Research On Signal Detection Techniques In Distance Measurement System Based On Fiber-sensor

Fiber optical ultrasonic detection technique is a traditional and practical non-contact measurement method. And compared with laser, eddy current and radio method, which has simple structure and low cost, used for measure range, it has the merit of not subject to external optical and electrical impact, and even in the bad environment, it also has a certain resilience, so in the industrial control, building surveying and the robot position it's to be widely used.Fiber optical ultrasonic detection technique is one of the focus issues in the field of smart structure and health monitoring. In this thesis, the development of acoustic detecting using fiber optic sensing techniques in recent years are overviewed. Based on the experimental setup, the detected acoustic emission signals are analyze by the FFT (Fast Fourier Transform) method, which can implements frequency identification. In this work, Mach-Zehnder interferometer FOG has been constructed for acoustic emission detecting. In this way fiber acousto-optic measuring system can be used for measuring the depth of wells field. The method of FOG to detect outer angle-velocity is by capture slender photoelectric signals, so the characters of fiber and optic signal and the influence of fiber's character in optic signals have great effect on FOG's performance.Extracting weak signal from irregular noise is the most important in highly sensitive distance measurement system based on fiber-sensor. Because the especial request of the system, such as the faraway distance to be measured, there are many difficulties in signal detection using conventional methods. Based on phase modulation and interference detection of two beams of Mach-Zehnder optical fiber interferometer, a detecting scheme is designed. Weak signal examination technique of arithmetic correlating figures using DSP can improve the test accuracy to a great deal.