Optical fiber temperature sensor based on modal interference in multimode fiber lengthened by a short segment of polydimethylsiloxane

A fiber optics structure for temperature measurement is presented and demonstrated. This structure is composed of segments of single mode fiber (SMF), no-core fiber (NCF), hollow core fiber (HCF), and cured polydimethylsiloxane (PDMS) which is inserted into the cavity of HCF. Owning to the high thermal expansion coefficient (TEC) and thermo-optic coefficient (TOC) of PDMS, the optical path length and the effective refractive index (RI) all register much larger change, leading to the higher temperature sensitivity of the sensor. Simulation showed similar result with experiment. The temperature sensitivity of 580.6 pm/degrees C is achieved in the range of 28 degrees C to 50 degrees C.