DOUBLE-CORE FIBER, OPTICAL COUPLING DEVICE USING THE SAME, SIGNAL LIGHT EXCITATION OPTICAL COUPLING DEVICE, FIBER AMPLIFIER, AND FIBER LASER

摘要

PROBLEM TO BE SOLVED: To provide a double-core fiber which can maintain an optical confinement level having a resistance to disturbance over the longitudinal direction of waveguide structure of a core even when the variation rate of outside diameter is large and can perform rigid waveguide.;SOLUTION: The double-core fiber is a mode field converting fiber which converts a mode field diameter while changing the outside diameter over the longitudinal direction, and composed essentially of silica glass, wherein the refractive-index structure of the core is a double layer structure, on the thicker outside diameter side, a single layer core of the inner side substantially acts as a single mode waveguide of only a fundamental mode and, on the thinner outside diameter side, a double layer core substantially acts as the single mode waveguide of only the fundamental mode.;COPYRIGHT: (C)2008,JPO&INPIT