The Study Of Arm-Based Distributed Optical Fiber Bragg Grating Temperature Demodulation

In recent years, with the development of economic, power load has been increasing in the large-scale metallurgy, chemical industry, power plants, and other enterprises. There is a potential of fire if the temperature of these important hot spots can not be monitored in real-time. As a result, it may bring incalculable economic losses. The fiber grating sensor which recently was more and more widely used as a new kind product of optical fiber sensor. Wavelength modulation-based fiber Bragg grating sensors, which not only has the general advantages of fiber-optic sensors, but also its measurement signal is not affected by the optical fiber bending loss, connection loss, the light source interference and detector aging and so on. These advantages are unmatched by other sensors.Firstly, the fundamental theory of the fiber grating is introduced in this paper. The spectrum of FBG is analyzed by the coupling-mode theory together with FBG sensing theory for strain and temperature is analyzed.Secondly, a novel distributed sensor system based on Fiber Bragg Grating sensing technology is proposed in this paper. In huge project, there are often one hundred positions to be monitored. If these positions are grouping to several groups and every group has four same wavelength fiber gragg gratings, it can implement one hundred fiber gragg gratings on one fiber. If the temperature of one point was varied, the largest temperature of the group can be obtained and the system will alarm if this temperatur is over set value. Based on the theory analysis, temperature experiments of different wavelength have been done. It has been seen in experiments that the characteristics of the measured precisions of good reliability and low cost, application in distributed multimetering. Finally, a signal processing system for FBG sensor is designed. In this system, the core ARM chip is S3C2440A. The system includes: photoelectric conversion, amplifier circuit, and FFP-TF scanning voltage generator. The host computer program is written in the Linux software development platform, and the function of data processing and visualization output is achieved.