We studied a tiber-optic strain sensor based on interference between LP01-L
P02 modes of a circularly symmetric few-mode fiber (FMF). A simple theoreti
cal analysis fdr predicting the performance characteristics of such a senso
r is developed. Fiber elongations producing differential phase shift of 2 p
i (deltal(2 pi)) between the two modes are measured, which is found to be i
ndependent of sensing length of the fiber as predicted by theory. A good ag
reement between the experimental and theoretical values of deltal(2 pi) is
observed. Theoretical calculations predict that the sensitivity of such a s
ensor is maximum for fibers with V = 4.82 and increases with the increase i
n the core cladding index difference Deltan.