Method and device for improving signal to noise ratio of laser micro-vibration sensing system

Abstract

The invention relates to a method and device for improving the signal to noise ratio of a laser micro-vibration sensing system. The light emitted by a laser is divided into two light beams by an optical fiber coupler, the weak light beam is directly converted into an electrical signal through a third photoelectric detector, and the strong light beam is emitted through an optical fiber collimator to serve as a light source of an interferometer. The light emitted by the optical fiber collimator is divided into reflected light and transmission light through a first polarizing beam splitting device, the reflected light serves as reference light, and the transmission light serves as signal light. The reference light and the signal light are input to a first photoelectric detector and a second photoelectric detector respectively through a second wave plate and a second polarizing beam splitting device. The output of the second photoelectric detector is subtracted from the output of the first photoelectric detector, then the difference is divided by the output of the third photoelectric detector, two orthogonal signals are obtained by frequency mixing and filtering on the result, A / D conversion is carried out on the two orthogonal signals, and a carrier wave demodulation algorithm is generated through a phase position so that demodulation can be achieved. The signal to noise ratio can be improved by 5dB to 10dB, and the measurement capability of weak vibration signals is enhanced.

Description

technical field [0001] The invention relates to a laser micro-vibration sensing system, in particular to a method and a device for improving the signal-to-noise ratio of a laser micro-vibration sensing system, belonging to the field of laser interferometry. Background technique [0002] Laser Doppler interferometry technology is a new type of technology with the emergence of lasers. It has unique advantages such as high precision and sensitivity, long-distance non-contact measurement, high temporal and spatial resolution, and high responsivity. It has become an indispensable detection method in scientific research and many industries. Its technical applications can cover the monitoring of the safe vibration range of large structures, buildings, and bridges, to the vibration measurement of various engines and transmission mechanisms, to micro-nano devices, micro-electromechanical systems (MEMS), micro-opto-electromechanical systems (MOEMS) and Nano-optical electromechanical ...

AI Technical Summary

Problems solved by technology

However, in the dual-path balanced detection optical path, due to the existence of interference beat amplitude, the additional light source intensity noise cannot be completely eliminated by subtracting the signals of the two detectors after photoelectric conversion.

Therefore, research on the method of eliminating the additional light source intensity noise on the interference beat amplitude can further improve the signal-to-noise ratio of the laser micro-vibration sensing system, and the relevant patents and literature have not been reported.

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