since the amplified signal light is attenuated using the VOA, it is not preferable in view of amplification efficiency.

  An object of the present invention is to equalize the output of signal light of all wavelength components included in signal light including a plurality of wavelength components without attenuating the signal light.

  In the semiconductor optical amplification system according to the present invention, signal light including a plurality of wavelength components input from a first input / output port is demultiplexed for each wavelength component, and the plurality of demultiplexed lights are second input / output ports. Are combined and a plurality of demultiplexed lights respectively input from the second input / output port are combined and a signal light including the plurality of wavelength components is output from the first input / output port. A demultiplexer provided for each of the demultiplexer and the plurality of demultiplexed lights, and output from the second input / output port of the multiplexer / demultiplexer and input to the first end face is formed along the light transport direction. The optical waveguide including the active layer is propagated and amplified, and at least a part of the light is reflected at the second end face, and the optical waveguide is propagated in the opposite direction to be amplified again. Semiconductor input to the input / output port A light receiving element provided for each of the optical amplifier group and the plurality of demultiplexed lights, receiving light output without being reflected at the second end face of the semiconductor optical amplifier group, and outputting a current corresponding to the amount of received light ( Based on a plurality of currents output from the photoelectric conversion element) group and the light receiving element group, the semiconductor device is configured so that all of the demultiplexed light has a predetermined output when output from the first input / output port. A control device for independently controlling the gain of each demultiplexed light in the optical amplifier group is provided.

  The multiplexer / demultiplexer that demultiplexes the signal light including a plurality of wavelength components into the demultiplexed light for each wavelength component and combines the demultiplexed light into the signal light including the plurality of wavelength components is preferably an array waveguide. It is comprised by a waveguide diffraction grating (AWG: Arrayed Waveguide Grating). In one embodiment, the multiplexer / demultiplexer and the semiconductor optical amplifier group are manufactured monolithically. The coupling loss can be reduced, the number of parts can be reduced, and the size can be reduced.

  The semiconductor optical amplifier group is composed of a plurality of semiconductor optical amplifiers. The semiconductor optical amplifier includes a first end surface (front end surface) on which the demultiplexed signal light (demultiplexed light) is incident and a second end surface (rear end surface, reflection end surface) that reflects the demultiplexed light, An optical waveguide including an active layer formed along the light transport direction is formed between the second end surface. Each of the demultiplexed light is reciprocated in the active layer (optical waveguide), amplified independently, and then emitted from the first end face. That is, the demultiplexed light incident from the first end face of the semiconductor optical amplifier passes through the active layer, reaches the second end face (forward light), is reflected by the second end face, passes through the active layer again, and passes through the active layer. 1 reaches the end face of 1 and is emitted (reverse light). Since the demultiplexed light passes through the active layer twice, a large gain can be obtained as compared with the case where it passes only once.

  Most of the light is reflected at the second end face of the semiconductor optical amplifier group, but there is also light that is slightly output (emitted) from the second end face. Light slightly emitted from the second end face of the semiconductor optical amplifier group is received for each of the plurality of demultiplexed lights and is received by a light receiving element group that outputs a current corresponding to the amount of received light. A plurality of currents output from the light receiving element group (a plurality of currents corresponding to each of the plurality of demultiplexed light outputs) are supplied to the control device.

  By controlling the drive current supplied to the active layer, the gain for each wavelength component in the semiconductor optical amplifier group is controlled. The control device adjusts the drive currents supplied to the plurality of semiconductor optical amplifiers constituting the semiconductor optical amplifier group, and thereby controls the gain for the demultiplexed light for each wavelength component in the semiconductor optical amplifier group.

  According to the present invention, the gain for each wavelength component in the semiconductor optical amplifier group is independently controlled by the control device so that the demultiplexed light for all the wavelength components reaches a predetermined output (target value). Light attenuation using an optical attenuator is not performed at all, and light output is made uniform only by light amplification. Outputs of demultiplexed light of all wavelength components can be efficiently aligned.

  In one embodiment, the control device is amplified by being guided from the first end face toward the second end face by the semiconductor optical amplifier group based on a plurality of currents output from the light receiving element group. Subsequent detection means for detecting demultiplexed light output for each wavelength component, demultiplexed light output for each wavelength component detected by the detection means, and drive current currently supplied to the semiconductor optical amplifier group for each demultiplexed light, And determining whether the predetermined output is obtained when the demultiplexed light is reflected from the second end face, guided from the second end face toward the first end face, and amplified again. Judgment means is provided.

