Abstract: Provided is a mode controller which includes an optical fiber coupled body and at least one pair of bobbins, and the mode controller is configured so that: the one pair of bobbins includes two bobbins arranged, spaced from one another; the optical fiber coupled body includes a step-index fiber and a graded-index fiber, which are coupled with each other; the step-index fiber and/or the graded-index fiber is/are wound around the at least one pair of bobbins, and twisted to form a helical area(s); light is launched into the step-index fiber, propagates through the step-index fiber, is emitted from the step-index fiber, and is launched into the graded-index fiber; propagation mode of the light is converted to an equilibrium mode distribution during the propagation of the light through the step-index fiber; and the propagation mode of the light launched into the graded-index fiber is converted to a low-order mode.

Abstract: Provided is a mode controller which includes an optical fiber coupled body and at least one pair of bobbins, and the mode controller is configured so that: the one pair of bobbins includes two bobbins arranged, spaced from one another; the optical fiber coupled body includes a step-index fiber and a graded-index fiber, which are coupled with each other; the step-index fiber and/or the graded-index fiber is/are wound around the at least one pair of bobbins, and twisted to form a helical area(s); light is launched into the step-index fiber, propagates through the step-index fiber, is emitted from the step-index fiber, and is launched into the graded-index fiber; propagation mode of the light is converted to an equilibrium mode distribution during the propagation of the light through the step-index fiber; and the propagation mode of the light launched into the graded-index fiber is converted to a low-order mode.

Abstract: Provided is an optical branching/coupling device in which optical transmission quality is improved by preventing a reduction in optical transmission quality, the reduction being due, for example, to an optical waveguide core affecting a light of another optical waveguide core in the vicinity of a joining section of the two optical waveguide cores. This optical branching/coupling device includes: a first optical waveguide that is provided extending from one end side to other end side; a second optical waveguide that is provided extending on a separate route from the one end side to the other end side, the other end side of the second optical waveguide being joined to the other end side of the first optical waveguide; and a cladding layer that covers the periphery of the first optical waveguide and the second optical waveguide, wherein the first and second optical waveguides comprise a cured product of a photocuring resin.

Abstract: Provided is a low-loss mode scrambler in which a steady mode distribution can be obtained in a short distance and switch to an entire mode distribution state is easy even when incident light is smaller than a numerical aperture of a fiber to be measured in a multimode fiber having a core diameter exceeding several tens of ?m and a numerical aperture of 0.2 or more. One fiber 2 is wound around a plurality of bobbins 3a and 3b having a radius larger than a minimum bending radius of the fiber to form a bundle, and the fiber 2 is twisted by rotating the bobbins 3a and 3b to form a twisted portion 5, whereby it is possible to perform output of a steady mode from light incident on the fiber 2.

Abstract: Provided is an optical branching/coupling device in which optical transmission quality is improved by preventing a reduction in optical transmission quality, the reduction being due, for example, to an optical waveguide core affecting a light of another optical waveguide core in the vicinity of a joining section of the two optical waveguide cores. This optical branching/coupling device includes: a first optical waveguide that is provided extending from one end side to other end side; a second optical waveguide that is provided extending on a separate route from the one end side to the other end side, the other end side of the second optical waveguide being joined to the other end side of the first optical waveguide; and a cladding layer that covers the periphery of the first optical waveguide and the second optical waveguide, wherein the first and second optical waveguides comprise a cured product of a photocuring resin.

Abstract: Provided is a low-loss mode scrambler in which a steady mode distribution can be obtained in a short distance and switch to an entire mode distribution state is easy even when incident light is smaller than a numerical aperture of a fiber to be measured in a multimode fiber having a core diameter exceeding several tens of ?m and a numerical aperture of 0.2 or more. One fiber 2 is wound around a plurality of bobbins 3a and 3b having a radius larger than a minimum bending radius of the fiber to form a bundle, and the fiber 2 is twisted by rotating the bobbins 3a and 3b to form a twisted portion 5, whereby it is possible to perform output of a steady mode from light incident on the fiber 2.