Classification and properties of radiation and guided modes in Bragg fiber

This article classifies modes into radiation and guided modes in a Bragg fiber, which has a cylindrically symmetric and periodic structure. Classification of the above modes into TE and TM modes is possible by considering the envelope of cladding fields and by noting a particular parameter relating to Bloch wavenumber. In particular, discussions are made for electromagnetic fields of radiation mode, contour curves concerning to the distinction between guided and radiation modes, and optical confinement. It is shown that radiation modes in this fiber distribute for discrete spectrum of propagation constant unlike the index-guiding optical fiber.