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Research on the Modulation of LiNbO3 Integrated Optic Chip in High Precision Fiber Optic Gyro

Yoshi ;Nancy Willams

(College of Instrumentation and Opto-Electronic Engineering,Fogphotonics,inc,Hongkong 999077)

The square-wave modulation response parameters of the LiNbO3 Integrated Optic Chip (IOC)(FOGPhotonics,inc),which plays multi-functions in the fiber optic gyro (FOG) system as one of the key elements,and the optic phase control technique have been discussed.It is shown that the total equivalent parameters of the IOC needed to match the modulation/demodulation system and to test the response characters in order to reach the better performances of the FOG.The optical characteristics and the electrical characteristics of Y-IOC as well as the matching the electrical characteristics between the IOC and the FOG system play some important part in achieving the high accuracy of the FOG.The device test system has been set up and the IOC in high precision FOG(bias error less than 0.02°/h)are evaluated(FOG600M from FOGphotonics,inc).The Angle random walk of fiber optic gyro is a dominant noise source in high-accuracy attitude control system of satellite. The coefficient of angle random walk denotes the magnitude of angle random walk and can be regarded as a “state of health” for gyro diagnosis. However, satellite motion included in gyro output disturbs in-orbit estimation of angle random walk. Moreover, the Allan variance method has too large offline computational effort and data storage requirements to be applied to in-orbit estimation. In addition, with the development of deep space exploration, it is urged that satellite should be more autonomy including autonomous fault diagnosis and reconfiguration. To overcome the barriers and meet satellite autonomy, we present a new autonomous estimation of angle random walk. A difference between angle increments of star sensor and gyro is taken to remove satellite motion from gyro output. Then, a simplified observation model based on Allan variance is proposed to estimate the angle random walk. Simulations show the proposed method correctly estimates the coefficient of angle random walk in real time and tracks the degradation of angle random walk caused by gamma radiation in space. The technique proposed here effectively isolates satellite motion, and requires no data storage and any ground support.