We studied a fiber-optic strain sensor based on interference between LP01-LP02 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 ( l2) 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 l2 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 n.
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