Analysis of polarization‐maintaining optical fibers with circular pits outside a circular core

Abstract

This paper investigates the polarization‐maintaining optical fibers with one circular hollow pit (SCF) and two circular hollow pits (DCF) outside a circular core. The modal birefringence of the following fibers are investigated: with homogeneous core, with radially inhomogeneous core. The relation between the modal birefringence (ΔB) and the polarization dispersion (Δτ) is also investigated. The homogeneous core fibers are analyzed by the improved point‐matching method. To analyze the inhomogeneous core fibers, the core is divided into several homogeneous layers and the improved point‐matching method is then applied. The main conclusions drawn in this paper are as follows: (1) the maximum modal birefringence for DCF can be attained 3.5 times larger than that for SCF; (2) the modal birefringence for inhomogeneous core fiber cannot be greater than that for homogeneous core fiber, even if the core index is chosen equal to the maximum index value of inhomogeneous core; (3) zero polarization mode dispersion can be attained near the wavelength where the modal birefringence takes the maximum value; however, it is not zero at that very wavelength. The relative error of propagation constant computed by our method is less than 10−9 so that the relative errors of the modal birefringence and polarization mode dispersion are less than 10−4.