Method for producing an Anti-resonant hollow-core fiber

Abstract

The invention relates to a method for producing an anti-resonant hollow-core fiber, wherein preforms and preform elements having larger outer and inner diameters than usual are used. The invention also relates to a primary preform and to a structural unit which are semi-finished products of the method according to the invention.

Description

[0001] 2024PF00059

[0002] 1

[0003] METHOD FOR PRODUCING AN ANTIRESONANT HOLLOW CORE FIBER

[0004] INTRODUCTION

[0005] The invention relates to a method for producing an antiresonant hollow-core fiber, which has a hollow core extending along a longitudinal fiber axis and a sheath surrounding the hollow core, comprising a number of antiresonant elements. Various preforms, having a diameter defined according to the invention, are used for the method.

[0006] BACKGROUND OF THE INVENTION AND STATE OF THE ART

[0007] Conventional solid-material single-mode optical fibers have a glass core surrounded by a cladding layer of glass with a lower refractive index. Light transmission is based on total internal reflection between the core and cladding. However, the interactions of the guided light with the solid material are associated with increased latency in data transmission and relatively low damage thresholds to high-energy radiation.

[0008] These disadvantages are avoided or reduced by hollow-core fibers, in which the core comprises an evacuated cavity filled with gas or liquid. In hollow-core fibers, the interaction of light with the glass is less than in solid-core fibers. The refractive index of the core is lower than that of the cladding, so light transmission by total internal reflection is not possible, and the light would normally escape from the core into the cladding. Depending on the physical mechanism of light transmission, hollow-core fibers are subdivided into photonic bandgap fibers and antiresonant reflection fibers.

[0009] In "photonic bandgap fibers," the hollow core is surrounded by a cladding in which small hollow channels are arranged periodically. The periodic structure of these hollow channels in the cladding causes the effect known as the "photonic bandgap," a term borrowed from semiconductor technology. This effect means that light of certain wavelengths scattered by the cladding structures interferes constructively in the central cavity due to Bragg reflection and cannot propagate transversely within the cladding.

[0010] In the embodiment of the hollow-core fiber known as antiresonant hollow-core fiber (ARHCF), the hollow core is surrounded by an inner cladding in which so-called "antiresonant elements" (AREs) are arranged. The walls of the antiresonant elements, evenly distributed around the hollow core, can act as antiresonant Fabry-Perot cavities that reflect the incident light and guide it through the fiber core. 2024PF00059

[0011] 2

[0012] This fiber technology promises low optical attenuation, a very broad transmission spectrum (also in the UV or IR wavelength range) and low latency in data transmission.

[0013] Potential applications of hollow core fibers lie in the field of data transmission, high-performance beam guidance, for example for material processing, modal filtering, and nonlinear optics, especially for supercontinuum generation, from the ultraviolet to infrared wavelength range.

[0014] One difficulty in manufacturing antiresonant hollow-core fibers is the poor scalability of their production for industrial-scale manufacturing. Antiresonant hollow-core fibers consist of sometimes extremely delicate, glass components that must be joined together and their shape—in terms of length, outer diameter, and inner diameter—must be adjustable without damage. Since the components must be subjected to high temperatures, mechanical stress, and extreme pressures for this purpose, the development of suitable process parameters for large-scale industrial production is highly desirable.

[0015] Several methods are already known in the prior art that should enable the production of antiresonant hollow core fibers on a large scale.

[0016] EP 3 323 791 A and EP 3 590 899 A each describe a variant of a so-called upward-draw process and a suitable device for it. In this process, a semi-finished product is moved upwards through a hot-forming zone while collapse, elongation, or collapse steps are applied. The upward-draw process is fundamentally the opposite of the downward-draw process, in which semi-finished products are moved downwards through a hot-forming zone. The upward direction of pull ensures better control over the hot-forming process steps.

[0017] EP 4 289 798 A relates to a process for the production of photonic crystal fibers (PCF). The process first requires the selection of capillaries based on their diameter and wall thickness. The selected capillaries are then arranged on the inside of a sheath tube. The semi-finished products thus arranged are subsequently processed into a preform using a conventional drawing process, which is then drawn into a hollow core fiber, also using a drawing process. A disadvantage of the process described in EP 4 289 798 A, besides the cumbersome selection of the capillaries, is that increased thermal and mechanical stresses act on the capillaries during the drawing process. 2024PF00059

[0018] 3

[0019] EP 4 011 840 A relates to a method for manufacturing a preform for an antiresonant hollow core fiber. The preform consists of at least one sheath tube and at least one antiresonant element preform, which is fixed to the inside of the sheath tube by means of a thermal input. A contact element between the sheath tube and the at least one antiresonant element preform is necessary to avoid the risk of damaging the antiresonant preform through the thermal input.

[0020] EP 3 766 849 A discloses a method for producing an antiresonant hollow core fiber and a primary preform for producing an antiresonant hollow core fiber. In this process, a sheath tube is collapsed onto the primary preform, resulting in a secondary preform. The primary preform has an outer diameter ranging from 20 mm to 70 mm.

[0021] EP 3 766 844 A describes a method for producing an antiresonant hollow-core fiber from a primary and a secondary preform. In this method, additional sheath material is collapsed onto the primary preform to create a secondary preform. The method is characterized by the fact that the primary preform is closed at its end face during the tensile process to prevent changes in the hollow channel dimensions during deformation, ensuring that the fiber hollow channels retain the geometry established in the preform. The secondary preform has an outer diameter ranging from 30 to 90 mm.

[0022] EP 3 766 848 A discloses a method for producing an antiresonant hollow core fiber and a preform for producing an antiresonant hollow core fiber. In this process, a large sheathing tube is collapsed onto the preform to create a primary preform. The sheathing tube has strictly defined geometric dimensions relating to its outer diameter and tube length. Furthermore, the antiresonant element preforms fixed within the sheathing tube also have strictly defined dimensions. The method has the disadvantage that the antiresonant element preforms are small. Therefore, only small angular deviations between the antiresonant element preform and the sheathing tube are possible, which complicates the process. Furthermore, attempts are being made to shield the antiresonant element preforms from thermal and mechanical influences during the hot forming process steps by using a particularly large sheathing tube.However, this has the disadvantage that particularly thick-walled casing tubes tend to crack when heated.

[0023] TASK OF INVENTION

[0024] Antiresonant hollow-core fibers, especially those with nested structural elements, have complex internal geometries, which makes their precise and reproducible manufacturing difficult. This is all the more true since even small dimensional deviations on the order of 2024PF00059 are necessary to maintain the resonance or antiresonance conditions.

[0025] 4

[0026] The operating wavelength of the light being guided is not tolerable. Deviations from the target geometry can be caused by the configuration of the fiber preform, and they can also occur due to unintended, non-scale deformations during the fiber drawing process.

[0027] Prior art processes often require the precise assembly of many elements. For example, to manufacture the antiresonant hollow core fiber described in EP 3 766 348 A, the antiresonant element preforms must be placed at strictly defined target positions.

[0028] Other methods described in the prior art place a strong emphasis on the pre-selection of the antiresonance element preforms, or use large sheathing tubes to process the antiresonance element preforms gently.

[0029] The aim of the invention is to provide a method for the cost-effective production of an antiresonant hollow core fiber, which avoids the limitations of conventional manufacturing methods.

[0030] In particular, the object of the invention is to provide a method for producing an antiresonant hollow core fiber and a preform for antiresonant hollow core fibers, with which a high precision of the structural elements and an exact positioning of the antiresonance elements in the fiber can be achieved reproducibly in a sufficiently stable manner, even on an industrial scale.

[0031] The method sought according to the invention is further intended to enable the production of hollow core fiber preforms with a larger size than the prior art, wherein the preforms are then drawn into corresponding fibers. This is intended to provide an industrially advantageous process. Currently, it is not known that hollow core fiber preforms with sizes > 20 km / preform or assembly can be produced on an industrial scale.

[0032] The inventors of the present invention have surprisingly succeeded in solving these problems by providing capillaries or other antiresonance element preforms, sheathing or casing tubes, and the resulting semi-finished products with relatively large dimensions, particularly with regard to diameter, and processing them into antiresonant hollow-core fibers in one or more steps according to the invention. 2024PF00059

[0033] 5

[0034] BRIEF DESCRIPTION OF THE INVENTION

[0035] The present invention relates to a method for producing an antiresonant hollow core fiber according to the following points:

[0036] [1] A method for producing an antiresonant hollow core fiber having a hollow core extending along a fiber longitudinal axis and a sheath surrounding the hollow core comprising several antiresonance elements, comprising the process steps of being carried out at least once: a) providing a primary preform (stack), comprising at least one sheath having an inner sheath bore and a sheath longitudinal axis along which a sheath wall bounded by an inner sheath surface and an outer sheath surface extends, and comprising antiresonance element preforms; and

[0037] a) Providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing tube wall bounded by an inner casing surface and an outer casing surface extends, and inserting the primary preform (stack) into the casing tube; and b) Performing a fiber drawing while simultaneously collapsing the casing tube, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0038] [2] A method for producing an antiresonant hollow core fiber having a hollow core extending along a fiber longitudinal axis and a sheath surrounding the hollow core comprising several antiresonance elements, comprising the process steps of being carried out at least once: a) providing a primary preform comprising at least one sheath tube having an inner sheath tube bore and a sheath tube longitudinal axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and

[0039] Further processing of the primary preform into a primary preform (cane) by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; and b) providing at least one cane having a cane bore and a cane longitudinal axis along which a 2024PF00059

[0040] 6

[0041] a) the inner shell surface and an outer shell surface of the shell tube extends, and inserting the primary preform into the shell tube; and c) performing a fiber pull while simultaneously collapsing the shell tube, characterized in that the shell tube has an outer diameter of 100 mm to 240 mm.

