In embodiments, a mode selective optical fiber coupler may include a first propagation waveguide and a second propagation waveguide joined along a coupling length L. The first propagation waveguide and the second propagation waveguide may be tapered from an input face and an output face of the coupler to a midpoint of the coupler. An LP01 mode of an optical signal with a wavelength of 800-950 nm coupled into the first propagation waveguide propagates through the first propagation waveguide and is emitted from the first propagation waveguide. An LP01 loss of the coupler at the output face is less than 1.0 dB. An LP11 mode of the optical signal coupled into the first propagation waveguide is cross-coupled to the second propagation waveguide and is emitted from the second propagation waveguide. An LP11 loss of the coupler at the output face is less than 1.5 dB.

A high-bandwidth bend-insensitive multimode optical fiber includes a core and a cladding. A refractive index profile of the core has a parabola shape and a distribution index thereof is . The core has a radius of 23-27 m. A maximum relative refractive index difference of a central position of the core is 0.9%-1.2%. The core is a germanium-fluorine co-doped silicon dioxide glass layer. The central position of the core has a minimum amount of fluorine doped, and a mass percentage of fluorine content is C.sub.F,min. A mass percentage of fluorine content of the core changes with the radius according to a function. The cladding successively comprises an inner cladding, a trench cladding, and an outer cladding from inside to outside. The optical fiber reduces bandwidth-wavelength sensitivity while improving bandwidth performance; is compatible with existing OM3/OM4 multimode optical fibers, and support wavelength-division multiplexing technology in a wavelength range of 850-950 nm.

A high-bandwidth bend-insensitive multimode optical fiber includes a core and a cladding. A refractive index profile of the core has a parabola shape and a distribution index thereof is . The core has a radius of 23-27 m. A maximum relative refractive index difference of a central position of the core is 0.9%-1.2%. The core is a germanium-fluorine co-doped silicon dioxide glass layer. The central position of the core has a minimum amount of fluorine doped, and a mass percentage of fluorine content is C.sub.F,min. A mass percentage of fluorine content of the core changes with the radius according to a function. The cladding successively comprises an inner cladding, a trench cladding, and an outer cladding from inside to outside. The optical fiber reduces bandwidth-wavelength sensitivity while improving bandwidth performance; is compatible with existing OM3/OM4 multimode optical fibers, and support wavelength-division multiplexing technology in a wavelength range of 850-950 nm.

Apparatus (10) for laser processing a material (11), which apparatus comprises a laser (1) and a beam delivery cable (2), wherein: the laser (1) is connected to the beam delivery cable (2); the beam delivery cable (2) is configured to transmit laser radiation (13) emitted from the laser (1), and the laser radiation (13) is defined by a beam parameter product (4); and the apparatus (10) is characterized in that: the apparatus (10) includes at least one squeezing mechanism (5) comprising a periodic surface (6) defined by a pitch (7); a length (8) of optical fibre (9) that forms part of the laser (1) and/or the beam delivery cable (2) is located adjacent to the periodic surface (6); and the squeezing mechanism (5) is configured to squeeze the periodic surface (6) and the length (8) of the optical fibre (9) together with a squeezing force (12); whereby the beam parameter product (4) is able to be varied by adjusting the squeezing force (12).

The invention relates to a method for producing a lighting device, comprising the steps of: (a) weaving a fabric comprising warp and weft yarns that form the core of the fabric, weft- or warp-woven optical fibres within the fabric, said optical fibres being formed by a core and a sheath surrounding the core, and binding yarns forming part of the warp or weft yarns, maintaining the optical fibres inside the fabric; (b) treating the surface of the fabric comprising the binding yarns in order to form surface modifications on the surface of the fibres; (c) removing the optical fibres fully from the treated textile; and (d) inserting a portion of the fibres, grouped together in a bundle, into a translucent casing.

Application of non-uniform strain to discrete segments of a fiber grating mechanically changes the structure type of the associated device, e.g., the refractive index perturbation profile of the fiber grating is changed from uniform to phase shifted superstructured, or from chirped to superstructured. The strain may be applied with one or more deformable corrugated slides which are bonded to the fiber grating between the discrete segments. The applied strain changes the local period of fiber grating. Complex changes may be achieved via variations of corrugated slide dimensions. An LPFG may be provided with bare fiber by applying periodically longitudinal axial strain to fiber at multiple discrete segments on the fiber.

An optical fiber has a central axis. The optical fiber includes a core made of silica glass and extending along the central axis, a cladding made of silica glass and surrounding the core, the cladding extending along the central axis, and a coating layer made of resin and surrounding the cladding, the coating layer extending along the central axis. An outer diameter of the cladding varies along the central axis. A residual stress in a direction along the central axis varies along the central axis, the residual stress being averaged over the core and the cladding in a cross section perpendicular to the central axis. A deviation from an average value of the outer diameter and a deviation from an average value of the residual stress have signs opposite to each other.

A method of manufacturing an optical fiber includes heating a distal end portion of an optical fiber preform made of glass; drawing a glass fiber from the distal end portion softened by the heating; and forming a coating layer made of resin on the glass fiber to form an optical fiber. The drawing includes periodically varying a tension that is applied to the glass fiber to vary a diameter of the glass fiber and a residual stress in an axial direction of the glass fiber so as to be in phases opposite to each other along the axial direction.

An optical fiber may include a core region and a cladding region surrounding the core region. The cladding region may include an inner cladding region surrounding the core region, a depressed-index cladding region surrounding the inner cladding region, and an outer cladding region surrounding the depressed-index cladding region. The inner cladding region may include a thickness greater than or equal to 1 m. The depressed-index cladding region may include a first region and a second region, wherein a relative refractive index of the depressed-index cladding region may decrease monotonically with increasing radius in the first region, and wherein the relative refractive index of the depressed-index cladding region may be substantially constant in the second region. The optical fiber may achieve low microbend loss with large mode field diameter, while also maintaining low macrobend loss, low cable cutoff, and/or a zero dispersion wavelength between 1300 nm and 1324 nm.

In embodiments, a mode selective optical fiber coupler may include a first propagation waveguide and a second propagation waveguide joined along a coupling length L. The first propagation waveguide and the second propagation waveguide may be tapered from an input face and an output face of the coupler to a midpoint of the coupler. An LP01 mode of an optical signal with a wavelength of 800-950 nm coupled into the first propagation waveguide propagates through the first propagation waveguide and is emitted from the first propagation waveguide. An LP01 loss of the coupler at the output face is less than 1.0 dB. An LP11 mode of the optical signal coupled into the first propagation waveguide is cross-coupled to the second propagation waveguide and is emitted from the second propagation waveguide. An LP11 loss of the coupler at the output face is less than 1.5 dB.