Temperature-compensated multi-point refractive index sensing based on a cascaded Fabry-Perot cavity and FMCW interferometry

We proposed a novel temperature-compensated multi-point refractive index (RI) sensing system by the combination of the cascaded Fabry-Perot (FP) sensors and the frequency modulated continuous wave (FMCW) interferometry. The former is used for simultaneous sensing of RI and temperature, and the latter is used for multiplexing a series of the cascaded FP sensors to realize multi-point sensing. By means of Fourier transform-based algorithms, the interference spectra of each sub-FP sensors can be divided and demodulated independently. Experimentally, three cascaded FP sensors are multiplexed to verify multi-point RI and temperature sensing ability. RI sensitivity up to similar to 1200 nm/RIU is obtained within RI range from 1.3330 to 1.3410, and temperature sensitivity up to similar to 0.17 nm/degrees C is obtained within temperature range from 20 degrees C to 80 degrees C. The RI precision is as high as 10-5 RIU and the temperature precision is as high as 0.05 degrees C. In addition, the prospective multiplexing number could reach about 4000 estimated by the minimum detectable light power. The proposed sensing system has potential advantages in the practical applications that require a large number sensing points. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

A novel temperature-compensated multi-point refractive index sensing system was proposed, combining cascaded FP sensors and FMCW interferometry. Experimental results showed high precision and sensitivity, making it suitable for practical applications requiring a large number of sensing points.