High-performance all-fiber Mach-Zehnder interferometer based on D-shaped two-mode fiber coated with polydimethylsiloxane for temperature sensing

摘要

A novel fiber sensor, an all-fiber Mach-Zehnder interferometer based on D-shaped two-mode fiber (DTMF-MZI) coated with polydimethylsiloxane (PDMS), is proposed and demonstrated. When light is incident from a single-mode fiber (SMF) to a two-mode fiber (TMF), two modes will be excited in the TMF and interfere with each other, just like a two-beam fiber Mach-Zehnder interferometer (MZI). Due to the high negative thermo-optical coefficient, the proposed sensor is sensitive to temperature. Our theoretical analysis and experimental results prove that as the temperature increases, the dips in the transmitted spectrum of DTMF-MZI will blue-shift. Furthermore, we demonstrate the influences of the distance from the center of the fiber core to the polished plane (parameter h) and the length of the polished area (parameter L-po) of TMF on the temperature sensitivity. In the experiments, the maximum temperature sensitivity of the proposed sensor reaches -305.6 pm/degrees C in the temperature range of 30 similar to 80 degrees C, and the linearity is as high as 0.9890. In addition, the sensor shows good stability at 30 degrees C and 80 degrees C in 60 min with the maximum variations of 0.16 nm. The proposed sensor has many advantages, such as being highly temperature-sensitive, compact, and stable.