  As described above, the demultiplexed light passes through the active layer of the semiconductor optical amplifier group twice and is amplified each time. Here, the light slightly emitted from the second end face of the semiconductor optical amplifier group passes through the active layer of the semiconductor optical amplifier group once, and is amplified only once. Since the light slightly emitted from the second end face of the semiconductor optical amplifier group is proportional to the demultiplexed light output after being amplified once, the semiconductor optical amplifier group is based on the light emitted from the second end face. The demultiplexed light output for each wavelength component after being amplified once by can be detected. Further, the current gain by the active layer for each wavelength component can be grasped based on the drive current currently supplied to the plurality of semiconductor optical amplifiers constituting the semiconductor optical amplifier group. Therefore, the detected demultiplexed light output for each wavelength component after the first amplification, the drive current (gain corresponding to the drive current) currently supplied to the semiconductor optical amplifier group (each of the plurality of semiconductor optical amplifiers), and Based on the above, it is possible to estimate the demultiplexed light output for each wavelength component when the second amplification is performed.

  It is determined whether the demultiplexed light output for each wavelength component after the second amplification is performed becomes a predetermined output. This determination can be performed using the detected demultiplexed light output after the first amplification is performed, or can be performed using the estimated demultiplexed light output after the second amplification is performed. You can also. When the determination is made using the detected demultiplexed light output after the first amplification, the output (intermediate output) that reaches the predetermined output by the second amplification is obtained as follows: A calculation is made based on the predetermined output and the currently supplied drive current (gain corresponding to the drive current), and this intermediate output is compared with the detected demultiplexed light output after the first amplification. That's fine. When the determination is made using the estimated demultiplexed light output when the second amplification is performed, the detected demultiplexed light output after the first amplification and the currently supplied drive current ( The demultiplexed light output when the second amplification is performed based on the gain corresponding to the drive) is estimated, and the estimated demultiplexed light output may be compared with the predetermined output.

  The detection unit and the determination unit may be configured by hardware, or may be realized by software that causes a computer (control device, control circuit) to function as the detection unit and the determination unit.

  Preferably, when the demultiplexed light output for each wavelength component when amplified again is determined not to be the predetermined output, the control device matches the demultiplexed light output when amplified again with the predetermined output. Thus, the drive current supplied for each demultiplexed light in the semiconductor optical amplifier group is increased or decreased. The demultiplexed light output is increased / decreased by increasing / decreasing the drive current to match the predetermined output.

  The control device may independently control the gain of each demultiplexed light in the semiconductor optical amplifier group so that the demultiplexed light of all wavelength components reaches the saturated light output. A plurality of semiconductor optical amplifiers (SOA: Semiconductor Optical Amplifiers) constituting a group of semiconductor optical amplifiers are utilized because there is a power limit (saturated light output) that cannot be increased any more.

  In this case, when the control device determines that the demultiplexed light output after the first amplification does not reach the output that will reach the saturated light output when the second amplification is performed, the control device adds the wavelength component to the wavelength component. The drive current supplied to the corresponding semiconductor optical amplifier is increased. As the drive current increases, the gain in the active layer increases, so that the demultiplexed light output after the first amplification and the demultiplexed light output after the second amplification increase. The demultiplexed light after the second amplification can reach the saturation light output.

  Furthermore, when it is determined that the demultiplexed light output after the first amplification has reached an output that will exceed the saturated light output when the second amplification is performed, the wavelength component corresponding to the wavelength component will be described. The drive current supplied to the semiconductor optical amplifier may be reduced. As described above, since the semiconductor optical amplifier does not output light having an output higher than the saturation light output, it is necessary to obtain an unnecessarily high gain by supplying a larger driving current to the semiconductor optical amplifier group than necessary. Not necessarily. When it is determined that the demultiplexed light output after the first amplification reaches the output that exceeds the saturated light output when the second amplification is performed, the semiconductor optical amplifier corresponding to the wavelength component By reducing the drive current supplied to, wasteful power consumption can be suppressed.

1 shows an overall configuration of a semiconductor optical amplification system. It is a flowchart which shows the flow of the processing operation of the control circuit of 1st Example. The graph for demonstrating the process by a control circuit is shown. It is a flowchart which shows the modification of the processing operation of a control circuit. The graph for demonstrating the process by the control circuit in a modification is shown. It is a flowchart which shows the flow of a processing operation of the control circuit of 2nd Example. (A), (B) shows the graph for demonstrating the process by the control circuit of 2nd Example.

