US 12,215,048 B2
Methods for producing a hollow-core fiber and for producing a preform for a hollow-core fiber
Manuel Rosenberger, Hanau (DE); Michael Hünermann, Hanau (DE); Martin Trommer, Hanau (DE); Kay Schuster, Hanau (DE); and Steffen Weimann, Hanau (DE)
Assigned to HERAEUS QUARZGLAS GMBH & CO. KG, Hanau (DE)
Appl. No. 17/625,175
Filed by HERAEUS QUARZGLAS GMBH & CO. KG, Hanau (DE)
PCT Filed Jul. 15, 2020, PCT No. PCT/EP2020/070004
§ 371(c)(1), (2) Date Jan. 6, 2022,
PCT Pub. No. WO2021/009231, PCT Pub. Date Jan. 21, 2021.
Claims priority of application No. 19186863 (EP), filed on Jul. 17, 2019.
Prior Publication US 2022/0267193 A1, Aug. 25, 2022
Int. Cl. C03B 37/027 (2006.01); G02B 6/032 (2006.01)
CPC C03B 37/02781 (2013.01) [G02B 6/032 (2013.01); C03B 2203/16 (2013.01)] 14 Claims
OG exemplary drawing
 
14. A method for producing a preform for an anti-resonant hollow-core fiber comprising a hollow core extending along a longitudinal axis of the fiber and an inner sheath region surrounding the hollow core, which sheath region comprises several anti-resonance elements (AREs), comprising the method steps of:
(a) providing a primary preform for the hollow-core fiber which comprises at least one cladding tube having an inner bore of the cladding tube and a longitudinal axis of the cladding tube along which a cladding tube wall delimited by an inner side and an outer side extends,
(b) forming a number of precursors or preforms for AREs at desired positions of the cladding tube wall, and
(c) further processing the primary preform to form a secondary preform for the hollow-core fiber, wherein the further processing comprises a single or repeated performance of one or more of the following hot-forming processes:
(i) elongation,
(ii) collapse,
(iii) collapse and simultaneous elongation,
(iv) collapse of additional sheath material,
(v) collapse of additional sheath material and subsequent elongation,
(vi) collapse of additional sheath material and simultaneous elongation,
wherein, when performing a process in accordance with method step (c), components of the primary preform made of quartz glass and/or components made of quartz glass surrounding the primary preform are heated and softened together, wherein the quartz glass of at least one of the preform components and/or the quartz glass of at least one of the components surrounding the preform contains at least one dopant that lowers or increases the viscosity of quartz glass, and
wherein at least a portion of the precursors for AREs is present as tubular ARE preforms, which are composed of multiple nested structural elements, comprising an anti-resonance outer tube and an ARE inner tube inserted therein, and the ARE preforms include quartz glass which at a measured temperature of 1250° C. has a viscosity higher by at least 0.4 dPa·s than the quartz glass of the cladding tube.