ALL-FIBER-OPTIC GYROSCOPE WITH EXTENDED LINEAR DYNAMIC RANGE

The single-mode fiber-optic gyroscope is a potential alternative to mechanical and ring laser gyroscopes in many application areas. High sensitivity rotation rate measurements have been demonstrated near zero rotation rate. The fiber-optic gyroscope, however, becomes practical only when the periodic response of the interferometer to the rotation rate is linearized over a wide dynamic range.; This dissertation describes a number of new methods that provide a wide linear dynamic range without complicating the optical circuit of an all-fiber-optic gyroscope.; One approach to getting a linear dynamic range is to operate the gyroscope in a closed-loop mode where a non-reciprocal phase shifter provides a cancellation of the rotation-induced phase shift. The difficulty was that such a non-reciprocal phase shifter in fiber form did not exist for the use in gyroscopes. Three different ways of getting a linear scale factor using a fiber-optic phase modulator in place of a non-reciprocal phase shifter are described in this thesis. A good linearity of the scale factor over a wide dynamic range is experimentally demonstrated.; Another approach to linear dynamic range described and demonstrated here is to translate the optical phase difference in the interferometer into a phase shift in a low frequency electronic signal using an optical phase modulation in conjunction with simple electronic signal processing. This system provides a direct reading of the optical phase shift in a digital form and a strictly linear scale factor.; None of these approaches compromise the all-fiber configuation of the optical circuit and no new fiber-optic components are required.; A fiber-optic gyroscope with a broadband optical source and a highly birefringent fiber is analyzed. This gyroscope configuration provides stable rotation sensing with less Rayleigh scattering noise and polarization related error. A novel method to determine the birefringent axes of highly birefringent fibers is presented, which is an important procedure for the gyroscope construction.