Highly Sensitive Temperature and High Pressure Sensor Based on a Cascaded Optical Fiber Fabry-Perot Interferometer

A highly sensitive cascaded Fabry–Perot optical fiber sensor for simultaneous measurement of temperature and high pressure is proposed. The sensor comprises a UV glue filled hollow core fiber (HCF) cascaded with an air cavity sealed in a silica capillary tube. The temperature and pressure can be measured simultaneously by monitoring the resonance wavelength. The proposed sensors with different optical path length (OPL) ratios are fabricated and investigated. Experimental results show that when the OPL2/OPL1 ratio is 0.22, the proposed sensor exhibits high temperature and pressure sensitivities, which can reach to 0.641 nm/°C and −5.396 nm/MPa, respectively, in the temperature range of about$21~^{\circ }$C–$95~^{\circ }$C and pressure range of 0–20 MPa. Due to its easy fabrication, low cost, and structure flexible, the proposed sensor is suitable for practical applications.