Preform for antiresonant hollow-core fiber and method for separating a preform with a target length

Abstract

A method for manufacturing an HCF preform is described in which preform blanks (stacks) are subjected to hot forming process steps in order to obtain a preform. After the hot forming process steps, the preforms are cut by means of an annular saw cut method according to the invention such that their end faces have desirable properties for fiber drawing.

Description

[0001] 2023PF00113

[0002] 1

[0003] HCF preform with prepared end surface for fiber pulling

[0004] INTRODUCTION

[0005] The invention relates to a method for producing an HCF preform. For this purpose, preforms (stacks) are subjected to hot forming process steps to obtain a preform. After the hot forming process steps, the preforms are cut using an annular saw cut method according to the invention such that their end surfaces exhibit desirable properties for fiber drawing.

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

[0007] In the production of antiresonant hollow-core fibers (AR-HCF), it has been shown that their industrial-scale production is particularly feasible when starting with preforms (canes) that are significantly larger than the final antiresonant hollow-core fiber. These preforms are tubular glass bodies in which the components of an antiresonant hollow-core fiber, such as the sheath or jacket tube, various capillaries, and / or antiresonant element preforms, are already fixed together.

[0008] It is desirable that the size ratios between glass components such as sheath and casing tubes, capillaries, and / or antiresonance element preforms do not fundamentally change between the preforms and the antiresonance hollow core fiber. Furthermore, various forces act on the capillaries and / or antiresonance element preforms during the forming process, which can damage or deform them undesirably.

[0009] Such preforms can be produced from preforms (stacks). In this process, prepared assemblies of individual glass components, which are not yet fully bonded together, are fixed together using hot forming process steps.

[0010] When continuously drawing preforms from a preform, the problem arises of having to cut the glass strand into segments of suitable length. This is usually done by cutting the preform on the outer sheath surface as it moves along its longitudinal axis. 2023PF00113

[0011] 2. First, a predetermined breaking point is created by damaging the outer casing surface, for example by a scratch, a crack, a cut, or by deliberately introducing a stress ring, at which the glass strand is then broken using snap-cuts.

[0012] In the snap-cut method, which mostly involves breaking the glass body rather than making a complete cut, the penetration of cutting particles or liquids into the hollow core area of ​​the separated glass bodies is to be avoided.

[0013] However, this separation process always carries the risk of chipping at the outer edge and an undefined, slanted, or uneven end surface of the preform. End surfaces with such properties are unsuitable for attaching connection systems that can generate internal overpressure and may be necessary to stabilize antiresonant element preforms during the subsequent deformation processes of the preform into the antiresonant hollow core fiber. Furthermore, the snap-cut process retains the risk of unwanted contaminants penetrating the hollow interiors of the glass bodies.

[0014] Several systems are already known in the prior art with which glass bodies can be separated from each other along an induced predetermined breaking point, for example with a snap-cut.

[0015] Document JP 2009-167040 A describes a method for cutting glass bodies in which the glass body is first pretreated along the cutting zone using a suitable scoring or marking device. The pretreated area is then contacted with a coolant, such as liquid nitrogen, and the body separates.

[0016] In JP 2009-149482 A, another method for cutting tubular glass bodies is described. The glass body is first pretreated along the desired cutting zone, e.g., by rotation along a scoring or scoring device. Subsequently, overpressure is applied to the tubular glass body, which causes it to separate.

[0017] US 2008 / 0202298 A relates to a method for cutting a glass body. In this method, a separation zone is first created on the glass body using a suitable cutting device. 2023PF00113

[0018] 3. The surface is scratched. The separation zone is then treated with a mixture of various acids such as HF, HCl, and HNO3. Finally, the glass body can be separated by applying mechanical stress.

[0019] JP 2009-126757 A describes a method for cutting tubular glass bodies. A suitable cutting or scoring device is used to first prepare a separation zone. The tubular glass body is then heated internally to temperatures of 900 °C to 1600 °C, thus inducing separation of the body.

[0020] WO 2021 / 123738 A describes a method for separating a glass body. In this method, a glass body is heated at a predetermined point using a laser or plasma beam or a directed flame. The heated area then allows a portion of the glass body to be separated.

[0021] WO 2014 / 048004 A describes a method for cutting glass bodies by first pretreating the interface with a laser. The glass body is then cut along the pretreated area using a pneumatic device. Furthermore, a device suitable for carrying out the method is described.

[0022] Document JP 2018-080091 A describes a method for cutting a tubular glass body. A defect is cut into the glass body along its circumference using a sawing device, without completely separating it. The resulting defect is then used to obtain a separate portion of the glass body by applying force.

[0023] Another method for producing glass preforms of a predetermined length is described in WO 2016 / 114779 A. For this method, a notch is first induced in a glass body using an air saw or an abrasive wheel. A tensile stress is then applied, and the preform with the predetermined length properties is obtained by separating it from the glass body.

[0024] Document JP 2012-025594 A describes a method for cutting glass bodies. A disc cutter with a blade is used to score the glass body along the cutting line. Simultaneously, a vertically directed tensile force is applied to the glass body, which is reduced as the cutting process progresses. 2023PF00113

[0025] 4

[0026] Document DE 10 2006 012 582 A1 describes a device and a method for separating sections of tubular glass bodies. First, a separation zone is prepared using a scoring wheel. The scored glass body is then cut with a snap-off device.

[0027] Document WO 03 / 029155 A discloses a device and a method for separating a glass strand during a drawing process. A predetermined breaking point is applied to the glass strand using a cutting tool. Subsequently, a bending device, which generates a bending moment, is used to continuously act on the glass strand, causing it to separate.

[0028] JPH 11-343134 A describes a method for separating glass bodies. In this method, a cutting device is pressed against the outside of a glass body. The glass body is then rotated and pressed against the cutting device until it is separated.

[0029] WO 2017 / 186246 A discloses a method for manufacturing a microstructured optical fiber. In this process, an overpressure is applied to a preform having continuous longitudinal channels to stabilize the geometry of these channels during fiber drawing. For this purpose, gas inlet tubes, referred to as "pressure tubes," are connected to the preform.