[0042] [3] A method for producing an antiresonant hollow core fiber having a hollow core extending along a fiber longitudinal axis and a sheathing region surrounding the hollow core, comprising several antiresonance elements, comprising the process steps of being carried out at least once: a) providing a primary preform, comprising at least one sheath having an inner bore and a longitudinal axis along which a sheath wall bounded by an inner surface and an outer surface extends, and comprising antiresonance element preforms; and optionally

[0043] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation, or iii) collapse and subsequent elongation; and b) providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing wall bounded by an inner and outer surface extends, and inserting the primary preform or primary preform into the casing tube by i) collapse; or ii) collapse and simultaneous elongation, or iii) collapse and subsequent elongation; forming a final preform characterized by an outer diameter of 28 mm to 60 mm; and c) performing a fiber drawing, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0044] [4] A method for producing an antiresonant hollow core fiber having a hollow core extending along a fiber longitudinal axis and a sheath surrounding the hollow core comprising several antiresonant elements, comprising the process steps performed at least once: a) providing a primary preform comprising at least one sheath having a sheath internal bore and a sheath longitudinal axis along which 2024PF00059

[0045] 7. A casing wall bounded by an inner casing surface and an outer casing surface extends, and comprises antiresonance element preforms; and, if applicable,

[0046] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation, or iii) collapse and subsequent elongation; and b) providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing wall bounded by an inner and outer surface extends, and inserting the primary preform or primary preform into the casing tube by i) collapse, or ii) collapse and simultaneous elongation, or iii) collapse and subsequent elongation; forming a secondary preform characterized by an outer diameter of 100 mm to 200 mm;and c) producing a final preform, characterized by an outer diameter of 28 mm to 60 mm, from the secondary preform by i) collapsing, or ii) collapsing and simultaneous elongation, or iii) collapsing and subsequent elongation; and d) carrying out a fiber drawing, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0047] [5] Method according to [1] and [2], characterized in that steps a) and b) or steps b) and c) are carried out continuously on the same system.

[0048] [6] Method according to [3] and [4], characterized in that primary preforms, secondary preforms or final preforms are produced and / or further processed on several different plants.

[0049] [7] Method according to [1] to [6], characterized in that the elongation, collapse, collapse and carrying out a fiber pull are performed as hot forming process steps.

[0050] [8] Method according to [1] to [7], characterized in that the casing tube for primary preforms has a length of 500 to 1500 mm.

[0051] [9] Method according to [1] to [8], characterized in that the casing tube for primary 2024PF00059

[0052] 8

[0053] Preforms have an inner diameter of 25 to 80 mm.

[0054]

[0010] Method according to [1] to [9], characterized in that the casing tube for primary preforms has an outer diameter of 41 to 100 mm.

[0055]

[0011] Method according to [1] to

[0010] , characterized in that the casing tube for primary preforms has a wall thickness of 4 mm to 25 mm.

[0056]

[0012] Method according to [1] to

[0011] , characterized in that the casing tube for primary preforms has an inner circumference of 100.0 mm to 500.0 mm.

[0057]

[0013] Method according to [1] to

[0012] , characterized in that the capillaries for primary preforms have an outer diameter of 2.50 to 30.00 mm.

[0058]

[0014] Method according to [1] to

[0013] , characterized in that the primary preforms have a length of greater than 600 mm to greater than 3000 mm.

[0059]

[0015] Method according to [1] to

[0014] , characterized in that the primary preforms have an outer diameter greater than 24 mm.

[0060]

[0016] Method according to [1] to

[0015] , characterized in that the primary preforms have a wall thickness of the sheathing tube wall of greater than 4.00 mm.

[0061]

[0017] Method according to [1] to

[0016] , characterized in that the capillaries in the primary preform have an outer diameter greater than 2.00 mm.

[0062]

[0018] Method according to [1] to

[0017] , characterized in that the antiresonance element preforms in the primary preform with the largest outer diameter have an outer diameter of at least 5.00 mm to 16.00 mm.

[0063]

[0019] Method according to [1] to

[0018] , characterized in that the antiresonance elements in the primary preform have an angular deviation relative to the sheathing tube of less than 4.000° to less than 0.05°.

[0064]

[0020] Method according to [1] to

[0019] , characterized in that the casing tube has a length of 1500 mm to 3000 mm.

[0065]

[0021] Method according to [1] to

[0020] , characterized in that the casing tube is in the form of a cylinder. 2024PF00059

[0066] 9

[0067]

[0022] Method according to [1] to

[0021] , characterized in that the jacket tube is collapsed in a hot forming step by applying a vacuum between the inside of the jacket tube and the outside of the primary preform or primary preform onto the primary preform or primary preform to form the secondary preform.

[0068]

[0023] Method according to [1] to

[0022] , characterized in that the antiresonance element preforms or the antiresonance elements are sealed during enlongation steps and structurally stabilized with a gas flow at an applied pressure.

[0069]

[0024] Method according to

[0023] characterized in that the applied pressure is 50 pa to 400 pa.

[0070]

[0025] Method according to

[0023] or

[0024] , characterized in that elongated preforms or preforms are sealed at the end face by sealing them at the end face with a suitable sealing compound.

[0071]

[0026] Method according to

[0023] or

[0024] , characterized in that elongated preforms or preforms are closed at the end face by melting them at the end face.

[0072]

[0027] Method according to

[0023] or

[0024] , characterized in that elongated preforms or preforms are closed at the end face by means of a suitable device by means of force-locking closure.

[0073]

[0028] Method according to [1] to

[0027] , characterized in that hot forming process steps are carried out at a temperature of 1750 °C to 2100 °C.

[0074]

[0029] Method according to [1], [2], [5] and [7] to

[0028] , comprising the steps of: a) providing a primary preform comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and optionally further processing the primary preform into a primary preform by i) collapsing, or ii) collapsing and simultaneously elongating; and 2024PF00059

[0075] 10 b) Providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing tube wall bounded by an inner casing surface and an outer casing surface extends, and inserting the primary preform or primary preform into the casing tube; and c) Performing a fiber drawing while simultaneously collapsing the casing tube, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0076]

[0030] Method according to

[0029] , comprising the steps of: a) providing a primary preform comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and

[0077] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation; and b) providing at least one jacket tube having an inner jacket tube bore and a jacket tube longitudinal axis along which a jacket tube wall bounded by an inner jacket surface and an outer jacket surface extends, and inserting the primary preform into the jacket tube; and c) performing a fiber drawing while simultaneously collapsing the jacket tube, characterized in that the jacket tube has an outer diameter of 100 mm to 240 mm.

[0078]

[0031] Method according to [3] and [6] to

[0028] , comprising the steps of: a) providing a primary preform, comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and optionally

[0079] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation; and b) providing at least one casing tube having a casing tube inner bore and a casing tube longitudinal axis along which a casing tube wall bounded by an inner casing surface and an outer casing surface 2024PF00059

[0080] 11 extends, and insertion of the primary preform or primary preform into the jacket tube by i) collapsing, or ii) collapsing and simultaneous elongation; forming a final preform characterized by an outer diameter of 28 mm to 60 mm; and c) carrying out a fiber pull, characterized in that the jacket tube has an outer diameter of 100 mm to 240 mm.

[0081]

[0032] Method according to

[0031] , comprising the steps of: a) providing a primary preform, comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and

[0082] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation, or b) providing at least one jacket tube having an inner jacket tube bore and a jacket tube longitudinal axis along which a jacket tube wall bounded by an inner jacket surface and an outer jacket surface extends, and inserting the primary preform into the jacket tube by i) collapse, or ii) collapse and simultaneous elongation; forming a final preform characterized by an outer diameter of 28 mm to 60 mm; and c) performing a fiber drawing, characterized in that the jacket tube has an outer diameter of 100 mm to 240 mm.

[0083]

[0033] Method according to [4] and [6] to

[0028] , comprising the steps of: a) providing a primary preform comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and optionally further processing the primary preform into a primary preform by i) collapsing, or ii) collapsing and simultaneously elongating, or 2024PF00059

[0084] 12 b) Providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing tube wall bounded by an inner and an outer surface extends, and inserting the primary preform into the casing tube by i) collapsing, or ii) collapsing and simultaneously elongating; forming a secondary preform characterized by an outer diameter of 100 mm to 200 mm; and c) producing a final preform, characterized by an outer diameter of 28 mm to 60 mm, from the secondary preform by i) collapsing, or ii) collapsing and simultaneously elongating; and d) performing a fiber drawing, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0085]

[0034] Method according to

[0033] , comprising the steps of: a) providing a primary preform, comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and

[0086] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation, or b) providing at least one jacket tube having an inner jacket tube bore and a jacket tube longitudinal axis along which a jacket tube wall bounded by an inner jacket surface and an outer jacket surface extends, and inserting the primary preform into the jacket tube by i) collapse, or ii) collapse and simultaneous elongation; forming a secondary preform characterized by an outer diameter of 100 mm to 200 mm; and c) producing a final preform, characterized by an outer diameter of 28 mm to 60 mm, from the secondary preform by i) collapse, or ii) collapse and simultaneous elongation; and d) performing a fiber drawing, characterized in that the jacket tube has an outer diameter of 100 mm to 240 mm. 2024PF00059

[0087] 13

[0088]

[0035] Primary preform for an antiresonant hollow core fiber, characterized in that it has an outer diameter greater than 24 mm.

[0089]

[0036] Primary preform according to

[0034] , characterized in that it has an inner diameter of 14 mm to 55 mm.

