Vibration Measurement And Signal Processing Based On Fiber Optic Self-Mixing Interferometer

Self-mixing interferometer as a common means of optical detection,the use of semiconductor lasers as a light source makes detection costs greatly reduced,and combined with computer technology to achieve real-time detection of object information,changing the traditional detection method of laser detection equipment,large size,time delay,optical path is not simple and low detection accuracy and other problems,for long-distance,long-period and strong electromagnetic interference and other conditions of vibration detection to provide a New ideas.The combination of optical fibres and self-mixing interferometric techniques can improve the detection accuracy of interferometers and enable them to be used in a wider range of applications.In order to improve the accuracy of vibration detection,the interference immunity and the miniaturisation of the interferometer,the structure and signal processing methods of the fibre optic self-mixing interferometer are improved.Firstly,a self-mixing interferometer based on microsphere superlenses and fringe filters is proposed to solve the problem of large errors in the detection of vibration signals.Using UV adhesive to form microspheres at the tip of an optical fibre probe,a photonic nano-jet phenomenon occurs when the microspheres are irradiated by light from the optical fibre.The photonic nano-jets are focused on the surface of the target object to enhance the reflected light from the target object to the surface of the microsphere.The swift field generated by the photonic nano-jets has an important enhancing and sharpening effect on the detection of nano-vibrations at the near-field surface.The conversion of amplitude modulated signals to frequency modulated signals using Mach-Zendel edge filters at the end of the sensor improves signal quality,reduces measurement errors and is important for the miniaturisation of optical devices.Secondly,in order to solve the problems of complex structure of vibration detection equipment and difficulties in detecting nanoscale vibrations,the signal of the microsphere superlens self-mixing interferometer is processed using a variable mode decomposition algorithm to reduce the influence of noise on the detection results.In particular,the filtered self-mixed signal using the variable mode decomposition algorithm has a higher reconstruction accuracy in a noisy environment.Finally,to evaluate the performance of a microsphere superlens self-mixing interferometer based on a variable mode decomposition algorithm filter,the sensor was applied to respiratory vibration measurements of household yeasts,enabling the detection of different active yeast respiratory vibration frequencies and the differentiation between dead and differently active yeast cells,providing a potential tool for nanoscale vibration detection and biosensing.