Miniature optical fiber Fabry-Perot sensor based on PDMS end-cap structure

This paper presents a method for fabricating a low-cost, highly reproducible miniature optical fiber Fabry-Perot (FP) sensor based on a polydimethylsiloxane (PDMS) end-cap structure. The FP cavity end-cap is formed by the optical fiber end-face and a PDMS droplet deposited onto it. The PDMS deposition is achieved by immersing the fiber end into pre-cured PDMS at a fixed speed, a process requiring careful control of PDMS viscosity and surface tension. By leveraging PDMS’s excellent thermal expansion coefficient, Poisson’s ratio, and other parameters, this method achieves high reproducibility via viscosity-optimized pre-curing, enhanced sensitivity for temperature measurements, and significant cost reduction versus commercial counterparts. Fiber FP sensors are increasingly widely used in biomedical and precision detection fields owing to their significant advantages, including small size, light weight, high sensitivity, and immunity to electromagnetic interference. In the fabrication of fiber FP sensors, using polymer materials is an effective technical approach. These polymers can be applied as coatings on the optical fiber end-face or as interlayer materials embedded between fibers to form the FP cavity structure, which not only significantly improves the overall sensor performance, but also enhances its sensitivity to changes in temperature, pressure, and refractive index. In the final part of this study, we successfully validated the exceptional performance of the PDMS end-cap based fiber FP sensor in detecting different temperatures conditions. Experimental results demonstrate a temperature sensitivity of 0.752 nm/℃ for sensors with a 60-μm PDMS end-cap, further confirming the sensor’s reliability and efficiency in practical applications.