Highly Sensitive Optoelectronic Oscillator-Based FBG Sensor via Coarse Sampling and Vernier Effect

A highly sensitive method utilizing coarse frequency sampling and Vernier effect for optoelectronic oscillator (OEO) based fiber Bragg grating (FBG) sensing system is proposed and experimentally demonstrated. To generate the Vernier effect, the frequency sampling interval is set close to the free spectral range of the OEO. Cubic spline fitting and power normalization were applied to obtain smooth sampling curve. The peak frequency of the fitted curve was chosen to measure the spectral shift. In the temperature test experiment, a controllable sensitivity was achieved by changing the sampling interval. The sensitivity of 222.84kHz $/^{\circ }$ C was obtained, which was 127.26 times higher than that of traditional single-loop OEO. Our method requires no modifications to the sensing circuit. Furthermore, it can be used in other OEO-based sensors, indicating promising application prospects.