A resin composition for coating an optical fiber comprises a base resin containing an oligomer, a monomer, and a photopolymerization initiator, and hydrophobic inorganic oxide particles, wherein the oligomer comprises urethane (meth)acrylate and epoxy (meth)acrylate, and the mass ratio of the content of urethane (meth)acrylate to the content of epoxy (meth)acrylate is 0.25 or more.

An optical fiber comprises a glass fiber comprising a core and a cladding, and a coating resin layer covering the outer periphery of the glass fiber, wherein the average linear expansion coefficient of the coating resin layer at −50° C. or more and 0° C. or less is 3.3×10.sup.−5/° C. or more and less than 9.0×10.sup.−5/° C.

The present disclosure relates to an optical fiber comprising a glass fiber including a core and a clad; a primary resin layer that coats the glass fiber by being in contact with the glass fiber; and a secondary resin layer that coats the primary resin layer, in which the secondary resin layer is formed from a cured product of a resin composition that includes a base resin containing a urethane (meth)acrylate oligomer, a monomer, and a photopolymerization initiator; and inorganic oxide particles, a volume average particle size of the inorganic oxide particles as measured by a small angle X-ray scattering method is 800 nm or less, and a standardized dispersion of the volume average particle size is 60% or less.

An optical fiber according to an embodiment includes a core, a cladding, and a coating layer. At the boundary between the core and the cladding, the local sound velocity decreases in the direction from the core side toward the cladding side. At least in the cladding, the local sound velocity changes continuously in a radial direction. Further, the line width of the Brillouin gain of the light beam guided by the fundamental mode is 60 MHz or more.

A method for manufacturing an optical device includes a hydrogen-loading step, a laser irradiation step, and a light condensing point movement step. The laser irradiation step and the light condensing point movement step are alternately repeated, or are performed in parallel. In the hydrogen-loading step, hydrogen is loaded into a glass member containing B.sub.2O.sub.3 and has a content of GeO.sub.2 less than 10% by mass fraction based on an oxide. In the laser irradiation step, a femtosecond laser beam having a repetition frequency of 10 kHz or higher is condensed and emitted into the glass member into which the hydrogen is loaded, and a light-induced change in refractive index is caused in the glass member. In the light condensing point movement step, a light condensing point position of the femtosecond laser beam is moved relative to the glass member.

Provided is a glass having excellent infrared transmittance and being suitable for use in infrared sensors. A chalcogenide glass material has an oxygen content of 100 ppm or less.

Bromine doping of silica glass is demonstrated. Bromine doping can be achieved with SiBr.sub.4 as a precursor. Bromine doping can occur during heating, consolidation or sintering of a porous silica glass body. Doping concentrations of bromine increase with increasing pressure of the doping precursor and can be modeled with a power law equation in which doping concentration is proportional to the square root of the pressure of the doping precursor. Bromine is an updopant in silica and the relative refractive index of silica increases approximately linearly with doping concentration. Bromine can be used as a dopant for optical fibers and can be incorporated in the core and/or cladding regions. Core doping concentrations of bromine are sufficient to permit use of undoped silica as an inner cladding material in fibers having a trench in the refractive index profile. Co-doping of silica glass with bromine and chlorine is also demonstrated.

Multimode optical fibers are disclosed herein. In some embodiment disclosed herein, a multimode optical fiber having a bandwidth of greater than 2 GHz.Math.km includes: a glass matrix having a front endface, a back endface, a length (L), a refractive index n.sub.20 and a central axis (AC); and a plurality of cores arranged within the glass matrix, wherein the plurality of cores run generally parallel to the central axis between the front and back endfaces and having respective refractive indices n.sub.50, wherein n.sub.50>n.sub.20, wherein the glass matrix serves as a common cladding for the plurality of cores so that each core and the common cladding define a waveguide, wherein each core is a single mode at an operating wavelength; and wherein any two cores have an center-to-center spacing s of 3 m to 20 m and a coupling coefficient of greater than 10 m.sup.1 but less than 200 m.sup.1.

A resin composition includes a base resin containing a urethane (meth)acrylate oligomer, a monomer having a phenoxy group, a photopolymerization initiator, and a silane coupling agent and hydrophobic inorganic oxide particles, wherein the content of the inorganic oxide particles is 1% by mass or more and 45% by mass or less based on the total amount of the resin composition.

An optical fiber includes: a core that includes quartz glass doped with a core updopant; an inner cladding that includes quartz glass doped with a cladding updopant and a downdopant and that covers a circumferential surface of the core; and an outer cladding that includes quartz glass and that covers an outer circumferential surface of the inner cladding. A refractive index of the inner cladding is substantially equal to a refractive index of the outer cladding. The inner cladding contains the cladding updopant at a concentration such that a refractive index increase rate ascribed to the cladding updopant falls within a range of 0.25% to 0.5%.