A plastic scintillating fiber according to an aspect of the present invention includes: an outermost peripheral layer containing a fluorescent substance that emits scintillation light when it is irradiated with at least one of neutron radiation and heavy-particle radiation; a core disposed inside the outermost peripheral layer and containing at least one type of fluorescent substance that absorbs the scintillation light and wavelength-converts the absorbed light into light having a wavelength longer than that of the absorbed light; and a cladding layer covering an outer peripheral surface of the core and having a refractive index lower than that of the core. A wavelength shifting fiber including the core and the cladding layer, and the outermost peripheral layer covering an outer peripheral surface of the wavelength shifting fiber are integrally formed.

An optical fiber configured to improve the pump conversion efficiency of an L-band fiber amplifier which uses the multimode pump source. By directly absorbing multimode light including 915 nm, an active fiber core region co-doped with both erbium and ytterbium can provide gain to the L-band signals via stimulated emission. The unwanted C-band amplified spontaneous emission (ASE) light generate from this active fiber core region can be absorbed by another active fiber core region doped with erbium, then provides additional gain to the L-band signals. Active regions and cladding can be configured to match a given spatial mode of the optical signal. Signal-pump combiners with end-coupling or side coupling can be used.

The present disclosure provides a universal optical fiber (100). The universal optical fiber (100) includes a core (102) extended from a central longitudinal axis (110) to a first radius r.sub.1. In addition, the universal optical fiber (100) includes a buffer clad (104) region extending from the first radius r.sub.1 to a second radius r.sub.2. Further, the universal optical fiber (100) includes a trench region (106) extending from the second radius r.sub.2 to a third radius r.sub.3. Furthermore, the universal optical fiber (100) includes a cladding (108) extending from the third radius to a fourth radius r.sub.4. Moreover, the core (102), the buffer clad region (104), the trench region (106) and the cladding (108) are concentrically arranged.

An optical fiber has a structure uniform in a longitudinal direction. This optical fiber includes a core and a cladding that surrounds the core in a cross-section perpendicular to the longitudinal direction. A refractive index of the cladding is lower than a refractive index of the core. The cladding has, in the cross-section, an inner cladding layer including an inner circumferential surface of the cladding, and an outer cladding layer including an outer circumferential surface of the cladding. The inner cladding layer contains fluorine. The inner and outer cladding layers have refractive indexes different from each other. The outer cladding layer includes a local maximum portion where a residual stress, which is a tensile stress, becomes local maximum. A radial distance between the local maximum portion and an inner circumferential surface of the outer cladding layer is 10 μm or less.

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.

The present disclosure relates to an optical fiber having a structure that has a low transmission loss and can be produced with high productivity. An optical fiber according to an embodiment includes a core and a cladding. The core is comprised of silica glass to which bromine is added, and the cladding has a refractive index lower than a maximum refractive index of the core. The core has compressive stress.

An array-type polarization-maintaining multi-core fiber includes a main outer cladding, fiber core units, and stress units. The fiber core units and the stress units are arranged to form a unit array including one central unit and any unit in the unit array being equidistantly arranged from adjacent units thereof. Provided is at least one pair of stress units, each pair of stress units being arranged symmetrical about one fiber core unit to form a polarization-maintaining fiber core unit. The fiber core units each include a fiber core and an inner cladding surrounding a core layer. A portion outside the fiber core units and the stress units is the main outer cladding. The fiber can greatly enhance spectral efficiency of an optical transmission system, and improve fiber communication capacity.

A method of processing by controlling one or more beam characteristics of an optical beam may include: launching the optical beam into a first length of fiber having a first refractive-index profile (RIP); coupling the optical beam from the first length of fiber into a second length of fiber having a second RIP and one or more confinement regions; modifying the one or more beam characteristics of the optical beam in the first length of fiber, in the second length of fiber, or in the first and second lengths of fiber; confining the modified one or more beam characteristics of the optical beam within the one or more confinement regions of the second length of fiber; and/or generating an output beam, having the modified one or more beam characteristics of the optical beam, from the second length of fiber. The first RIP may differ from the second RIP.

The invention relates to an optical fiber 1 comprising a core 2 and a cladding 3 surrounding the core 2 and having an outer diameter of 125 μm, the optical fiber 1 comprising a cured primary coating 4 directly surrounding the cladding 3 and a cured secondary coating 5 directly surrounding the cured primary coating 4, said cured primary coating 4 having a thickness t.sub.1 between 10 and 18 μm and an in-situ tensile modulus Emod.sub.1 between 0.10 and 0.18 MPa, said cured secondary coating 5 having a thickness t.sub.2 between 10 microns and 18 microns and an in-situ tensile modulus Emod.sub.2 between 700 and 1200 MPa, wherein said first and second thicknesses and said first and second in-situ tensile moduli satisfy the following equation:
4%<(t.sub.1×t.sub.2×E mod.sub.1×E mod.sub.2.sup.3)/(t.sub.1_norm×t.sub.2_norm×E mod.sub.1_norm×E mod.sub.2_norm.sup.3)<50%.

An optical fiber can include a core comprising silica co-doped with nitrogen and chlorine and an outer cladding surrounding the core. In some aspects, the core can be characterized by an annealing temperature of less than or equal to about 1150° C. and/or the core can include a relative refractive index Δ.sub.core in a range of from about 0.15% to about 0.45%.