Refractive index insensitive triple cladding quartz specialty fiber temperature sensor with D-type microcavity structure

A refractive index insensitive triple cladding quartz specialty fiber temperature sensor with D-type microcavity structure is proposed. It consists of a triple cladding quartz specialty fiber(TCQSF) with a D-type microcavity structure fused between two sections of single-mode fiber(SMF). Because the SMF and TCQSF mode fields do not match, the excited modes form a Mach-Zehnder(M-Z) interferometer, resulting in a mode interference phenomenon. Experimental results show that in the range of 30-90°C, the transmission spectrum has a red shift phenomenon, the temperature sensitivity is 138.03 pm/°C, and the wavelength shift has a good linear relationship with temperature change. When the external refractive index changes in the range of 1.3350-1.3466, the sensor has a low sensitivity to the refractive index, which can avoid the cross-sensitivity of simultaneous measurement of temperature and refractive index. The sensor is not only simple to fabricate and high in sensitivity, but also has good repeatability and stable response, and has wide application prospects in the field of sensing.