POLARIZATION INTERFEROMETER, OPTICAL MODULE, AND OPTICAL RECEIVER
A interferometer includes a first splitter for splitting one of a signal and a reference lights into a first and a second branch lights; a second splitter for splitting the other of a signal and a 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 detection light; a second coupler for causing the second and the fourth branch light to interfere with each other, and outputting a second detection light; a first polarization phase controller provided between the first beam splitter and the first coupler, 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, and outputting the phase-controlled polarization components of the fourth branch light.
1 . A interferometer for receiving a signal light and a reference light and for outputting phase detection signal lights, comprising:
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.
2 . The interferometer according to claim 1 , further comprising a polarization splitter for splitting each of the first and the second phase detection signal lights into different polarizations orthogonal to each other.
3 . The interferometer according to claim 1 , wherein the first and the second interferometer is a half mirror or an optical coupler.
4 . The interferometer according to claim 1 , wherein the optical phase shifter shifts the optical phase by 90 degrees between the third and the fourth branch lights inputted into the first or second coupler.
5 . The interferometer according to claim 1 , further comprising a plurality of reflectors provided between the first beam splitter and the first coupler, and provided between the second beam splitter and the second coupler.
6 . The interferometer according to claim 2 , wherein the first polarization phase controller includes:
a first wave plates disposed in tandem on the first optical path, the first and the second wave plates each having a fast axis and a slow axis vertical with respect to the fast axis, the fast axis of the first wave plate being vertical with respect to the fast axis of the second wave plate; and
a first temperature controller for controlling each temperature of the first and the second wave plates,
wherein the second polarization phase controller includes:
a third and a fourth wave plates disposed in tandem on the second optical path, the third and the fourth wave plates each having a fast axis and a slow axis vertical with respect to the fast axis, the fast axis of the third wave plate being vertical with respect to the fast axis of the fourth wave plate; and
a second temperature controller controlling each temperature of the first, the second, the third and the fourth wave plates.
7 . The interferometer according to claim 2 , wherein the reference light is a linearly-polarized light whose polarization directions are tilted by 45 degrees with respect to the polarization directions of the different polarizations split by the polarization splitter.
8 . The interferometer according to claim 1 , wherein the second polarization phase controller and the optical phase shifter integrally being provided between the second beam splitter and the second coupler.
9 . The interferometer according to claim 1 , further comprising at least a collimator for collimating the first phase detection signal light outputted by the first coupler and the second phase detection signal light outputted by the second coupler.
10 . The interferometer according to claim 1 , wherein the first beam splitter and the one of the first and the second couplers are composed of a first half mirror integrally provided, and the second beam splitter and the other of the first and the second couplers are composed of a second half mirror integrally provided.
11 . 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.
12 . 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.