A comparison of temperature sensing characteristics of SMS structures using step and graded index multimode fibers

A comparative study of the temperature sensitivities of the single-multi-single mode (SMS) fiber structures employing step-index and graded-index multimode fibers (MMFs), for two different doping concentrations of GeO2 in MMF core, is carried out. The temperature sensitivity for graded-index MMF is found to be much larger (approx. 45-285 times) for the entire range of wavelength operation (0.7-1.6 µm). A physical explanation of the observed behavior is also presented. The study should be useful in designing various fiber optic multimode interference based devices with high or low temperature sensitivities.