Study Of The Measure System Of Large-Span Body Deformation With Two-Frequency Laser Optical Fiber

The optical fiber sensing technique is a new one that was developed in the middle of 1970s, based on optical and electronic techniques. It has been applied widely in many physical measurements, in advance of many other sensing techniques. This technique has huge potential of measurements in industry, military, medicine, science and technology etc.; it will be a more and more important in the future science and technology. The two-frequency laser optical fiber sensing measurement system of the displacement for a body with large span is discussed in detail, and it is related to many fields of science and technique. The main work is as follows:First, the basic principle and the development of optical fiber sensor are introduced, and some new related techniques and research with the sensor are given also.Second, the polarization maintaining optical fiber, which is an important sensing material, is analyzed in detail. With ray theories, the gathering light ability of the optical fiber, the transmission losses in the optical fiber are discussed. This method is simple and used easily. The propagation of electromagnetic wave in the optical fiber is analyzed accurately by the mode theories. The gradient optical fiber used in the experiment is analyzed approximately by the weak conducting optical fiber. The properties of optical polarization, the variety of polarized state and the polarization maintaining properties of optical fiber, etc. are studied in detail also.Third, the property of each kind light source in optical fiber sensors technique is analyzed in detail. With comparing of different conditions, the He-Ne laser is chosen as the light source for the experiment. The basic structure, the principle, Zeeman effect, frequency draught and frequency steady principle of the He-Ne lasers are discussed. The principle and feature of the photo-electronic multiplier as a photo detector is introduced. The main parameters of the GDB-423 (a type of photo-electronic multiplier) in the experiment are introduced also.