Fabry-Perot Interference Fiber Acoustic Wave Sensor Based on Laser Welding All-Silica Glass

Abstract

Due to the small difference between the thermal expansion coefficients of silica optical fiber and silica glass, they are used as probe materials of optical fiber acoustic wave sensors. According to the light absorption characteristics of a pressure-sensitive silica diaphragm and silica glass, the laser welding of an all-silica Fabry–Perot (FP) interference optical fiber acoustic wave sensor with a CO2 laser is proposed. For understanding the influence of thermal expansion of sealing air in an FP cavity and the drift of interference-intensity demodulation working point of a FP interference acoustic wave sensor, we designed a process for the laser welding of an ultra-thin silica diaphragm and sleeve and optical fiber and sleeve. The exhaust hole of the FP cavity is reserved in the preparation process, and an amplified spontaneous emission light source and a tunable optical-fiber FP filter are introduced to stabilize the working point. The sensor is tested with a 40 kHz sound vibration signal. The results show that the sound pressure sensitivity of the sensor to an acoustic source of 0.02–0.1 W/cm2 is 6.59 mV/kPa. The linearity coefficient is 0.99975, indicating good linearity.

Low-Coherence Homodyne Interferometer for Sub-Megahertz Fiber Optic Sensor Readout

“…This greatly complicates the use of FBG for high-frequency process detection since deformation and temperature lead to a large shift in the entire spectral curve of the FBG and complicate signal processing. So, for fast process detection, interferometric sensors are usually used [ 6 , 7 , 8 , 9 ]. The main configurations of the interferometric sensors are Michelson interferometric sensors [ 10 ], Mach–Zehnder interferometric sensors [ 11 ], Sagnac interferometric sensors [ 12 ], and Fabry–Perot interferometric sensors [ 13 ].…”

Fiber Optic Impact Location System Based on a Tracking Tandem Low-Coherence Interferometer

“…This greatly complicates the use of high-frequency demodulation methods, since all these methods are based on work on the slope of the spectral response of the FBG, but deformation and temperature lead to a big shift of the entire spectral curve of the FBG. So, for acoustic detection, the Fabry–Pérot sensors are usually used [ 12 , 13 , 14 , 15 ]. Generally Fabry–Pérot FOS found many applications for detecting various physical quantities, such as temperature, pressure, etc.…”

A Review of Optical Fiber Sensing Technology Based on Thin Film and Fabry–Perot Cavity

“…Therefore, a lengthy optical fiber is necessary for high sensitivity, which in turn, creates poor thermal stability and increased vulnerability to vibration. Additionally, the phase noise produced by the light source has a significant impact on the interferometer structure, requiring a highly coherent light source for optimal sensor performance [9]. Additionally, in the sensing experiment, fiber optic FP interferometric sensors can effectively mitigate optical power fading caused by polarization.…”

“…Due to the birefringent nature of optical fibers, Mach-Zehnder and Michelson interferometers split a light beam into two independently propagating beams, each with varying polarization states in a random manner. This leads to a decrease in the efficiency of interference when the two beams recombine, resulting in reduced contrast of interference fringes [9]. Sagnac interferometers can employ polarization control techniques or high birefringent fibers to maintain the polarization characteristics of transmitted light, but this undoubtedly adds complexity and cost to the system [10,11].…”