Highly Sensitive Miniature All-Silica Fiber Tip Fabry–Perot Pressure Sensor

This letter presents the design, fabrication, and testing of a diaphragm-based, all-silica fiber tip pressure sensor. A piece of 1.2-μm-thick silica diaphragm was thermally bonded to the end face of an etched fiber with an outer diameter (OD) of 125 μm to form a Fabry-Perot (FP) interferometer. The diameter of the etched FP cavity is 105 μm, enabling the sensing area to be large, and thus, a static pressure sensitivity of 12.4 nm/kPa (85.3 nm/psi) is accomplished without the need for any post polishing or etching. The sensor also shows a low-temperature cross sensitivity during tests, owing to its all-silica structure. It is suitable for extensive production, and it has a great potential to work in applications, where miniature size and high sensitivity are essential such as medical applications.