Polarization mode dispersion of spun fibers with randomly varying birefringence.

We show analytically how periodic spinning affects the polarization mode dispersion of a fiber in three different practical regimes that are determined by the values of three length scales: the beat length, the birefringence correlation length, and the spin period. We determine in which limits the spin is effective in reducing the mean differential group delay.

Measurement of birefringence correlation length in long, single-mode fibers.

Measurements of birefringence correlation length performed on long single-mode telecommunication fibers are reported. The proposed technique relies on the statistical properties of the backscattered-field polarization, which was measured by means of a polarization-sensitive optical time-domain reflectometer. Experimental results are reported that show good agreement with the underlying theory based on stochastic differential equations.

Measurements of beat length and perturbation length in long single-mode fibers.

Experimental results of measurement of the beat length and the differential group delay of several types of long single-mode fiber are presented. The proposed measurement technique is based on a polarization-sensitive analysis of the backscattered signal and allows one to calculate the correlation length of the random birefringence affecting the fiber.

Statistical characterization of fiber random birefringence.

The statistical properties of the random birefringence that affects long single-mode fibers are experimentally evaluated by means of a polarization-sensitive optical time-domain reflectometry. The measurements are in good agreement with theoretical predictions and show, for what we believe is the first time, that the components of the local birefringence vector are Gaussian random variables.

Theory of linearly birefringent fibers: an alternative approach.

We tackle the theory of linearly birefringent single-mode dielectric fibers in terms of magnetic fields, instead of the usual electric fields. The new approach simplifies the analysis of the minor field component as a function of the radial coordinate. Several previous results are reconfirmed and unified. New closed-form expressions are found for the field in a fiber in which the physical index seen by the minor component matches, in a part of the cross section, the guided-mode equivalent index.

Experimental investigation of linear polarization in high-birefringence single-mode fibers.

We report on measurements of linear polarization ratio in high-birefringence fibers as a function of wavelength. Comparison with standard step-index and with dispersion-shifted fibers reconfirms that the modes of polarization-maintaining fibers are not linearly polarized.

Second-order perturbation theory of rectangular waveguides and directional couplers.

Perturbation theory is applied to rectangular-core coupled waveguides, whose cladding can be homogeneous or not. Second-order corrections are evaluated for the phase constants of the guided modes and for the coupling coefficient. This requires the full spectrum of radiation modes, which are found within the same approximation as Marcatili's guided modes. It is found that the second-order terms are negligible in most cases of practical interest. However, there are cases for which these terms are so large that the usual first-order theory collapses.