Patent ID: 7409128
Filing Date: 2008-08-05
Classification: G02B,H01S

Abstract:
1. A method for operating a cladding-pumped fiber amplifier (CPFA) that is susceptible to an undesired optical propagation of radiation in higher-order core optical modes, comprising: (a) delivering optical pump radiation to the CPFA from a tapered fiber bundle having a plurality of multimode fibers clustered around a center fiber; (b) delivering an optical input signal to the CPFA, or extracting an amplified optical signal from the CPFA, via the center fiber of the tapered fiber bundle; and (c) during (a) and (b), suppressing the coupling of amplified optical radiation into the multimode fibers by confining amplified radiation from higher-order core optical modes of the CPFA in an optical waveguiding structure located in the tapered fiber bundle, the optical waveguiding structure including: at least an outer cladding, an inner cladding, an index pedestal, and a core, wherein the refractive index of the index pedestal is intermediate between that of the core and the inner cladding, wherein the refractive index of the outer cladding is less than the refractive index of the inner cladding, and wherein the index pedestal can act as an inner optical waveguide of the inner cladding, the suppression occurring due to the index pedestal acting as the inner optical waveguide for the higher-order optical modes that would otherwise propagate in the inner cladding.