Temperature fiber sensor without cross sensitivity based on the multi-thin-no-thin-multi fiber coated with PDMS

A novel temperature fiber sensor based on the multi-thin-no-thin-multi fiber (MTNTM-F) with Mach-Zehnder interference was presented. By comparing the interference spectra of the multi-thin-multi fiber and MTNTM-F, the MTNTM-F with more available dips and greater extinction ratio was selected. By simulating the energy distribution in the fiber, it was proved that there was a lot of energy in the cladding, which was beneficial to the interaction between the light and the external material. In order to improve the temperature sensitivity of the sensor, polydimethylsiloxane with large thermo optic coefficient and thermal expansion coefficient was selected to coat the fiber. Identical temperature sensing experiments were performed for untreated and coated fibers. The temperature sensitivity changed from 25.38 pm °C−1 to 65.24 pm °C−1, which was a 2.56 times improvement, and an ideal temperature stability was demonstrated. At the same time, an anti-turbulence adjunct experiment was conducted to investigate the ability of the sensor to avoid turbulence cross sensing.