Abstract: According to one embodiment, in an optical fiber bundle, in the cross section, arrangement of cores of a first multi-core fiber and arrangement of cores of a second multi-core fiber are the same as each other, arrangement of cores of a third multi-core fiber and arrangement of cores of a fourth multi-core fiber are the same as each other, and when the first multi-core fiber is rotated 180° in a circumferential direction of the first multi-core fiber, the arrangement of the cores of the first multi-core fiber is the same as the arrangement of the cores of the fourth multi-core fiber.

Abstract: An optical fiber connection structure includes: a tubular member; a first collimator attached to a first end of the tubular member in an axial direction; and a second collimator attached to a second end of the tubular member. The first collimator includes a first optical fiber, a first ferrule, a first lens, and a first sleeve. The second collimator includes a second optical fiber, a second ferrule terminating the second optical fiber, a second lens, and a second sleeve. The first sleeve is fixed to the first end via adhesive in a state where the first lens faces the tubular member, and the second sleeve is fixed to the second end via adhesive in a state where the second lens faces the tubular member. An outer diameter of the second ferrule is larger than that of the second lens.

Abstract: A method of producing a nonlinear optical device is provided. In a surface of a semiconductor substrate, a recessed part is formed. In an environment under reduced pressure, the first liquid material is filled into the recessed part. A second liquid material is brought into contact with a first liquid material filled in the recessed part, and thereby a third liquid material is prepared. The third liquid material is solidified, and thereby an embedded portion is formed. The first liquid material includes a first solute and a first solvent, or the first liquid material consists of the first solvent. The second liquid material includes a second solute and a second solvent. The second solute includes a nonlinear optical polymer. The concentration of the second solute in the second liquid material is higher than the concentration of the first solute in the first liquid material.

Abstract: An optical fiber connection structure includes: a tubular member; a first collimator attached to a first end of the tubular member in an axial direction; and a second collimator attached to a second end of the tubular member. The first collimator includes a first optical fiber, a first ferrule, a first lens, and a first sleeve. The second collimator includes a second optical fiber, a second ferrule terminating the second optical fiber, a second lens, and a second sleeve. The first sleeve is fixed to the first end via adhesive in a state where the first lens faces the tubular member, and the second sleeve is fixed to the second end via adhesive in a state where the second lens faces the tubular member. An outer diameter of the second ferrule is larger than that of the second lens.

Abstract: An optical fiber connection structure includes: a multi-core fiber; a plurality of single-core fibers; a first lens having a focal length of f1 (mm); and a second lens having a focal length of f2 (mm). A core pitch of the multi-core fiber is P1 (?m), a mode field diameter on the first end face of each core is MFD1 (?m), a core pitch of multiple single-core fibers is P2 (?m), a mode field diameter of a light beam on the second end face of each core is MFD2 (?m), and the following formulas are satisfied. (P1/P2)×0.9?f1/f2?(P1/P2)×1.1, and (P1/P2)×0.9?MFD1/MFD2?(P1/P2)×1.

Abstract: A wavelength multiplexer/demultiplexer includes a first collimator, M-number of second collimators, M-number of wavelength selective filters, and a base plate. Each of the wavelength selective filters includes a substrate having optical transparency and a multilayer film. The substrate includes a first main surface and a second main surface, and a bottom surface facing a placement surface of the base plate. The multilayer film is formed on the first main surface and transmits an optical signal in a specific transmission wavelength band and reflect an optical signal in a wavelength band other than the specific transmission wavelength band. Each of the wavelength selective filters is fixed to the placement surface by a cured adhesive. The cured adhesive is in contact with the bottom surface and is in non-contact with the multilayer film in at least one wavelength selective filter among the wavelength selective filters.

Abstract: A wavelength multiplexing/demultiplexing device includes a first collimator, an M number of second collimators, and the M number of filters. The filters have transmission wavelength bands differing from each other. An optical path connecting the first collimator and the second collimator in first order to each other passes through the filter in first order. An optical path connecting a surface opposite to a multilayer film of the filter in mth (m=1, . . . , M) order and the second collimator in (m+1)th order to each other passes through the filter in (m+1)th order. The filter in (m+1)th order is optically coupled on the surface opposite to the multilayer film to the filter in mth order and is optically coupled on a surface of the multilayer film to the second collimator in (m+1)th order.

