Evaluation of phase fluctuations of orthogonal optical eigen modes guided in an axially vibrating birefringent single-mode fiber

An optical heterodyne correlation-processing system is devised to process the phase fluctuations of the orthogonal linearly polarized two-frequency components guided in a length of axially vibrating birefringent single-mode fiber. Two wideband phase demodulators make it possible to take out separately both of the phase fluctuations of the two-frequency components from two generated beat photocurrents. The processing system provides the spectrum, the correlation, and the transfer function, as well as the coherency for the mechanically induced phase fluctuations. The phase-fluctuation characteristics and the system linearity are evaluated in terms of the statistical functions and the parameters obtained