Polarization mode coupling in highly birefringent optical-fiber ring resonators

The transmission characteristics of a polarization-maintaining optical-fiber ring resonator are examined. The resonator’s response is found to be strongly dependent on the differential phase delay between the fiber birefringence axes. Large cross talk of as much as 40% between the fiber modes and splitting of the resonance notch can occur, even for very good (better than −35-dB) isolation between the fiber polarization modes.