[0030] Document WO 2021 / 110338 A concerns a connection with which a preform for an anterior hollow core fiber can be connected to a pressure regulator and a method for connecting such a pressure connection to the preform. For this purpose, it is necessary that the connection surface of the glass body can be gas-tightly connected to the connection by means of a suitable sealant.

[0031] WO 98 / 00266 A describes a method and a device for cutting hollow glass bodies. In this method, a laser is used to make a circumferential cut around the glass body, which does not, however, completely cut through the wall of the glass body. Thermal and mechanical forces then separate the glass body along the cut.

[0032] CN 116 730 603 A discloses a method for cutting quartz tubes with a device designed for this purpose. It is provided that the laser-cutting operation is carried out by 2023PF00113

[0033] The cut in step 5 did not completely penetrate the outer wall of the quartz tube. The cut quartz tube was then separated by mechanical force.

[0034] TASK OF INVENTION

[0035] The object of the invention is to provide a separation process for preforms of antiresonant hollow core fibers that enables production on an industrially relevant scale. This means that the process according to the invention must guarantee a high production rate of consistently high-quality products.

[0036] The problem of the invention was solved, firstly, by the fact that the inventors surprisingly succeeded in providing a separation process for preforms and antiresonant hollow core fibers that does not lead to contamination of the hollow interiors of the preforms or antiresonant hollow core fibers.

[0037] Secondly, the present invention provides a method for cutting preforms for antiresonant hollow core fibers in such a way that they are reliably equipped with end faces that enable connection to pressure systems. This allows pressure to be applied internally to the preforms in subsequent process steps, thereby geometrically stabilizing the antiresonant element preforms within the preforms during processing into antiresonant hollow core fibers. This ensures consistent production quality with high productivity.

[0038] Surprisingly, the inventors of the present invention have succeeded in fulfilling both requirements by preparing the preforms by means of a circumferential incision which, however, does not completely cut through the preform but leaves part of the glass body intact, and then completing the separation by applying force.

[0039] BRIEF DESCRIPTION OF THE INVENTION

[0040] [1] Method for producing preforms for antiresonant hollow core fibers which a) have a glass body with hollow structures, with a glass body internal bore and a 2023PF00113

[0041] 6

[0042] a) glass body longitudinal axis along which a glass body wall bounded by an inner glass body surface and an outer glass body surface extends, and b) antiresonance element preforms, and wherein

[0043] The glass body and the antiresonance element preform are partially or completely fixed to one another, corresponding to a target length, comprising the following process steps, performed at least once: i) circumferential cutting of a target separation point on the outer glass body surface without completely penetrating the glass body wall and without completely separating the preform, by means of a suitable cutting device, and ii) exerting a force on the glass body until a preform of target length breaks off along the target separation point by means of a suitable device.

[0044] [2] Method according to [1], characterized in that the glass body is rotated during the cutting process or that rotation and cutting are carried out successively.

[0045] [3] Method according to [1] and [2], characterized in that the cutting device comprises mechanical cutting devices or high-energy cutting devices.

[0046] [4] Method according to [3], characterized in that mechanical cutting devices include saws, in particular circular saws and band saws, cut-off grinders or water jet cutters.

[0047] [5] Method according to [3], characterized in that high-energy cutting devices comprise laser cutters, plasma cutters or oxyfuel cutters.

[0048] [6] Method according to [1] to [5], characterized in that the circumferential incision is made at an angle of 85° to 95°, preferably at an angle of 90° to the longitudinal axis of the glass body.

[0049] [7] Method according to [1] to [6], characterized in that the circumferential incision has a incision width which corresponds to the width of the cutting element of the 2023PF00113

[0050] 7

[0051] Cutting device complies.

[0052] [8] Method according to [1] to [7], characterized in that the circumferential incision leaves a residual glass body with a residual glass body wall thickness (dAsc distance annular-saw-cut [mm]).

[0053] [9] Method according to [1] to [8], characterized in that the residual glass body wall thickness dAsc is half the difference between the outer diameter of the residual glass body (OD) res outer diameter residue glass [mm]) and the diameter of the hollow structure of the glass body (ID pre inner diameter preform [mm]) according to the following formula:

[0054]

[0010] Method according to [1] to [9], characterized in that the outer diameter of the residual glass body OD res smaller than the outer diameter of the glass body OD pre .

[0055]

[0011] Method according to [1] to

[0010] , characterized in that the cutting depth of the circumferential cut (d cu t distance cut [mm]) from half the difference between the outer diameter of the glass body (OD) pre outer diameter preform [mm]) and the outer diameter of the remaining glass body OD res according to the following formula:

[0056] OD pre OD res -CUt

[0057]

[0012] Method according to [1] to

[0011] , characterized in that the cutting depth of the circumferential cut d cu t is less than the glass body wall thickness (d) pre distance preform wall [mm]).

[0058]

[0013] Method according to [1] to

[0012] , characterized in that the ratio between the cutting depth of the circumferential cut d cut and the residual glass body wall thickness dAsc is between 15.0 and 0.1, preferably between 13.0 and 0.2, more preferably between 12.0 and 0.3, more preferably between 11.0 and 0.4, more preferably between 10.0 and 0.5, more preferably between 9.0 and 0.8, more preferably between 8.0 and 1.0, more preferably between 7.0 and 1.5, more preferably between 6.0 and 2.5, more preferably between 5.0 and 0.2, more preferably between 4.0 and 2.5. 2023PF00113

[0059] 8

[0060]

[0014] Method according to [1] to

[0013] , characterized in that the ratio between the cross-sectional area of ​​the circumferential incision CSA cu t (Cross-Section-Area cut [mm 2 ]) and the cross-sectional area of ​​the residual glass body CSAASC (Cross-Section-Area Annular-Saw-Cut [mm²] 2 ]) between 35.0 and 0.5, preferably between 20.0 and 0.5.

[0061]

[0015] Method according to [1] to

[0014] , characterized in that after step i) at least one additional notch is inserted along the intended separation point.

