Characteristics of polarization splitters constructed from a circular hollow pit outside the cores

Abstract

AbstractIn this paper, a polarization splitter is proposed in which a single‐core fiber (Fiber 1) and a fiber with a circular hollow pit outside the core (Fiber 2) are coupled. Corresponding to the extraction of the two linear polarizations (x and y polarizations) from the HE11 mode excited in to Fiber 1, the polarization splitting method can be clasified into the x‐polarization type or the y polarization type. In the x‐polarization type, the x‐polarization is extracted from Fiber 1 and the y‐polarization from Fiber 2. In the y‐polarization type, the y‐polarization is extracted from Fiber 1 and the x polarization from Fiber 2. This paper discussed the structural parameters (core radius, relative refractive index difference, and core spacing), which reduce the device length of the x polarization and y polarization types and at the same time make the extinction ratio small. The main results are as follows: (1) When the relative refractive index difference of Fiber 2 was made constant, the minimum values of the device length and the extinction ratio of the x polarization type can be made smaller than those of the y polarization type. (2) When the relative refractive index difference of Fiber 2 is increased from 0.4 percent to 1.0 percent, 1 the device lengths of both the x‐ and y‐polarization types can be reduced by 0.26 times, and 2 the minimum value of the extinction ratio of the x polarization type increases +4.1 dB from ‐38.2 dB and that of the y polarization increases +4.3 dB from ‐34.1 dB.