A method of producing a photonic crystal fiber (PCF) preform, the method including measuring a wall thickness of each of a plurality of preform capillaries along at least a portion of its periphery at one or more axial positions; selecting a number of preform capillaries from the plurality of preform capillaries at least based on a thickness criterion; and placing the selected preform capillaries in a tube to form a PCF preform having at least one ring arrangement including the selected preform capillaries, wherein the selected preform capillaries are oriented such that the portion of each of the selected preform capillaries, within which the measured wall thickness varies from a nominal wall thickness by no more than a maximum thickness variation, faces a longitudinal axis of the tube, the tube being substantially symmetrical about the longitudinal axis.

The disclosure relates to an integrated hollow-core optical fiber preform, an optical fiber and a fabrication method thereof. Initially, holes are drilled to obtain a preform which is then subjected to a drawing process with gas fed into the drilled holes for pressurization control, resulting in an optical fiber with an anti-resonant ring structure. This method employs mechanical drilling to achieve precise positioning of the azimuth angle of the anti-resonant unit, ensuring axial uniformity and preventing any azimuthal shift during the drawing process. Furthermore, no additional materials are introduced for positioning the anti-resonant unit, thereby minimizing contamination from impurities and enhancing properties such as attenuation and strength of the optical fiber. Additionally, gas pressure control expands the anti-resonant unit during the drawing process, reducing its wall thickness and consequently lowering attenuation in this hollow-core optical fiber.

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.

A method for producing an anti-resonant hollow-core fiber having an outer diameter of less than 500 mm, having the steps of: providing a sheath tube, which comprises a sheath tube inner bore and a sheath tube longitudinal axis along which a sheath tube wall extends, the sheath tube wall being delimited by a sheath tube inner face and a sheath tube outer face; preparing a number of anti-resonance units, each comprising an ARU outer tube; inserting at least parts of the anti-resonance units into the sheath tube inner bore; and creating a hollow-core assembly comprising the sheath tube and the anti-resonance units by at least partially connecting the anti-resonance units to the sheath tube inner face; preparing a jacket tube, which comprises a jacket tube inner bore and a jacket tube longitudinal axis along which a jacket tube wall extends.

A method includes heating a hollow-core preform comprising an outer tube and an inner tube. The outer tube includes an inner radius r.sub.ocp and an outer radius R.sub.ocp. The inner tube includes an inner radius r.sub.cp and an outer radius R.sub.cp. The method further includes drawing a hollow-core optical fiber from the hollow-core preform at a draw tension T.sub.g in grams, thereby elongating the outer tube into an outer cladding of the hollow-core optical fiber and the inner tube to a capillary of the hollow-core optical fiber. The draw tension T.sub.g and/or a differential capillary pressure p.sub.c are selected at least in part based on a non-dimensional parameter

[00001]$X_1=\frac{3\left(R_{\mathrm{ocp}}^2-r_{\mathrm{ocp}}^2\right)R_{\mathrm{cp}}\left(p_c{r}_{\mathrm{cp}}-2{}_c\right)}{4{\mathrm{Tr}}_{\mathrm{cp}}\left(R_{\mathrm{cp}}-r_{\mathrm{cp}}\right)},$

where T is the draw tension in dynes and T=981T.sub.g, p.sub.c is in dynes/cm.sup.2, .sub.c in dyne/cm is a surface energy of a glass material forming the inner tube, and 0.5X.sub.10.75.

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 dl, wherein d1/d2 is equal to or larger than about 0.8. Also, a laser system.

A method of manufacturing a preform for a hollow core optical fiber including: a redraw step including: (1) heating a workpiece including: (a) a cladding tube including (i) a cladding interior, (ii) a cladding outer surface at a cladding outer radius, and (iii) a cladding thickness; and (b) a capillary disposed within the cladding interior, the capillary including (i) a capillary interior, (ii) a capillary outer radius, (iii) a capillary inner radius, (iv) a capillary thickness, and (v) a capillary aspect ratio corresponding to the ratio of the capillary inner radius to the capillary outer radius, and (2) manipulating a gas pressure within the capillary interior or the cladding interior, via a source of gas or a vacuum, to vary the aspect ratio of the capillary. Both the cladding outer radius and the cladding thickness change during the redraw step by less than 20%.

Methods and systems for producing a hollow-core optical fiber preform and/or components thereof are described herein. In some embodiments, the method may include providing a precursor material, extruding the precursor material through a die assembly to a shaped body, and forming a hollow-core optical fiber preform or a component thereof from the shaped body. In some embodiments, providing the precursor material may include one of: heating the precursor material such that a viscosity of the precursor material reaches about 10.sup.3 to about 10.sup.7 poise, or forming a paste comprising a glass powder and a binder. In some embodiments, the hollow-core optical fiber preform may include an outer tube. In some embodiments, the hollow-core optical fiber preform may further include one of an inner tube coupled to the outer tube, or a spiral coupled to the outer tube.

An anti-resonant hollow core optical fiber including: (a) a cladding tube including a cladding inner surface at a cladding inner radius from a fiber longitudinal axis, the cladding inner radius varying azimuthally around the fiber longitudinal axis, the cladding inner surface defining recesses, and each of the recesses merging with adjacent recesses so that the cladding inner surface forms peaks pointing inward toward the fiber longitudinal axis; (b) a plurality of primary capillaries, each of the plurality of primary capillaries (i) disposed within a different one of the recesses and contacting the cladding inner surface and (ii) contacting or merging with an adjacent primary capillary in both azimuthal directions around the fiber longitudinal axis; and (c) an effective core region tangential to the plurality of primary capillaries at a core radius from the fiber longitudinal axis, the plurality of primary capillaries disposed radially outward of the effective core region.

A furnace assembly for manufacturing a hollow-core optical fiber from a hollow-core fiber preform includes a furnace having a body defining a body cavity extending along a longitudinal axis between a preform input port and a hollow-core fiber output port. The body cavity is configured to locate the hollow-core optical fiber preform and a process gas. At least one primary heating element is proximate a necking region of the hollow-core optical fiber preform and configured to maintain the necking region at a draw temperature, the draw temperature sufficient to soften the necking region. The process gas occupies a flow field surrounding a cladding outer surface. The flow field extends from the necking region to the preform input port and the process gas has a flow with an average Grashof number less than 1.610.sup.4 in the flow field.