[0062]

[0016] Method according to

[0015] , characterized in that the additional notch is inserted with the same or a different cutting device as the circumferential cut.

[0063]

[0017] Method according to

[0015] and

[0016] , characterized in that the notch has a greater cutting depth than the circumferential cut.

[0064]

[0018] Method according to

[0015] to

[0017] , characterized in that the cutting depth of the notch is 0.01 to 1.50 times deeper than the cutting depth of the circumferential notch.

[0065]

[0019] Method according to [1] to

[0018] , characterized in that the notch has a length corresponding to a fraction of 0.2 to 1.7 of the radius of the glass body.

[0066]

[0020] Method according to [1] to

[0019] , characterized in that the fixation of the antiresonance element preforms in the glass bodies is either carried out completely or the fixation of the antiresonance element preforms in the glass bodies is carried out partially at the locations where the circumferential incision is to be made.

[0067]

[0021] Method according to [1] to

[0020] , characterized in that before step i) the existing end surface of the glass body is sealed watertight.

[0068]

[0022] Method according to [1] to

[0021] , characterized in that the force applied to the cut glass body is exerted by exerting a tensile stress, a torsional force or a bending of the glass body, preferably by exerting a tensile stress or a torsional force.

[0069]

[0023] Method according to [1] to

[0022] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t has a surface roughness at which the mean arithmetic height Sa is no more than 2.000 pm. 2023PF00113

[0070] 9

[0071]

[0024] Method according to [1] to

[0023] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t has a surface roughness where the maximum height Sz is no more than 25,000 pm.

[0072]

[0025] Method according to [1] to

[0024] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t has a surface roughness where the aspect ratio of the surface texture Str is no more than 0.400.

[0073]

[0026] Method according to [1] to

[0025] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t has a surface roughness where the arithmetic mean of the tip curvature Spc is not less than 1000,000 mm -1 amounts.

[0074]

[0027] Method according to [1] to

[0026] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t has a surface roughness at which the developed interface ratio Sdr is no more than 0.3000.

[0075]

[0028] Method according to

[0023] to

[0027] , characterized in that the surface roughness parameters are determined by means of 3D laser scanning microscopy.

[0076]

[0029] Method according to [1] to

[0028] , characterized in that after the preform has been cut off, the cut end surface of the antiresonance element preforms is extended over the cross-sectional area of ​​the circumferential incision CSA to a maximum of the cutting width of the circumferential incision, preferably 0.00 mm. cu protrudes from the glass body.

[0077]

[0030] Method according to [1] to

[0028] , characterized in that after separating the preform, the cross-sectional area of ​​the circumferential incision CSA cu of the glass body protrudes at most 1.00 mm, but preferably 0.00 mm, beyond the separated end surface of the antiresonance element preforms.

[0078]

[0031] Method according to [1] to

[0030] , characterized in that after separating the preform, the cross-sectional area of ​​the circumferential incision CSA cuprotrudes at most 1.00 mm, but preferably 0.00 mm, beyond the cross-sectional area of ​​the residual glass body CSAASC.

[0079]

[0032] Method according to [1] to

[0030] , characterized in that after separating the preform, the cross-sectional area of ​​the residual glass body CSAASC extends at most to the cut- 2023PF00113

[0080] 10 width of the circumferential incision, preferably 0.00 mm, mm across the cross-sectional area of ​​the circumferential incision CSA cu t protrudes.

[0081]

[0033] Method according to [1] to

[0032] , characterized in that a terminal edge piece with a length between 15 mm and 75 mm is removed from the glass body by applying method steps i) and ii).

[0082]

[0034] Method for separating preforms for the production of antiresonant hollow core fibers according to [1] to

[0033] , comprising the following process steps, performed at least once: i) sealing the end surface watertight, and ii) circumferentially cutting a predetermined separation point on the outer glass body surface without completely penetrating the glass body wall and without completely separating the preform, by means of a saw, and optionally iii) making at least one additional notch along the predetermined separation point by sawing out with the rotating saw blade a piece that is 0.01 to 1.50 times deeper than the predetermined separation point and corresponds to a length of 0.2 to 1.7 times the radius of the glass body, and iv) applying a force to the glass body until a preform of predetermined length breaks off along the predetermined separation point by means of a tensile stress or a torsional force.

[0083]

[0035] Preform of nominal length for the production of an antiresonant hollow core fiber, characterized in that it has at least one end surface compatible with a pressure connection, which has a cross-sectional area of ​​the circumferentially circumferential cut CSA. cu t (Cross-Section-Area cut [mm 2 ]), a cross-sectional area of ​​the residual glass body CSAASC (Cross-Section-Area Annular-Saw-Cut [mm²] 2 ]) and comprises an end surface of antiresonance element preforms.

[0084]

[0036] Preform according to

[0035] , characterized in that the surface properties of the cross-sectional area of ​​the circumferential incision CSA cu t and the surface texture of the cross-sectional area of ​​the residual glass body CSAASC are different.

[0085]

[0037] Preform according to

[0035] and

[0036] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cut has a surface roughness in which the mean arithmetic height Sa is not more than 2,000 pm, determined by the method on

[0028] .

[0086]

[0038] Preform according to

[0035] to

[0037] , characterized in that the cross-sectional area of ​​the 2023PF00113

[0087] 11 extensive circumferential cut CSA cu t has a surface roughness in which the maximum height Sz is no more than 25,000 pm, determined by the method on

[0028] .

[0088]

[0039] Preform according to

[0035] to

[0038] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t has a surface roughness in which the aspect ratio of the surface texture Str is no more than 0.400, determined by the method on

[0028] .

[0089]

[0040] Preform according to

[0035] to

[0039] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t has a surface roughness where the arithmetic mean of the tip curvature Spc is not less than 1000,000 mm -1 , determined using the method on

[0029] , is.

[0090]

[0041] Preform according to

[0035] to

[0040] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t has a surface roughness in which the developed interfacial ratio Sdr is no more than 0.3000, determined by the method on

[0028] .

