Patent ID: 7463361

Claim:
An apparatus, comprising: a polarization splitter to separate light into a first polarization component and a second orthogonal polarization component; a first optical interferometer coupled to receive light of the first and second polarization components from the splitter at separate optical inputs and configured to interfere part of the light of the first polarization component with part of the light of the second polarization component; and a second optical interferometer coupled to receive light of the first and second polarization components from the splitter at separate optical inputs and configured to interfere a portion of the light of the first polarization component with a portion of the light of the second polarization component; and wherein the second optical interferometer is configured to produce a different relative phase between interfering light of the two polarization components than the first optical interferometer, the second interferometer being configured to interfere portions of the light of the two polarization components with a relative phase shift whose magnitude is 120 degrees ±10 degrees.