Strain force sensor with ultra-high sensitivity based on fiber inline Fabry-Perot micro-cavity plugged by cantilever taper

A strain force sensor based on fiber inline Fabry-Perot (FP) micro-cavity plugged by cantilever taper was proposed. The structure was fabricated by simple and cost-effective method only including fiber cleaving, tapering and splicing. The active-length of the FP micro-cavity reached 1360 μm, while the interference length was only 3.5 μm. Owing to the ultra-long active-length and ultra-short interference length, the strain force sensitivity of the fiber inline FP micro-cavity plugged by cantilever taper reached as high as 841.59 nm/N. Besides, the proposed structure showed good linearity (99.9%) in the sensing process and small temperature crosstalk (11 pm/°C). It can be used as a practical and reliable strain force sensor.