A technique for fabricating a hollow core optical fiber with a controllable core region (in terms of diameter) is based upon regulating conditions (gas flow, volume, and/or temperature) within the hollow core region during the fiber draw process. The introduction of a gas, or any change in volume or temperature of the hollow core region, allows for the diameter of the hollow core region to self-regulate as a multistructured core rod (MCR) is drawn down into the final hollow core optical fiber structure. This self-regulation provides a core region having a diameter that selected and then stabilized for the duration of the draw process. The inventive process is also useful in controlling the diameter of any selected hollow region of an MCR including, but not limited to, shunts and corner capillaries disposed around the core region.

An optical fiber manufacturing method includes setting a first holding member and a rod inside a glass pipe, the first holding member made of glass and having plural holes formed, so that the rod is supported by the first holding member; filling glass particles between the rod and a glass pipe inner wall; holding the rod such that the rod and the filled glass particles are enclosed by the glass pipe inner wall and the first and second holding members, and sealing one end of the glass pipe and manufacturing an intermediate; and manufacturing an optical fiber from the intermediate, wherein a bulk density of the first and second holding members is set with reference to a bulk density of a filling portion made from the glass particles, and the predetermined range is determined according to a core diameter permissible variation range in its longitudinal direction.

A hollow core photonic crystal fiber (PCF) comprising an outer cladding region and 7 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 is disclosed.

The invention relates to the production of an anti-resonant hollow-core fiber consisting of a capillary blank and a sleeve tube. The capillary blank comprises an external capillary and a nested internal capillary, and is stretched to a maximum external diameter ODARE_cap and a maximum wall thickness WTARE_caP. The blank is mounted on the inside of the sleeve tube. In order to retain the advantages of the pre-produced capillary blank with respect to ease of assembly and precision, while keeping the associated drawbacks owing to ovality low and predictable, it is proposed that the geometric internal diameter and external diameter of the external capillary and of the internal capillary, as well as ODARE_cap and WTARE_caP, are aligned in relation to one another in such a way that the ARE-external capillary of the capillary blank has a degree of ovality of less than 1.025.

Methods are known for producing an anti-resonant hollow-core fiber which has a hollow core extending along a fiber longitudinal axis and an inner jacket region that surrounds the hollow core, said jacket region comprising multiple anti-resonant elements. The known methods have the steps of: providing a cladding tube that has a cladding tube inner bore and a cladding tube longitudinal axis along which a cladding tube wall extends that is delimited by an interior and an exterior; providing a number of tubular anti-resonant element preforms; arranging the anti-resonant element preforms at target positions of the interior of the cladding tube wall, thereby forming a primary preform which has a hollow core region and an inner jacket region; further processing the primary preform in order to form a secondary preform, including an elongation process; and drawing the secondary preform in order to form the hollow-core fiber. The aim of the invention is to achieve a high degree of precision and an exact positioning of the anti-resonant elements in a sufficiently stable and reproducible manner on the basis of the aforementioned methods. This is achieved in that after the primary preform is elongated, at least some of the formerly tubular anti-resonant element preforms of the primary preform have an oval outer cross-sectional shape with a longest cross-sectional axis A.sub.L and a shortest cross-sectional axis A.sub.K, wherein the ratio A.sub.L/A.sub.K of the length of the axes ranges from 1.01 to 1.27, and the shortest cross-sectional axis A.sub.K runs in a radial direction when viewed from the cladding tube longitudinal axis.

A method for producing a preform of an anti-resonant hollow-core fiber, which has a hollow core extending along a fiber longitudinal axis, and a cladding region surrounding the hollow core and includes at least one anti-resonance element. The method includes (a) providing a cladding tube having a cladding tube inner surface and a cladding tube outer surface, at least one anti-resonance element preform being arranged at the cladding tube inner surface, (b) providing an overlay tube including an overlay tube inner surface, the overlay tube having an inner diameter larger than an outer diameter of the cladding tube, (c) arranging the cladding tube inside the overlay tube, so that the overlay tube inner surface surrounds the cladding tube outer surface, and (d) adding the overlay tube to the cladding tube, so that the overlay tube inner surface connects to the cladding tube outer surface.

The invention relates to microstructured optical fibers that are drawn through hollow channels and have a core region, which extends along a fiber longitudinal axis, and a jacket region surrounding the core region. The aim of the invention is to reduce a damping increase due to corrosion and to reduce the emission of chlorine on the basis of the microstructured optical fibers. This is achieved in that at least some of the hollow channels are delimited by a wall material made of synthetic quartz glass which has a chlorine concentration of less than 300 wt. ppm and oxygen deficiency centers in a concentration of at least 21015 cm-3.

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 method for producing a preform of an anti-resonant hollow-core fiber, comprising the method steps of a) providing a cladding tube, which has a cladding tube inner bore and a cladding tube longitudinal axis, along which a cladding tube wall extends, which is limited by an inner side and an outer side b) preparing a number of anti-resonance element preforms, which consist of several nested tubular structural elements, comprising an ARE outer tube and an ARE inner tube inserted therein, wherein the structural elements have a structural element longitudinal axis, c) arranging the anti-resonance element preforms on the inner side of the cladding tube wall, and d) thermal fixing of the anti-resonance element preforms to the cladding tube wall by means of heat input.

The invention relates to an anti-resonance ele-ment preform for producing an anti-resonant hollow-core fiber, in an axial top view comprising a circular first cir-cle element with a first circle radius and a circular arc-shaped first circular arc element with a first circular arc radius. Furthermore, the invention relates to a method for producing an anti resonance element preform, a preform for producing an anti-resonant hollow-core fiber comprising at least one anti-resonance element preform and an anti-resonant hol-low-core fiber. According to the invention, it is provided that the first circle element and the first circular arc element are connected to one another at two contact points.