Nanometer-Resolution and Large-Dynamic-Range Optical Fiber Displacement Sensor Based on Single Pound–Drever–Hall Feedback Loop

Displacement measurement with high resolution and large dynamic range is highly demanded in various fields. In this paper, a wide range nanometer displacement measurement system based on Fiber Fabry-Perot Interferometer (FFPI) and Pound-Drever-Hall (PDH) technique was proposed and experimentally demonstrated. Single PDH feedback loop based on incremental Proportion Integration Differentiation (PID) algorithm was constructed through field programmable gate array (FPGA) to read the resonant wavelength variation of the FFPI, which greatly simplifies the demodulation system. Due to the inherently narrow resonant bandwidth of FFPI and the single PDH feedback loop, the displacement measurement with high resolution and large dynamic range was realized. Displacement resolution of 8 nm, noise floor of 12 pm/Hz^1/2 at 10 Hz and dynamic range of 127 dB at 10 Hz were achieved experimentally. The proposed optical fiber displacement sensor based on single PDH feedback loop is simple yet robust, facilitating the practical applications in the fields of structural engineering, aerospace, geophysics, and nanotechnology.