Abstract: The specification describes multimode optical fibers produced by improved methods that reduce the manufacturing cost. These methods may also be more efficient in terms of power loss. In one of the embodiments, the improved design has a large core of pure silica derived from a rod-in-tube method. In the embodiment, a down-doped cladding is produced by depositing fluorine-doped silica on the inside of a silica starting tube using isothermal radio frequency plasma deposition. The silica core is inserted and the starting tube collapsed. The silica starting tube is removed and optical fiber is drawn from the fluorine-doped glass coated silica rod.

Abstract: Optical fibers are provided for modal discrimination which include a central core and a cladding disposed about the central core. The central core has a non-circular and non-elliptical cross-section, and it is rotated about a central axis of the optical fiber along the length of the optical fiber at a selected pitch resulting in the capability of a fundamental mode beam output for large core sizes. An optical system includes a seed optical source configured to provide a seed beam and an optical amplifier configured to receive and amplify the seed beam. The optical amplifier also includes an active optical fiber having a large mode area non-circular and non-elliptical core rotated about a central axis of said active optical fiber to provide modal discrimination and fundamental mode output.

Abstract: The present disclosure is directed to optical fibers having glass buffers. As such, some embodiments comprise an optical fiber having a core, a cladding, and a glass buffer. For some embodiments, the glass buffer has an index of refraction that is greater than the index of refraction of the cladding.

Abstract: A multi-mode interference (MMI) device includes a substrate layer, a core layer grown on the substrate layer for propagating an optical signal, and a cladding layer grown on the core layer for guiding the optical signal. The MMI device also includes a non-uniform pattern of patches forming a non-uniform refractive index distribution within the MMI device.

Abstract: Described herein are devices and techniques for suppressing parasitic modes in planar waveguide amplifier structures. One or more of the side and end facets of a planar waveguide amplifier are angled with respect to a fast axis defined in a transverse plane perpendicular to a core region. A relationship between glancing in-plane angles of incidence and threshold bevel angles ?T can be used to select side bevel angles ?S to suppress parasitics by redirecting amplified spontaneous emission (ASE) from the core. It is possible to select the one or more bevel angles ?S to be great enough to substantially redirect all but ballistic photons of any guided modes, effectively narrowing a numerical aperture of the planar waveguide amplifier along a slow axis, defined in a transverse plane perpendicular to the fast axis. Beneficially, such improvements can be realized for three part waveguide structures (e.g., cladding-core-cladding), with substantially smooth edge facets.

Abstract: A waveguide can have a first longitudinal section, with at least one core having a first refractive index and at least one sheath surrounding the core. The sheath can be made of a material having a second refractive index so the waveguide will guide at least one optical signal in the core. A third longitudinal section has a sheath and a coating surrounding the sheath having a third refractive index so the third longitudinal section of the waveguide will guide at least one optical signal in the sheath. A second longitudinal section, arranged between the first longitudinal section and the third longitudinal section being adapted to guide an optical signal from the core into the sheath.

Abstract: An optical fiber comprising: (i) a core having a refractive index profile; (ii) an annular cladding surrounding the core; (iii) a primary coating contacting and surrounding the cladding, the primary coating having an in situ modulus of less than 0.35 MPa and an in situ glass transition temperature of less than ?35° C.; and (iv) a secondary coating surrounding the primary coating, the secondary coating having an in situ modulus of greater than 1200 MPa; wherein the refractive index profile of said core is constructed to provide an LP11 theoretical cutoff wavelength greater than 2.0 ?m and an effective area greater than 110 microns2 at 1550 nm.

Abstract: The present invention relates to a multimode optical fiber provided with a region where a refractive index in a peripheral region of a core has deviation from an ideal shape of an ?-power refractive-index profile and where an absolute value of an amount of the deviation is not less than 0.005%, so as to generate radiation modes, and a refractive index of a cladding is higher than that of the deviation region.

Abstract: Methods and systems for managing pulse energy scaling are disclosed, including generating electromagnetic radiation; coupling the electromagnetic radiation to a fiber geometrical management system comprising: a tapered fiber comprising: an elliptical or rectangular core centrally positioned within a single or double cladding shell, wherein the core comprises a fiber material and a doped gain medium; an input face wherein the doped core comprises a major axis and a minor axis, wherein the ratio of the major to minor axis at the input face ranges from about 1 to about 100; an output face wherein the doped core comprises a major axis and a minor axis, wherein the ratio of the major to minor axis at the output face ranges from about 1 to about 100; and wherein the major (minor) axis is adiabatically or linearly tapered from the input face to the output face. Other embodiments are described and claimed.

