Stress-location measurement along an optical fiber by synthesis of triangle-shaped optical coherence function

A triangle-shaped optical coherence function is synthesized, and is applied to real-time stress-location measurement along an optical fiber. We utilize a polarization-maintaining fiber (PMF) as the sensing element. Stress-induced coupling from one eigenpolarization mode to the other is used as the sensing mechanism. The stress-position on PMF linearly corresponds to the delay difference between the two eigenpolarization modes, which is measured with a slope of the synthesized triangle coherence function. The degree of coherence changes linearly from one to zero with respect to the delay difference. By extracting the coherence value, the stress point is figured out in real time.