An all-fiber diaphragm-based extrinsic Fabry-Perot sensor for the measurement of pressure at ultra-low temperature

An all-fiber diaphragm-based extrinsic Fabry-Perot interferometer (EFPI) sensor for the measurement of pressure at ultra-low temperature is proposed and experimentally demonstrated. The sensor head is manufactured at the end of a single mode fiber with a micro hole and a fiber diaphragm. By femtosecond (fs) laser micromachining, sensors with different sensitivities can be fabricated with different diameter of the micro hole and different thickness of the diaphragm. The deformation of the diaphragm has a linear relationship with the applied pressure. This EFPI is used to measure the pressure at temperature of -196 °C by monitoring the cavity length of the interferometer. Experiment results show the sensor exhibits good linearity within a pressure range from 0 to 7 MPa, and the pressure sensitivities at -196 °C during the process of pressure increasing and decreasing are 111.17 and 111.22 nm MPa-1, respectively. The proposed all-fiber pressure sensor can find applications in ultra-low temperature environment.