Correlation processing of fluctuating optical waves guided in an externally perturbed birefringent single-mode fiber by optical heterodyne interferometry

A description is given of experimental studies on the correlation processes for the optical waves guided in a birefringent single-mode fiber exposed to random vibrations. A laser beam with orthogonally polarized two-frequency components is launched into the fiber in such a way that the polarization directions of the two-frequency components coincide with the birefringent axes of the fiber. On leaving the fiber, its orthogonal components, modulated at random in phase and amplitude, are superimposed with a reference laser beam with two-frequency components; two beat photocurrents are produced from the combination of different frequency components of the signal and reference laser beams. The beat photocurrents can yield the fluctuating phase and amplitude components of the guided optical waves, which are statistically processed by use of a signal analyzer. Autocorrelation and cross-correlation functions for the fluctuation components are given together with their corresponding power spectra. Characteristic features extracted from the measured results are explained