A visible-light spectral demodulation system for fiber-optic SiC Fabry-Perot sensors

A visible-light spectral demodulation system for fiber-optic SiC Fabry-Perot (FP) sensors is proposed. Considering transmission characteristic of SiC, a visible-light broadband LED with a 3-dB spectral range of 470–850 nm is selected as the illuminating source. By acquiring the reflected spectra through a miniature optical spectrum analyzer module, absolute cavity lengths of SiC FP sensors are interrogated through a square-cross-correlation algorithm. Simulation shows that a maximum relative error of 0.0437% can be realized in a cavity length range of 15–25 µm. A SiC FP pressure sensor with a cavity length of ~16 µm is experimentally interrogated by the demodulation system. In a pressure range of 100–500 KPa, its cavity length is found to be changed from 15.911 to 15.840 µm. The results manifest that high-precision demodulation of SiC FP sensors can be realized by the proposed demodulation system.