Research And Analysis On Performance Of Fiber Optic Current Sensor

As a new type of electrical testing equipment, fiber optic current sensor with its unique advantages has a good market and application prospects. In this paper, it takes all-fiber optic current sensor's application as the background, and makes researches on the principles and characteristics of the system in-depth, mainly for Sagnac-type fiber optic current sensor.Firstly, based on the principle of Faraday magneto-optical effect, it used the theory of Jones matrix to build up the mathematical models of fiber-optic current sensor and make polarization error analysis of key optical device in sensor system, then pointed out the main factors of the target parameters of sensor system and gave related improvements.Secondly, it is elaborated several common kinds of signal modulation and demodulation principles of fiber optic current sensor, with making comparative analysis. In the system of fiber-optic current sensor with digital closed-loop, signal processing system's main role is to build closed-loop feedback system and make signal timing control and data processing, for real-time generating bias phase and compensating for the external Faraday magneto-optical rotation phase which real-time tracks and detects the current situation of the real fluid. In order to meet the system's detection accuracy and real-time processing requirements, the system adopted the signal processing program of digital closed-loop square-wave + ladder-wave signal modulation, and the result is more desirable.Thirdly, it is the innovative application of optical system simulation software for sensor systems functional real-time simulation in order to achieve real-time verification purposes, while system parameters can be reasonably set, which will effectively shorten its product-oriented, engineering process, and save costs and time. It is designed the digital controller of closed-loop system on the steady-state and dynamic performance, and used of the MATLAB/SIMULINK to complete the control system of modules'design and simulation. Simulation results show that the all-digital closed-loop fiber-optic current sensor which used PID control law can improve the system dynamic response speed.In addition, in order to have a better understanding of performance parameters in fiber-optic current sensor system, the experimental prototype is built. The key components of the system (such as optical fiber sensing head, 1/4 wave plate) is designed to make related experiment, then it is proposed a new vibration compensation program of optical fiber sensing head and a preliminary circuit modulation system design.In the end, a new type of dual-mode fiber-optic current sensor structure is also proposed, which abandons the method of using phase modulator to produce theπ/ 2 phase bias in the usual fiber-optic current sensor system. In the new sensor system, it is used of Gouy phase shift in dual-mode optical fiber to produce fixedπ/ 2 phase shift, and used of mode selector coupler for splitter design. System structure is more simple, flexible and more conducive to open-loop system design and implementation.