Patent ID: 9217840
Filing Date: 2015-12-22
Classification: G02B

Abstract:
1. A low-mode (“LM”) high power combiner, comprising: a plurality of single mode (“SM”) passive fibers guiding respective SM outputs, the SM fibers being bundled together to define a taper narrowing to an end fiber, the end fiber having a core guiding combined LM signal light in a propagating direction, and at least one cladding; a multitimode combiner output fiber butted to the end fiber to define a splice, the output fiber having a cladding surrounding a core which guides the LM light, the LM light being incident on a workpiece partially reflecting the incident light so that a portion of the reflected light is coupled into the core of the output fiber guiding the reflected light in a counter-propagating direction; and a clad mode absorber (“CMA”) surrounding the end fiber and extending over a part of the combiner output fiber, the absorber being configured with: an upstream zone extending along the end fiber and terminating at a distance upstream from the splice, the upstream zone being configured to strip a portion of the reflected light coupled into the core of the combiner output fiber and bled through the splice into the cladding of the end fiber, an intermediary zone extending over the splice and regions of respective end and output fibers bordering the splice, the intermediary zone being configured to prevent decoupling of a portion of the LM light bled into the cladding of the output fiber, a downstream, zone extending over the output fiber and terminating at a distance from a downstream end thereof, the downstream zone being configured to scatter low numerical aperture (“NA”) rays of the LM light guided along the cladding.