A high signal-to-noise ratio fiber optic ultrasonic sensor based on PTFE film

Abstract

A high signal-to-noise ratio optical fiber ultrasonic sensor based on polytetrafluoroethylene (PTFE) film, including a standard single-mode optical fiber. A section of graded refractive index multi-mode optical fiber is fused to one end of the standard single-mode optical fiber to form an optical fiber collimator. The optical fiber collimator The end surface and the PTFE film constitute the two reflective surfaces of the F-P interferometer. The PTFE film serves as the response medium for ultrasonic waves. The PTFE film is pasted on one end of the aluminum tube. There is a plexiglass tube inside the aluminum tube. The moving parts are fixed with AB glue. The volume of the present invention It is small, low-cost, easy to make, has excellent ultrasonic response and high signal-to-noise ratio. Applying the invention to seismic physical model scanning imaging can clearly distinguish multi-layer model structures and reconstruct model ultrasonic images, indicating that it has application in structural health monitoring. , biomedicine and other technical fields, because the invention has high temperature resistance and corrosion resistance, it can also be used in harsh environments such as high-temperature ultrasonic flaw detection.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensors, and in particular relates to an optical fiber ultrasonic sensor with high signal-to-noise ratio based on a polytetrafluoroethylene film. Background technique [0002] The basic sensing principle of the film-based optical fiber Fabry-Perot ultrasonic sensor is that ultrasonic waves act on the film to cause film vibration and film thickness changes, resulting in changes in the length of the F-P cavity and shifting the hypotenuse of the F-P interference spectrum. By detecting the hypotenuse of the spectrum The drift amount can know the amplitude of the ultrasonic wave. The traditional piezoelectric ceramic transducer (PZT) has the following disadvantages: its material will be damaged in a high temperature and strong corrosion environment, and it is extremely susceptible to environmental electromagnetic field interference, so it is not suitable for working in harsh environments with str...

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Problems solved by technology

The traditional piezoelectric ceramic transducer (PZT) has the following disadvantages: its material will be damaged in a high temperature and strong corrosion environment, and it is extremely susceptible to environmental electromagnetic field interference, so it is not suitable for working in harsh environments with strong electromagnetic fields such as large electromechanical equipment; Sensitive response to narrow-band ultrasonic signals; its sensitivity will weaken as the volume of the transducer decreases and is greatly affected by capacitance; the received signal will broaden as the distance between the transmitting source and the receiver increases, resulting in signal distortion; multiplexing The performance is poor, and the multi-channel real-time monitoring system is complicated, which further restricts its use

In 2009, Morris P et al. designed a F-P ultrasonic hydrophone consisting of a gold-plated film on both sides of the parylene layer placed on the end face of a single-mode optical fiber; in 2013, Wonuk Jo produced a fiber optic acoustic wave based on a photonic crystal film. Sensors, Ma et al. proposed a fiber optic acoustic wave sensor based on multilayer graphene films; in 2014, Xu F et al. designed a fiber optic acoustic pressure sensor based on silver films; but for films of these materials, the preparation process is complex , high cost, low chemical stability and temperature resistance limit its long-term use in harsh environments, and high Young's modulus reduces its acoustic response range

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