Abstract: A component for peeling the coating and breaking the optical fiber, which comprises the first member made of resin material including a groove portion enabling to receive a coated optical fiber, an optical fiber cutting blade and a coat removing blade integrally formed within the groove portion, and a breaking portion in an intermediate portion, and the second member made of resin material including a groove portion corresponding to the groove portion in the first member enabling to receive a coated optical fiber, a coat removing blade corresponding to the coat removing blade in the first member, and a breaking portion in an intermediate portion corresponding to the breaking portion in the first member.

Abstract: Various embodiments of optical fiber designs and fabrication processes for ultra small core fibers (USCF) are disclosed. In some embodiments, the USCF includes a core that is at least partially surrounded by a region comprising first features. The USCF further includes a second region at least partially surrounding the first region. The second region includes second features. In an embodiment, the first features are smaller than the second features, and the second features have a filling fraction greater than about 90 percent. The first features and/or the second features may include air holes. Embodiments of the USCF may provide dispersion tailoring. Embodiments of the USCF may be used with nonlinear optical devices configured to provide, for example, a frequency comb or a supercontinuum.

Abstract: An optical waveguide element includes a cladding portion made of a silica-based glass, and an optical waveguide positioned in the cladding portion and made of a silica-based glass in which a ZrO2 particle is dispersed.

Abstract: Disclosed method and apparatus embodiments provide a photonic device with optical isolation from a supporting substrate. A generally rectangular cavity in cross section is provided below an element of the photonic device and the element may be formed from a ledge of the supporting substrate which is over the cavity.

Abstract: The present invention generally relates to the field of fiber optics, and more specifically to optical fibers, methods of manufacturing optical fibers, and methods of classifying optical fibers. In an embodiment, the present invention is a multimode optical fiber which comprises a core and clad material system where the refractive indices of the core and cladding are selected to minimize chromatic dispersion in the 850 nm wavelength window and the refractive index profile is optimized for minimum modal-chromatic dispersion in channels utilizing VCSEL transceivers. Multimode optical fibers according to this embodiment may have increased channel bandwidth.

Abstract: An IR supercontinuum source for generating supercontinuum in the MIR or possibly LWIR spectral bands comprises a supercontinuum fiber formed from a heavy metal oxide host glass having low optical loss and high non-linearity over the spectral band that is stable, strong and chemically durable. The supercontinuum fiber is suitably a depressed inner clad fiber configured to support only single transverse spatial mode propagation of the pump signal and supercontinuum. The source suitably includes a tapered depressed inner clad fiber to couple the pump signal into the supercontinuum fiber. The source may be configured as an “all-fiber” source.

Abstract: Methods of converting silica to silicon and fabricating silicon photonic crystal fiber (PCF) are disclosed. Silicon photonic crystal fibers made by the fabrication methods are also disclosed. One fabrication method includes: sealing silica PCF and a quantity of magnesium within a container, the quantity of magnesium defined by 2Mg(g)+SiO2(s)?2MgO(s)+Si(s); converting silica PCF to a reacted PCF through magnesiothermic reduction; and converting the reacted PCF to the fabricated silicon PCF by selective dissolution of the reacted PCF in an acid. Another fabrication method includes: adding silica PCF and a quantity of solid magnesium to an unsealed container, the quantity of magnesium substantially in excess of that defined by 2Mg(g)+SiO2(s)?2MgO(s)+Si(s); converting silica PCF to a reacted PCF through magnesiothermic reduction; and converting the reacted PCF to the fabricated silicon PCF by selective dissolution of the reacted PCF in an acid.

Abstract: The fibre comprises a core (2) having an index N and diameter of 10 ?m or more, surrounded by a ring (4) having an index N+?n and thickness ?R, and cladding (6) surrounding the ring and comprising for example air gaps (8). According to the invention: ?n?10?3 and ?R=?/(?n)? [1] where: 5×10?4 ?m???5×10?2 ?m and 0.5???1.5. The numbers ? and ? are dependent on the wavelength ? of the light guided by the fibre, the number of missing gaps therein, the diameter d of the gaps, the spacing ? thereof and N. To design the fibre, ?, the number of missing gaps, d/?, the core doping content, ?0 and ?n are chosen; and ?R is determined using equation [1] so as to obtain a flattened fundamental mode.

