Research Of Communication Interface Technology For Fiber Grating Sensors' Demodulation System

Fiber Bragg grating (FBG) sensor, which uses the property that the Bragg wavelength is sensitive to temperature and strain, is a novel fiber optic sensor. In addition to have the same functions as the traditional electric sensors, the FBG sensor also has some special characteristics such as distributed sensing, immune to electromagnetic interference, high precision and long-term stability. So it has widely been used in various fields such as civil structure, aeronautics and space, ship and marine, oil and chemical industry, electric and nuclear power industry, medicine and railway systems. Some FBG sensors have been commercialized for structural monitoring and oil/natural gas reservoir monitoring.The demodulation system of the fiber grating sensor is the absolutely necessary apparatus for the fiber gating sensor used in the commerce. At present, the fiber grating sensor's demodulation system, which made in WUTOS, use the serial interface. For the application on the PC are very complex ,while the user usually need only one or several parameters such as wavelength, the DLL will be used to develop the driver of the fiber grating sensor's demodulation system. To realize the high-integration of the enterprise information system with the fiber grating sensor and fit in with the requirements of the integrated modern enterprise management and control, so that the fiber grating sensor can be suitable for the application of engineering more better, the data communication based on the network interface and the data communication based on the OPC technology are both examined. Firstly, the recent developments in the area of fiber grating sensors are reviewed; the problems about it in our country are also indicated. The basic structure of fiber Bragg gratings is introduced systematically and the temperature, strain and pressure sensing mechanisms of fiber Bragg gratings are also introduced systematically. Various signal demodulation techniques, including spectral analysis method, grating matching method, tunable Fabry-Perot cavity method, and tunable narrow-band light source method, etc are described. With emphasis on the identity of the tunable Fabry-Perot filter and its demodulation principles, a solution based on the tunable Fabry-Perot filter is provided.The communication interface technology is a very important fact that can incarnate the integrative performance of the fiber grating sensor's demodulation system; it has highly significance of theoretical and engineering practice. The communication interface technology for fiber grating sensor's demodulation system has beendiscussed from three parts: the data communication based on the serial interface, which used in the fields that need not high baud rate but low size, short distance and portable, the data communication based on the network interface, which used in the fields that need lots of data about wavelength, long-distance access and distributed measure, and the data communication based on the OPC technique, which denotes the future trend of the data communication standard of industry. So it is very necessary for us to develop the fiber grating sensor's demodulation system which can support OPC specification. In the end, after compared the three techniques we provide the next step of the research.