A light-emitting module includes a substrate, a surface light-emitting element, and an optical waveguide. The surface light-emitting element includes light sources and is attached to the substrate. The optical waveguide is attached to the surface light-emitting element in a state in which the optical waveguide covers the light sources. The optical waveguide extends in an axial direction with a refractive index distribution in a radial direction. The optical waveguide condenses light beams emitted from the surface light-emitting element.

A plastic optical fiber for a medical device lighting decreases the cost of a lens and simplify the design of a lighting apparatus, wherein the plastic optical fiber for a medical device includes a core composed of a (co)polymer containing methyl methacrylate as a main component and is characterized by including a cladding material composed of a copolymer having a fluorine weight composition ratio of 60 to 74%, and by having a theoretical numerical aperture, NA, of 0.48 to 0.65 and, thus, the plastic optical fiber has a high numerical aperture and also has excellent translucency and flexibility.

An optical fiber according to an embodiment has a structure for enabling determination of improvement in transmission loss at a preform stage. The optical fiber includes: a core containing Cl and having an average refractive index lower than a refractive index of pure silica glass; a first cladding containing F; a second cladding; and a resin coating, in which an effective area at a wavelength of 1550 nm is 135 m.sup.2 or more and 170 m.sup.2 or less, a ratio of the effective area to a cutoff wavelength .sub.C is 85.0 m or more, a bending loss of an LP01 mode at a wavelength of 1550 nm and at a bending radius of R15 mm is less than 4.9 dB per 10 turns, and the resin coating includes a primary resin layer having a Young's modulus of 0.3 MPa or less.

The present invention provides a polymer optical waveguide containing a core and a cladding having a refractive index lower than that of the core, in which each of the core and the cladding is a cured product of a curable composition cured by light irradiation, and the cladding has an absorbance of 0.23 or low per 50 m of film thickness at a wavelength of 365 nm.

A plastic optical fiber including a first cladding; a first core forming a first sea portion inside the first cladding; and a first island portion formed inside the first core with at least an outer periphery having a lower refractive index than the first sea portion, wherein the first core includes a polymethyl methacrylate-based resin.

Provided is an optical fiber cable which allows for high-quality signal transmission in short-distance transmission. The optical fiber cable is designed for use in optical communication based on transmitting an optical beam from a light-emitting device, to a light-receiving device. The optical fiber cable has: a proximal end which is one end thereof on the side of the light-emitting device, and a distal end which is the other end thereof on the side of the light-receiving device, wherein an optical beam returning from the side of the distal end toward the side of the light-emitting device has an M.sup.2 factor of 1.7 or more; and a length of 50 m or less.

A light distribution structure 10 and a related element 100, such as a light guide, are provided. The structure 10 is preferably an optically functional layer comprising an at least one feature pattern 11, 11A established in a light-transmitting carrier by a plurality of three-dimensional optical features variable in terms of at least one of the cross-sectional profile, dimensions, periodicity, orientation and disposition thereof within the feature pattern. In some instances, the optical features are embodied as internal optical cavities 12 capable to establish the total internal reflection (TIR) function at a horizontal surface and at an essentially vertical surface thereof. A method for manufacturing the light distribution structure is further provided.

An optical element is produced by introducing a first liquid and a second liquid into respective inlets of a mold. The inlets are connected to a channel that extends to an outlet of the mold, the channel being tapered towards the outlet. The first and second liquids have different refractive indices and partially diffuse into each other inside the channel to form a multi-layer structure. The multi-layer structure is extruded through the outlet, onto a substrate. Curing the first and second liquids forms a solid optical element having a spatially varying refractive index profile in at least one dimension.

In a multicore optical fiber sensor, an absorptive material integrated into the cladding, or into a waveguide core not used for sensing, may facilitate sensing. The absorptive material is absorptive to light in a wavelength band in which the fiber sensor is configured to operate. Coating such a fiber sensor with a material whose refractive index is smaller than that of the cladding may be done with reduced signal mixing.

The glass-based THz optical waveguides (10) disclosed herein are used to guide optical signals having a THz frequency in the range from 0.1 THz to (10) THz and include a core (20) surrounded by a cladding (30). The core has a diameter D1 in the range from (30) m to 10 mm and is made of fused silica glass having a refractive index n.sub.1. The cladding is made of either a polymer or a glass or glass soot and has a refractive index n.sub.2<n.sub.1 and an outer diameter D2 in the range from 100 m to 12 mm. The THz optical waveguides can be formed using processes that are extensions of either fiber, ceramic and soot-based technologies. In an example, the THz waveguides have a dielectric loss D.sub.f<0.005 at 100 GHz.