Optimization of detection system for low-coherence interferometric sensorsbased on highly birefringent fibers

A demodulation system employing birefringent crystalline plates for decodin g low-coherence interferometric sensors based on highly birefringent fibers was numerically analyzed in order to find its optimum construction. A nume rical approach proposed in this paper allowed us to calculate how the param eters of the decoding system such as thickness and orientation of the cryst alline plates, type of birefringent material, position of the detectors, an d polarization characteristics of beam splitting plates influence the contr ast of differential interference signals. Calculations were based on vector ial ray tracing algorithm applicable to isotropic as well as anisotropic me dia. The algorithm allowed determination of intersection coordinates with d etector surface for ordinary and extraordinary rays, their phases, polariza tions, and amplitudes, and finally the contrast of differential interferenc e signals. Based on modeling results, general principles concering system c onstruction were formulated, which assure the highest possible contrast of interference signals and therefore maximum operation range of the sensor.