[0090]

[0037] Primary preform according to

[0034] or

[0035] , characterized in that antiresonance element preforms are arranged therein in a nested design.

[0091]

[0038] Primary preform according to

[0035] to

[0037] , characterized in that the capillaries arranged therein have an outer diameter of at least 2.00 mm with the smallest outer diameter.

[0092]

[0039] Primary preform according to

[0035] to

[0038] , characterized in that the antiresonance element preforms arranged therein have an outer diameter of at least 5.00 mm with the largest outer diameter.

[0093]

[0040] Primary preform according to

[0035] to

[0039] available as an intermediate of a process according to [2] to

[0033] ,

[0094]

[0041] Assembly for an antiresonant hollow core fiber comprising a primary preform, characterized in that the primary preform comprises at least one sheath tube having an inner bore and a longitudinal axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprises antiresonant element preforms; or a primary preform according to

[0034] to

[0039] ; and a jacket tube, characterized in that the jacket tube has an outer diameter between 100 mm and 240 mm.

[0095]

[0042] Assembly unit according to

[0041] , available as an intermediate product of a process according to [1] to

[0034] ,

[0096]

[0043] Second preform, obtainable as an intermediate product of a process according to [4] to

[0028] and

[0032] to

[0034] ,

[0097]

[0044] Final preform, obtainable as an intermediate product of a process according to [3] to

[0028] and 2024PF00059

[0098] 14

[0099]

[0030] to

[0034] ,

[0100]

[0045] Antiresonant hollow core fiber obtainable by a method according to [1] to

[0034]

[0101]

[0046] Uses of preforms and / or construction units according to

[0035] to

[0044] for the production of antiresonant hollow core fibers.

[0102] DETAILED DESCRIPTION OF THE INVENTION

[0103] The present invention is described in detail as follows:

[0104] I. Definitions

[0105] For the purposes of the present invention, the term "collapse" refers to a process in which the geometry of a semi-finished product is altered such that its outer and inner diameters decrease. For example, a tubular semi-finished product collapses in a controlled manner. Typically, but not necessarily, collapse steps are carried out together with elongation steps and / or also with expansion steps under the influence of temperature and, optionally, negative pressure.

[0106] In the context of the present invention, the term elongation refers to a process in which the geometry of a semi-finished product is altered such that its length is increased. Elongation steps cannot be carried out without the collapse of the semi-finished products as described in the invention. They can optionally also be carried out in parallel with collapse steps. Elongation steps are performed under the influence of temperature and, optionally, pressure.

[0107] For the purposes of the present invention, the term "collapse" refers to a process in which a first tubular semi-finished product with a smaller outer diameter is placed inside a second tubular semi-finished product with an inner diameter larger than the outer diameter of the first semi-finished product and subsequently joined. This is generally achieved by reducing the outer and inner diameters of the second semi-finished product, causing the second semi-finished product to collapse onto the first. Typically, but not necessarily, collapse steps are carried out together with collapse and / or elongation steps under the influence of temperature and, optionally, pressure. 2024PF00059

[0108] 15

[0109] In the context of the present invention, the term fiber drawing or fiber pulling refers to the inventive step in which an antiresonant hollow core fiber is drawn from a semi-finished product. According to the invention, both elongation and collapse occur simultaneously during this step. In principle, the fiber drawing can be carried out starting from primary preforms or stacks, primary preforms or canes, building blocks, secondary preforms, or final preforms. Preferably, the fiber drawing is carried out using building blocks or final preforms. The fiber drawing process is characterized by a high drawing speed. When the fiber drawing is carried out starting from building blocks, the fixation of antiresonant element preforms in at least one sheath tube and the collapse of at least one sheath tube onto the at least one sheath tube preferably occur simultaneously.

[0110] For the purposes of the present invention, the term semi-finished product is a collective term which includes any intermediate product according to the invention which can be further processed into an antiresonant hollow core fiber within a process step according to the invention.

[0111] In the context of the present invention, the term capillaries refers to tubular bodies, typically made of glass. According to the invention, capillaries have larger diameters than are typically found in the prior art. The capillaries according to the invention have an inner bore and a longitudinal axis along which a capillary wall extends, bounded by an inner capillary surface and an outer capillary surface. The term capillaries, as used in the invention, refers exclusively to individual tubular units. On the one hand, capillaries can be individually fixed, for example, in a sheathing tube as part of the inventive method, and further processed into an antiresonance element.On the other hand, capillaries can, for example, first be placed inside one another and, if necessary, fixed in a nested design, so that at least one inner capillary surface of one capillary touches the outer capillary surface of the other capillary, thereby obtaining an antiresonance element preform comprising capillaries arranged in a nested design.

[0112] For the purposes of the present invention, the term "antiresonance element preform" refers to those components of the antiresonance hollow-core fibers produced according to the inventive method that become antiresonance elements of the antiresonance hollow-core fibers during the process. This can include, for example, capillaries, nested capillaries (where the capillaries are not yet fixed to one another), or nested capillaries (where the capillaries are already fixed to one another). Other possible arrangements of single or multiple capillaries, placed in an inner sheath and further processed into an antiresonance element, are also conceivable within the scope of the invention, as shown in 2024PF00059.

[0113] 16

[0114] The term "antiresonance element preform" is used to refer to any element processed in the inventive process that constitutes an antiresonance element in the antiresonant hollow core fiber. During the inventive process, the antiresonance element preforms can change their shape, such as their outer or inner diameter or their length. This includes antiresonance element preforms that have already undergone at least one inventive process step but have not yet attained their final shape as an antiresonance element.

[0115] In the context of the present invention, the term "nested design" refers to a particular arrangement of capillaries or a method by which at least two capillaries can form an antiresonance element preform. In this arrangement, at least two capillaries are positioned such that one capillary is placed inside another capillary in such a way that the outer capillary surface of one capillary comes into contact with the inner capillary surface of the other capillary. In principle, any number of capillaries can be arranged in a nested design to form an antiresonance element preform according to the invention, comprising capillaries arranged in a nested design. Such antiresonance element preforms arranged in a nested design can, for example, be in a form in which the capillaries are simply placed inside one another. In this form, they can then be placed in a sheathing tube and further processed according to the invention.The capillaries arranged in this way are then fixed to each other and / or to the sheathing tube. However, the invention also includes fixing the capillaries, which are arranged in a nested design to form an antiresonance element preform, to each other before they are placed in or fixed to a sheathing tube.

[0116] In the context of the present invention, the term antiresonance element refers to the final form of the antiresonance element preforms after all process steps of the inventive method have been carried out in the finished antiresonant hollow core fiber. This means that antiresonance element preforms, such as capillaries or tubes arranged, for example, in a nested design, no longer change their geometric characteristics, such as inner or outer diameter, or their length, in the form of antiresonance elements through further process steps of the inventive method.

[0117] In the context of the present invention, the term "sheathing tube" refers to an object that has an inner bore and a longitudinal axis along which a sheathing tube wall extends, bounded by an inner surface and an outer surface. The sheathing tube, as defined in the invention, is a component of primary preforms (stacks) in addition to the antiresonance element preforms. 2024PF00059

[0118] 17

[0119] For the purposes of the present invention, the term primary preform or "stack" refers to a semi-finished product in which at least one type of antiresonance element preform has been placed in at least one sheathing tube. The antiresonance element preform(s) are not yet fully fixed within the sheathing tube, but are merely attached at both ends of the sheathing tube, for example, by means of a suitable adhesive or by fusion. It is also possible to use a suitable device or template, to which the antiresonance element preforms are screwed, to force-fit the antiresonance element preforms within the interior of the sheathing tube. In principle, it is possible to process the finished primary preform or "stack" by fiber drawing up to the antiresonance hollow core fiber.

[0120] For the purposes of the present invention, the term primary preform or "cane" refers to a semi-finished product of the inventive process in which a primary preform has been subjected to at least one collapse or collapse and elongation step, optionally performed simultaneously or successively. In the context of the inventive process, a collapse or collapse and elongation step is carried out, in particular, under thermal influence in a tensile process as a hot forming process step. It is, in principle, possible to process the finished primary preform or cane by means of fiber drawing down to the antiresonant hollow core fiber.

[0121] For the purposes of the present invention, the term "jacket tube" refers to an object that can also be understood as a "cylinder" or "jacket." It has an inner bore and a longitudinal axis along which a jacket tube wall extends, bounded by an inner and an outer surface. In contrast to a sheath tube as a component of the primary preform, the jacket tube is collapsed, for example, onto the existing primary preform to form a final or secondary preform. According to the invention, in addition to collapsing the jacket tube onto the primary preform, fiber drawing is also carried out in the same step by continuously collapsing and elongating it during the collapse process.

[0122] For the purposes of the invention, the term "building unit" refers to a system in which a primary preform or stack, or a primary preform or cane, has been inserted into the inner bore of a sheath tube such that the outer sheath surface and the inner sheath surface face each other. According to the invention, subsequent collapse and / or elongation steps, optionally performed simultaneously or successively, can lead to further semi-finished products or to the antiresonant hollow-core fiber. 2024PF00059

[0123] 18

[0124] For the purposes of the present invention, the term secondary preform refers to the result of at least one hot forming process step of the inventive method, which is carried out on a primary preform or cane, or on a primary preform or stack, wherein a sheath tube has been collapsed onto the primary preform or the primary preform. According to the invention, it is possible for the secondary preform to be directly processed into an antiresonant hollow core fiber by fiber drawing. However, it is also according to the invention if the secondary preform, optionally on a different machine than the one on which the secondary preform was produced, is first processed into another semi-finished product, such as a final preform, and then into an antiresonant hollow core fiber. For example, it can be simply collapsed, collapsed and simultaneously elongated, or collapsed and subsequently elongated and processed into a final preform.Further processing of the secondary preform into a final preform is preferred according to the invention.

