Implementation of digital detection scheme for fiber optic gyroscope

Abstract

Fiber optic gyroscope (FOG) is a kind of inertial sensor that can be used for navigation, control and guidance of air, naval, land and space vehicles. A FOG measures rotation rate dependent on phase difference between two counterpropagating light waves through a rotating fiber loop. In this thesis, the main principles of FOG such as Sagnac effect and reciprocity are described. The optical scheme consists of a broadband light source, a coupler, a polarizer, an integrated optic chip and a fiber coil, is developed and established. The modulation and demodulation techniques used in FOG are also investigated in detail. The digital detection system is built with a photodetector, a transimpedance amplifier, a voltage amplifier and a data acquisition (DAQ) system. A transceiver module and an FPGA processor are the components of DAQ system. The modulation and demodulation processes are implemented by using LabVIEW FPGA module. The program created in LabVIEW environment allows to characterize scale factor and phase modulator parameters. Rotation rate measurements are performed and analyzed by Allan variance method. The impacts of different noise types to the performance of FOG are analyzed. Angle random walk (ARW), noise component to determine short-term accuracy of FOG, is reduced by integration of spike-free signal. We also show that we obtain similar noise parameters even if the output power of the system is very low. It is proven and tested that ARW is reduced by the optimization of modulation depth. Theoretical and experimental results are quite consistent at every stages of the work.