Detection of Refractive Index With a Temperature-Compensated MZI-Based Optical Sensor Using Few-Mode Fiber

A temperature-compensated MZI-based optical sensor using few-mode concentric multilayer-core fiber (CMCF) was designed, and surrounding refractive index (SRI) sensing via interference spectra was successfully proposed and experimentally demonstrated. This sensor with sandwich structure generated lots of resonance dips in the interference spectra, which had differentiated sensitivities to SRI and temperature. The homemade CMCF only supported few mode groups, and variability of the resonance drift could be influenced by different mode excitation and sensitivity. For the two selected dips of this proposed sensor, the SRI sensitivities experimentally achieved were −76.88 and −50.51 nm per refractive index unit (RIU), and the temperature ones were 80.2 and 50.1 pm/°C, respectively. The experimental mechanism and results have been analyzed in brief. The standard matrix inversion method could be used for simultaneous two parameter determination. Therefore, the SRI detection could show good accuracy and sensitivity by temperature compensation.