Abstract: An optical combiner includes: a plurality of first input optical fibers that each include a core; a bridge fiber that includes a bridge input surface connected to the cores of the plurality of first input optical fibers, a diameter reduction portion having a diameter that decreases away from the bridge input surface along an optical axis of the optical combiner, and a bridge output surface located opposite to the bridge input surface along the optical axis; an intermediate optical fiber that includes a core connected to the bridge output surface of the bridge fiber; a second input optical fiber that includes a core; and an output optical fiber that includes a first optical waveguide connected to the core of the intermediate optical fiber, and a second optical waveguide connected to the core of the second input optical fiber.

Abstract: An optical combiner includes: an optical fiber bundle formed by a plurality of first optical fibers; and a second optical fiber including an end surface joined to an end surface of the optical fiber bundle by fusion-splicing. The plurality of first optical fibers includes a predetermined first optical fiber and other first optical fibers. The predetermined first optical fiber is composed of one or more materials having higher softening temperatures than one or more materials of the other first optical fibers.

Abstract: An optical fiber securing structure includes: an optical fiber including a coating, and a coating-removed section in which a partial section of the coating is removed from the optical fiber; a reinforcement member including main surfaces and a groove formed from one of the main surfaces toward an inside of the reinforcement member, where the groove has a pair of side walls and a bottom wall; and a resin member that secures the coating-removed section to the pair of side walls and the bottom wall. A bottom part of the groove that includes the bottom wall has a widthwise cross-sectional shape where the bottom wall constitutes a trapezoidal shape such that a distance between the pair of side walls becomes greater in a direction away from the bottom wall.

Abstract: An optical combiner includes: first optical input portions each including a first optical input waveguide; and an optical output portion to which the first optical input portions are connected and that includes a first core that allows light to propagate therethrough, and a cladding layer disposed outside of the first core and that has a refractive index lower than a refractive index of the first core. The first optical input portions are connected to a connection end face of the optical output portion such that the first optical input waveguide of at least one of the first optical input portions is optically coupled to the first core of the optical output portion.

Abstract: An optical combiner includes: a plurality of first input optical fibers that each include a core; a bridge fiber that includes a bridge input surface connected to the cores of the plurality of first input optical fibers, a diameter reduction portion having a diameter that decreases away from the bridge input surface along an optical axis of the optical combiner, and a bridge output surface located opposite to the bridge input surface along the optical axis; an intermediate optical fiber that includes a core connected to the bridge output surface of the bridge fiber; a second input optical fiber that includes a core; and an output optical fiber that includes a first optical waveguide connected to the core of the intermediate optical fiber, and a second optical waveguide connected to the core of the second input optical fiber.

Abstract: An optical fiber securing structure includes: an optical fiber including a coating, and a coating-removed section in which a partial section of the coating is removed from the optical fiber; a reinforcement member including main surfaces and a groove formed from one of the main surfaces toward an inside of the reinforcement member, where the groove has a pair of side walls and a bottom wall; and a resin member that secures the coating-removed section to the pair of side walls and the bottom wall. A bottom part of the groove that includes the bottom wall has a widthwise cross-sectional shape where the bottom wall constitutes a trapezoidal shape such that a distance between the pair of side walls becomes greater in a direction away from the bottom wall.

Abstract: An optical combiner includes: an optical fiber bundle formed by a plurality of first optical fibers; and a second optical fiber including an end surface joined to an end surface of the optical fiber bundle by fusion-splicing. The plurality of first optical fibers includes a predetermined first optical fiber and other first optical fibers. The predetermined first optical fiber is composed of one or more materials having higher softening temperatures than one or more materials of the other first optical fibers.

Abstract: A cladding mode stripper, includes: a resin part that covers a coating-removed section of an optical fiber and has a refractive index not less than that of an outermost shell of the optical fiber in the coating-removed section. A surface of the resin part includes an incident angle reducing structure. The surface is opposite to an interface between the resin part and the outermost shell. The incident angle reducing structure reduces a first incident angle or a first average incident angle at which cladding mode light that has entered the resin part from the optical fiber enters the surface.

Abstract: A fiber laser includes: a gain fiber; a first low-reflective mirror and a second high-reflective mirror disposed in an optical path of laser light that is emitted from a first end of the gain fiber; a second low-reflective mirror and a first high-reflective mirror disposed in an optical path of laser light that is emitted from a second end of the gain fiber; a first delivery fiber that accepts the laser light emitted from the first end; a second delivery fiber that accepts the laser light emitted from the second end; and an operation mode switching mechanism that switches between a first operation mode and a second operation mode. A first resonator is constituted by the first low-reflective mirror and the first high-reflective mirror. A second resonator, which is constituted by the second low-reflective mirror and the second high-reflective mirror.

Abstract: An optical device includes: first optical fibers, a second optical fiber, a fiber connection portion, a fiber support portion; and a fixation resin that fixes the first optical fibers to the fiber support portion. The first optical fibers form a tapered portion including a taper initiation portion and a taper body reduced in diameter toward the fiber connection portion. The core of the second optical fiber has a core exposure area exposed outside of the first optical fibers. At least a portion of a periphery of the fixation resin is disposed closer to an optical axis of the second optical fiber than to a first reference line that is an extension of a line that passes through a closest point of the taper initiation portion to the optical axis on a plane perpendicular to the optical axis.

