Sensitivity Characteristics of Multimode-Interference Optical-Fiber Temperature-Sensor With Solid Cladding Material

A simple analytical calculation method providing convenient design criteria for the realization of high sensitivity temperature sensor is presented. Such an approach is applicable to any type of multimode interference (MMI) structure with different core/cladding compositions. A low-complexity optical-fiber temperature sensor, based on MMI using epoxy resin as a solid cladding material, is evaluated with wavelengths ranging from 1200 to 1700 nm. We analytically proved a mechanism providing high temperature sensitivity of the MMI sensor with solid cladding material, whose refractive index depends on the wavelength. The temperature sensitivity around a wavelength of 1200 nm is -0.96 nm/°C, while at 1650 nm is -5.96 nm/°C, which is more than six times larger. These results agree well with the proposed simple calculation model.