The Characterization of Polarization-Holding in Birefringent Single-Mode Fibers

Abstract

In single-mode fibers, irregular mechanical stresses from bending, twisting, clamping, non-uniform coating, cabling, etc. introduce perturbing birefringences. These birefringences vary sensitively and erratically with environmental conditions and thus, cause unpredictable changes in the state of polarization (SOP) along the fiber and at the fiber output. However, in several applications of single-mode fibers like interferometric sensors and coherent communications, polarization instabilities lead to noise and signal fading and must be suppressed to a very high degree if highly sensitive devices are to be realized. One approach to overcoming these instabilities has led to the development of various types of fibers specifically designed to hold, or propagate, a particular, well-defined, SOP stably along the entire fiber length, even in the presence of irregular and varying stresses [1]. These fibers exhibit a very high internal birefringence, far exceeding the mentioned perturbing birefringences.