The Research Of Passive Optical Fiber Sound Sensor In Emergency

When the complex underground areas such as mine in case of an emergency, power supplement may be damaged, the traditional ways of communication were disable to pass information to the emergency command, and the optical fiber sensor can replace the traditional electrical sensor effective. The optical fiber sensing technology has a series of unique advantages such as high sensitivity, strong electromagnetic interference resistance, can be distributed network and so on. It can instead of traditional sensors to be used in emergency situation. The optical fiber sensing technology involves optics, optoelectronics, signal processing, automatic control, precision machinery, and many other high-tech field, At present all the developed countries are vigorously promoting the development of research in this area,The interferometric fiber optic sensor is one of the important part of fiber optic sensor which can measure precisely and quickly, and the signal demodulation technology is directly related to the measurement resolution, sensitivity, dynamic range and so on.This paper firstly discusses the basic principle of optical fiber sensor, and makes a simple analysis of the math structure of fiber Michelson interferometer, The Faraday rotation mirror is verified to reduce the impact on the optical fiber sensing system for demodulation signal phase random fading effect.The paper focuses on 3*3 coupler phase demodulation method, and the principle and mathematical model are analyzed. we design a kind of FOSS in emergency which based on fiber Michelson interferometer and 3*3 coupler phase demodulation principle, The FOSS system contain the host and slave system,and support duplex communication.The main work of this paper is as follows:1. This paper complete theoretical analysis of FOSS in emergency which based on the theory of 3*3 coupler phase demodulation method, the mathematical model has carried on the Matlab simulation experiments, The paper gave out the expression of the three output signal phase difference. And then the least square method was used to get the average phase difference of three output signals,It got the simulation experiment data and made comparison to the actual test data.2. The system of FOSS based on the principle of optical fiber Michelson interferometer was accomplished, which was established by analyzing the recording principle of elastic disc and the method of adhesive optical fiber. The method of 3*3 coupler phase demodulation also was used to improve the performance of general signal phase demodulation. Experimental results demonstrate that the FOSS system can restore the sound signals accurately and effectively in designed bandwidth. The test results verify the feasibility of the FOSS system. The FOSS system could be used in some special situation such as emergency environment.3. The stability of SLD light source has important influence on the performance of optical fiber sensing system. A constant current and constant temperature system of that based on STM32 was designed in order to improve precision of the system. The method of operational amplifier as device for constant current source circuit technology was used to ensure that the stability of current, and the PID controller was used to ensure stability of the temperature. The result of the test experiment proved that the system can meet the demand whose output power remain stable in appropriate temperature.