A simple ultrasensitive displacement sensor based on a high bend loss single-mode fibre and a ratiometric measurement system

An all-fibre displacement sensor with a simple configuration and capable of monitoring sub-50 nm displacements is proposed and investigated experimentally. The proposed fibre displacement sensor consists of a half-loop structure of bare high bend loss single-mode fibre 1060XP and a ratiometric power interrogation system. By measuring the change in transmission ratio in the ratiometric system, a change in displacement can be measured. The displacement sensor is sensitive to temperature and an experimental investigation of this sensitivity is presented. It is found that the peak shift response has a linear variation with temperature; therefore, temperature dependence can be mitigated by a suitable displacement correction process. The proposed macrobending fibre based displacement sensor benefits from simplicity and low cost and achieves a comparable resolution as compared with other conventional fibre optic sensors.