Abstract: Various apparatus and methods for reducing inter-core crosstalk in a multicore optical fiber are disclosed. A multicore optical fiber may include a plurality of cores capable of transmitting optical signals, and a cladding surrounding the cores, the cladding having a heterogeneous refractive index such that the optical signals propagate at different velocities in different ones of the cores. A multicore optical fiber may include a first length including cores having heterogeneous modal velocities and a second length, adjacent to the first length, including cores having heterogeneous modal velocities, and the cores in the first length are aligned with cores in the second length having a different modal velocity. Inter-core cross talk in a multicore optical fiber may also be reduced by transmitting optical signals through cores of a multicore optical fiber and pumping light into the cores to create unequal modal velocities in the cores.

Abstract: An optical fiber that propagates light over a use wavelength bandwidth of 100 nm or wider in a plurality of propagation modes is provided. The optical fiber has: a confinement loss equal to or less than 1 dB/km in each of the plurality of propagation modes over the use wavelength bandwidth; and a bending loss equal to or less than 100 dB/m in each of the plurality of propagation modes over the use wavelength bandwidth when the optical fiber is bent at a diameter of 20 mm.

Abstract: The multi-core fiber of the present invention uses a multi-core fiber configuration, compatible with the “coupled” operation mode in which coupling between cores is positively utilized, to carry out mode division multiplexing transmission via a multi-core fiber that contains multiple single-mode cores in one optical fiber. The multi-core fiber of the present invention uses a configuration in which mode multiplexing transmission is carried out using a multi-core fiber that contains multiple single-mode cores in one optical fiber, wherein multiple cores are strongly coupled intentionally to form a coupled multi-core fiber that makes the coupled modes correspond, one to one, to the transmission channels.

Abstract: An illumination system that includes at least one light-diffusing optical fiber is disclosed. The illumination system includes at least one low-scatter light-conducting optical fiber that optically couples the at least one light-diffusing optical fiber to at least one light source. The light-diffusing optical fiber includes a light-source fiber portion having a length over which scattered light is continuously emitted. The light-source fiber portion can be bent, including wound into a coil shape. The light-diffusing optical fiber includes a plurality of nano-sized structures configured to scatter guided light traveling within the light-diffusing optical fiber out of an outer surface of the fiber.

Abstract: A tellurium oxide glass that is stable, strong and chemically durable exhibits low optical loss from the UV band well into the MIR band. Unwanted absorption mechanisms in the MIR band are removed or reduced so that the glass formulation exhibits optical performance as close as possible to the theoretical limit of a tellurium oxide glass. The glass formulation only includes glass constituents that provide the intermediate, modifiers and any halides (for OH— reduction) whose inherent absorption wavelength is longer than that of Tellurium (IV) oxide. The glass formulation is substantially free of Sodium Oxide and any other passive glass constituent including hydroxyl whose inherent absorption wavelength is shorter than that of Tellurium (IV) oxide. The glass formulation preferably includes only a small residual amount of halide.

Abstract: A single-mode optical fiber includes a central core surrounded by an outer optical cladding. The optical fiber includes an inner depressed cladding, a ring, and an outer depressed cladding positioned between the central core and the outer optical cladding. The central core typically has a refractive-index difference (Dn1) with the outer optical cladding of between about ?0.5×10?3 and 0.5×10?3. The ring typically has an inner radius (rring1) of between about 21 microns and 35 microns and a refractive-index difference with the outer optical cladding (Dnring) of between about ?0.5×10?3 and 0.5×10?3. The outer depressed cladding typically has a volume (Vout) of between about 15 ?m2 and 30 ?m2. The ratio of the volume of the central core over the width of the ring (Vcore/wring) is typically between about 0.12 micron and 0.2 micron.

Abstract: The present invention relates to a GI-type multi-mode optical fiber in which the outer diameter 2a of a core is 47.5 to 52.5 ?m or 60 to 65 ?m. In the multi-mode optical fiber, stress in the optical axis direction remaining in an outermost peripheral portion of the cladding is tensile stress of 0 to 25 MPa, the outermost peripheral portion of the cladding being defined as a region having a diameter of 1.8b or more when the diameter of the cladding is 2b.

