A high sensitivity sensor based on novel CLPFG with wavelength and intensity modulation for simultaneous measurement of SRI and temperature

Abstract

In this paper, a novel cascaded long-period fiber grating (CLPFG) sensor based on the modulation of both wavelength and intensity is demonstrated, which is able to simultaneously detect surrounding refractive index (SRI) and temperature. The appropriate grating periods are designed by theoretical simulations. One grating operate in single-peak resonance state and the other one operates at slight deviation of resonance (SDOR) state. When the SRI and temperature change, the wavelength of resonant peak in the single-peak resonance state shifts, and the intensity of the resonant peak at the SDOR state changes accordingly. In experiments, the CLPFG is inscribed based on the theoretical design and the responses of the sensor to SRI and temperature are investigated. The experimental results show that the SRI sensitivities are −177.6 nm/RIU and −202.7 dB/RIU, and the temperature sensitivities are 0.1175 nm/℃ and 0.0997 dB/℃. The SRI and temperature sensitivities of our proposed sensor are 30 times and 10 times higher than those of other sensors with dual-parameter modulation of wavelength and intensity. The proposed sensor with simplified structure, good linearity, and high sensitivity can be expanded to the area of multi-parameter sensing.