[0091]

[0042] Preform according to

[0035] to

[0041] , characterized in that the end surface of the antiresonance element preforms extends beyond the cross-sectional area of ​​the circumferential incision CSAcut of the glass body to the cutting width of the circumferential incision, preferably 0.00 mm.

[0092]

[0043] Preform according to

[0035] to

[0042] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu The length of the glass body should not exceed 1.00 mm, but preferably 0.00 mm, beyond the end surface of the antiresonance element preforms.

[0093]

[0044] Preform according to

[0035] to

[0043] , characterized in that the cross-sectional area of ​​the circumferential incision CSA cu t protrudes at most 1.00 mm, but preferably 0.00 mm, beyond the cross-sectional area of ​​the residual glass body CSAASC.

[0094]

[0045] Preform according to

[0035] to

[0044] , characterized in that after separation of the preform, the cross-sectional area of ​​the residual glass body CSAASC extends at most to the cutting width of the circumferential incision, but preferably 0.00 mm beyond the cross-sectional area of ​​the circumferential incision CSA cu t protrudes.

[0095]

[0046] Preform for the production of an antiresonant hollow core fiber, obtainable according to a method according to [1] to

[0035] , 2023PF00113

[0096] 12

[0097]

[0047] Assembly unit for the production of an antiresonant hollow core fiber, comprising a preform according to

[0035] to

[0046] and a gas-tight pressure connection.

[0098] DETAILED DESCRIPTION OF THE INVENTION

[0099] The present invention is described in detail as follows:

[0100] I. Definitions

[0101] For the purposes of the present invention, the term "circumferential cut" refers to the cutting of a glass body, carried out according to the invention by means of a suitable cutting device. Either a cutting device is guided circumferentially along the circumference of a fixed glass body to create a cut that terminates along the circumference of the glass body, or the glass body is rotated along a fixed cutting device so that a cut is created that terminates along the circumference of the glass body. It is also possible for both the cutting device and the glass body to be rotated. For the purposes of the invention, the depth of the circumferential cut is defined as d cu t (distance cut [mm]) denotes and it leaves behind the separated cross-sectional area of ​​the circumferential cut CSA cu t (Cross-Section-Area cut [mm 2]). In cases where either the glass body, the cutting device, or both are rotated, the circumferential cut takes the form of a circular cut. This means that the cross-sectional area is the same at every point of the circumferential cut. The cross-sectional area of ​​the circumferential cut CSA cu In such a case, t can be described as a hollow circular surface. However, it is also conceivable to design the circumferential incision, which is a cut terminating along the circumference of the glass body, in such a way that other geometric hollow shapes than the hollow circle are obtained. All types of hollow polygons are conceivable, in particular those polygons in which one or more of the edges have a rounded shape. According to the invention, such shapes are achieved, for example, particularly when at least one optional notch is applied to the glass body.

[0102] 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 thus collapses in a controlled manner. 2023PF00113

[0103] 13. When the structure collapses, it is subjected to controlled collapse. Typically, but not necessarily, collapse steps are carried out together with elongation steps and / or also with re-collapse steps under the influence of temperature and, if necessary, negative pressure.

[0104] 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.

[0105] 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.

[0106] 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. It is possible, in principle, to carry out the fiber drawing starting from primary preforms or stacks, or preforms comprising at least one sheathing or at least one jacket tube. Preferably, the fiber drawing process, as defined by the invention, is carried out using modular units or final preforms. The fiber drawing process is characterized by a high drawing speed.

[0107] 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.

[0108] For the purposes of the present invention, the term capillaries refers to tubular bodies which 2023PF00113

[0109] 14 typically consist of glass. The capillaries according to the invention have an inner capillary bore and a longitudinal axis along which a capillary wall, bounded by an inner capillary surface and an outer capillary surface, extends. The term capillaries according to the invention refers exclusively to individual tube 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 optionally fixed, for example in a nested design, such 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.

[0110] For the purposes of the present invention, the term "antiresonance element preform" refers to those components of the antiresonant hollow-core fibers produced according to the inventive process that become antiresonance elements of the antiresonant 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). It is also conceivable, within the scope of the invention, to refer to other possible arrangements of single or multiple capillaries placed in an inner sheath and further processed into an antiresonance element as antiresonance element preforms.The term "antiresonance element preform" thus serves as a collective term for any element that constitutes an antiresonance element in the antiresonant hollow-core fiber. The antiresonance element preforms can still change their shape, such as their outer or inner diameter or their length. Therefore, the term also encompasses antiresonance element preforms that have already undergone at least one processing step but have not yet attained their final shape as an antiresonance element.

[0111] 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 the nested design to form an antiresonance element preform according to the invention, comprising capillaries arranged in the nested design. 2023PF00113

[0112] 15

[0113] The capillaries are arranged in a nested design to form the preforms. Such antiresonance element preforms arranged in a nested design can, for example, be in a mold in which the capillaries are simply placed inside one another. In this form, they can then be placed in a sheath tube and further processed according to the invention. The capillaries arranged in this way are then fixed to each other and / or to the sheath tube. It is also conceivable that the capillaries, which form an antiresonance element preform in a nested design, are already fixed to each other before they are placed in or fixed to a sheath tube.

[0114] For the purposes of the present invention, the term antiresonance element refers to the final form of the antiresonance element preforms after all process steps necessary for manufacturing an antiresonant hollow core fiber from the semi-finished products defined above have been carried out, as they are present 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, through further process steps when in the form of antiresonance elements.

[0115] For the purposes of the present invention, the term "glass body" refers to at least one sheath tube. However, according to the invention, the term "glass body" can also refer to a composite of several sheath tubes or of sheath and jacket tubes. Thus, the term "glass body" encompasses any composite of one or more sheath and jacket tubes as they are present in preforms or primary preforms according to the invention. This means that the term "glass body" includes all systems comprising at least one sheath tube, optionally at least one jacket tube, and at least one antiresonance element preform.

[0116] 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) alongside the antiresonance element preforms. In these preforms, the antiresonance element preforms are fixed to the at least one sheathing tube.

