A preform manufacturing method of the present invention has a hole forming step of forming a plurality of holes in a glass body to produce a glass pipe, and a heating integration step of heating the glass pipe with core rods including core portions being inserted in the respective holes, thereby to implement integration of the core rods and the glass pipe. In the hole forming step, a peripheral hole out of the holes to be formed in the glass body is formed at a position determined in consideration of positional variation of the core portion before and after the integration.

An anti-resonance element preform for producing an anti-resonant hollow-core fiber, comprising a first longitudinal axis, an ARE outer element designed in a circular arc-like manner, and an ARE inner element, wherein the ARE outer element and the ARE inner element are connected to one another along two connecting lines, which are arranged essentially in parallel to the first longitudinal axis. It is provided that the ARE outer element has an inner space, which is at least partially limited by an ARE outer wall and into which the ARE inner element, designed in a circular arc-like manner, protrudes at least partially.

A method for producing substrate tubes of quartz glass includes continuously supplying a hollow cylinder of quartz glass to a heating zone, softening the hollow cylinder zonewise in the heating zone, and drawing off a tubular strand from the softened portion. The hollow cylinder has an outer diameter C.sub.a, an inner diameter C.sub.i and an inner bore. The tubular strand has an outer diameter T.sub.a and an inner diameter T.sub.i. The following parameters are applicable to the hollow cylinder and the tubular strand: C.sub.a>180 mm, C.sub.r>3 with C.sub.r=C.sub.a/C.sub.i, T.sub.r<1.6 with T.sub.r=T.sub.a/T.sub.i and C.sub.i/T.sub.i<2.5. The blow pressure in an inner bore is adjusted to a value in the range of 4 to 10 mbar. Substrate tubes, obtained by cutting the tubular strand to the desired length, serve as semi-finished products for the manufacture of preforms for optical fibers.

A method for manufacturing an optical fiber. The method includes a drawing step of drawing a glass base material while feeding the glass base material to a heating furnace, to manufacture an optical fiber. The glass base material includes a core rod and a cladding tube into which the core rod is inserted. A support tube is bonded to an upper end of the cladding tube, to communicate with a gap between the core rod and the cladding tube. The drawing step includes bringing the gap and an internal space of the support tube into a state of being lower in pressure than atmospheric pressure.

The present application provides a method for recovering and reusing quartz powder waste in an out-of-tube deposition process. The quartz powder recovered by this method meets the optical performance requirements for the preparation of an optical fiber preform rod having a functional cladding, reduces the production cost, and solves the problem of environmental pollution. Also, the present invention further provides a method for preparing an optical fiber preform rod by using the recovered quartz powder. The method reduces and simplifies the difficulty in the manufacturing of a core rod of a preform rod, and simplifies the difficulty in the manufacturing of some preform rods of special structures.

An anti-resonance element preform for producing an anti-resonant hollow-core fiber, comprising a first longitudinal axis, an ARE outer element designed in a circular arc-like manner, and an ARE inner element, wherein the ARE outer element and the ARE inner element are connected to one another along two connecting lines, which are arranged essentially in parallel to the first longitudinal axis. It is provided that the ARE outer element has an inner space, which is at least partially limited by an ARE outer wall and into which the ARE inner element, designed in a circular arc-like manner, protrudes at least partially.

Anti-resonance element preform for producing an anti-resonant hollow-core fiber includes a first longitudinal axis, an ARE outer element designed in a circular arc-like manner, and an ARE inner element. The ARE outer element and the ARE inner element are connected to one another along two connecting lines, which are arranged essentially in parallel to the first longitudinal axis. The ARE outer element has an inner space, which is at least partially limited by an ARE outer wall and into which the ARE inner element, designed in a circular arc-like manner, protrudes at least partially.

A method of processing glass filament comprises: providing a length of glass filament from which a portion is to be separated from the remainder of the filament; directing energy onto the filament in order to cause a decrease in a width of the filament at a desired location for separation of the portion; and causing relative longitudinal movement between the portion and the remainder of the filament to separate the portion from the remainder of the filament at the desired location.

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.