Fiber cavity ring-down displacement sensor with picometre resolution using frequency-shifted interferometry.

A fiber cavity ring-down (FCRD) displacement sensor with picometer resolution using frequency-shifted interferometry (FSI) was developed. Compared with the traditional time-domain FCRD-based displacement sensor, the proposed sensor is based on space-domain measurement by combing FCRD with FSI, which reduces the requirements of the laser source and detector, showing low cost and high sensitivity. A piece of single-mode fiber wrapped on the piezoelectric transducer was used as the sensor head and displacement was monitored by measuring the ring-down distance. The experimental results show that the sensitivity of the displacement sensor is measured to be 0.246 (km−1·nm−1). Taking advantage of using differential detection method to eliminate direct current noise and the same-path interference to cancel common-mode noise, high stability of 0.06% was achieved. Due to the high sensitivity and good stability, the displacement resolution of 10 pm was achieved, which is about 3 orders of magnitude higher than that of traditional laser interferometry-based displacement sensors. [Display omitted] • A space-domain FCRD-based displacement sensor was proposed and investigated for achieving picometre level resolution. • A sensitivity of 0.246 (km-1·nm-1) was achieved, which was higher than that of traditional FCRD displacement sensor. • A displacement sensor with resolution of 10 pm was achieved due to high sensitivity and high stability. [ABSTRACT FROM AUTHOR]