Polarization interferometer, optical module, and optical receiver

An optical module comprising:

• a first beam splitter for splitting one of a signal and a reference lights into a first and a second branch lights;
• a second beam splitter for splitting the other of the signal and the reference lights into a third and a fourth branch lights;
• a first coupler for causing the first and the third branch lights to interfere with each other, and outputting a first phase detection signal light;
• a second coupler for causing the second and the fourth branch light to interfere with each other, and outputting a second phase detection signal light;
• an optical phase shifter for shifting the optical phase by an amount between the third and the fourth branch lights inputted into the first or second coupler;
• a first polarization phase controller provided between the first beam splitter and the first coupler, the first polarization phase controller individually controlling phases of two orthogonal polarization components of the first branch light and outputting the phase-controlled polarization components of the first branch light;
• a second polarization phase controller provided between the second beam splitter and the second coupler, the second polarization phase controller individually controlling phases of two orthogonal polarization components of the fourth branch light and outputting the phase-controlled polarization components of the fourth branch light;
• a polarization splitter for splitting each of the first and the second phased detection signal lights from the first and second couplers into different polarizations orthogonal to each other;
• and
• a plurality of light receivers provided at a stage subsequent to the polarization splitter, for receiving each of the different polarizations of the each of the first and the second detection lights.

A optical receiver comprising a polarization interferometer for receiving a signal light and a reference light and for outputting phase detection signal lights, the polarization coupler including:

• a first beam splitter for splitting one of the signal and the reference lights into a first and a second branch lights;
• a second beam splitter for splitting the other of the signal and the reference lights into a third and a fourth branch lights;
• a first coupler for causing the first and the third branch lights to interfere with each other, and outputting a first phase detection signal light;
• a second coupler for causing the second and the fourth branch light to interfere with each other, and outputting a second phase detection signal light;
• an optical phase shifter for shifting the optical phase by an amount between the third and the fourth branch lights inputted into the first or second coupler;
• a first polarization phase controller provided between the first beam splitter and the first coupler, the first polarization phase controller individually controlling phases of two orthogonal polarization components of the first branch light and outputting the phase-controlled polarization components of the first branch light;
• and
• a second polarization phase controller provided between the second beam splitter and the second coupler, the second polarization phase controller individually controlling phases of two orthogonal polarization components of the fourth branch light and outputting the phase-controlled polarization components of the fourth branch light.