An optical fiber having a coating that includes a photoreactive marking compound is described. The photoreactive marking compound has two states that differ in the intensity and/or wavelength of fluorescence. Exposure of the photoreactive marking compound to electromagnetic radiation induces a transformation of the photoreactive marking compound from one state to the other state. The difference in fluorescence between the two states provides a detectable contrast that can be used to mark the optical fiber. A pattern of marks can be customized to different optical fibers to provide unambiguous identification of individual fibers. The coating may also include a pigment, where either or both of the pigment and photoreactive marking compound may function as a marker for identifying the optical fiber. The method extends generally to marking of films, coatings, and articles made of polymers or plastics.

An optical fiber having a coating that includes a photoreactive marking compound is described. The photoreactive marking compound has two states that differ in the intensity and/or wavelength of fluorescence. Exposure of the photoreactive marking compound to electromagnetic radiation induces a transformation of the photoreactive marking compound from one state to the other state. The difference in fluorescence between the two states provides a detectable contrast that can be used to mark the optical fiber. A pattern of marks can be customized to different optical fibers to provide unambiguous identification of individual fibers. The coating may also include a pigment, where either or both of the pigment and photoreactive marking compound may function as a marker for identifying the optical fiber. The method extends generally to marking of films, coatings, and articles made of polymers or plastics.

A glass composition for glass fiber includes SiO.sub.2 in the range of 52.0% by mass or more and 56.0% by mass or less; B.sub.2O.sub.3 in the range of 21.0% by mass or more and 24.5% by mass or less; Al.sub.2O.sub.3 in the range of 9.5% by mass or more and 13.0% by mass or less; MgO in the range of 0% by mass or more and less than 1.0% by mass; CaO in the range of 0.5% by mass or more and 5.5% by mass or less; SrO in the range of 0.5% by mass or more and 6.0% by mass or less; and TiO.sub.2 in the range of 0.1% by mass or more and 3.0% by mass or less; and includes F.sub.2 and Cl.sub.2 in the range of 0.1% by mass or more and 2.0% by mass or less in total, with respect to the total amount.

An optical fiber according to an embodiment includes a core and a cladding. The average value n1_ave of the refractive index of the core, the minimum value nc_min of the refractive index of the cladding, and the refractive index n0 of pure silica glass satisfy relationships of n1_ave>nc_min and nc_min<n0. The cladding contains fluorine. The fluorine concentration in the cladding is adjusted to be minimum in the outermost portion of the cladding including the outer peripheral surface of the cladding.

The present invention relates to a method of manufacturing an optical fiber preform for obtaining an optical fiber with low transmission loss. A core preform included in the optical fiber preform comprises three or more core portions, which are each produced by a rod-in-collapse method, and in which both their alkali metal element concentration and chlorine concentration are independently controlled. In two or more manufacturing steps of the manufacturing steps for each of the three or more core portions, an alkali metal element is added. As a result, the mean alkali metal element concentration in the whole core preform is controlled to 7 atomic ppm or more and 70 atomic ppm or less.

The technology of this application relates to the field of communication technologies, and an optical fiber raw material composition, an optical fiber, and an optical fiber product. The optical fiber raw material composition includes components of the following molar percentages: AlF.sub.3 10%-50%, BaF.sub.2 3%-20%, CaF.sub.2 3%-20%, YF.sub.3 1%-15%, SrF.sub.2 3%-20%, MgF.sub.2 3%-20%, and TeO.sub.2 1%-35%. The optical fiber prepared by using the optical fiber raw material composition provided in this disclosure can be used in aspects such as a mid-infrared band transmission optical fiber, an optical fiber amplifier, a fiber laser, and an optical fiber sensor.

The optical fibers disclosed is a single mode optical fiber comprising a core region and a cladding region surrounding and directly adjacent to the core region. The core region can have a radius r.sub.1 in a range from 3 μm to 7 μm and a relative refractive index profile Δ.sub.1 having a maximum relative refractive index Δ.sub.1max in the range from 0.25% to 0.50%. The cladding region can include a first outer cladding region and a second outer cladding region surrounding and directly adjacent to the first outer cladding region. The first outer cladding region can have a radius r.sub.4a. The second outer cladding region can have a radius r.sub.4b less than or equal to 45 μm and comprising silica based glass doped with titania.

A borate glass includes from 25.0 mol % to 70.0 mol % B.sub.2O.sub.3; from 0.0 mol % to 10.0 mol % SiO.sub.2; from 0.0 mol % to 15.0 mol % Al.sub.2O.sub.3; from 3.0 mol % to 15.0 mol % Nb.sub.2O.sub.5; from 0.0 mol % to 12.0 mol % alkali metal oxides; from 0.0 mol % to 5.0 mol % ZnO; from 0.0 mol % to 8.0 mol % ZrO.sub.2; from 0.0 mol % to 15.0 mol % TiO.sub.2; less than 0.5 mol % Bi.sub.2O.sub.3; and less than 0.5 mol % P.sub.2O.sub.5. The optical borate glass includes a sum of B.sub.2O.sub.3+Al.sub.2O.sub.3+SiO.sub.2 from 35.0 mol % to 76.0 mol %, a sum of CaO+MgO from 0.0 mol % to 35.5 mol %. The borate glass has a refractive index, measured at 587.6 nm, of greater than 1.70, a density of less than 4.50 g/cm.sup.3, and an Abbe number, V.sub.D, from 20.0 to 47.0.

An optical system comprising: an optical assembly having a first optical surface and a rear optical surface, said optical assembly comprising at least three optical elements; an optical fiber comprising a core portion with a mode field diameter (MFD) expanded region optically coupled to the rear optical surface of the optical assembly, the optical fiber comprising a core region doped with chlorine in a concentration greater than 0.5 wt %, wherein the MFD expanded region is less than 5 cm in length, and has MFD at the fiber end coupled to the optical assembly that is a least 20% greater than the MFD at other end of the optical fiber; an optical signal source coupled to first optical surface of the optical assembly, such that the optical signal provided by the optical signal source is routed along an optical path formed by the optical assembly to the mode field diameter expanded region of said optical fiber.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50° C., preferably 50° C.<T.sub.h<250° C.