[0125] For the purposes of the present invention, the term final preform refers to the result of at least one hot forming process step of the inventive method, which is carried out on a primary preform (stack) onto which a jacket tube has been collapsed, a primary preform (cane) onto which a jacket tube has been collapsed, or a secondary preform, wherein the respective semi-finished product is collapsed, collapsed and simultaneously elongated, or collapsed and subsequently elongated.

[0126] When, within the meaning of the present invention, reference is made to explicitly designated numerical values ​​in a range from X to Y, or from at least X to at least Y, or from greater than X to greater than Y, etc., this includes, in particular, all implicitly intervening values ​​suggested by the indication of the zeros. Thus, if a value lies between 1 and 10, this includes, in particular, 2, 3, 4, 5, 6, 7, 8, and 9. If a value lies between 1.0 and 2.0, this includes, in particular, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. If a value lies between 1.00 and 1.10, this includes, in particular, 1.01, 1.02,

[0127] I ,03, 1,04, 1,05, 1 ,06, 1 ,07, 1 ,08 and 1,09 are included.

[0128] II. Procedure

[0129] The inventive method is a manufacturing process for antiresonant hollow core fibers, which is characterized in particular by the relatively large dimensions of the antiresonant element preforms and semi-finished products that are passed through as intermediate products after the various inventive process steps in the course of the process.

[0130] The simplest embodiment of the inventive method for producing an antiresonant hollow core fiber, comprising a hollow core extending along a fiber longitudinal axis and a sheath region surrounding the hollow core, 2024PF00059

[0131] 19, which comprises several antiresonance elements, includes the following process steps, each performed at least once: a) providing a primary preform (stack) comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and antiresonance element preforms; and

[0132] a) Providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing tube wall bounded by an inner casing surface and an outer casing surface extends, and inserting the primary preform (stack) into the casing tube; and b) Performing a fiber drawing while simultaneously collapsing the casing tube, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0133] In accordance with the inventive method, it is preferred if steps a) and b) are carried out on the same equipment. This makes the inventive method more attractive for the industrial-scale production of antiresonant hollow core fibers.

[0134] In order to carry out the inventive method, particularly on an industrial scale, it is advantageous if the semi-finished products or the primary preform are relatively large. In particular, large outer and inner diameters of sheathing and casing tubes, as well as of antiresonance element preforms, are advantageous.

[0135] In accordance with the inventive method, sheathing tubes that become part of primary preforms or stacks are 600 mm to 1000 mm long. This means the casing tubes are, for example, 600 mm, 610 mm, 620 mm, 630 mm, 640 mm, 650 mm, 660 mm, 670 mm, 680 mm, 690 mm or, for example, 700 mm, 710 mm, 720 mm, 730 mm, 740 mm, 750 mm, 760 mm, 770 mm, 780 mm, 790 mm or, for example, 800 mm, 810 mm, 820 mm, 830 mm, 840 mm, 850 mm, 860 mm, 870 mm, 880 mm, 890 mm or, for example, 900 mm, 910 mm, 920 mm, 930 mm, 940 mm, 950 mm, 960 mm. 970 mm, 980 mm, 990 mm or, for example, 1000 mm long.

[0136] Furthermore, the sheathing tubes, which become part of primary preforms or stacks, have inner diameters of 25 mm to 80 mm. This means the sheathing tubes have an inner diameter of, for example, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm or, for example, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm, 37 mm, 38 mm, 39 mm or, for example, 40 mm, 41 mm, 42 mm, 43 mm, 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm or, for example, 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm or, for example, 60 mm, 61 mm, 62 mm, 63 mm, 64 mm, 65 mm, 66 mm, 67 mm 2024PF00059

[0137] 20 mm, 68 mm, 69 mm or for example 70 mm, 71 mm, 72 mm, 73 mm, 74 mm, 75 mm, 76 mm, 77 mm, 78 mm, 79 mm or for example 80 mm.

[0138] Furthermore, the sheathing tubes, which become part of primary preforms or stacks, have outer diameters of 41 mm to 100 mm. This means the sheathing tubes have an inner diameter of, for example, 41 mm, 42 mm, 43 mm, 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm or, for example, 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm or, for example, 60 mm, 61 mm, 62 mm, 63 mm, 64 mm, 65 mm, 66 mm, 67 mm, 68 mm, 69 mm or, for example, 70 mm, 71 mm, 72 mm, 73 mm, 74 mm, 75 mm, 76 mm, 77 mm, 78 mm, 79 mm or, for example, 80 mm, 81 mm, 82 mm, 83 mm, 84 mm, 85 mm, 86 mm mm, 87 mm, 88 mm, 89 mm or for example 90 mm, 91 mm, 92 mm, 93 mm, 94 mm, 95 mm, 96 mm, 97 mm, 98 mm, 99 mm or for example 100 mm.

[0139] Furthermore, the sheathing tubes, which are part of primary preforms or stacks, have wall thicknesses ranging from 4 mm to 25 mm. This means that the sheathing tubes have a wall thickness of, for example, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or, for example, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, or, for example, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, or, for example, 25 mm.

[0140] Furthermore, the sheathing tubes, which become part of primary preforms or stacks, have an inner circumference of the sheathing tube inner bore of 100.0 mm to 500.0 mm. This means that the sheathing tubes have an inner circumference of the sheathing tube inner bore of, for example, 100.0 mm, 110.0 mm, 120.0 mm, 130.0 mm, 140.0 mm, 150.0 mm, 160.0 mm, 170.0 mm, 180.0 mm, 190.0 mm or, for example, 200.0 mm, 210.0 mm, 220.0 mm, 230.0 mm, 240.0 mm, 250.0 mm, 260.0 mm, 270.0 mm, 280.0 mm, 290.0 mm or, for example, 300.0 mm, 310.0 mm, 320.0 mm, 330.0 mm, 340.0 mm, 350.0 mm, 360.0 mm. 370.0 mm, 380.0 mm, 390.0 mm or for example from 400.0 mm, 410.0 mm, 420.0 mm, 430.0 mm, 440.0 mm, 450.0 mm, 460.0 mm, 470.0 mm, 480.0 mm, 490.0 mm or for example from 500.0 mm.

[0141] In accordance with the inventive method, capillaries that become part of primary preforms or stacks or of other antiresonance element preforms have an outer diameter of 2.50 mm to 30.00 mm. This means they have an outer diameter of, for example, 2.50 mm, 3.00 mm, 3.50 mm, 4.00 mm, 4.50 mm, or, for example, 5.00 mm, 5.50 mm, 6.00 mm, 6.50 mm, 7.00 mm, 7.50 mm, 8.00 mm, 8.50 mm, 9.00 mm, 9.50 mm, or, for example, 10.00 mm, 10.50 mm, 11.00 mm, 11.50 mm, 12.00 mm, 12.50 mm, 13.00 mm, 13.50 mm, 14.00 mm, 14.50 mm, or, for example, 15.00 mm, 15.50 mm, 16.00 mm, 16.50 mm, 17.00 mm, 17.50 mm mm, 18.00 mm, 18.50 mm, 19.00 mm, 19.50 mm or for example 20.00 mm, 20.50 mm, 21.00 mm, 21.50 mm, 22.00 mm, 22.50 mm, 23.00 mm, 23.50 mm, 24.00 mm, 24.50 mm or for example 25.00 mm 2024PF00059

[0142] 21

[0143] 25.50 mm, 26.00 mm, 26.50 mm, 27.00 mm, 27.50 mm, 28.00 mm, 28.50 mm, 29.00 mm, 29.50 mm or, for example, from 30.00 mm.

[0144] The antiresonance element preforms according to the invention change their diameters, their length and possibly other geometric parameters when processed in the course of the inventive method. Nevertheless, they are characterized in that their outer diameters remain relatively large.

[0145] If a primary preform or stack is produced from components of this size, and subsequently a primary preform or cane is manufactured in other process steps, higher angular accuracy or lower angular deviation is possible because the ratio between circumference (in mm) and angle (degrees) increases with a larger inner diameter. This means that with constant absolute positional accuracy or deviation from the target position, and with increasing inner diameter, the angular accuracy improves, i.e., the angular deviation is reduced. The angular deviation can be determined using the following formula:

[0146] 360° x Position deviation [mm]

[0147] This, in turn, minimizes so-called mid-draw contacts during any process steps that may include hot forming processes such as collapse, expansion, and elongation. The term mid-draw contact refers to unwanted contact between the antiresonant element preforms during a hot forming process step, which may impair the fiber's guiding properties or completely prevent light transmission within the fiber.

[0148] According to the invention, the angular deviation between the inner diameter of the sheathing tube and the antiresonance element preforms is between 0.050° and 4.000°. The angular deviation is therefore, for example, 0.050°, 0.100°, 0.150°, 0.200°, 0.250°, 0.300°, 0.350°, 0.400°, 0.450°, 0.500°, 0.550°, 0.600°, 0.650°, 0.700°, 0.750°, 0.800°, 0.850°, 0.900°, 0.950° or 1.000°, 1.050°, 1.100°, 1.150°, 1.200°, 1.250°, 1.300°, 1.350°, 1.400°, 1.450°, 1. 0.500°, 1.550°, 1.600°, 1.650°, 1.700°, 1.750°, 1.800°, 1.850°, 1.900°, 1.950° or 2.000°, 2.050°, 2.100°, 2.150°, 2.200°, 2.250°, 2.300°, 2.350°, 2.400°, 2.450°, 2.500°, 2.550°, 2.600°, 2.650°, 2.700°, 2.750°, 2.800°, 2.850°, 2.900°, 2.950° or 3,000°, 3,050°, 3,100°, 3,150°, 3,200°, 3,250°, 3,300°, 3,350°, 3,400°, 3,450°, 3,500°, 3,550°, 3,600°, 3,650°, 3,700°, 3,750°, 3,800°, 3,850°, 3,900°, 3,950° or 4,000°.

