Design and experimental research on miniature fiber-optic displacement sensor

A detecting method based on Fizeau interferometer for fiber-optic displacement sensing is presented to detect high-precision displacement in nanometer scale. On the basis of optical interferometry and common-path Fizeau interferometer, micro displacement can be detected by accurately measuring the distance changes between the surfaces of fiber-optic collimator and measuring mirror. Its characteristics are as follows: with common-path interferometer, dependence of energy transmitting fiber to ambient temperature is eliminated, then the effect of ambient temperature variation to the system is reduced; with the method of phase generated carrier modulation/demodulation instead of electric-control phase modulator, the optical path is formed with all-fiber components to improve the application flexibility in the system; by micro fiber-optic collimator with diameter of 1mm, the overall dimension of the displacement sensor is greatly reduced, which makes the use of the sensor more flexible. In the paper, the structure and parameters of miniature all-fiber common-path fiber-optic displacement sensor is studied, the experimental platform for high-precision displacement calibration is established, and a series of performance tests are completed. Experimental results show: with the working distance of 0-14mm, the measuring resolution of the miniature fiber-optic displacement sensor can reach 20nm, and the measuring dynamic range can get 116.9dB, which indicate that the miniature fiber-optic displacement sensor has superior performances with high resolution, high precision and large dynamic range.