Modal dependence of the photoelastic coefficient in multimode, step-index optical fiber time domain systems

A simple ray-optic approach for the analysis of strained step-index multimode fibers is shown to lead to the determination of the photoelastic coefficient in an optical-fiber time-domain system. The theoretical model includes the dependence of the photoelastic coefficient a on the modal content of the fiber and explains some of the experimental discrepancies observed in high-resolution reentrant-loop-based sensing systems. For high-step-index 200-240 mu m fibers with higher numerical resolution, the value of a is shown to vary from -0.2 to -0.3, which matches closely with experimental results.<
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