An optical fiber having an axial direction and a cross section perpendicular to the axial direction, and a method and preform for producing such an optical fiber. The optical fiber is adapted to guide light at a wavelength , and includes a core region, an inner cladding region surrounding said core region, and at least one of a first type of feature including a void and a surrounding first silica material. The core, the inner cladding region and the first type of feature extends along said axial direction over at least a part of the length of the optical fiber. The first silica material has a first chlorine concentration of about 300 ppm or less.

Processes and systems for producing glass fibers having regions devoid of glass using submerged combustion melters, including feeding a vitrifiable feed material into a feed inlet of a melting zone of a melter vessel, and heating the vitrifiable material with at least one burner directing combustion products of an oxidant and a first fuel into the melting zone under a level of the molten material in the zone. One or more of the burners is configured to impart heat and turbulence to the molten material, producing a turbulent molten material comprising a plurality of bubbles suspended in the molten material, the bubbles comprising at least some of the combustion products, and optionally other gas species introduced by the burners. The molten material and bubbles are drawn through a bushing fluidly connected to a forehearth to produce a glass fiber comprising a plurality of interior regions substantially devoid of glass.

A multicore fiber 1 includes a plurality of cores 3 disposed at predetermined intervals and surrounded by a cladding 5. The multicore fiber 1 also includes a marker 7 formed apart from the cores 3. The refractive index of the marker 7 is different from those of the cores 3 and the cladding 5. For example, the marker 7 may be made of a material having lower refractive index than that of the cladding 5. In this case, for example, the cores 3 may be made of germanium-doped quartz. The cladding 5 may be made of pure quartz. The marker 7 may be made of fluorine-doped quartz. Further, the marker 7 may be an empty hole.

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.

An optical fiber having an axial direction and a cross section perpendicular to the axial direction, and a method and preform for producing such an optical fiber. The optical fiber is adapted to guide light at a wavelength , and includes a core region, an inner cladding region surrounding said core region, and at least one of a first type of feature including a void and a surrounding first silica material. The core, the inner cladding region and the first type of feature extends along said axial direction over at least a part of the length of the optical fiber. The first silica material has a first chlorine concentration of about 300 ppm or less.

A hollow core photonic crystal fiber (PCF) including an outer cladding region and seven hollow tubes surrounded by the outer cladding region. Each of the hollow tubes is fused to the outer cladding to form a ring defining an inner cladding region and a hollow core region surrounded by the inner cladding region. The hollow tubes are not touching each other but are arranged with distance to adjacent hollow tubes. The hollow tubes each have an average outer diameter d2 and an average inner diameter d1, wherein d1/d2 is equal to or larger than about 0.8, such as equal to or larger than about 0.85, such as equal to or larger than about 0.9. Also, a laser system.

A preform for optical fiber made of a quartz glass sintered body which is made from quartz glass powder as a main raw material, in which at least a portion of the quartz glass sintered body is an opaque body, the opaque body has a visible light transmittance of 90% or less at a length of 5 mm or less in one direction, and the opaque body has a bulk density of 2.1 g/cm.sup.3 or more, or the opaque body has a visible light transmittance of 90% or less at a length of 5 mm or less in one direction, and the opaque body has an open porosity of 3.5% or less.

A method of manufacturing a hollow core optical fiber including a vapor deposition step comprising vapor depositing a silica soot coating from one or more source materials over an outer surface of a cladding substrate tube of a workpiece that further includes capillary tubes disposed within a cavity of the cladding substrate tube. The compositions of the capillary tubes, the cladding substrate tube, and the silica soot coating can be manipulated with one or more viscosity-raising dopants or one or more viscosity-lowering dopants, or neither, to achieve a desired compositional profile of a hollow core optical fiber preform with a cladding consolidated from the silica soot coating of the workpiece. The desired composition profile results in a viscosity profile that prevents the capillary tubes from contacting each other during a drawing step performed upon the hollow core optical fiber preform.

An optical fiber may include a cladding structure extending along a fiber length providing a hollow interior fiber region and one or more sets of anti-resonant (AR) elements formed as walled structures with walls extending along the fiber length. The one or more sets of AR elements may be distributed around an interior wall of the cladding structure and, configured to guide light along the fiber length in a central portion of the hollow interior fiber region based on optical anti-resonance. At least one of the one or more sets of AR elements may comprise a first AR element, two or more support structures disposed on an inner surface of the first AR element, and a second AR element disposed on at least one of the two or more support structures.

A hollow-core optical fiber may include a substrate having a tubular shape and an inner surface surrounding a central longitudinal axis of the hollow-core optical fiber; a hollow core extending through the substrate along the central longitudinal axis of the hollow-core optical fiber; and a plurality of cladding elements positioned between the central longitudinal axis of the hollow-core optical fiber and the substrate. Each of the plurality of cladding elements may extend in a direction parallel to the central longitudinal axis of the hollow-core optical fiber. Each of the plurality of cladding elements may include a wound glass sheet configured as a spiral, and each of the plurality of cladding elements may contact an interior surface of the substrate.