[First embodiment]
FIG. 1 shows the overall configuration of a semiconductor optical amplification system.

  The semiconductor optical amplification system includes a semiconductor optical amplifier module 1 and a control circuit 2.

  The semiconductor optical amplifier module 1 includes a semiconductor substrate (for example, an n-type InP substrate) 10, and an input / output port 11 and an arrayed waveguide grating (AWG) 12 (hereinafter referred to as AWG 12) on the semiconductor substrate 10. , I / O port 13, semiconductor optical amplifier (SOA) array (hereinafter referred to as SOA) array 14, and photodiode array 15 are formed monolithically except for photodiode array 15. It has been done. The input / output port 11, AWG 12, input / output port 13, SOA array 14, and photodiode array 15 are optically connected on the semiconductor substrate 10.

  Among the above-described plural types of optical elements on the semiconductor substrate 10, the input / output port 11, the AWG 12 and the input / output port 13 are a plurality of types of semiconductor layers (including a core layer and a clad layer) stacked on the semiconductor substrate 10. The AWG 12 is constituted by the slab waveguides 12a and 12b and the arrayed waveguide 12c. The SOA array 14 is formed so as to have an active layer (which may have a quantum well structure) in a semiconductor layer stacked on the semiconductor substrate 10, and performs optical amplification by current control. The photodiode array 15 is formed to have a light receiving surface facing the rear end surface of the SOA array 14, and outputs a current having a value corresponding to the amount of received light. In this embodiment, the SOA array 14 is composed of four SOAs 14a to 14d, and the photodiode array 15 is composed of four photodiodes 15a to 15d.

  Wavelength multiplexed signal light including a plurality of wavelength components is input (incident) to the input / output port 11. The wavelength multiplexed signal light is demultiplexed for each wavelength by the AWG 12 (in this embodiment, it is assumed that it is demultiplexed by 4). Four demultiplexed signal lights (hereinafter referred to as demultiplexed lights) having different wavelengths are input to the input / output port 13.

  The four demultiplexed lights from the input / output port 13 are incident on the SOAs 14a to 14d constituting the SOA array 14, respectively. As will be described later, the gains of the SOAs 14a to 14d are independently controlled, and each of the four demultiplexed lights is independently amplified.

  A light reflection preventing film 14A is formed on the front end face of the SOA array 14 (SOA 14a to 14d), and a high light reflection film 14B is formed on the rear end face. The demultiplexed light incident from the front end face of the SOA array 14 is reflected at a high reflectivity on the rear end face (high light reflecting film 14B). The demultiplexed light reflected at the rear end face is emitted from the front end face of the SOA array 14.

  That is, the demultiplexed light is incident from the front end face of the SOA array 14, passes through the active layer, reaches the rear end face, is reflected at the rear end face, passes through the active layer again, and is emitted from the front end face. Since the demultiplexed light travels back and forth through the active layer in the SOA array 14, a larger amplification can be performed as compared with one that allows the demultiplexed light to pass through only in one direction (light incident from the front end face is emitted from the rear end face).

  The demultiplexed light reflected at the rear end face of the SOA array 14 is transmitted in the reverse direction, that is, through the input / output port 13, the slab waveguide 12b, the arrayed waveguide 12c, and the slab waveguide 12a to the outside from the input / output port 11. Emitted. When traveling in the reverse direction, the demultiplexed light is multiplexed in the slab waveguide 12b, the arrayed waveguide 12c, and the slab waveguide 12a. The light emitted from the input / output port 11 becomes wavelength multiplexed signal light again.

  As described above, the light receiving surface of the photodiode array 15 faces the rear end surface of the SOA array 14. The demultiplexed light that has entered the front end face of the SOA array 14 and reached the rear end face is almost reflected by the rear end face (high light reflection film 14B) (for example, 90% reflectivity), but is not reflected from the rear end face. There is also a slight amount of emitted light (hereinafter referred to as reference light). The photodiode array 15 (photodiodes 15a to 15d) receives reference light slightly emitted from the rear end face of the SOA array 14. Since the light quantity of the reference light emitted from the rear end face is proportional to the light quantity of the demultiplexed light reaching the rear end face, a current having a value corresponding to each light quantity of the demultiplexed light is output from the photodiodes 15a to 15d.