Abstract: An optical connection structure includes a first spatial multiplex transmission line, a second spatial multiplex transmission line, a first lens arrangement, a second lens arrangement and a first beam diameter conversion portion. The first spatial multiplex transmission line has a plurality of first transmission lines. The second spatial multiplex transmission line has a plurality of second transmission lines. The first lens arrangement is optically coupled with the first spatial multiplex transmission line. The second lens arrangement is optically coupled with the second spatial multiplex transmission line. The first beam diameter conversion portion has a first end face and a second end face and arranged between the first spatial multiplex transmission line and the first lens arrangement. The first beam diameter conversion portion is configured such that an optical diameter at the second end face is larger than an optical diameter at the first end face.

Abstract: An optical fiber amplifier comprising a first optical fiber, a second optical fiber, a third optical fiber, and an excitation light source, is disclosed. Each optical fiber has cores and a cladding surrounding the cores. The third optical fiber transmits excitation light used for signal amplification in the second optical fiber. A rare-earth element is doped to the second optical fiber that amplifies an optical signal propagating therein by the excitation light. The third optical fiber includes a reduced-diameter portion. A distance between the cores of the third optical fiber in the reduced-diameter portion is shorter than a distance between the cores in other portion of the third optical fiber, and the excitation light entering from the excitation light source to one of the cores of the third optical fiber is mode-coupled with another core of the third optical fiber to distribute the excitation light in the reduced-diameter portion.

Abstract: An optical fiber amplifier comprising first, second and third optical fibers, and first, second and third lenses, is disclosed. First cores of the first optical fiber and second cores of the second optical fiber have homothetic arrangement each other in the arrangement of outer cores. The first core has a mode field diameter MFD1S when transmitting an optical signal and a core pitch P1, and the first lens has a focal distance f1S at the wavelength of the optical signal. The second core has a mode field diameter MFD2S when transmitting the optical signal and a core pitch P2, and the second lens has a focal distance f2S at the wavelength. The MFD1S of each first core is within ±25% of MFD2S×(P1/P2) of the corresponding second core, and the MFD1S of each first core is within ±25% of MFD2S×(f1S/f2S) of the corresponding second core.

Abstract: An optical connection structure includes a first spatial multiplex transmission line, a second spatial multiplex transmission line, a first lens arrangement, a second lens arrangement and a first beam diameter conversion portion. The first spatial multiplex transmission line has a plurality of first transmission lines. The second spatial multiplex transmission line has a plurality of second transmission lines. The first lens arrangement is optically coupled with the first spatial multiplex transmission line. The second lens arrangement is optically coupled with the second spatial multiplex transmission line. The first beam diameter conversion portion has a first end face and a second end face and arranged between the first spatial multiplex transmission line and the first lens arrangement. The first beam diameter conversion portion is configured such that an optical diameter at the second end face is larger than an optical diameter at the first end face.

Abstract: Problem to Be Solved: to provide a chromophore having a far superior nonlinear optical activity to conventional chromophores and to provide a nonlinear optical element comprising said chromophore. Solution: a chromophore comprising a donor structure D, a ?-conjugated bridge structure B, and an acceptor structure A, the donor structure D comprising an aryl group substituted with a substituted oxy group; and a nonlinear optical element comprising said chromophore.

Abstract: An optical connection component comprising optical fibers, a ferrule and a tube, is disclosed. The optical fibers are provided with coating removal portions and coated fiber portions. The coating removal portions includes first fiber portions held by a first inner hole of the ferrule and second fiber portions positioned between the first fiber portions and the coated fiber portions. The tube places, in a second inner hole, a part of the ferrule, the first fiber portions held by the part of the ferrule, the second fiber portions, and a part of the coated fiber portions adjacent to the second fiber portions. The first fiber portions are fixed onto an inner circumferential surface of the first inner hole with an adhesive agent, and a region, in which the second fiber portions are placed in the second inner hole, is not filled with an adhesive agent, and a void is provided there.