[0149] Another advantage that can be achieved by means of such relatively large components for primary preforms or primary preforms of the inventive method is that a greater stiffness of the primary preform or primary preform 2024PF00059

[0150] 22 can be achieved. This minimizes the risk of breakage or other damage during the process steps according to the invention.

[0151] A further advantage that can be realized by means of such relatively large components for primary preforms or primary preforms of the inventive method is that large diameters in antiresonance element preforms reduce the applied equilibrium pressure (ESP) required to stabilize the antiresonance element preforms during the processing steps and to prevent their undesired deformation or even complete collapse. The relationship between the equilibrium pressure and the radius of curvature of the antiresonance element preforms, as well as the material parameter surface tension, is illustrated by the following relationship: where TA denotes the outer radius of the antiresonance element preforms and n the inner radius of the antiresonance element preforms, and q the surface tension of the material used.

[0152] The relatively large antiresonance element preforms, with a large outer or inner diameter, ensure that the collapse of the antiresonance element preforms during the processing process is less pronounced.

[0153] Another advantage that can be realized by means of such relatively large components for primary preforms or primary preforms of the inventive method is that large diameters in antiresonance element preforms or capillaries make it possible to simplify a connection for any internal pressure or counter-pressure that may be generated to stabilize the antiresonance element preforms.

[0154] Another aspect of the inventive method is that at least one jacket tube is collapsed onto the primary preform. Jacket tubes that are collapsed onto primary preforms in the course of the inventive method have a length between 1500 mm and 3200 mm. They have lengths of, for example, 1500 mm, 1510 mm, 1520 mm, 1530 mm, 1540 mm, 1550 mm, 1560 mm, 1570 mm, 1580 mm, 1590 mm or, for example, 1600 mm, 1610 mm, 1620 mm, 1630 mm, 1640 mm, 1650 mm, 1660 mm, 1670 mm, 1680 mm, 1690 mm or, for example, 1700 mm, 1710 mm, 1720 mm, 1730 mm, 1740 mm, 1750 mm, 1760 mm, 1770 mm, 1780 mm, 1790 mm or, for example, 1800 mm, 1810 mm, 1820 mm, 1830 mm mm, 1840 mm, 1850 mm, 1860 mm, 1870 mm, 1880 mm, 1890 mm or for example 1900 mm, 2024PF00059

[0155] 23

[0156] 1910 mm, 1920 mm, 1930 mm, 1940 mm, 1950 mm, 1960 mm, 1970 mm, 1980 mm, 1990 mm or for example 2000 mm, 2010 mm, 2020 mm, 2030 mm, 2040 mm, 2050 mm, 2060 mm, 2070 mm, 2080 mm, 2090 mm or for example 2100 mm, 2110 mm, 2120 mm, 2130 mm, 2140 mm, 2150 mm, 2160 mm, 2170 mm, 2180 mm, 2190 mm or for example 2200 mm, 2210 mm, 2220 mm, 2230 mm, 2240 mm, 2250 mm, 2260 mm, 2270 mm, 2280 mm, 2290 mm or for example 2300 mm, 2310 mm, 2320 mm, 2330 mm, 2340 mm, 2350 mm, 2360 mm, 2370 mm, 2380 mm, 2390 mm or for example 2400 mm, 2410 mm, 2420 mm, 2430 mm, 2440 mm, 2450 mm, 2460 mm, 2470 mm, 2480 mm, 2490 mm or for example 2500 mm, 2510 mm, 2520 mm, 2530 mm, 2540 mm, 2550 mm, 2560 mm, 2570 mm, 2580 mm, 2590 mm or for example 2600 mm, 2610 mm, 2620 mm, 2630 mm, 2640 mm, 2650 mm, 2660 mm, 2670 mm, 2680 mm, 2690 mm or for example 2700 mm, 2710 mm, 2720 mm, 2730 mm, 2740 mm, 2750 mm, 2760 mm, 2770 mm, 2780 mm, 2790 mm or for example 2800 mm, 2810 mm, 2820 mm,2830 mm, 2840 mm, 2850 mm, 2860 mm, 2870 mm, 2880 mm, 2890 mm or for example 2900 mm, 2910 mm, 2920 mm, 2930 mm, 2940 mm, 2950 mm, 2960 mm, 2970 mm, 2980 mm, 2990 mm or for example 3000 mm, 3010 mm, 3020 mm, 3030 mm, 3040 mm, 3050 mm, 3060 mm, 3070 mm, 3080 mm, 3090 mm or for example 3100 mm, 3110 mm, 3120 mm, 3130 mm, 3140 mm, 3150 mm, 3160 mm, 3170 mm, 3180 mm, 3190 mm or, for example, 3200 mm.

[0157] Furthermore, the casing tubes, at least one of which can be collapsed onto primary preforms or stacks, have outer diameters ranging from 100 mm to 240 mm. This means, for example, that the outer diameter is 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, or 200 mm, 210 mm, 220 mm, 230 mm, or 240 mm.

[0158] In accordance with the inventive method, it is particularly preferred if the casing tube has an outer diameter greater than 120 mm.

[0159] The collapse of at least one outer casing onto the primary preform offers the advantage that the antiresonance element preforms are thus preferably protected within a particularly thick-walled shell from the high temperatures typically applied during the hot forming process steps. This further minimizes the risk of damage during the forming process.

[0160] In accordance with the inventive method, the casing tube is preferably provided in the form of a cylinder. 2024PF00059

[0161] 24

[0162] In accordance with the invention, it is preferred if the collapse of the casing tube is carried out by applying a negative pressure or drawing a vacuum between the inner surface of the casing tube and the outer surface of the primary preform. The primary preform is separated on the pressure side to allow the vacuum to be applied. According to the invention, this can be achieved, for example, by melting or applying a suitable sealant to the end face.

[0163] Using one or more outer casing tubes instead of a single, thick-walled casing tube offers the advantage of obtaining a thick-walled preform without the risk of damaging the casing tube during the thermal curing of the antiresonance element preforms. If an excessively large casing tube is used from the outset, uneven heat distribution can occur during welding of the antiresonance element preforms, potentially leading to cracking.

[0164] Another preferred embodiment of the inventive method for producing an antiresonant hollow core fiber, which has a hollow core extending along a fiber longitudinal axis and a sheath region surrounding the hollow core comprising several antiresonance elements, comprises the following process steps, carried out at least once: a) providing a primary preform comprising at least one sheath tube having an inner bore and a longitudinal axis along which a sheath wall bounded by an inner surface and an outer surface extends, and comprising antiresonance element preforms; and

[0165] Further processing of the primary preform into a primary preform (cane) by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; and b) providing at least one cane having a cane internal bore and a cane longitudinal axis along which a cane wall bounded by an inner cane surface and an outer cane surface extends; and

[0166] Insertion of the primary preform into the casing tube by collapse; and

[0167] Performing a fiber drawing process, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm. 2024PF00059

[0168] 25

[0169] In accordance with the invention, it is particularly preferred if the collapse of the casing tube onto the primary preform and the fiber drawing are carried out on the same system.

[0170] Manufacturing a primary preform before collapsing at least one casing tube preferably results in a lower risk of damage to the antiresonance element preforms compared to collapsing at least one casing tube onto a primary preform. In a primary preform, the antiresonance element preforms are typically not yet fully fixed within the casing tube, but are only attached at the ends of the casing tube. If a primary preform is first formed from the primary preform, the antiresonance element preforms are fixed within the casing tube and better protected against mechanical vibrations that may occur during the collapse of a casing tube.

[0171] According to the invention, primary preforms have at least the same dimensions as the sheathing tube that has become part of the primary preform, but according to the invention they can be reduced in diameter and extended in length, in particular.

[0172] Thus, primary preforms have a length of, for example, greater than 600 mm to greater than 3000 mm, i.e., greater than 600 mm, 610 mm, 620 mm, 630 mm, 640 mm, 650 mm, 660 mm, 670 mm, 680 mm, 690 mm or greater than 700 mm, 710 mm, 720 mm, 730 mm, 740 mm, 750 mm, 760 mm, 770 mm, 780 mm, 790 mm or greater than 800 mm, 810 mm, 820 mm, 830 mm, 840 mm, 850 mm, 860 mm, 870 mm, 880 mm, 890 mm or greater than 900 mm, 910 mm, 920 mm mm, 930 mm, 940 mm, 950 mm, 960 mm, 970 mm, 980 mm, 990 mm or, for example, larger than 1000 mm, 1100 mm, 1200 mm, 1300 mm, 1400 mm, 1500 mm, 1600 mm, 1700 mm, 1800 mm, 1900 mm or, for example, larger than 2000 mm, 2100 mm, 2200 mm, 2300 mm, 2400 mm, 2500 mm, 2600 mm, 2700 mm, 2800 mm, 2900 mm or, for example, larger than 3000 mm in length. Preferably, the primary preform is larger than 1000 mm in length.Since the primary preform can be elongated relative to the primary preform according to the invention, it is usually, but not necessarily, longer.

[0173] Furthermore, primary preforms have outer diameters greater than 24 mm. This means that the sheathing tubes have an inner diameter of, for example, at least 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm.

