POLARIZATION PRESERVING OPTICAL FIBER AND ABSOLUTE SINGLE POLARIZATION OPTICAL FIBER

摘要

A polarization preserving optical fiber and an absolute single polarization optical fiber capable of transmission over a long distance with the polarization condition of a signal light kept preserved. The polarization preserving optical fiber comprises a core unit 11, a photonic crystal structure clad 12 and a jacket unit 13. The photonic crystal structure clad 12 is divided into four divided portions 12a, 12b, 12c, 12d divided by broken lines extending from the center toward the outer periphery. The diameter d2 of lattice holes 14a, 14c in the vicinity of the core unit 11 out of a plurality of lattice holes provided by a pair of divided portions 12a and 12c facing each other across the core unit 11 is larger than the diameter d1 of a lattice holes provided by the other pair of facing divided portions 12b, 12d and larger than a lattice interval Λ.