Theoretic Analyse And Experiment Of Depolarized Fiber Optical Gyroscope And Its Key Elements

Gyroscope, as a major sensor in acquiring azimuth angle, plays an important role in both civil use and military use, such as guide for navigation, satellite position finding, geodetic surveying, astronomical telescope tracking, robotic motion and automobile navigation. The interferometric fiber optic gyroscope(FOG) based on Sagnac effect has became to one of the most important fiber sensor in developing due to light in quality, compact in dimension, high accuracy and long life. The interferometric FOG can be divided into two categories, PM-FOG and D-FOG, the former one employs polarization-maintaining fiber, which rejects the output drifting induced by variation of polarization state by means of keeping the stability of polarization state in fiber optic, hence, results in high accuracy and high cost; D-FOG uses depolarizer in single mode fiber, which can uniform light intensity on each axis of polarization, in order to minimize drifting of FOG and increase accuracy. Comparing to D-FOG, using PM-FOG would increase the costs dramatically, so D-FOG has a bright future in cost efficiency and low accurate FOG area.The objective of this project is to develop D-FOG, which is cost efficiency, low accurate and mainly for civil use. Firstly, the author reviewed the basic principle of FOG and the literature about FOG, and also introduced the photo-conducting devices in use of the PM-FOG and D-FOG. Secondly, for both polarization-maintaining system and ideal dual depolarizing system, mathematical model of optical paths were built separately using Jones matrix, and mathematical model of optical paths in un-ideal dual depolarizing FOG system was completed, so was deducing and calculating several parameters. At last, two different structures of depolarizer, key device of D-FOG, were analyzed and calculated theoretically. Manufacture and testing of two kinds of depolarizers was completed by means of experiments, and the result of testing Lyot depolarizer, which was used in this project, was acquired.Bsides, in this project the length is distinguishingly set to reduce the effect of birefringence in SM optical fiber and the single PM optical fiber depolarizer was testified by experiment, the optical circulator is also proved can take place of optical coupler.