Methods for producing a hollow-core fiber and for producing a preform for a hollow-core fiber

A method for producing a preform for an anti-resonant hollow-core fiber having a hollow core extending along a longitudinal axis of the hollow-core fiber and an inner sheath surrounding the hollow core, which sheath includes a plurality of anti-resonance elements, the method comprising the steps of:

• (a) providing a cladding tube having an inner bore and a longitudinal axis, along which a cladding tube wall delimited by an inner side and an outer side extends;
• (b) providing a plurality of anti-resonance element preforms;
• (c) arranging the anti-resonance element preforms at desired positions on the inner side of the cladding tube wall to form a primary preform for the hollow-core fiber by inserting a positioning template having holding elements into the inner bore of the cladding tube so that the holding elements position the anti-resonance element preforms at the desired positions;
• and
• (d) optionally further processing the primary preform into a secondary preform for the hollow-core fiber, wherein the further processing includes a single or repeated performance of one or more of the following hot-forming processes:
• (i) elongating the primary preform,
• (ii) collapsing the primary preform,
• (iii) collapsing and simultaneously elongating the primary preform,
• (iv) collapsing additional sheath material,
• (v) collapsing additional sheath material and subsequently elongating the primary preform,
• (vi) collapsing additional sheath material and simultaneously elongating the primary preform, wherein the positioning template has at least one latch which interacts with a counterpart latch in the cladding tube wall to form a force-fitting and/or positive-locking connection.

A method for producing an anti-resonant hollow-core fiber having a hollow core extending along a longitudinal axis of the hollow-core fiber and an inner sheath surrounding the hollow core, which sheath includes a plurality of anti-resonance elements, the method comprising the steps of:

• (a) providing a cladding tube having an inner bore, a pair of end faces, and a longitudinal axis, along which a cladding tube wall delimited by an inner side and an outer side extends;
• (b) providing a plurality of tubular anti-resonance element preforms with an outer tube surface;
• (c) arranging the anti-resonance element preforms at desired positions on the inner side of the cladding tube wall to form a primary preform for the hollow-core fiber by inserting a positioning template having holding elements into the inner bore of the cladding tube so that the holding elements position the anti-resonance element preforms at the desired positions, wherein the positioning template has a shaft that projects into the inner bore of the cladding tube and has a plurality of holding arms pointing radially outwards, each holding element has at least two points of contact with the outer tube surface of the anti-resonance element preform that is to be held, and the positioning template is used in the region of at least one of the end faces;
• and
• (d) elongating the primary preform to form the hollow-core fiber, or further processing the primary preform into a secondary preform from which the hollow-core fiber is drawn, wherein the further processing includes a single or repeated performance of one or more of the following hot-forming processes:
• (i) elongating the primary preform,
• (ii) collapsing the primary preform,
• (iii) collapsing and simultaneously elongating the primary preform,
• (iv) collapsing additional sheath material,
• (v) collapsing additional sheath material and subsequently elongating the primary preform,
• (vi) collapsing additional sheath material and simultaneously elongating the primary preform, wherein the positioning template has at least one latch which interacts with a counterpart latch in the cladding tube wall to form a force-fitting and/or positive-locking connection.