[0117] 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 or the 2023PF00113

[0118] 16

[0119] The antiresonance element preforms are not yet fully fixed within the sheathing tube, but are merely attached at both ends, for example, by means of a suitable adhesive or by fusion. For the purposes of the invention, such semi-finished products are also referred to as primary preforms, even if the antiresonance element preforms have been locally fixed within the sheathing tube to allow circumferential cutting without damaging the preforms. It is also possible to use a suitable device or template, to which the antiresonance element preforms are screwed, to force-fit the preforms within the interior of the sheathing tube. In principle, it is possible to process the finished primary preform or the "stack" by fiber pulling down to the antiresonant hollow core fiber.

[0120] For the purposes of the present invention, the term preform refers to a semi-finished product in which antiresonance element preforms are fixed within a sheathing tube. As long as only one sheathing tube is used, it is referred to as a primary preform. If at least one sheathing tube is collapsed onto the primary preform, it is referred to as a final preform.

[0121] 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 up to the antiresonant hollow core fiber.

[0122] 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, for example, collapsed onto the existing primary preform to form a final or secondary preform. It is also possible, in addition to collapsing the jacket tube onto the primary preform, to perform fiber drawing in the same step by... 2023PF00113

[0123] 17. The tendency of the collapse continues to collapse and elongate.

[0124] For the purposes of the invention, the term assembly refers to a system in which a preform is gas-tightly connected to a pressure connection at a first end surface, so that pressure can build up in the hollow interiors of the preform when the second end surface of the preform is closed or when, during fiber drawing, the hollow interiors in the capillaries have such a small cross-section that pressure equalization through the capillaries can only occur very slowly.

[0125] For the purposes of the present invention, the term final preform refers to the result of at least one hot forming process step 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, 1.03,

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

[0128] II. Procedure

[0129] The method according to the invention serves for the industrially applicable production of preforms, such as those commonly used in the production of antiresonant hollow core fibers. It enables the production of preforms to a specified length without the risk of contamination of the hollow interiors of the preforms. Furthermore, it allows the end face of the preforms to be accessible for a pressure connection. Preforms produced to a specified length using the method according to the invention include: 2023PF00113

[0130] 18 a) a glass body with hollow structures, with an internal glass body bore and a longitudinal glass body axis along which a glass body wall bounded by an internal glass body surface and an external glass body surface extends, and b) antiresonance element preforms.

[0131] In accordance with the invention, it is preferred that the antiresonance element preforms have already been at least partially fixed to the glass body, particularly if the glass body is a primary preform. The local fixation then preferably takes place where the desired separation point according to the invention is to be induced by means of a circumferential incision. It is particularly preferred if the antiresonance element preforms have already been completely fixed to the glass body and the glass body represents a primary or final preform within the meaning of the invention.According to the invention, the following process steps are carried out to achieve separation to the desired length: i) circumferential cutting of a desired separation point on the outer surface of the glass body without completely penetrating the glass body wall and without completely separating the preform, by means of a suitable cutting device, and ii) exerting a force along the desired separation point on the glass body by means of a suitable device until a preform of the desired length is broken off.

[0132] In contrast to the conventional method of cutting an outer glass body surface, as known in the prior art, the present method uses a circumferential cut. Such a cut offers the general advantage that the desired separation point is evenly distributed around the outer glass body, requiring only minimal force to cut the preform to the desired length.

[0133] According to the invention, it is conceivable to rotate the glass body during the cutting process, as well as to make various cuts and rotations sequentially. The result is then either a perfectly circular, circumferential cut if the glass body is rotated during the cutting process, or a polygonal, circumferential cut if several cuts are made at different positions.

[0134] The circumferential incision is made according to the invention by removing the preform 2023PF00113

[0135] 19. The preform is mounted horizontally on rollers, rotated, and cut with a suitable cutting device either during rotation or alternately between rotation and cutting. However, the preform is not completely severed, nor is it cut to such an extent that the inner glass body surface is exposed. According to the invention, it is preferable to take measures to avoid the risk of contamination of the preform's cavities by solid or liquid contaminants.

[0136] According to the inventive method, the circumferential incision of the outer surface of the glass body can be carried out with any conceivable cutting device. In general, the circumferential incision can therefore be made with both mechanical and high-energy cutting devices. The only requirement for its applicability is that the incision is controllable to the extent that the glass body is not cut too deeply, i.e., that the incision does not unintentionally penetrate into the hollow interior spaces.

[0137] Possible cutting devices include mechanical saws, angle grinders, or waterjet cutters. High-energy cutting devices such as laser cutters, plasma cutters, or oxyfuel cutters are also possible. For the purposes of the invention, it is particularly preferred to use mechanical cutting devices. These have the advantage of being easily scalable on an industrial scale. Circular saws and band saws, especially tilting saws with a rotating saw blade, are particularly preferred. This allows for precise control of the cutting depth.

[0138] Furthermore, in accordance with the inventive method, it is also preferred if the cut made into the outer surface of the glass body with a suitable cutting device is made at an angle of 85° to 95° to the horizontally positioned glass body. This means that the circumferential cut is made at an angle of 85°, 86°, 87°, 88°, 89°, or 90°, 91°, 92°, 93°, 94°, or 95°. Preferably, the circumferential cut is made at an angle of 89° to 91°, most preferably at 90°.

[0139] The cut is preferably perpendicular to produce the straightest and flattest possible end surface on the preform of the specified length. An end surface with such properties is preferred because it can be regularly connected to a pressure connection while maintaining consistent quality, thus allowing internal pressure to be applied during the processing of the preform into an antiresonant hollow core fiber. 2023PF00113

[0140] 20

[0141] The applied pressure stabilizes the round geometry of the antiresonant element preforms during hot forming process steps in the production of the antiresonant hollow core fiber and is preferably generated by means of a gas stream. Another preferred effect of the gas stream is that the size of the capillaries can also be influenced by the applied pressure. For example, a higher pressure can result in a larger diameter of the capillaries in the antiresonant hollow core fiber. An inert gas stream is introduced for this purpose, for example, a stream of argon, nitrogen, or synthetic air without water content.

