We examine the effect of modal interference on the performance of a single mode–multimode–single mode (SMS) fiber optic microbend sensor structure. The study shows that if the coupling from higher order modes of the sensing multimode fiber to the lead-out single mode (SM) fiber is not zero, the output power and hence the microbend sensitivity of the structure depends strongly on the position of the microbends in the fiber. A simple experiment is carried out to study the above effect whose results agree very well with the theoretical predictions.
A. Kumar, Varshney, R. K., and Dr. Rakesh Kumar, “SMS fiber optic microbend sensor structures: effect of the modal interference”, Optics Communications, vol. 232, pp. 239 - 244, 2004.