Investigation Of Optical Fiber Twist Sensor Based On The Polarization Of The Light

In recent years, with the development of optical fiber communication and semi-conductor photoelectric device, optical fiber sensors arise at the historic moment. They have been widely used in various fields of national economy and become the research focus and hotspot, due to their advantages of small volume, light weight, strong electromagnetic interference resistance, simple structure and high sensitivity.According to the modulation mode, optical fiber sensors can be divided into the modulation types of intensity, frequency, wavelength, phase, polarization. In this paper, we study the polarization-modulated optical fiber twist sensor and design its experimental system. The designed optical fiber twist sensor has the advantages of simple structure, easy maintenance, simple process, high sensitivity, good repeatability, etc. When it works in the area of the linear, namely the torsional angle of 30° to 70°, the sensitivity of the normalized intensity can up to 0.015/°.The main contents of this thesis are as follows:1. The basic principles, categories, research status and development trend at home and abroad of the optical fiber sensors are study. In particular, the recent progress and research significance of the optical fiber twist sensors are analyzed.2. The structure of the polarization-modulated optical fiber twist sensor is designed and the principles of the experiment are introduced. The Jones matrix expression of the polarized light is analyzed by using Jones matrix. Then the mathematical model of each sensor module in the experimental system is set up. At last, the Jones matrix expression of the whole experimental system is obtained during the process of transmission of the light waves. The intensity of the output light of the polarization-modulated optical fiber twist sensor is analyzed.3. The experimental procedure is designed, according which the experimental system is set up. The experimental data acquired in the experiment is analyzed and processed. With the help of MATLAB, the figures of the experimental data are drawn and the linear region of the experimental data is fitted. Finally, the effect of the single-mode fiber length in the sensor head to the performance of the sensor is studied.