[0142] The circumferential cut is characterized by a cut width that preferably depends solely on the width of the cutting element in the cutting device. Accordingly, it is in accordance with the invention if the cut width of a circumferential cut, which has been made on a glass body with a saw device, corresponds to the width of the saw blade.

[0143] As previously mentioned, according to the invention, the circumferential cut is preferably designed such that the glass body is not cut so deeply that the glass body wall is completely penetrated. The internal hollow structures of the glass bodies are therefore preferably not exposed. Accordingly, before the preform is cut to the desired length, a residual glass body with a residual glass body wall thickness of (dAsc distance annular-saw-cut [mm]) remains.

[0144] In the context of the present invention, the term "residual glass body" refers in particular to a glass body that has been circumferentially incised at the intended separation point without exposing the hollow internal structures. In principle, the residual glass body is thus identical in structure to the original glass body, except that its wall thickness is locally reduced compared to the overall thickness, corresponding to the width and depth of the incision. The width of the incision, in the context of the invention, depends on the width of the cutting element of the cutting device, such as the width of the saw blade, laser, or water jet, etc. The locally reduced wall thickness of the residual glass body is referred to, in the context of the invention, as the residual glass body wall thickness (dAsc).

[0145] In accordance with the inventive method, the residual glass body wall thickness (dAsc) is calculated as half the difference between the outer diameter of the residual glass body 2023PF00113

[0146] 21

[0147] (ODres outer diameter residue glass [mm]) and the diameter of the hollow structure of the glass body (IDpre inner diameter preform [mm]). The outer diameter of the residual glass body (ODres) is the locally smaller outer diameter across the width of the incision, which is less than the outer diameter of the glass body (OD). pre The following formula describes the situation:

[0148] In addition to the wall thickness of the residual glass body, the residual glass body is locally limited by the width of the incision and also by the depth of the circumferential incision (d). cut distance cut [mm]). In accordance with the inventive method, the cutting depth is half the difference between the outer diameter of the glass body (OD). pre ) and the outer diameter of the remaining glass body (OD) res ) according to the following formula:

[0149] OD pre OD res -CUt

[0150] In order to meet the requirement preferred according to the invention that the internal hollow structures of the glass body are not exposed by the cut, the cutting depth of the circumferential cut (d) must be cu t) have a smaller size than the glass body wall thickness (d) pre distance preform wall [mm]).

[0151] In accordance with the present invention, the cutting depth of the circumferential cut (d) differs. cut) of the size of the residual glass body wall thickness (dAsc) by a factor of 15.0 to 0.1. This means that the incision depth is, for example, 15.0 times greater than the residual glass body wall thickness or, for example, only 0.1 times greater than the residual glass body wall thickness. The factor between the incision depth of the circumferential incision (d cu t) and the residual glass body wall thickness (dAsc) is therefore 15.0, 14.5, 14.0, 13.5, 13.0, 12.5, 12.0, 11.5, 11.0, 10.5 or 10.0, 9.5, 9.0, 8.5, 8.0, 7.5, 7.0, 6.5, 6.0, 5.5 or 5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, or 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2 or 0.1. Preferably, the ratio between the cutting depth of the circumferential cut (d) is cut) and the size of the residual glass body wall thickness (dAsc) between 13.0 and 0.2, more preferably between 12.0 and 0.3, more preferably between 11.0 and 0.4, more preferably between 10.0 and 0.5, more preferably between 9.0 and 0.8, more preferably between 8.0 and 2023PF00113

[0152] 22

[0153] 1.0, more preferably between 7.0 and 1.5, more preferably between 6.0 and 2.5, more preferably between 5.0 and 2.0, more preferably between 4.0 and 2.5. The above-mentioned ratios are preferred because they define a compromise between the amount of material left and a sufficient cutting depth, so that efficient fracturing of the claimed preform is possible.

[0154] The outer diameter of the preform OD preIn accordance with the invention, the outer diameter is preferably between 240 mm and 2 mm. For example, the outer diameter is 240 mm, 230 mm, 220 mm, 210 mm, 200 mm, 190 mm, 180 mm, 170 mm, 160 mm, 150 mm, 140 mm, 130 mm, 120 mm, 110 mm, 100 mm, 90 mm, 80 mm, 70 mm, 60 mm, 50 mm, 40 mm, 30 mm, 20 mm, 10 mm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, or 2 mm. It results from the sum of the outer diameters of the at least one outer tube and the optional outer casing tube(s) that form the glass body of the preform.

[0155] According to the invention, large cutting depths and small residual glass body wall thicknesses are preferred to ensure that the preform can be cut to the desired length with minimal force. Furthermore, the cut portion of the desired separation point, or the end surface of the preform at the desired length, allows for better control over the surface finish than the broken portion. The choice of cutting device, the conditions during the cutting process (such as whether the cutting is dry or wet, or the rotation speed of the glass body) can all be influenced. Since a surface that is as flat as possible is preferred according to the invention, it is therefore advantageous to cut as large a proportion of the surface as possible.

[0156] Along the cutting width, a cross-sectional area CSAcut (Cross-Section-Area cut [mm²]) is created by the circumferential cut. 2]), where the remaining glass body is already separated. Since the circumferential cut does not extend completely through the entire width of the glass body, a cross-sectional area CSAASC (Cross-Section-Area Annular-Saw-Cut [mm²]) remains on the remaining glass body. 2 ]) present, which denotes the part of the cross-section of the circumferential incision of the remaining glass body that has not yet been separated by the circumferential incision and is only separated later in the process by the application of a force. Within the cavities of the glass body, the end surface of the antiresonance element preforms fixed in these cavities also remains, which is also only separated later in the process by the application of a 2023PF00113

[0157] 23

[0158] Force action will separate them.

