EXACT SOLUTION FOR PHASE-SHIFT OF TE AND TM MODES IN AN OPTICAL-FIBERDUE TO AXIAL STRAIN

Axial strain on an optical fiber can be determined by monitoring the p hase shift of a variety of optical fiber sensors. The exact analytical solutions for optical fields that propagate in a circular core optica l fiber are used here to determine the phase shifts that occur for TE and TM modes due to axial strain. Whenever an optical fiber is stresse d, the optical path length, the index of refraction, and the propagati on constant of each fiber mode change. In consequence, the modal phase term betaz of the fields is shifted by an amount DELTAphi. In certain cases, it is desirable to control the phase sensitivity to make fiber s that are either more or less sensitive to strain. We show that it ca n be accomplished by choosing appropriate fiber parameters.