Abstract: A method and apparatus, utilizing multiple light signals, for extending the dynamic range of an interferometric system such as an optical fiber gyroscope based on dual wavelength measurement of the Sagnac phase shift in order to determine the fringe number of the interferometric fiber system, thereby increasing the unambiguous range of the device. An analogue measure of the fringe number is provided, thus eliminating the need for digital fringe counting or tracking. An apparatus is described for measuring absolutely, within certain upper bounds determined by the exact wavelengths used, the rotation rate when the system is powered up in a rotating frame.

Abstract: A method of aligning the polarization-preserving axis of a receiving end of a polarization-preserving optical fiber with the linearly-polarized output of a semiconductor laser in which the fiber optic end is placed substantially adjacent the laser rather than being separated from the laser by a polarizing optical system.

Abstract: An acousto-optic frequency shifter in which two cylindrical acoustic resonators driven 90.degree. out of phase from one another are placed around a birefringent, single-mode optical fiber approximately three-quarters of a polarization beat length apart. The resonators interact with optical radiation propagating in one of two polarization modes of the fiber, the first to cross-couple two sidebands into the other polarization mode, and the second to suppress one of the sidebands in the cross-coupled mode and enhance the other, thereby creating a single sideband signal completely within the fiber.