Mode couplings due to external forces distributed along a polarization-maintaining fiber: an evaluation

Abstract

A new interferometric scheme for measuring mode conversion distributed locally along a polarizationmaintaining fiber is presented. Using this technique the power coupling coefficient, varying with magnitude and angle of external pressure transversely applied to a fiber, was evaluated both theoretically and experimentally. The coupling point location is determined with +/- 1.5-cm accuracy and resolution of better than 10 cm for a 220-m long fiber having modal birefringence of 4.4 x 10 (- 4). The coupling coefficient was proportional to the external force in the range from 5 x 10 (- 3) to 0.1 kg/mm. The relationships determined experimentally reflected those predicted by theory.