Miniature all-silica fiber optic pressure and acoustic sensors

We present a miniature diaphragm-based Fabry–Perot (F-P) interferometric fiber optic sensor fabricated by novel techniques for pressure or acoustic wave measurement that is only ∼0.32mm in diameter. By choosing different diaphragm thicknesses and effective diameters, we obtain a sensor measurement range from 5 to 10,000 psi (1psi=51.72Torr) and a frequency response up to 2 MHz. In addition, the sensor’s F-P cavity can be set from micrometers to millimeters with a precision of several nanometers. With the all-silica structure, the sensor is reliable, biocompatible, and immune to electromagnetic interference and has high-temperature sensing capability.