Abstract: Plasmons on a waveguide may deliver energy to photocatalyze a reaction. The waveguide or other energy carrier may be configured to carry electromagnetic energy and generate plasmon energy at one or more locations proximate to the waveguide, where the plasmon energy may react chemically with a medium or interaction material.

Abstract: An optical fiber includes a glass core and a protective coating consisting of a single coating layer disposed to surround the glass core, wherein the single coating layer is formed from a cured polymeric material obtained by curing a radiation curable composition including: (i) a radiation curable urethane (meth)acrylate oligomer, preferably including a backbone derived from polyoxytetramethylene glycol, (ii) at least one monofunctional reactive monomer, (iii) at least one multifunctional reactive monomer, and (iv) an adhesion promoter.

Abstract: An optical system comprising: a light source providing light in 300-700 nm range; and an optical fiber optically coupled to the source; the optical fiber is structured to transmit the light provided by the source and comprises Al doped silica based core with 0 to 1 wt % of Ge and no rare-earth metal(s); and at least one silica based cladding surrounding the core. According to some embodiments the fiber includes: a core having a radius of no more than 2.0 ?m and having a first index of refraction n1 and a relative refractive index delta with respect to the cladding between 0.15 and 1.0%. The Al doped silica core comprises less than 0.5 wt % of Ge and includes no rare-earth metals; and the silica based cladding surrounding the core has a second index of refraction n2, such that n1>n2, the cladding having an outer diameter of 80 ?m or greater.

Abstract: Optical energy in excess of that which is properly coupled into the core of an optical fiber is non-destructively redirected and benignly dissipated so as to minimize damage in a fiber coupled system.

Abstract: The specification describes an optical fiber color coding scheme that uses two colors, where each of the two colors constitutes one half of the surface of the optical fiber coating. If a longitudinal portion of the coating is considered a hollow cylinder, then each of the two colors is a hollow hemi-cylinder. To ensure that each of the two colors is always plainly visible to an installer, the two colors are formed with a twist. Using two colors for coding substantially increases the number of available unique color codes. Coloring the entire coating reduces the chances of error in identifying the optical fibers.

Abstract: An optical fiber includes a graphene oxide and a reduced graphene oxide and a gas sensor includes the optical fiber. A method for manufacturing the optical fiber includes coating a graphene oxide layer and reducing a part of the graphene oxide layer, and a method for manufacturing the gas sensor includes coating a graphene oxide layer and reducing a part of the graphene oxide layer.

Abstract: Device for the emission or amplification of a signal, comprising an optical fiber (1) having a solid core (2) of refractive index nc, made of a silica glass doped with a rare earth, such as erbium, ytterbium or neodymium, said core being surrounded by an optical cladding (3, 4, 5, 6, 7, 8) comprising at least a pair of silica layers composed of a first, inner layer (3), having a refractive index greater than the refractive index nc of the core (2), covered by a second, outer layer (4). The optical fiber (1) comprises several pairs of silica layers (3, 4; 5, 6; 7, 8) around the core (2), each pair comprising an inner layer (3, 5, 7) of refractive index ni and an outer layer (4, 6, 8) of refractive index ne, the refractive index ne of the outer layer being lower that the refractive index ni of the inner layer of the same pair.

Abstract: Provided is an extreme bending insensitive optical fiber. The optical fiber includes a core comprising a maximum refractive index difference ?n1 in the optical fiber, an inner layer comprising a refractive index difference ?n2 that is smaller than the maximum refractive index of the core and decreases in a direction away from the core, the inner layer being positioned outside the core, and a trench layer comprising an inner-circumference refractive index difference ?n3 that is smaller than the refractive index difference of the inner layer and an outer-circumference refractive index difference ?n4 that is a minimum refractive index difference in the optical fiber.

Abstract: Optical analytical devices and their methods of use are provided. The devices are useful in the analysis of highly multiplexed optical reactions in large numbers at high densities, including biochemical reactions, such as nucleic acid sequencing reactions. The devices include optical waveguides for illumination of the optical reactions. The devices further provide for the efficient coupling of optical excitation energy from the waveguides to the optical reactions. Optical signals emitted from the reactions can thus be measured with high sensitivity and discrimination using features such as spectra, amplitude, and time resolution, or combinations thereof. The devices of the invention are well suited for miniaturization and high throughput.