[0174] 36 mm, 37 mm, 38 mm, 39 mm or, for example, at least 40 mm, 41 mm, 42 mm,

[0175] 43 mm, 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm or for example at least

[0176] 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm or for example at least 60 mm, 61 mm, 62 mm, 63 mm, 64 mm, 65 mm, 66 mm, 67 mm, 68 mm, 69 mm or for example at least 70 mm, 71 mm, 72 mm, 73 mm, 74 mm, 2024PF00059

[0177] 26

[0178] 75 mm, 76 mm, 77 mm, 78 mm, 79 mm or, for example, at least 80 mm, 81 mm, 82 mm, 83 mm, 84 mm, 85 mm, 86 mm, 87 mm, 88 mm, 89 mm or, for example, at least 90 mm, 91 mm, 92 mm, 93 mm, 94 mm, 95 mm, 96 mm, 97 mm, 98 mm, 99 mm or, for example, at least 100 mm. Since the primary preform can be collapsed relative to the primary preform according to the invention, it has a smaller outer diameter.

[0179] Furthermore, primary preforms have wall thicknesses greater than 4 mm. This means that the sheathing tubes have a wall thickness of, for example, at least 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or, for example, at least 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm or, for example, at least 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm or, for example, at least 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm, 37 mm, 38 mm, 39 mm or, for example, at least 40 mm, 41 mm, 42 mm, 43 mm, 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm or for example at least 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm or for example at least 60 mm, 61 mm, 62 mm, 63 mm, 64 mm, 65 mm, 66 mm, 67 mm, 68 mm, 69 mm or for example at least 70 mm, 71 mm, 72 mm, 73 mm, 74 mm or for example at least 75 mm.Since the primary preform can be collapsed relative to the primary preform according to the invention, it has a lower wall thickness.

[0180] In accordance with the inventive method, it is conceivable that the antiresonance element preforms, such as capillaries or capillaries arranged in a nested design or any other conceivable arrangement, change their geometric properties, such as outer or inner diameter, length, or ovality, during the processing of the primary preform into the primary preform. The geometry of the antiresonance element preforms is also influenced by the hot forming process steps required to obtain a primary preform from a primary preform, or by the hot forming process steps required to produce another semi-finished product from a primary preform.

[0181] In principle, capillaries or other antiresonance element preforms are initially circular, and a circular geometry is preferred for them. However, during hot forming process steps, the circular cross-sectional shape of the capillaries or other antiresonance element preforms can assume an oval shape, characterized by a long axis and a short axis. The outer diameter of such a more oval capillary or antiresonance element preform is then calculated according to the following formula: 2024PF00059

[0182] 27

[0183] It is preferred according to the invention if the axis lengths correspond to a ratio between the long and short axes preferred according to the invention, ranging from 1.00 (circular) to a maximum of 2.00 (oval). The ratio between the axes is thus determined according to the following formula:

[0184] This means that, according to the invention, the ratio between the long and short axes is 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, or 1.30, 1.35, 1.40, 1.45, 1.50, or 1.55, 1.60, 1.65, 1.70, 1.75, or 1.80, 1.85, 1.90, 1.95, or 2.00. A particularly preferred ratio is a maximum of 1.20 to 1.60.

[0185] According to the invention, it is conceivable that capillaries can directly become part of a primary preform or a primary preform without being processed into another antiresonance element preform, such as an arrangement of capillaries in a nested design.

[0186] It is therefore particularly preferred if a capillary that has become part of a primary preform has an outer diameter of at least 2.00 mm, for example 2.00 mm, 2.50 mm, 3.00 mm, 3.50 mm, 4.00 mm, 4.50 mm or for example 5.00 mm, 5.50 mm, 6.00 mm, 6.50 mm, 7.00 mm, 7.50 mm, 8.00 mm, 8.50 mm, 9.00 mm, 9.50 mm or for example 10.00 mm, 10.50 mm, 11.00 mm, 11.50 mm, 12.00 mm, 12.50 mm, 13.00 mm, 13.50 mm, 14.00 mm, 14.50 mm or for example 15.00 mm or as such. As previously described for capillaries or antiresonance element preforms in the primary preform, the only difference is that the change in geometry allows for a smaller lower limit of 2.00 mm for the outer diameter of the capillaries.

[0187] However, if the antiresonance element preforms are further processed, for example, as capillaries arranged in a nested design, it is preferred that the outer diameter of such an antiresonance element preform as part of a primary preform is at least 5.00 mm. This means that the outer diameter of the outermost capillary of the capillaries arranged in the nested design of this antiresonance element preform, which has become part of a primary preform, is at least 5.00 mm.

[0188] In accordance with the invention, for antiresonance element preforms, the capillaries, which are arranged in a nested design and have become part of primary preforms, are preferably to have an outer diameter of at least 5.00 to 16.00 mm, as described above. 2024PF00059

[0189] 28

[0190] According to a further preferred embodiment of the inventive method for producing an antiresonant hollow core fiber, which has a hollow core extending along a fiber longitudinal axis and a sheath region surrounding the hollow core comprising several antiresonance elements, the following method steps are preferably carried out at least once: a) Providing a primary preform comprising at least one sheath tube having an inner bore and a longitudinal axis along which a sheath wall bounded by an inner surface and an outer surface extends, and comprising antiresonance element preforms; and optionally

[0191] Further processing of the primary preform into a primary preform by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; and b) providing at least one jacket tube having an inner jacket tube bore and a jacket tube longitudinal axis along which a jacket tube wall bounded by an inner jacket surface and an outer jacket surface extends, and inserting the primary preform or primary preform into the jacket tube by i) collapsing; or ii) collapsing and simultaneously elongating; or iii) collapsing and subsequently elongating; forming a final preform characterized by an outer diameter of 28 mm to 60 mm; and c) performing a fiber drawing, characterized in that the jacket tube has an outer diameter of 100 mm to 240 mm.

[0192] During fiber drawing, there is a risk of mid-draw contact of the capillaries, which can occur particularly when the wall thickness of the capillaries within the fiber is below 1 pm. To avoid this problem, a primary preform with a maximum outer diameter of 60 mm is produced before fiber drawing. If the outer diameter falls below the lower limit of 28 mm, the thermal stress on the preform increases, potentially leading to deformation and collapse of the capillaries.

[0193] The production of the final preform from the primary preform is preferably carried out using a continuous draw process. In the continuous draw process, a preform or component is held at one end and slowly guided downwards through a heated zone. A capstan / tractor is used for the continuous drawing process. The 2024PF00059

[0194] 29

[0195] The section is cut at a previously determined length.

[0196] The difference to fiber drawing lies in the drawing speed, with the speed in fiber drawing usually being chosen higher than in the continuous-draw process.

[0197] Another difference between fiber drawing and the continuous-draw process is the diameter of the drawn semi-finished product or the antiresonant hollow-core fiber. Generally, slowly drawn semi-finished products processed using the continuous-draw process have diameters greater than 2 mm. In contrast, antiresonant hollow-core fibers produced via fiber drawing typically have diameters between 40 pm and 2 mm.

[0198] Other differences include the fact that an antiresonant hollow core fiber is usually coated and continuously wound without being cut after 1 m to 10 m, as is usually the case for semi-finished products.

[0199] The final preform according to the invention is thus a primary preform or a primary preform onto which at least one sheathing tube has collapsed and which has subsequently already been reduced in diameter, but not yet to the antiresonant hollow core fiber. In principle, a secondary preform according to the present invention is also formed in this process; however, this is preferably not isolated but further processed into the final preform on the same equipment. Interrupting the manufacturing process at the final preform reduces the mechanical and thermal stress that acts on the antiresonant element preforms in a short time. The two-stage loading is generally gentler and reduces the risk of the antiresonant element preforms being damaged or deformed.

[0200] Final preforms according to the invention are characterized by an outer diameter between 28 mm and 60 mm. This means that final preforms have an outer diameter of 28 mm, 29 mm, or 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm, 37 mm,

[0201] 38mm, 39mm, or 40mm, 41mm, 42mm, 43mm, 44mm, 45mm, 46mm, 47mm, 48mm,

[0202] 49 mm, or 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm, or 60 mm.

[0203] To further reduce the stress on the antiresonance element preforms in accordance with the inventive method, it is also possible to carry out a further process step, wherein the following process steps are preferably applied at least once to produce an antiresonance hollow core fiber, which has a hollow core extending along a fiber longitudinal axis and a sheath region surrounding the hollow core, which comprises several antiresonance elements: 2024PF00059

[0204] 30 a) Providing a primary preform comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and optionally

[0205] Further processing of the primary preform into a primary preform by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; and b) providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing wall bounded by an inner and an outer surface extends, and inserting the primary preform or primary preform into the casing tube by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; forming a secondary preform characterized by an outer diameter of 100 mm to 200 mm;and c) producing a final preform, characterized by an outer diameter of 28 mm to 60 mm, from the secondary preform by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; and;

[0206] Performing a fiber drawing process, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0207] The production of the secondary preform introduces a further step into the inventive process, which generally reduces mechanical and thermal stresses on the antiresonance element preforms. For the purposes of the present invention, it is preferred if the production of the secondary preform is carried out in an upward draw process. In an upward draw process, the semi-finished product is moved upwards during processing. In contrast to downward draw processes, in which the semi-finished product is moved downwards, better control of the drawing speed can generally be achieved and the risk of undesired deformations is minimized. This intermediate step stabilizes the preform geometry during the drawing step to the primary preform. In particular, it is not absolutely necessary for the preform to be cut during the drawing process because the preform is only elongated to a limited extent. 2024PF00059

[0208] 31

[0209] The secondary preform according to the invention is characterized by an outer diameter between 100 mm and 200 mm. It therefore has a diameter of 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or for example 160 mm, 170 mm, 180 mm, 190 mm, or for example 200 mm.

[0210] In a preferred embodiment of the inventive method, the secondary preform is further processed into a final preform as described above using a continuous-draw process.

