Wavelength division multiplexing optical receiver and driving method for same

1. A wavelength division multiplexing optical receiver, comprising:

a polarization splitting optical coupler configured to separate wavelength division multiplexing signal light into respective polarization components;

a first semiconductor optical amplifier configured to amplify a first polarization component that has been separated by the polarization splitting optical coupler;

a second semiconductor optical amplifier configured to amplify a second polarization component that has been separated by the polarization splitting optical coupler;

a wavelength demultiplexer configured to demultiplex the outputs from the first semiconductor optical amplifier and the second semiconductor optical amplifier into respective wavelengths;

a photodetector configured to detect the outputs of the wavelength demultiplexer for the respective wavelengths;

a first monitor photodetector configured to monitor the light intensity of the first polarization component in the front stage of the first semiconductor optical amplifier;

a second monitor photodetector configured to monitor the light intensity of the second polarization component in the front stage of the second semiconductor optical amplifier; and

a control circuit configured to optically amplify the first semiconductor optical amplifier and the second semiconductor optical amplifier with different optical gains in accordance with the intensity ratio of the output from the first monitor photodetector to the output of the second monitor photodetector.

2. The wavelength division multiplexing optical receiver according to claim 1 , wherein

the wavelength demultiplexer is a first wavelength demultiplexer that demultiplexes the output of the first semiconductor optical amplifier into respective wavelengths,

the wavelength division multiplexing optical receiver further comprises a second wavelength demultiplexer that demultiplexes the output of the second semiconductor optical amplifier into respective wavelengths, and

the photodetector is a bi-directional input type photodetector.

3. The wavelength division multiplexing optical receiver according to claim 1 , further comprising:

a multiplexer configured to multiplex the outputs from the first semiconductor optical amplifier and the second semiconductor optical amplifier into a single optical waveguide between the wavelength demultiplexer and the first semiconductor optical amplifier and the second semiconductor optical amplifier, wherein

the wavelength demultiplexer is a single wavelength demultiplexer.

4. The wavelength division multiplexing optical receiver according to claim 3 , wherein the multiplexer is either a 2×1 type wavelength division multiplexing interferometer or a Y-branch waveguide.

5. The wavelength division multiplexing optical receiver according to claim 1 , wherein the first semiconductor optical amplifier and the second semiconductor optical amplifier are formed in an array on the same substrate.

6. The wavelength division multiplexing optical receiver according to claim 1 , wherein the polarization splitting optical coupler is a polarization splitting grating coupler.

7. The wavelength division multiplexing optical receiver according to claim 1 , wherein the polarization splitting optical coupler comprises:

a spot size converter into which the wavelength division multiplexing signal light is inputted;

a polarization beam splitter configured to separate the wavelength division multiplexing signal light from the spot size converter into an S polarization component that propagates in a TE mode and a P polarization component that propagates in a TM mode; and

a polarization rotator configured to convert the P polarization component that has been separated by the polarization beam splitter and that propagates in a TM mode into a TE mode.

8. The wavelength division multiplexing optical receiver according to claim 1 , wherein the control circuit controls the driving current that is injected into the first semiconductor optical amplifier and the second semiconductor optical amplifier so that the intensity of light received by the photodetector is constant by using the outputs detected by the photodetector for detecting the outputs of the wavelength demultiplexer for respective wavelengths.

9. A driving method for a wavelength division multiplexing optical receiver, comprising:

comparing a first monitor output resulting from the monitoring of the light intensity of a first polarization component separated by a polarization splitting optical coupler configured to separate wavelength division multiplexing signal light into the respective polarization components to a second monitor output resulting from the monitoring of a second polarization component separated by the polarization splitting optical coupler,

driving a first semiconductor optical amplifier configured to amplify the first polarization component and a second semiconductor optical amplifier configured to amplify the second polarization component by different optical gains each other in response to the intensity ratio of the first monitor output to the second monitor output,

separating the optically amplified wavelength division multiplexing signal light into the respective wavelengths; and detecting the optically amplified wavelength division multiplexing signal light into the respective wavelengths by photodetectors.

10. The driving method for the wavelength division multiplexing optical receiver according to claim 9 ,

wherein providing a optical gain by injecting a current into only one of the first semiconductor optical amplifier or the second semiconductor optical amplifier in response to the intensity ratio of the first monitor output to the second monitor output.

11. The driving method for the wavelength division multiplexing optical receiver according to claim 9 ,

wherein driving the first semiconductor optical amplifier and the second semiconductor optical amplifier at the same time in the case where the intensity ratio of the first monitor output to the second monitor output is within a preset range, and driving only one of the first semiconductor optical amplifier and the second semiconductor optical amplifier in the case where the intensity ratio of the first monitor output to the second monitor output is out of the preset range.

12. The driving method for the wavelength division multiplexing optical receiver according to claim 9 ,

wherein controlling the driving current being injected into the first semiconductor optical amplifier and the second semiconductor optical amplifier in such a manner that the light gain provided before being inputted into the photodetector after wavelength separation is constant irrelevant of the polarization state of the wavelength division multiplexing signal light.

13. The driving method for the wavelength division multiplexing optical receiver according to claim 9 ,

wherein controlling the driving current being injected into the first semiconductor optical amplifier and the second semiconductor optical amplifier in such a manner that the intensity of light received by the photodetector is constant.