The Study Of Plastic Optical Fiber Sensor For Acoustic Emission Detection

As a nondestructive testing method，Acoustic Emission technique has been widely usedin many fields. With the advantages such as wide frequency bandwidth, small volume, fastresponse, no electromagnetic interference, no contact with the measured object, highsensitivity and electronic devices and sensors can be far away, fiber-optic acoustic emissionsensor technology has developed rapidly. Gradually developed in recent years, plastic opticalfiber (POF) is drawn by the advantages of its simple process, low cost, light, soft, lowconnection loss and damage resistance. Usually, single mode optical fiber sensor is used todetect shock wave. The article tries to design and use a plastic optical fiber acoustic emissiondetection system to achieve acoustic emission signal detection, which should be verified andcontrast by experiment.This article begins with the theory and knowledge of acoustic emission and optical fibersensor, and then introduces the transmission principle, material and performance parametersof plastic optical fiber, and describes the advantages, disadvantages and application of plasticoptical fiber. Next with the law of the radial and axial intensity distribution in optical fiberend and based on the law of the use of fiber optic displacement sensor modulationcharacteristics, you can measure the work of plastic optical fiber rising and falling curve.Using high sensitive cutting-edge work area and with analysis of changes in light intensityreflected back, you can detect the nature of the acoustic signal in objects. Using this principle,a system of plastic fiber optic acoustic emission sensor is been designed, and realizes acousticemission detection.Based on the coherent effect of modes in multiple optical fiber, facula will be formed atthe output end of fiber, however, the same signals can lead to different influence on differentmodes in one plastic optical fiber, which makes the output facula change. So we can achieverelated properties by detecting the changes of facula, then to realize the acoustic emissiondetecting. The detecting process is as follows: when the light of semi-conductor laserpropagates in the plastic optical fiber, some high-order modes will allocate its power to eachmode, and then reach the acoustic emission field. So the output light will be obtained byphotoelectric conversion and amplification device. In addition, we use both single mode fiber and plastic optical fiber to detect acoustic emission simultaneously, through the comparisonof them, we have tested and verified the feasibility of the experimental approach to detectacoustic emission with plastic fiber optic.At the end of the experiment, the trial is done by the traditional single mode Sagnacoptical fiber sensor and the plastic optical fiber sensors at the same time to test and validat theaccuracy and sensitivity of the plastic optical fiber sensor. The experiment proved that theplastic optical fiber can be applied to detect acoustic emission signal, and thus can be inferredthat using plastic optical fiber sensors to detect acoustic emission signal is very broad.Experimental proof of plastic optical fiber sensors for acoustic emission signal detectionaccuracy, as well as a description of this sensor for acoustic emission testing can be practical.