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An integrated phase modulator is made by coating single-mode fibers with a radially poled vinylidene fluoride-trifluoroethylene copolymer. The performance of the fiber as an optical phase modulator was demonstrated over a wide frequency range of 20-50 MHz. A phase sensitivity of 2.1 x 10(-5) rad/(V/m) per meter of fiber is measured in the low-frequency region and 3.5 x 10(-6) rad/(V/m) per meter of fiber is measured in the high-frequency region. At frequencies higher than 1 MH(z), the optical response is dominated by radial resonances of the fiber-jacket composite.

The mean-square fluctuations of log amplitude and phase are studied theoretically for guided beam modes propagating in an asymmetric slab waveguide having random inhomogeneities of the refractive index. The study is based on a method of the Rytov approximation, which has been mainly employed in analyzing the beam fluctuations in an atmosphere. The results show that the mean-square fluctuations of log amplitude and phase increase proportionally to the propagation distance for z/λ > 103, z and λ being the actual propagation distance and the wavelength of light, whereas the log-amplitude fluctuations increase obeying a square law of the distance for z/λ < 102. It is also found that an abrupt reduction of these fluctuations is observed near the center of the slab waveguide where the irradiance of the beam field has a maximum.

The excitation efficiencies of the dominant and low-order modes in an optical fiber are theoretically determined for an incident Gaussian beam that is offset with respect to the fiber axis. The excitation efficiencies are shown to be strongly influenced by both the numerical aperture of the fiber and the wavefront curvature of the incident beam.

Angular misalignment between the birefringent axes of two connecting fibers and coupling misalignment with respect to the birefringent axes of an input fiber give rise to polarization noise, resulting in a reduction of as much as 7 dB in signal-to-noise ratio. Standard deviations for fluctuations in the phase delay and the azimuth of the birefringent axes have been determined by comparing experimental data with numerical results assuming Gaussian statistics for the random variables.