[0159] According to the invention, the surface areas of the cross-sectional area of ​​the circumferentially circumferential cut (CSA) preferably differ. cut) and the cross-sectional area of ​​the residual glass body (CSAASC) by a factor of 35.0 to 0.5. This means that the cross-sectional area of ​​the circumferential incision is, for example, 35.0 times larger than the cross-sectional area of ​​the residual glass body, or, for example, only 0.5 times larger than the cross-sectional area of ​​the residual glass body. The factor between the cross-sectional area of ​​the circumferential cut (CSAcut) and the cross-sectional area of ​​the remaining glass body (CSAASC) is therefore 35.0, 34.5, 34.0, 33.5, 33.0, 32.5, 32.0, 31.5, 31.0, 30.5 or 30.0, 29.5, 29.0, 28.5, 28.0, 27.5, 27.0, 26.5, 26.0, 25.5 or 25.0, 24.5, 24.0, 23.5, 23.0, 22.5, 22.0, 21.5, 21.0, 20.5 or 20.0, 19.5, 19.0, 18.5, 18.0, 17.5, 17.0, 16.5, 16.0, 15.5 or 15.0, 14.5, 14.0, 13.5, 13.0, 12.5, 12.0, 11.5, 11.0, 10.5 or 10.0, 9.5, 9.0, 8.5, 8.0, 7.5, 7.0, 6.5, 6.0, 5.5 or 5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, or 1.0, 0.9, 0.8, 0.7, 0.6 or 0.5.Preferably, the ratio between the area of ​​the cross-sectional area of ​​the circumferential cut (CSA) is cu t) and the cross-sectional area of ​​the residual glass body (CSAASC) between 20.0 and 0.5, preferably between 19.0 and 1.0, preferably between 18.0 and 1.5, preferably between 17.0 and 1.5, preferably between 16.0 and 2.0, preferably between 15.0 and 2.5, preferably between 14.0 and 3.0, preferably between 13.0 and 3.5, preferably between 12.0 and 4.0, preferably between 11.0 and 4.5, preferably between 10.0 and 5.0.

[0160] According to the invention, large cross-sectional areas of the circumferential cut are preferred to ensure that the preform can be cut to the desired length with minimal force. As already described, a large cut surface also allows for better control over the surface finish of the end face of the preform at the desired length. A flat end face enables a pressure connection, which, during the further processing of the preform into an antiresonant hollow core fiber, allows for the application of pressure that stabilizes the antiresonant element preforms inside the preforms.

[0161] In accordance with the present invention, it is optionally also possible to induce an additional notch over a limited portion of the cutting width, in addition to the circumferential cut that represents the intended separation point. For example, using the same or a different cutting device with which the circumferential cut of the intended separation point was made, an additional notch can be made along a portion of the length of the circumferential cut.

[0162] 24. A circumferential cut is made, which is characterized by a greater cutting depth compared to the circumferential cut.

[0163] Inducing a notch can be advantageous if the force required to completely separate the preform at a specified length is to be applied by bending the preform. However, according to the invention, it is preferred if the circumferential cut is made without inducing an additional notch; nevertheless, the notch is also included within the scope of the invention.

[0164] If a notch is induced, it is preferably 0.010 to 1.50 times as deep as the cutting depth of the circumferential notch; that is, it is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00 or 1.01.

[0165] 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, or 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17,

[0166] 1.18, 1.19, or 1.20, 1.21, 1.22, 1.23, 1.24, 1.25, 1.26, 1.27, 1.28, 1.29, or 1.30, 1.31, 1.32,

[0167] 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, or 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48,

[0168] 1.49, or 1.50 times as deep as the cutting depth of the circumferential cut.

[0169] If a notch is induced, it is more preferably 0.1 to 1.00 times as deep as the cutting depth of the circumferentially circumferential blank, more preferably 0.15 to 0.95 times as deep as the cutting depth of the circumferentially circumferential blank, more preferably 0.20 to 0.90 times as deep as the cutting depth of the circumferentially circumferential blank, more preferably 0.25 to 0.85 times as deep as the cutting depth of the circumferentially circumferential blank, more preferably 0.30 to 0.80 times as deep as the cutting depth of the circumferentially circumferential blank, more preferably 0.30 to 0.75 times as deep as the cutting depth of the circumferentially circumferential blank, more preferably 0.30 to 0.70 times as deep as the cutting depth of the circumferentially circumferential blank.

[0170] According to the invention, the induced notch preferably extends over a length fraction of the glass body circumference corresponding to 0.2 to 1.7 times the total radius of the glass body (including its hollow structures). This means that the notch has a length that corresponds to 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or 1.7 times the total radius of the glass body.

[0171] According to the invention, it is preferred to perform the circumferential cutting and the optional induction of the notch on preforms in which the antiresonance element- 2023PF00113

[0172] 25

[0173] The preforms are already fixed to the glass body along their entire length. According to the invention, preforms are manufactured from primary preforms or "stacks." Stacks are characterized by the fact that the anti-resonance element preforms, as described above, are only fixed at their ends to a glass body. If a circumferential cut is made on a glass body in which the anti-resonance element preforms are not yet fixed, the mechanical vibration of the stack caused by the cut can damage the anti-resonance element preforms or affect their position within the hollow structures, thus reducing geometric accuracy.However, it is conceivable, within the scope of the invention, that the antiresonance element preforms are partially fixed away from the terminal fixation in the glass body, and that a circumferential cut is made at the point where the antiresonance element preforms are already fixed to the glass body. In this way, preforms of the desired length can also be produced where the antiresonance element preforms are not yet fixed along their entire length, and the antiresonance element preforms are nevertheless protected from damage or displacement during the circumferential cut.

[0174] The inventive method comprising a circumferential cut, in which the cavities of the glass body are not cut into, has, among other things, the significant advantage that contaminants generated during a cutting process cannot penetrate the cavities. This includes, for example, glass dust or liquids such as water, which are applied during the cutting process to cool the glass body during the cutting and to prevent the formation of glass dust clouds. It may optionally be advantageous according to the invention to seal the end face of the preform, which is located at a distance of the predetermined length from the predetermined separation point induced by the circumferential cut and optionally a notch, with a suitable insulator in order to prevent the penetration of contaminants at this point as well.