  The photodiodes 15 a to 15 d constituting the photodiode array 15 and the SOAs 14 a to 14 d constituting the SOA array 14 are all electrically connected to the control circuit 2. The control circuit 2 includes a power supply circuit (not shown), and the SOAs 14a to 14d constituting the SOA array 14 based on a current having a value corresponding to the amount of reference light (demultiplexed light) output from the photodiodes 15a to 15d. Each gain (drive current given to the SOAs 14a to 14d) is controlled (details will be described later).

  An SOA is an optical amplifier that amplifies incident light and emits the amplified light. However, the light of any power is not linearly amplified, but the power limit (saturated light) that cannot be further increased. Output) exists. For example, if the SOA saturated light output is 10 mW, light having a power exceeding 10 mW is not emitted from the SOA. In other words, even if light having a power slightly lower than 10 mW is incident on the SOA, light having a power of 10 mW is emitted from the SOA.

  In the semiconductor optical amplification system of the first embodiment, as will be described below, all of the signal light having a plurality of wavelength components included in the wavelength multiplexed signal light is output as the saturated light output by utilizing the presence of the saturated light output of the SOA. Thus, the respective gains of the SOAs 14a to 14d (drive currents given to the SOAs 14a to 14d) are controlled.

  FIG. 2 is a flowchart showing a flow of processing operation of the control circuit 2. FIG. 3 shows a graph for explaining the amplification processing by the control circuit 2.

  Demultiplexed light (reference light) that has been amplified by passing through the active layer of the SOA array 14 is incident on the photodiode array 15. As described above, since the demultiplexed light is reflected at the rear end face of the SOA array 14, the demultiplexed light travels back and forth through the active layer of the SOA array 14 (amplification is performed twice). Hereinafter, the demultiplexed light received by the photodiode array 15 (the light after only being amplified once) is referred to as “forward light”, and is output from the SOA array 14 to be wavelength multiplexed light (2 The light after the degree of amplification is called “backward light” to distinguish.

The counter i (i = 1 to 4) is initialized and incremented (step 30, step 31). Four on the basis of the current corresponding to the light amount of the received the advance light output from one of the photodiodes 15 a to 15 d, advance light output (power) p _i is detected (step 32).

In the control circuit 2, the detected forward light output p _i reaches the SOA saturated light output M when it becomes reverse light (hereinafter referred to as “forward light saturated light output m”). Is determined (step 33). The SOA saturation output M is stored in a memory (not shown) of the control circuit 2, for example. The forward light saturation light output m can be calculated from the SOA saturation output M and the current gain corresponding to the drive current.

  Since the control circuit 2 knows the drive current currently supplied to each of the SOAs 14a to 14d, it can grasp the current gain of each of the SOAs 14a to 14d (for example, the drive current value and the corresponding SOA gain). Is stored in a memory (not shown) of the control circuit 2). Therefore, by detecting the forward light output, it is possible to predict (estimate) the value of the backward light output by driving the SOAs 14a to 14d with the current drive current (current gain).

For example, the control circuit 2 detects that the forward light output from a certain SOA is a (dBm) based on the current supplied from the photodiode, and the current corresponding to the drive current currently supplied to the SOA. Assume that the gain is G ₁ . In this case, the backward light output b can be estimated by the following equation.

Reverse light output b = forward light output a × G ₁

  The forward light saturation light output m is calculated by the following equation.

Forward light saturation light output m = SOA saturation output M / G ₁

  As described above, the control circuit 2 determines whether or not the forward light reaches the output (forward light saturated light output m) that reaches the SOA saturated light output M when the backward light becomes backward light. , It is determined whether the backward light output b is equal to or greater than the SOA saturated light output M. Of course, the backward light output b may be estimated, and it may be determined whether the estimated backward light output b is greater than or equal to the SOA saturated light output M (the estimated backward light output b and the SOA saturation). Comparison with optical output M). Even if a value equal to or greater than the SOA saturated light output M is calculated as the estimated backward light output b (such forward light output a is detected), the SOA is the SOA saturated light output M as described above. Since the light having the above power is not output, the backward light output matches the SOA saturated light output M.

If the forward light output p _i is greater than or equal to the forward light saturated light output m (YES in step 33), the control circuit 2 does not perform any special processing. The control circuit 2 continuously supplies the drive current I _i currently supplied to the SOA that outputs the forward light output p _i as it is (step 34).