[0211] All embodiments of the inventive method have in common that they are carried out starting from semi-finished products or components of semi-finished products that have relatively large diameters in accordance with the previously defined limits. The large dimensions inherently make it possible to shield the antiresonance element preforms from thermal and mechanical stresses during the processing steps. This has enabled the inventors to surprisingly provide a method in which the fixing of the antiresonance element preforms in a sheathing tube and its encasing with a jacket tube can take place on the same machine. In another preferred embodiment of the inventive method, the sheathing of the jacket tube and the fiber drawing can take place on the same machine.

[0212] In accordance with the present invention, it is also possible to carry out the inventive process in a more gentle manner by either producing a final preform from the described components or a secondary and then a final preform from the described components before the fiber drawing is carried out.

[0213] In a preferred embodiment of the process steps of the method according to the invention, it is provided that pressure is applied to the antiresonance element preforms or capillaries of the various preforms or preforms during the hot forming process steps. This counteracts the collapse pressure of the antiresonance element preforms and stabilizes a desirable, round geometry of the antiresonance element preforms. Collapse pressure describes the tendency of the antiresonance element preforms to collapse in on themselves during hot forming process steps according to the invention. For example, it is possible according to the invention to melt the end face of the primary preform or the various preforms or to seal them with a suitable material and then to generate an equilibrium pressure using a suitable gas. On the other hand, a desired geometry of the capillaries or preforms can also be achieved by means of the applied pressure.Antiresonance element preforms can be achieved, for example, by expanding the antiresonance element preforms from the inside through the applied pressure, in order to preferentially stabilize a round geometry. 2024PF00059.

[0214] 32

[0215] The applied pressure stabilizes a round, desirable geometry of the antiresonance element preforms during the hot forming process steps and is preferably generated by means of a gas stream. Preferably an inert gas stream is introduced, particularly preferably a stream of argon, nitrogen, or synthetic air without water content.

[0216] In accordance with the inventive method, the applied pressures can be selected to be relatively low due to the relatively large diameters of the components of the inventive semi-finished products, as explained by the formula shown above. This reduces the risk of damaging the antiresonance element preforms due to internal pressure.

[0217] For the purposes of the invention, pressures between 50 pa and 400 pa are preferred. This means that the equilibrium pressure between the gas flow and the collapse pressure can be 50 Pa, 55 Pa, 60 Pa, 65 Pa, 70 Pa, 75 Pa, 80 Pa, 85 Pa, 90 Pa, 95 Pa, or for example 100 Pa, 105 Pa, 110 Pa, 115 Pa, 120 Pa, 125 Pa, 130 Pa, 135 Pa, 140 Pa, 145 Pa, 150 Pa, 155 Pa, 160 Pa, 165 Pa, 170 Pa, 175 Pa, 180 Pa, 185 Pa, 190 Pa, 195 Pa, or for example 200 Pa, 205 Pa, 210 Pa, 215 Pa, 220 Pa, 225 Pa, 230 Pa, 235 Pa, 240 Pa. 245pa, 250pa, 255pa, 260pa, 265pa, 270pa, 275pa, 280pa, 285pa, 290pa, 295pa or for example 300pa, 305pa, 310pa, 315pa, 320pa, 325pa, 330pa, 335pa, 340 pa, 345 pa, 350 pa, 355 pa, 360 pa, 365 pa, 370 pa, 375 pa, 380 pa, 385 pa, 390 pa, 395 pa or, for example, 400 pa.

[0218] Larger diameters in the antiresonance cells or capillaries of the semi-finished products require lower equilibrium pressures than smaller diameters. In the primary preform, the applied equilibrium pressure during hot forming process steps is preferably between 65 Pa and 205 Pa; in the primary preform and beyond, the applied equilibrium pressure during hot forming process steps is preferably between 110 Pa and 350 Pa.

[0219] According to the invention, hot forming steps such as elongation, collapse, out-collapse, or fiber drawing are preferably carried out at temperatures between 1750 °C and 2100 °C. This means that the process temperature can be, for example, 1750 °C, 1760 °C,

[0220] 1770 °C, 1780 °C, 1790 °C, or for example 1800 °C, 1810 °C, 1820 °C, 1830 °C, 1840 °C,

[0221] 1850 °C, 1860 °C, 1870 °C, 1880 °C, 1890 °C or, for example, 1900 °C, 1910 °C, 1920 °C,

[0222] 1930 °C, 1940 °C, 1950 °C, 1960 °C, 1970 °C, 1980 °C, 1990 °C, or for example 2000 °C,

[0223] The temperature may be 2010 °C, 2020 °C, 2030 °C, 2040 °C, 2050 °C, 2060 °C, 2070 °C, 2080 °C, 2090 °C, or, for example, 2100 °C. A person skilled in the art understands that, depending on the type of glass used, the temperature may also be above 2100 °C or below 1750 °C. 2024PF00059

[0224] 33

[0225] Particularly preferred within the meaning of the invention are the following three embodiments of the method according to the invention:

[0226] A first method comprising the process steps of: a) providing a primary preform comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and

[0227] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation; and b) providing at least one jacket tube having a jacket tube inner bore and a jacket tube longitudinal axis along which a jacket tube wall bounded by an inner jacket surface and an outer jacket surface extends, and inserting the primary preform into the jacket tube; and c) performing a fiber drawing while simultaneously collapsing the jacket tube.

[0228] characterized in that the casing tube has an outer diameter of 100 mm to 240 mm and characterized in that steps a) and b) or steps b) and c) take place on the same system.

[0229] A second method comprising the process steps of: a) providing a primary preform, comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and

[0230] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation; and b) providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing wall bounded by an inner and outer surface extends, and inserting the primary preform into the casing tube by i) collapse, or ii) collapse and simultaneous elongation; forming a final preform characterized by an outer diameter of 28 mm to 60 mm; and 2024PF00059

[0231] 34

[0232] Performing a fiber drawing process, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0233] A third method comprising the process steps of: a) providing a primary preform, comprising at least one sheath tube having an inner sheath tube bore and a longitudinal sheath tube axis along which a sheath tube wall bounded by an inner sheath tube surface and an outer sheath tube surface extends, and comprising antiresonance element preforms; and

[0234] Further processing of the primary preform into a primary preform by i) collapse, or ii) collapse and simultaneous elongation; and b) providing at least one casing tube having an inner casing bore and a longitudinal casing axis along which a casing wall bounded by an inner casing surface and an outer casing surface extends, and inserting the primary preform into the casing tube by i) collapse, or ii) collapse and simultaneous elongation; forming a secondary preform characterized by an outer diameter of 100 mm to 200 mm; and c) producing a final preform, characterized by an outer diameter of 28 mm to 60 mm, from the secondary preform by i) collapse, or ii) collapse and simultaneous elongation; and

[0235] Performing a fiber drawing process, characterized in that the casing tube has an outer diameter of 100 mm to 240 mm.

[0236] As already described, the semi-finished products, in particular primary preforms, secondary preforms, building units and final preforms, have relatively large outer diameters and are characteristic of the process according to the invention.

[0237] III. Products

[0238] Primary preforms according to the invention are manufactured from primary preforms comprising at least one sheathing tube and antiresonance element preforms. Both the sheathing tubes and the antiresonance element preforms are characterized in particular by their relatively large outer and inner diameters. Sheathing tubes in this sense preferably have an inner diameter of 25 mm to 80 mm and a 2024PF00059

[0239] 35

[0240] Outer diameters from 41 mm to 100 mm, as described above.

[0241] These large diameters make it possible to place antiresonance element preforms or capillaries in the primary preforms or canes according to the invention in such a way that only a small angular deviation, as described above, is achieved.

[0242] Sheathing tubes with such diameters have the advantage that they do not tend to exhibit uneven heat distribution when welding on the antiresonance element preforms, thus reducing the risk of sheathing tube cracking. At the same time, such sheathing tubes are large enough not to deform during the welding or melting process and therefore are not mechanically unstable.

[0243] Sheathing tubes for primary preforms, from which primary preforms according to the invention are preferably produced using the inventive method, have lengths between 600 mm and 1000 mm as described above. If sheathing tubes that are too long are selected, the dead weight increases, which increases the risk of undesirable bending that is too large. Conversely, sheathing tubes that are too short have the disadvantage that the cane produced from them will be too small to achieve the dimensions preferred according to the invention, which are particularly well suited for carrying out the inventive method.

[0244] A primary preform, or cane, within the meaning of the present invention is preferably a large cane with a length greater than 600 mm to greater than 3000 mm as previously described; preferably, the cane is greater than 1000 mm. Such large canes preferably ensure that an industrially significant yield of antiresonant hollow core fibers is achieved by means of the process according to the invention.

[0245] The primary preforms (canes) according to the invention preferably have an outer diameter between 24 mm and 60 mm, meaning their outer diameter is preferably 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm,

[0246] 35 mm, 36 mm, 37 mm, 38 mm, 39 mm or for example 40 mm, 41 mm, 42 mm, 43 mm,

[0247] 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm or for example 50 mm, 51 mm, 52 mm,

[0248] 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm or, for example, 60 mm. Preferably, the outer diameter of the primary preforms according to the invention is greater than 24 mm.

[0249] Primary preforms (canes) according to the invention preferably have an inner diameter between 14 mm and 55 mm, for example 14 mm, 15 mm, 16 mm, 17 mm, 18 mm,

[0250] 19 mm, or for example 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm,

[0251] 28 mm, 29 mm or for example 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm,

[0252] 37 mm, 38 mm, 39 mm or for example 40 mm, 41 mm, 42 mm, 43 mm, 44 mm, 45 mm, 2024PF00059

[0253] 36

[0254] 46 mm, 47 mm, 48 mm, 49 mm or for example 50 mm, 51 mm, 52 mm, 53 mm, 54 mm or for example 55 mm.