Abstract: An optical fiber includes an optical waveguide, a first coating layer disposed to surround the optical waveguide and a second coating layer disposed to surround the first coating layer, wherein the first coating layer is formed by a cured polymeric material obtained by curing a radiation curable composition including at least one (meth)acrylate monomer esterified with at least one branched alcohol having from 9 to 12 carbon atoms, and the second coating layer is formed by a cured polymeric material obtained by curing a radiation curable (meth)acrylate composition including from 0.8% to 1.5% by weight of silica, based on the total weight of the composition.

Abstract: According to the invention, the intermediate sheath (13) is formed by assembling longitudinal elements (13A) and includes: a first optical material, the refractive index of which differs from the refractive index of the monomode core by at most 10?3; and a second optical material, the refractive index of which is lower than the refractive index of said monomode core and differs therefrom by at least 10?3.

Abstract: The invention aims to provide a holey fiber that can release leak light propagating through the clad at a desired location, and a laser device using the holey fiber. A holey fiber includes: one end and the other end; a core; an inner clad coating the core; a hole layer having a large number of holes formed therein and coating the inner clad; and an outer clad coating the hole layer. In this holey fiber, a collapse region is formed, and the holes in the collapse region are squashed by a predetermined length in the length direction of the fiber.

Abstract: An optical fiber end processing method includes fixing two portions of an optical fiber, heating and fusing the optical fiber between the two fixed portions, to form a first heat fusion region, heating and fusing the optical fiber fixed between the two fixed portions unit while fixing the two fixed portions, moving a heat fusion unit from a side of the first heat fusion region toward a base end side of the optical fiber, and pushing a heat fusion portion of the optical fiber in a direction of shortening a length of the heat fusion portion, to form a second heat fusion region continuous to the first heat fusion region and in which the air holes of the optical fiber disappear; and removing the first heat fusion region by cutting the optical fiber within the second heat fusion region after the second heat fusion forming.

Abstract: A single-mode optical fiber for use as a stub fiber in an optical fiber connector is disclosed. The optical fiber is configured minimize the adverse effects of multipath interference (MPI) that can arise in a short, single-mode conventional stub fiber that has a large group index difference. The optical fiber is also configured to have a mode-field diameter that is substantially the same as that of single-mode optical fibers intended for use as field fiber in a mechanical splice connector, along with a cutoff wavelength ?C?1200 nm. An optical fiber connector that uses the optical fiber as a stub fiber is also disclosed.

Abstract: A solid state light source comprising a light pump outputting light energy; a waveguide optically coupled to the light pump source for receiving the light energy; and a down-converter for converting the light energy from the waveguide to a lesser light energy.

Abstract: The specification describes an optical fiber color coding scheme that uses two colors, where each of the two colors constitutes one half of the surface of the optical fiber coating. If a longitudinal portion of the coating is considered a hollow cylinder, then each of the two colors is a hollow hemi-cylinder. To ensure that each of the two colors is always plainly visible to an installer, the two colors are formed with a twist. Using two colors for coding substantially increases the number of available unique color codes. Coloring the entire coating reduces the chances of error in identifying the optical fibers.

Abstract: An optical connector includes a ferrule having first and second ends. At least one substantially circular channel extends between the first and second ends. The at least one channel has an inner diameter. A substantially circular optical fiber, having an outer diameter, resides within the channel. At least one groove is formed into the inner diameter of the channel, and/or at least one notch is formed into the outer diameter of the optical fiber. Epoxy resides within the at least one groove and/or at least one notch to attach the optical fiber within the channel.

Abstract: An amplification optical fiber includes a core and a clad which covers the core. The core propagates light having a predetermined wavelength in at least an LP01 mode, an LP02 mode, and LP03 mode and, in the core, when the LP01 mode, the LP02 mode, and the LP03 mode are standardized by a power, in at least a part of a region where an intensity of at least one of the LP02mode and the LP03 mode is stronger than an intensity of the LP01 mode, an active element which stimulates and emits light having a predetermined wavelength is added with a higher concentration than that in at least a part of a region where the intensity of the LP01 mode is stronger than the intensities of the LP02 mode and the LP03 mode.

Abstract: An optical fiber may be constructed of a material having at least first and second constituents. The constituents and their relative abundance are selected such that the aggregate Brillouin frequency-shift response exhibited by a fiber constructed using the combined material is insensitive to a selected physical condition, such as temperature or strain, or the sensitivity is below an acceptable application-specific level, over an acceptable range of conditions. The constituents are selected such that the slopes or derivatives of the Brillouin frequency-shift response (with respect to the selected physical condition) of two of the constituents have opposite signs, and are combined in proper quantities such that the constituents balance each other to reduce the slope or derivative of the aggregate Brillouin frequency-shift response of the combined material to zero, or to an acceptable application-specific level, over an acceptable range of conditions.

