Ultrasensitive Pressure Measurement Using an Extrinsic Fabry–Pérot Interferometer (EFPI) Sensor

This paper advances the development of Extrinsic Fabry-Pérot interferometry (EFPI) for high-precision pressure sensing. Presented is an EFPI featuring a diameter of 800 μm with a 7.4 μm diaphragm thickness, demonstrating a resolution of 3.35 mPa and a sensitivity of 149 nm/kPa positioning it amongst the most sensitive fibre optic pressure sensors ever developed, establishing a new benchmark for EFPI pressure-based systems. Numerous fabrication methods, including resin bonding, fusion splicing, and additive manufacturing, are investigated. In conjunction with this, multiple diaphragm reduction techniques such as manual polishing, automated polishing, and hydrofluoric acid etching are explored. The reason why we have not seen development of large core/diameter silica EFPI sensors, with advantages in sensitivity and resolution, is that the construction technique is difficult and unknown. The design construction, testing, and development of said large-diameter sensor is novel. This sub-Pascal resolution opens new possibilities for applications in microfluidics, atmospheric monitoring, and medical diagnostics where detecting minute pressure variations is critical. Finally, a comparative analysis of the sensor construction and diaphragm reduction methods provides insight into the future development of these high-performance EFPI sensors.