Fiber Bragg grating guided laser interferometer-based highly sensitive vacuum pressure sensor

Abstract

Vacuum sensing and metrology pave the way for promising solutions to fulfill the scientific and technological demands of various contemporary industries and research fields. This study introduces an innovative vacuum pressure sensor, employing a fiber Bragg grating (FBG) guided Michelson interferometer. The sensor works on the principle of interferometric measurement of precisely gauging the displacement of an elastic diaphragm with pressure variation connected to a vacuum chamber in terms of interference fringe counts due to arm-length variation of the interferometer. The elastic silicone diaphragm and stainless steel cantilever, being critical components of the sensor, were examined using finite element analysis and subsequently demonstrated experimentally. The diaphragm’s position is continuously monitored in real time through the Bragg’s wavelength of the FBG, continuously updating the interferometer after each 15 ms for the accurate measurement of fluctuating vacuum pressures. The strain-induced shift in the FBG’s Bragg wavelength follows a linear trend with pressure variation, exhibiting a sensitivity of 12.7 pm/mbar. With a dynamic range spanning 0.05–100 mbar, the sensor demonstrates a sensitivity of 16.073 fringe counts/mbar and a notable resolution of 0.3364 mbar. Moreover, the sensor exhibits good repeatability, with a hysteresis of up to 2.59% during full span cyclic operation. The coupling of the interferometer with FBG makes it a unique secondary standard solution for precision vacuum measurement.