Study On The Fiber-optic Interferometric Sensor Detecting Weak Electric-field

The fiber optic sensor becomes more and more popular due to its unique characteristics of immunity to electro-magnetic interference and high sensitivity. With the rapid development of narrow linewidth laser, single-mode fiber and related fiber-optic devices, more types of fiber optic sensors have been developed and the performances are been improved. Among them, the fiber-optic interferometric sensor detecting weak electric-field is the one, which is considered as the most competitive alternatives for a pure electrical detection. The trend in the design and implementation technology of weak electric field sensor in fiber optics evolves from Mach-Zehnder structure to Michelson structure and from linear piezoelectric material to nonlinear electrostrictive materials. This dissertation studies the principle of fiber-optic weak electric field sensor. A high-sensitivity, high-resolution interferometric fiber-optic weak electric-field sensor is designed and implemented. The main content includes:(1) The principle of weak electric-field sensor based on the all-fiber Michelson interferometer and the electrostrictive material is studied. Formula regarding the performance is derived. And the structure of the fiber-optic weak electric-field sensor system is designed.(2) The characteristics of the electrostrictive material are analyzed in details. A novel structure, which utilizes the electrostrictive ceramic (e.g., PLZT) as the sensitive element, is designed. The key issues related to the implementation technique are presented.(3) A sensor system detecting slow-varying weak electric-field based on above principle and material is implemented. The sensitivity and resolution of the sensor system are examined by a series of experiments. The results show that the system can overcome the1/ f noise issue and has good linear response to the weak DC electric-field. The sensor has a minimum detectable electric field of 0.022(V/m)//(Hz)^1/2 at 5 Hz, which well matches the design goal.(4) The author has been engaged in the research of fiber optic sensor detecting the weak magnetic field. This study will not be included as part of the content in the dissertation due to the limitation in length. Based on this aspect of knowledge, a multiplexing integrated system for detecting electric and magnetic field is proposed. A three-dimensional vector field measurement method is demonstrated using the weak magnetic field fiber optic sensor.