Abstract: This invention discloses a bend insensitive single mode fiber, which is composed by a bare glass fiber with a round cross section and two resin protective layers with circular cross sections surrounding the outer of the bare glass fiber. It is characterized in that the bare glass fiber is composed by a core layer with a round cross section and two claddings with circular cross sections. The refractive index of the core layer is higher than the index of the two claddings and the refractive index difference between the core layer and the first cladding is larger than the difference between the first and second claddings. The second cladding is made of pure SiO2. The refractive index profile of the core layer follows a power function, and the refractive index profile of the two claddings follow a ladder-type distribution. The loss of the invented fiber is insensitive to the bending of the fiber, which meets the requirements of ITU.T G.657.A and G.657.B standards, respectively.

Abstract: An optical coupling module includes a substrate, a circuit board defining two through holes, an optical waveguide positioned between the substrate and the circuit board, and an optical assembly. The optical waveguide includes a core and a clad, each core comprises two coupling surfaces corresponding to the two through holes. At least one coupling surfaces is in an arcuate shape. The clad covers the core, except for the two coupling surfaces exposing out of the clad. The optical assembly formed on the circuit board comprises an optical emitting element and an optical receiving element. The optical emitting element and the optical receiving element are positioned above the two through holes, respectively. Light emitted from the optical emitting element enters the optical waveguide via one of the coupling surface, and leaves from another coupling surface to reach the optical receiving element. The coupling surface is capability of focusing light.

Abstract: A source of optical supercontinuum radiation comprises a microstructured optical fibre and a pump laser adapted to generate lasing radiation at a pump wavelength, the microstructured optical fibre comprising a core region and a cladding region which surrounds the core region; the core of the microstructured fibre comprising a first refractive index and the cladding region comprising an effective refractive index such that the ?-value is greater than 0.03; the fibre comprising a zero dispersion wavelength within ±200 nm of said pump wavelength; wherein the fibre can support a plurality of modes at said pump wavelength; and wherein the pump laser is adapted to launch said lasing radiation at said pump wavelength into said core region of said microstructured optical fibre to excite the fundamental mode of the fibre. In one practice, the source of optical supercontinuum radiation does not include a pump laser arranged to pump said microstructured optical fibre at a wavelength different from said pump wavelength.

Abstract: The present technology provides an illustrative method for preparing fibers with desirable optical characteristics. The method includes providing a fiber that comprises a core layer and a cladding layer located around the core layer. The method further includes applying a nanostructure template to the cladding layer to form one or more photonic nanostructures having nanostructure scales and compressing the core layer to cause the core layer to bulge and form air gaps between the core layer and the one or more photonic nanostructures.

Abstract: Optical fiber refractive index profile designs having an alpha core profile and a negative index trench to control bend loss, are modified by truncating the edge of the alpha core profile and adding a ledge to the truncated core. The result is low bend loss and preservation of low differential mode delay and high bandwidth.

Abstract: The present invention relates to a preform manufacturing method and others for effectively reducing variation in refractive index due to chlorine used in manufacture of an optical fiber preform. The manufacturing method includes a dechlorination step carried out between a point of an end time of a dehydration step and a point of a start time of a sintering step, the dechlorination step being a step of heating a porous preform after dehydrated, in an atmosphere containing no chlorine-based dehydrating agent, for a given length of time while maintaining a temperature lower than a sintering temperature, thereby removing chlorine from the porous preform after dehydrated.

Abstract: There are provided an optical waveguide forming resin composition, an optical waveguide and a light transmission flexible printed board both produced by using the composition, and a production method for the optical waveguide, wherein the resin composition is superior in coatability, capable of omitting a solvent drying step in coating film formation, and suitable as a material for forming an optical waveguide which allows only a low waveguide loss and which has a higher Tg and higher flexibility. An optical waveguide forming resin composition comprises the following components (A) through (D), wherein the optical waveguide forming resin composition is free from a solid resin component and the viscosity thereof under a 25° C. environment is within the range of 10 to 20 mPa·s: (A) a liquid oxetane compound; (B) a liquid epoxy compound; (C) an alkylene glycol; and (D) a photoacid generator.