On the other hand, when the forward light output p _i is less than the forward light saturated light output m (NO in step 33), if the currently supplied drive current I _i is continuously supplied as it is, the backward light output becomes the SOA saturated light output M. It may be lower. In this case, the control circuit 2 increases the drive current I _i which is supplied to the SOA (step 35). The drive current is increased so that the forward light output p _i reaches the forward light saturation light output m. Of course, a margin, advance light output p _i may be gains that will exceed the advance light output saturation power m.

The above-described processing is performed for all the SOAs 14a to 14d constituting the SOA array 14 (NO in step 36, steps 31 to 35). When the processing for all (four in this embodiment) SOAs 14a to 14d is completed, the process proceeds to the next turn (YES in step 36). In this way, the forward light outputs p _i (i = 1 to 4) output from the SOAs 14a to 14d are constantly monitored.

  The processing of the control circuit 2 will be specifically described with reference to the graph of FIG.

In Case 1, the forward light output p ₁ exceeds the forward light saturation light output m. In this case, when the forward light having the forward light output p ₁ becomes the backward light, the backward light output reaches the SOA saturated light output M. The control circuit 2 continuously supplies the drive current currently supplied to the SOA as it is.

In Case 2, the forward light output p ₂ is less than the forward light saturation light output m. In this case, when the forward light of the forward light output p ₁ becomes backward light, the backward light output may be lower than the SOA saturated light output M. The control circuit 2 increases the drive current supplied to the SOA so that the forward light output p ₂ reaches the forward light saturation light output m. As a result, the forward light output p ₂ is raised to the forward light saturation light output m (see the broken line portion of the graph of case 2). A new drive current value to be supplied to the SOA is determined.

  In this way, the output (power) of the demultiplexed light (backward light) of all wavelength components included in the wavelength multiplexed signal light incident on the semiconductor optical amplifier module 1 is aligned with the SOA saturated light output M. Without performing optical attenuation, it is possible to obtain wavelength-multiplexed signal light having no variation in optical output for each wavelength.

  FIG. 4 is a flowchart showing a modification of the processing operation of the control circuit 2. FIG. 5 shows a graph for explaining processing by the control circuit 2 in the modification. In FIG. 4, the same processes as those in the flowchart shown in FIG.

Referring to FIG. 5, case 3, similarly to the case 1 described above (see FIG. 3), since the forward light output p ₃ is greater than the advance light saturation optical output m, backward light output SOA saturation optical output M will be reached. However, in case 3, the forward light output p ₃ already has a power close to the SOA saturated light output M. For this reason, even if the forward light output p ₃ is lowered to some extent, when it becomes backward light, it reaches the saturated light output M.

Referring to FIG. 4, when the forward light output p ₃ reaches the forward light saturation light output m (the forward light saturation light output m may exceed the predetermined power or more), the control circuit 2 performs the SOA. Is reduced (YES in step 33, step 37). The amount of decrease in drive current is such that the forward light output p ₃ does not fall below the forward light saturation light output m. Since the current supplied to the SOA array 16 is reduced, the power consumption can be improved.

[Second Embodiment]
The control circuit 2 according to the first embodiment described above controls all the drive currents supplied to the SOA so that the forward light output of all wavelength components reaches the forward light saturation light output m. The backward light output is matched with the SOA saturation output M. In the second embodiment, by controlling the drive current supplied to the SOA so that the forward light output of all the wavelength components reaches the forward light target value n, the backward light output of all the wavelength components is changed to the backward light. It matches the target value N.

  With reference to the flowchart showing the processing operation of the control circuit 2 of the second embodiment shown in FIG. 6 and the graphs of FIGS. 7A and 7B, the processing of the control circuit 2 in the second embodiment will be described. In the flowchart shown in FIG. 6, the same processes as those in the flowchart shown in FIG.

  In the second embodiment, as described above, the control circuit 2 operates so that the backward light outputs of all the wavelength components coincide with the backward light target value N. The reverse light target value N is stored in advance in the memory of the control circuit 2. The target output (forward light target value n) for the forward light whose reverse light output becomes the reverse light target value N is currently supplied to the reverse light target value N and the SOA, as in the first embodiment. It can be calculated from the current gain corresponding to the drive current.

Whether advance light output p _i matches the advance light target value n is determined (step 41).

