Research On The Distributed Fiber Optic Temperature Measurement And The Data Processing

The distributed fiber temperature detection technology employed the physics characteristics to obtain the real-time spatial-temporal information of the detected field. Fiber sensor, As a new technology, based on the waveguide theory, has the advantages such as low dissipation, broad bandwidth, fine fiber line, low weight, easy coil, resistant to electromagnetism disturbance and the chemical erosion etc. With the rapid technique progress of photoelectron, computer and microelectronics, the fiber detecting technology is progressing rapidly and being broaden more and more applications in engineering. The fiber detection technology has solved many cases that were difficult with conventional measuring technique and became a research hotspot in detection technique field. In the sensing system, the fiber is not only the laser propagating medium but also the measuring signal carrier. The fiber temperature sensing system can detect the temperature vibration along the fiber which can be several kilometers or even long, and the system can reach high spatial resolution and small measurement error. Comparing with the point measuring method in the large space, the fiber measuring system can be used in industry, national defense, aeronautics and astronautics, traffic and living field with high performance.The dissertation researched the distributed fiber detection system with Raman scatting and the data processing in detail, and the system was applied in long transmission line for temperature measure and fire alarm. The main contributions are as follows:1. With the optical theory and quantum mechanics, the principle of fiber detection technique is analyzed, and the transmitting characteristics and the temperature relation between the anti-stokes and stokes signal are deduced, and the formula of temperature with signals are achieved.2. Based on temperature measurement applications in long transmission line, the design of distributed fiber temperature detection system is discussed, and the practical system is completed on the LabVIEW platform. In the system, the advanced computer and database technique are used in the data processing system so that the device can well meet the distributed measure demand in practice, the temperature measurement results are reasonable on the long transmission line, and the experiments put forward the system into production.3. Measurement distance, spatial resolution, temperature resolution and measurement time were researched and the relations among these factors were analyzed. Different from the other detection techniques, these factors are associated with each other can be evaluated respectively.4. Due to the measurement signals of anti-stokes and stokes are very weak, the weak signal processing technique is very important in a system and studied at length. Some new signal processing methods are analyzed and one practical method is given based on high resolution A/D converter.5. Sigma Delta modulator is used in the data processing and can get high precision. Based on the period calculating method and reducing redundancy method, the data calculating time can be decreased and the system precision can be adjusted according to measurement demand.6. Employed LabVIEW platform and database technique, the measurement development period is...