Optical-fiber resonant rings based on polarization-dependent couplers

A theoretical and experimental analysis has been carried out on optical-fiber resonant rings based on polarization-dependent couplers. The analysis includes the use of optical-fiber polarization splitters and polarization-preserving fiber as particular cases. Two resonant configurations are presented and their sensor applications discussed. The changes of polarizations that take place in the ring are used as an effective distributed coupling which in one configuration feeds power into a resonance, and in the other introduces a variable attenuation, changing the effective losses of the resonant mode. The experimental characteristics of the system enable detection of small polarization changes. The experimental characteristics of a resonant ring about 2.5-m long and a polarization-selecting coupler are presented.>