[0255] According to the invention, it is preferred if the antiresonance element preforms in the primary preforms are capillaries arranged in a nested design. For the purposes of the present invention, the term nested design refers to a state in which antiresonance element preforms are placed one inside the other and subsequently positioned in the sheath tube at the designated locations. This means that a capillary having a hollow core extending along a longitudinal axis and a capillary sheath surrounding the hollow core is placed inside the hollow core of at least one other capillary with a larger inner and outer diameter. According to the invention, this process can, in principle, be repeated any number of times. It is also conceivable according to the invention that the capillaries arranged in the nested design are already fixed inside one another before being placed in the sheath tube.However, this is not strictly necessary; the fixation also occurs during the further processing of the primary preform via the hot forming process steps according to the invention. The capillaries arranged in this way are then generally placed in the hollow core of a suitable sheathing tube and generally fixed at the ends of the sheathing tube to produce a primary preform. The primary preform is then preferably simultaneously collapsed and elongated to produce a primary preform.

[0256] In accordance with the present invention, the capillary with the largest outer diameter, which in the nested design is therefore the outermost capillary of at least two capillaries, has an outer diameter of at least 5.00 mm when the antiresonance element preform thus described has become part of a primary preform. Overall, the capillaries that become part of the primary preform according to the invention preferably have outer diameters of at least 2.00 mm, as described above.

[0257] A further advantage of the invention, which is preferably achieved by the relatively large diameters of the various half-rounds according to the invention, is that the pressures that arise when generating an equilibrium pressure or when expanding the antiresonance element preforms by means of a gas flow as described above can remain relatively low. These low pressures stabilize the round shape of the antiresonance element preforms and simultaneously reduce the risk of damaging them due to the pressure of the gas flow.

[0258] The invention also encompasses assembly units, which describe primary preforms or primary preforms that have been inserted into a casing tube before a collapse step has taken place. Assembly units within the meaning of the invention are a semi-finished product or intermediate product of the inventive method in each of its possible embodiments. 2024PF00059

[0259] 37

[0260] In accordance with the inventive method, further preforms can be produced from the primary preform or the primary preform via a construction unit step, which are not necessarily isolated and are characterized by at least one additional jacket tube which has been collapsed onto the primary preform or the primary preform.

[0261] As the at least one sheath tube collapses, so-called chlorine rings form at the interfaces between the sheath tube and the sheath tube, or between two sheath tubes. These are areas where the glass is depleted of chlorine compared to the rest of the glass body. Typically, glass is used to manufacture the semi-finished products according to the invention, or antiresonant hollow-core fibers, which is terminally shielded with a Si-Cl bond instead of a Si-OH bond. This generally prevents unwanted adsorption of water molecules to the surfaces. During the process according to the invention, the corresponding areas between the outer surface of the sheath tube and the inner surface of the sheath tube become depleted of chlorine. The chlorine rings influence the refractive behavior in the finished antiresonant hollow-core fiber and generally improve the light-guiding properties compared to antiresonant hollow-core fibers manufactured using other methods.

[0262] Secondary preforms according to the invention are preferably not isolated before being further processed into antiresonant hollow core fibers or final preforms. Secondary preforms within the meaning of the present invention are characterized in that at least one sheath tube has been collapsed onto a primary preform or a primary preform blank, thereby obtaining an outer diameter between 100 mm and 200 mm. Antiresonant hollow core fibers produced from secondary preforms within the meaning of the invention therefore also have at least one chlorine ring. Secondary preforms are a possible intermediate product in some embodiments of the process according to the invention.

[0263] The final preforms according to the invention are preferably isolated, at least from, the equipment on which they were manufactured and / or processed. By reducing the outer diameter, the antiresonant element preforms are generally further protected during the manufacturing process of the antiresonant hollow core fiber and are subjected to less thermal and mechanical stress. Final preforms are possible intermediate products in some embodiments of the process according to the invention.

[0264] According to the invention, the preforms can be used to produce antiresonant hollow core fibers in one or more hot forming process steps. 2024PF00059

[0265] EXAMPLES

[0266] Examples of primary preforms and primary preforms within the meaning of the invention

[0267] Examples of inventive stacks (sheathing tube with loosely / point-attached capillaries) and canes that can be produced from them (extended stack, where capillaries are connected to the sheathing tube along its entire length) as well as sheathing tubes that can be collapsed:

[0268] The inventive method was carried out starting from various sheath tube, capillary and jacket tube sizes, and the equilibrium pressures for the corresponding geometries were determined.

[0269] Table 1. Selected geometries for the sheathing tube and the largest capillary arranged in the nested design. OD corresponds to the outer diameter in mm, ID to the inner diameter in mm, the ratio of outer to inner diameter, and PGGW to the equilibrium pressure in Pa.

[0270] Table 1 shows ten examples of sheath tube and capillary geometries that are used, for example, in primary preforms according to the invention. It can be seen from the table that, in particular, combinations of sheath tube and capillaries with large outer and inner diameters result in low equilibrium pressures, which are minimally required to stabilize the geometry of the capillaries during the processing.

[0271] Table 2. The table shows the change in the outer and inner diameters, the change in their ratios and the change in equilibrium pressure after processing the primary preforms into primary preforms in accordance with the invention. 2024PF00059

[0272] 39

[0273] The inventive method was carried out on the ten primary preforms, and they were converted into primary preforms. The large capillaries and sheathing tubes required by the invention also necessitate the use of large jacket tubes to carry out the inventive method. Table three shows the geometric parameters of the jacket tubes that were collapsed onto the various primary preforms.

[0274] Table 3. Geometries of the casing tubes which were collapsed onto the primary preforms.

Claims

2024PF00059 40 REQUIREMENTS 1. A method for producing an antiresonant hollow-core fiber comprising a hollow core extending along a fiber longitudinal axis and a sheathing region surrounding the hollow core, comprising several antiresonance elements, wherein the method comprises the following process steps, performed at least once: a) providing a primary preform comprising at least one sheath having an inner bore and a longitudinal axis along which a sheath wall bounded by an inner surface and an outer surface extends, and comprising antiresonance element preforms; and optionally Further processing of the primary preform into a primary preform by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; and b) providing at least one jacket tube having an inner jacket tube bore and a jacket tube longitudinal axis along which a jacket tube wall bounded by an inner jacket surface and an outer jacket surface extends, and inserting the primary preform or primary preform into the jacket tube; and c) performing a fiber drawing while simultaneously collapsing the jacket tube, characterized in that the jacket tube has an outer diameter of 100 mm to 240 mm, preferably larger than 120 mm.

2. The method according to claim 1, characterized in that steps b) and c) are modified as follows: b) providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing tube wall bounded by an inner and an outer surface extends, and inserting the primary preform or preform into the casing tube by i) collapsing; or ii) collapsing and simultaneously elongating, or iii) collapsing and simultaneously elongating; forming a final preform characterized by an outer diameter of 28 mm to 60 mm; and c) performing a fiber pull.

3. Method according to claims 1 and 2, characterized in that the 2024PF00059 41 Process steps b) and c) are modified as follows, and a step d) is added: b) providing at least one casing tube having an inner casing bore and a longitudinal axis along which a casing tube wall bounded by an inner and an outer surface extends, and inserting the primary preform or preform into the casing tube by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; forming a secondary preform characterized by an outer diameter of 100 mm to 200 mm; and c) producing a final preform, characterized by an outer diameter of 28 mm to 60 mm, from the secondary preform by i) collapsing, or ii) collapsing and simultaneously elongating, or iii) collapsing and subsequently elongating; and d) performing a fiber pull.

4. Method according to claim 1, characterized in that steps b) and c) are carried out on the same system.

5. Method according to claims 2 and 3, characterized in that one or more method steps are carried out on different systems.

6. Method according to claims 1 to 5 characterized in that the diameter of the antiresonance element preforms is greater than 2.00 mm.

7. Method according to claims 1 to 6, characterized in that the antiresonance elements in the primary preform have an angular deviation relative to the sheathing tube of less than 4.000° to less than 0.05°.

8. Method according to claims 1 to 7, characterized in that the jacket tube is collapsed onto the primary preform or primary preform in a hot forming step under the application of a vacuum between the inside of the jacket tube and the outside of the primary preform. 2024PF00059 42 9. Method according to claims 1 to 8, characterized in that a pressure of 50 Pa to 400 Pa is applied in the antiresonance element preforms by means of a gas stream.

10. Method according to claims 1 to 9, characterized in that the primary preforms have a wall thickness of the sheathing tube wall of greater than 4.00 mm.

11. Primary preform for the production of antiresonant hollow core fibers, characterized in that it has an outer diameter between 24 mm and 60 mm, preferably between 33 mm and 60 mm, and that the capillary fixed therein with the smallest outer diameter has an outer diameter of at least 2.00 mm.

12. Primary preform for the production of antiresonant hollow core fibers, characterized in that it has an outer diameter between 24 mm and 60 mm, preferably between 33 mm and 60 mm, and that at least one antiresonance element preform with an outer diameter of at least 5.00 mm to 16.00 mm, preferably 6.50 mm to 16.00 mm, is fixed in it.

13. Assembly unit comprising a primary preform according to claims 11 to 12 and at least one jacket tube, characterized in that the at least one jacket tube has an outer diameter of 100 mm to 240 mm.

14. Use of primary preforms and components according to claims 11 to 13 in a method according to claims 1 to 10.

15. Antiresonant hollow core fiber obtainable according to a method according to claims 1 to 10.

Images