Sensitivity Analysis of the Sagnac-Effect,Optical-Fiber,Ring Interferometer.

摘要

The sensitivity of a recently reported optical-fiber, ring interferometer as a gyro has been analyzed. Photomixing signal-to-noise ratios were derived for the detection schemes using outputs based on both single and complementary fringes. Light-scattering processes, ubiquitous in the optical fiber, such as the Rayleigh, Brillouin, Mie, and core-cladding interface scattering, are assessed quantitatively because they induce, as does the signal, shot noises that set an upper limit to the minimum-detectable rotational rate. Mode stripping is a necessary feature because it can reduce the trapped scattered light level by about a factor of 100. A thorough discussion of the problems and their solutions associated with the dc detector scheme reveals that, in order to achieve the highest photon-noise-limited sensitivity, a nonreciprocal 90 deg phase bias with phase modulation, or a heterodyne technique, is essential. Optimum gyro sensitivities are discussed via numerical examples in terms of laser input wavelengths and power limits. Results show that a longer wavelength such as 1.1 micrometers is more desirable than a shorter wavelength such as 0.633 micrometers because at lambda = 1.1 micrometers the fiber's ultimate scattering loss rate is much lower, hence longer fibers can be used to increase sensitivity; and that high-power operation, where the only noise is due to stimulated Brillouin scattering, gives a better sensitivity than the lower power case.