Cladding light filter for double-cladding optical fiber and preparation method for cladding light filter

The invention discloses a cladding light filter for a double-cladding optical fiber and a preparation method for the cladding light filter. The cladding light filter comprises the light filtering double-cladding optical fiber, a water cooled plate and an encapsulation piece, wherein the light filtering double-cladding optical fiber comprises a fiber core, an inner cladding and an outer light filtering cladding; the outer light filtering cladding comprises section-A outer claddings and a section-B outer cladding which are arranged alternately; the second-B outer cladding consists of a polymer section and an ultraviolet glue section or fully consists of the ultraviolet glue section; the ultraviolet adhesive section is a light filtering section. The preparation method comprises the steps of stripping off part or all of the outer claddings from a middle section or multiple spaced sections of the double-cladding optical fiber along the circumferential direction, coating ultraviolet glue on stripped parts to form the light filtering section to obtain the light filtering double-cladding optical fiber, and fixing and encapsulating the light filtering double-cladding optical fiber to obtain the cladding light filter. The cladding light filter disclosed by the invention can effectively filter out cladding light; the conventional local temperature rising is converted into overall uniform temperature rising, so that laser with high light beam quality can be output; the preparation method is simple, feasible and low in cost.