Design And Application Of Vibration Detecting System Based On FBG

Fiber Bragg grating (FBG) is one of the most developed passive fiber devices in the last few years. FBG sensor, which uses the property that the Bragg wavelength is sensitive to temperature and strain, is a new kind of fiber optic sensor and can be used as sensor transmitting medium at the same time. It has the advantages of small volume, lightweight, immune to electromagnetic interference, better insulation, high Signal-to-Noise and high sensitivity, easy to realize distributed measure and transmission of long distance and so on. So it has widely applicable perspective in many fields such as the health monitoring of bridge, the safety monitoring of the tunnel and the underground project, the petroleum and chemical industry, the aviation and spaceflight, etc.The main contents are taken as follows:Researches of optic fiber grating sensing technology and several questions need to be solved in the practical application are introduced. The principle of FBG sensing technology, the temperature and strain sensing characteristic as well as the coupling problems of them have been analyzed. Then, the contrast and comparison of current demodulation methods is done.A vibration detecting system based on FBG is proposed and designed. Firstly, the types of the devices and the principle of optic-route are introduced. Several questions such as the temperature influence to the system are pointed out and the related solutions have been put forward. The key of the optic-route demodulation is the edge of Wavelength Pumped Multiplexing (WPM). The reflected wavelength of FBG is controlled in the edge of WPM, so the wavelength-drift caused by environment results in the change of optic intensity and the system can be demodulated through the analysis to this change. Secondly, the paper introduces the project of the whole system, the function of each part and the principle of the system. Finally, the photodiode, amplified circuit, filter circuit, data collection and the LabVIEW software of the system are selected to the parameters and detailed designed in this paper. In the hardware, the system selects the LPC2148 ARM chip based on 32 bit of PHILIPS which has two 10-bit A/D converters. The system communicates with computer via USB controller and the data is transmitted to computer in order to realize the LabVIEW software. The vibration experiment is done to validate the solution by using the system. Also the relation to signal of each part has been analyzed.According to the wide application of FBG sensor in many fields, the paper mainly introduces the application in colliery safety monitoring. Basing on the introduction of the causation and form of coal mine disasters, this paper analyzes the purpose and importance of colliery vibration monitoring. Then the vibration detecting system based on FBG which is designed in this paper is applied in a colliery laneway modal founded by our laboratory. The test is done and we get good results. Also through the analysis and studying of the fiber-optic microphone, the FBG fiber-optic microphone is realized by using the above system. These two tests indicate that the system is hopeful for engineering application. In addition, approach to study the next emphases is put forward according to the single channels characteristic of the system, the advantages and wide application of multiplexing.