Abstract: A cladding mode stripper, includes: a resin part that covers a coating-removed section of an optical fiber and has a refractive index not less than that of an outermost shell of the optical fiber in the coating-removed section. A surface of the resin part includes an incident angle reducing structure. The surface is opposite to an interface between the resin part and the outermost shell. The incident angle reducing structure reduces a first incident angle or a first average incident angle at which cladding mode light that has entered the resin part from the optical fiber enters the surface.

Abstract: A combiner includes: an input fiber bundle including input fibers; and a bridge fiber including a GI fiber section. A beam bundle emitted from the input fiber bundle enters the GI fiber section, the bridge fiber has a diameter smaller at an exit end surface of the bridge fiber than at an entrance end surface of the bridge fiber, and the GI fiber section converges the beam bundle.

Abstract: The present invention comprises a core (11) and a primary coating (12) that is lower in refractive index than the core (11) and that covers the side surface of the core (11) except in a coating-removed section (I0). The side surface of the core (11), in at least part of the coating-removed section (I0), is covered with an intermediate-refractive-index resin part (14) that is lower in refractive index than the core (11) and that is higher in refractive index than the primary coating (12).

Abstract: A cladding mode light removal structure includes: an input-side exposure portion where a covering is removed from an end of an input-side optical fiber to expose a cladding of the input-side optical fiber; an output-side exposure portion where a covering is removed from an end of an output-side optical fiber to expose an output-side cladding of the output-side optical fiber; a fusion splice portion at which the input-side exposure portion and the output-side exposure portion are connected by fusion splice; a fiber housing portion having an accommodation space that receives the input-side exposure portion, the output-side exposure portion, and the fusion splice portion; a high refractive index resin having a refractive index equal to or higher than that of the cladding exposed at the input-side exposure portion; and a low refractive index portion of a medium.

Abstract: An optical fiber includes: an optical waveguide; and a resin coating that is lower in refractive index than the optical waveguide and covers a side surface of the optical waveguide except in a coating-removed section of the side surface. The coating-removed section of the side surface is covered throughout with an inorganic layer that is lower in refractive index than the optical waveguide.

Abstract: A cladding mode light removal structure includes: an input-side exposure portion where a covering is removed from an end of an input-side optical fiber to expose a cladding of the input-side optical fiber; an output-side exposure portion where a covering is removed from an end of an output-side optical fiber to expose an output-side cladding of the output-side optical fiber; a fusion splice portion at which the input-side exposure portion and the output-side exposure portion are connected by fusion splice; a fiber housing portion having an accommodation space that receives the input-side exposure portion, the output-side exposure portion, and the fusion splice portion; a high refractive index resin having a refractive index equal to or higher than that of the cladding exposed at the input-side exposure portion; and a low refractive index portion of a medium.

Abstract: The optical fiber fusion splice structure has a fusion splice portion at which the bare fibers exposed from the coverings are connected to each other by fusion splicing, a fiber accommodation portion having a fiber accommodation groove formed along an axis of the optical fibers, and fixation resins for fixing a portion of the coverings on both sides of the fusion splice portion within the fiber accommodation groove. The fiber accommodation groove receives a portion of the optical fibers including the fusion splice portion. The fixation resins are formed so as to fill the fiber accommodation groove in a depth direction. A pipe member that allows an infrared ray to pass therethrough is attached around the fiber accommodation portion so as to surround a space between the fixation resins on both sides of the fusion splice portion within the fiber accommodation groove.

Abstract: An optical fiber includes: an optical waveguide; and a resin coating that is lower in refractive index than the optical waveguide and covers a side surface of the optical waveguide except in a coating-removed section of the side surface. The coating-removed section of the side surface is covered throughout with an inorganic layer that is lower in refractive index than the optical waveguide.

Abstract: The present invention comprises a core (11) and a primary coating (12) that is lower in refractive index than the core (11) and that covers the side surface of the core (11) except in a coating-removed section (I0). The side surface of the core (11), in at least part of the coating-removed section (I0), is covered with an intermediate-refractive-index resin part (14) that is lower in refractive index than the core (11) and that is higher in refractive index than the primary coating (12).

Abstract: The optical fiber fusion splice structure has a fusion splice portion at which the bare fibers exposed from the coverings are connected to each other by fusion splicing, a fiber accommodation portion having a fiber accommodation groove formed along an axis of the optical fibers, and fixation resins for fixing a portion of the coverings on both sides of the fusion splice portion within the fiber accommodation groove. The fiber accommodation groove receives a portion of the optical fibers including the fusion splice portion. The fixation resins are formed so as to fill the fiber accommodation groove in a depth direction. A pipe member that allows an infrared ray to pass therethrough is attached around the fiber accommodation portion so as to surround a space between the fixation resins on both sides of the fusion splice portion within the fiber accommodation groove.