Patent ID: 8526775
Filing Date: 2013-09-03
Classification: G02B

Abstract:
1. A fiber laser comprising: a pumping light source; a rare-earth doped optical fiber; and a fiber fuse terminator having an optical fiber which includes a core and a cladding having holes extending in a longitudinal direction thereof, wherein: a refractive index of the core of the optical fiber is higher than a refractive index of a portion of the cladding excepting portions of the holes; when it is assumed that a mode field diameter at a used wavelength of the optical fiber is MFD, and a distance, in a cross section perpendicular to the longitudinal direction of the optical fiber, between a center of the core and a position, closest to the center of the core, of the hole that is closest to the core is Rmin, a value expressed by 2×Rmin/MFD is no less than 1.2 and no more than 2.1; when it is assumed that a width, in a diameter direction, of a region where the holes present in the cladding is W, a value expressed by W/MFD is no less than 0.3; and when it is assumed that a diameter of the cladding of the optical fiber is D each end of the optical fiber is fusion-spliced to an optical fiber having no holes, and the fusion-splicing loss per one point thereon is no greater than 0.50 dB; a portion of a surface of the optical fiber, excepting a fusion-splice portion between the optical fiber and the optical fiber having no holes and a periphery thereof, is covered with a resin coating; and the fusion-splice portion and the periphery thereof of the surface of the optical fiber are covered with a flameproof protective layer.