Scattering matrix analysis on the use of a wide-band laser source in a passive fiber rate sensor

Recent results obtained in experiments with passive fiber-optics rotation sensors have suggested that a wideband laser source of suitable characteristics can appreciably reduce low frequency random noise at the sensor output. The possibility has been considered that the use of a fluctuating, or random, state of polarization (SOP) at each source may further reduce the low-frequency noise. The present investigation is concerned with this possibility. A theoretical analysis shows that the use of a random SOP for each mode is not only unnecessary but, in general, produces a nonreciprocal phase (NRP) shift between the countertraveling beams in the fiber ring at each mode. It is found that the use of a nonrandom SOP at each source wavelength on the basis of suitably oriented polarizers and analyzers eliminates the NRP.