Studies on a few-mode fiber-optic strain sensor based on LP01-LP02 mode interference

We studied a tiber-optic strain sensor based on interference between LP01-LP02 modes of a circularly symmetric few-mode fiber (FMF). A simple theoretical analysis fdr predicting the performance characteristics of such a sensor is developed. Fiber elongations producing differential phase shift of 2 pi (deltal(2 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 deltal(2 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 Deltan.