Highly precise in-plane displacement sensor based on an asymmetric fiber Fabry–Perot interferometer
Zihao Wang, Zhilin Xu, Liuyang Chen, Yi Shi, Xiaoyun Wang, Junhui Wu, Ji Fan, Liangcheng Tu
Abstract
An in-plane displacement sensor based on an asymmetric extrinsic fiber Fabry–Perot interferometer (EFPI) is proposed and demonstrated. The asymmetric EFPI composed of a step-shaped external reflector and a cleaved fiber end face can be equivalent to two parallel FPIs with slightly different cavity lengths. By calculating the peak intensity difference of the two FPIs, the in-plane displacement can be demodulated with enhanced sensitivity and suppressed common mode noise. Both theoretical analyses and experimental results show that the sensitivity and the linear range of the in-plane displacement sensor are dependent on the cavity length. A displacement resolution of 5 nm and a linear range of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mo>±</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>7</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mtext>µ</mml:mtext> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> under the cavity length of 250 µm are achieved in the experiment. The proposed in-plane displacement sensor with a nanometric resolution and compact size can be widely used in the fields of metrology, accelerometers, and semiconductor manufacture.