Studies on a few-mode fiber-optic strain sensor based on LP/sub 01/-LP/sub 02/ mode interference

We studied a fiber-optic strain sensor based on interference between LP/sub 01/-LP/sub 02/ modes of a circularly symmetric few-mode fiber (FMF). A simple theoretical analysis for predicting the performance characteristics of such a sensor is developed. Fiber elongations producing differential phase shift of 2/spl pi/ (/spl delta/l/sub 2/spl pi//) between the two modes are measured, which is found to be independent of sensing length of the fiber as predicted by theory. A good agreement between the experimental and theoretical values of /spl delta/l/sub 2/spl pi// is observed. Theoretical calculations predict that the sensitivity of such a sensor is maximum for fibers with V=4.82 and increases with the increase in the core cladding index difference /spl Delta/n.