Geophysical Fiber Interferometer Gyroscope.

Abstract : This report describes a development effort of the University of Utah Research Institute aimed at perfecting a North-seeking device based on the passive interferometer gyroscope concept. The rotation sensing mechanism of the interferometer is based on the Sagnac effect. The form of the interferometer is a fiber ring. The performance requirements of the device are developed in terms of desired pointing accuracy vs. measurement resolution or sensitivity. The interferometer performance will be compared to that of a typical ring-laser gyro. Methods by which the sensitivity of the interferometer could be potentially increased will be discussed. Two of these methods, namely the electro-optic phase shifter and acousto-optic frequency shifter, were evaluated and their limitations regarding the performance of a fiber interferometer gyroscope will be addressed. Additionally, signal processing requirements will also be discussed. Finally, the theoretical limit for performance of a fiber-optic interferometer will be discussed in terms of the so-called 'photon noise limit.' This is the limit to performance that several researchers have alluded to in arriving at the ultimate sensitivity of a passive interferometer laser gyroscope. Suggestions for a device in which the photon noise limit may be approached will also be discussed.