When the forward light output p _i matches the forward light target value n, the control circuit 2 continuously supplies the drive current I _i currently supplied to the SOA that outputs the forward light output p _i as it is ( Step 34).

If the forward optical output p _i is less than the advance light target value n (p _i <n in step 41), when it continues supplying the drive current I _i currently supplied to the reverse light output backward light target value N Does not reach (see FIG. 7A). In this case, the control circuit 2 increases the drive current I _i supplied to the SOA (step 42). The increase amount of the drive current is an increase amount at which the forward light output p _i becomes the forward light target value n. For example, the difference (dBm) between the forward light output p _i and the forward light target value n is calculated, and the SOA gain corresponding to the calculated difference (to eliminate the calculated difference) is calculated. A drive current value (or an increase amount of the drive current) corresponding to the obtained SOA gain is obtained in the control circuit 2.

On the other hand, when the forward light output p _i exceeds the forward light target value n ( _pi > n in step 41), if the currently supplied drive current I _i is continuously supplied as it is, the reverse light output becomes the reverse light target. The value N is exceeded (see FIG. 7B). In this case, the control circuit 2 decreases the drive current I _i supplied to the SOA (step 43). Reduction range of the drive current is a decrease width of the forward optical output p _i is the advance light target value n.

  Thus, in the second embodiment, the output (power) of demultiplexed light (backward light) of all wavelength components included in the wavelength multiplexed signal light incident on the semiconductor optical amplifier module is set as the backward light target value to be set. N.

1 Semiconductor Optical Amplifier Module 2 Control Circuit
11, 13 I / O port
12 arrayed waveguide grating
14 Semiconductor optical amplifier array
15 Photodiode array

Claims (6)

The signal light including a plurality of wavelength components input from the first input / output port is demultiplexed for each wavelength component, the plurality of demultiplexed lights are respectively output from the second input / output port, and the second A multiplexer / demultiplexer that multiplexes a plurality of demultiplexed lights respectively input from the input / output port and outputs a signal light including the plurality of wavelength components from the first input / output port;
An active layer provided along each of the plurality of demultiplexed lights and formed along the light carrying direction for the demultiplexed light output from the second input / output port of the multiplexer / demultiplexer and input to the first end face. A second optical waveguide including the first and second optical waveguides, and amplifying the optical waveguide again by propagating the optical waveguide in the opposite direction by reflecting at least a portion thereof at the second end face. Semiconductor optical amplifier group to be input to the port,
A light receiving element group provided for each of the plurality of demultiplexed lights, receiving light output without being reflected at a second end face of the semiconductor optical amplifier group, and outputting a current corresponding to the amount of received light; Based on a plurality of currents output from the element group, the gain for each demultiplexed light in the semiconductor optical amplifier group is such that all the demultiplexed light has a predetermined output when it is output from the first input / output port. Control device for independently controlling
A semiconductor optical amplifying system. The controller is
On the basis of a plurality of currents output from the light receiving element group, demultiplexed light for each wavelength component after being guided and amplified by the semiconductor optical amplifier group from the first end face toward the second end face. Detection means for detecting the output;
The demultiplexed light is reflected at the second end face based on the demultiplexed light output for each wavelength component detected by the detection means and the drive current currently supplied to the semiconductor optical amplifier group for each demultiplexed light. Determining means for determining whether the predetermined output is obtained when the light is guided from the second end face toward the first end face and amplified again;
The semiconductor optical amplification system according to claim 1, comprising: The controller is
When the determination means determines that the demultiplexed light output for each wavelength component when amplified again does not become the predetermined output, any of the demultiplexed light outputs for each wavelength component when amplified again is the predetermined value. The drive current supplied for each demultiplexed light in the semiconductor optical amplifier group is increased or decreased independently so as to match the output.
The semiconductor optical amplification system according to claim 1 or 2. The control device independently controls the gain of each demultiplexed light in the semiconductor optical amplifier group so that the demultiplexed light of all wavelength components reaches the saturated light output;
The semiconductor optical amplification system according to any one of claims 1 to 3. The multiplexer / demultiplexer is constituted by an arrayed waveguide grating;
The semiconductor optical amplification system according to any one of claims 1 to 4. The multiplexer / demultiplexer and the semiconductor optical amplifier group are manufactured monolithically.
The semiconductor optical amplification system according to any one of claims 1 to 5.

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