Abstract: An optical fiber amplifier comprising a first optical fiber, a second optical fiber, a third optical fiber, and an excitation light source, is disclosed. Each optical fiber has cores and a cladding surrounding the cores. The third optical fiber transmits excitation light used for signal amplification in the second optical fiber. A rare-earth element is doped to the second optical fiber that amplifies an optical signal propagating therein by the excitation light. The third optical fiber includes a reduced-diameter portion. A distance between the cores of the third optical fiber in the reduced-diameter portion is shorter than a distance between the cores in other portion of the third optical fiber, and the excitation light entering from the excitation light source to one of the cores of the third optical fiber is mode-coupled with another core of the third optical fiber to distribute the excitation light in the reduced-diameter portion.

Abstract: An optical fiber amplifier comprising first, second and third optical fibers, and first, second and third lenses, is disclosed. First cores of the first optical fiber and second cores of the second optical fiber have homothetic arrangement each other in the arrangement of outer cores. The first core has a mode field diameter MFD1S when transmitting an optical signal and a core pitch P1, and the first lens has a focal distance f1S at the wavelength of the optical signal. The second core has a mode field diameter MFD2S when transmitting the optical signal and a core pitch P2, and the second lens has a focal distance f2S at the wavelength. The MFD1S of each first core is within ±25% of MFD2S×(P1/P2) of the corresponding second core, and the MFD1S of each first core is within ±25% of MFD2S×(f1S/f2S) of the corresponding second core.

Abstract: An optical connection component comprising optical fibers, a ferrule and a tube, is disclosed. The optical fibers are provided with coating removal portions and coated fiber portions. The coating removal portions includes first fiber portions held by a first inner hole of the ferrule and second fiber portions positioned between the first fiber portions and the coated fiber portions. The tube places, in a second inner hole, a part of the ferrule, the first fiber portions held by the part of the ferrule, the second fiber portions, and a part of the coated fiber portions adjacent to the second fiber portions. The first fiber portions are fixed onto an inner circumferential surface of the first inner hole with an adhesive agent, and a region, in which the second fiber portions are placed in the second inner hole, is not filled with an adhesive agent, and a void is provided there.

Abstract: Problem to Be Solved: to provide a chromophore having a far superior nonlinear optical activity to conventional chromophores and to provide a nonlinear optical element comprising said chromophore. Solution: a chromophore comprising a donor structure D, a ?-conjugated bridge structure B, and an acceptor structure A, the donor structure D comprising an aryl group substituted with a substituted oxy group; and a nonlinear optical element comprising said chromophore.

Abstract: Problem to Be Solved: to provide a chromophore having a far superior nonlinear optical activity to conventional chromophores and to provide a nonlinear optical element comprising said chromophore. Solution: a chromophore comprising a donor structure D, a ?-conjugated bridge structure B, and an acceptor structure A, the donor structure D comprising an aryl group substituted with a substituted oxy group; and a nonlinear optical element comprising said chromophore.

Abstract: An optical device is equipped with an input/output module having at least one optical fiber, a movable mirror which deflects, toward the input/output module, light that is received from the input/output module, and a lens which couples the input/output module and the deflection unit to each other optically and has a focal length that is greater than or equal to 2.0 mm and shorter than 3.5 mm. A dispersion index ? of the optical device that is given by an equation: ?={n(1.45)?1}/{n(1.2)?n(1.7)} where n(1.45), n(1.2), and n(1.7) are refractive indices of a glass material of the lens at wavelengths 1.45 ?m, 1.2 ?m, and 1.7 ?m, respectively, is larger than or equal to 100. The wavelength dependence of an optical characteristic of this optical device is weaker than that of conventional optical devices.

Abstract: A wavelength selective switch includes a dispersion optical system dispersing wavelength multiplexing light obtained by multiplexing the plurality of frequency components to the plurality of frequency components by giving a dispersion angle having nonlinear frequency dependency to each of a plurality of frequency components; a light deflection element deflecting the plurality of frequency components; a condensing element condensing the plurality of frequency components on the light deflection element; and a prism optical system optically coupled to the dispersion optical system and the condensing element, and adapting spatial positions of the frequency components incident on the light deflection element to change linearly for frequencies by linearizing the frequency dependency of the dispersion angles and making incident the plurality of frequency components on the condensing element.