[0175] In accordance with the invention, in process step ii) the preform is broken off to the desired length along the predetermined separation point created by the circumferential cut, which is optionally equipped with an additional notch. According to the invention, the break-off is induced by the application of a force. In principle, various types of force are conceivable, such as the application of a tensile stress, a torsional force, or the application of a bending force. According to the invention, it is preferred if a tensile stress or a torsional force is applied. In the context of the invention, torsional force means that the cut 2023PF00113

[0176] 26

[0177] The glass body is fixed in one position while the portion to be processed into a preform of the desired length is rotated. During this process, the uncut portion of the intended separation point is broken off. The force can be applied manually or using a specially designed device.

[0178] Due to the preferably large cross-section CSA cu Preferably, only a small portion of the remaining glass body in cross-section CSAASC is still connected and can be separated cleanly with a relatively small force. It is therefore advantageous to apply a horizontal tensile stress, for example, from a horizontal position of the preform. This ensures that the force acting on cross-section CSAASC is uniform and the separation occurs by forming a flat end surface for the preform at the desired length.

[0179] End surfaces obtained using the inventive method for preforms of the specified length are characterized by exceptionally flat surfaces, despite the fact that they were at least partially produced by fracturing. When the end surfaces are examined using 3D laser scanning microscopy, various parameters can preferably be recorded that quantify the flatness of the end surface.

[0180] According to the invention, the cut portion of the intended separation point, i.e., the cross-section CSAcut, has a mean arithmetic height (Sa) of no more than 2,000 pm. The mean arithmetic height (Sa) is determined using 3D laser scanning microscopy. This means that Sa is 2.000 pm, 1.990 pm, 1.980 pm, 1.970 pm, 1.960 pm, 1.950 pm, 1.940 pm, 1.930 pm, 1.920 pm, 1.910 pm, or 1.900 pm, 1.890 pm, 1.880 pm, 1.870 pm, 1.860 pm, 1.850 pm, 1.840 pm, 1.830 pm, 1.820 pm, 1.810 pm, or 1.800 pm, 1.790 pm, 1.780 pm, 1.770 pm, 1.760 pm, 1.750 pm, 1.740 pm, 1.730 pm, 1.720 pm. 1,710 pm, or 1,700 pm, 1,690 pm, 1,680 pm, 1,670 pm, 1,660 pm 1,650 pm, 1,640 pm 1,630 pm, 1,620 pm, 1,610 pm, or 1,500 pm, 1,490 pm, 1,480 pm, 1,470 pm, 1,460 pm 1,450 pm, 1,440 pm 1,430 pm, 1,420 pm, 1,410 pm, or 1,400 pm, 1,390 pm, 1,380 pm, 1,370 pm, 1 ,360 pm 1,350 pm, 1,340 pm 1,330 pm, 1,320 pm, 1,310 pm, or 1,300 pm, 1,290 pm, 1,280 pm, 1,270 pm, 1,260 pm 1,250 pm, 1,240 pm 1,230 pm, 1,220 pm, 1 ,210 pm, oder 1 ,200 pm, 1,190 pm, 1,180 pm, 1,170 pm, 1,160 pm 1,150 pm, 1,140 pm 1,130 pm, 1,120 pm, 1 ,110 pm, oder 1,100 pm, 1,090 pm, 1 ,080 pm, 1 ,070 pm, 1,060 pm 1,050 pm, 1,040 pm 1 ,030 pm, 1,020 pm, 1,010 pm, oder 1 ,000 pm, 0,990 pm, 0,980 pm, 0,970 pm, 0,960 pm 0,950 pm, 0,940 pm 0,930 pm, 0,920 pm, 0,910 pm, oder 0,900 pm, 0,890 pm, 0,880 pm, 0,870 pm, 0,860 pm 0,850 pm, 0,840 pm 0,830 pm, 0,820 pm, 0,810 pm, oder 0,800 pm, 0,790 pm, 0,780 pm, 0,770 pm, 0,760 pm 0,750 pm, 0,740 pm 0,730 pm, 0,720 pm, 2023PF00113,

[0181] 27

[0182] 0.710 m, or 0.700 pm, 0.690 pm, 0.680 pm, 0.670 pm, 0.660 pm, 0.650 pm, 0.640 pm, 0.630 pm, 0.620 pm, 0.610 pm, or 0.500 pm, or even less than 0.500 pm. The mean arithmetic height expresses the magnitude of the elevation difference of each point compared to the arithmetic mean of the surface. This parameter is the extension of the line roughness parameter Ra (arithmetic mean) to the area. It represents the magnitude of the elevation difference of each point compared to the arithmetic mean of the surface.

[0183] In accordance with the invention, the cut portion of the intended cutting point, i.e. the cross-section CSAcut, has a maximum height (Sz) of 25,000 pm. This means the maximum height Sz is not greater than 25,000 pm, 24,500 pm, 24,000 pm, 23,500 pm, 23,000 pm, 22,500 pm, 22,000 pm, 21,500 pm, 21,000 pm, 20,500 pm or 20,000 pm, 19,500 pm, 19,000 pm, 18,500 pm, 18,000 pm, 17,500 pm, 17,000 pm, 16,500 pm, 16,000 pm, 15,500 pm or 15,000 pm, 14,500 pm, 14,000 pm, 13,500 pm, 13,000 pm, 12,500 pm, 12,000 pm, 11,500 pm, 11,000 pm, 10,500 pm or 10,000 pm, 9,500 pm, 9,000 pm, 8,500 pm, 8,000 pm, 7,500 pm, 7,000 pm, 6,500 pm, 6,000 pm, 5,500 pm or not greater than 5,000 pm or also less than 5,000 pm. The maximum height (Sz) expresses the sum of the height value of the highest peak and the height value of the deepest depression within the definition area on the surface of the end face.

[0184] In accordance with the invention, the cut portion of the intended separation point, i.e. the cross-section CSAcut, has an aspect ratio of the surface texture (Str) which does not exceed 0.400. This means the value exceeds 0.400, 0.390, 0.380, 0.370, 0.360, 0.350, 0.340, 0.330, 0.320, 0.310, 0.300, 0.290, 0.280, 0.270, 0.260, 0.250, 0.240, 0.230, 0.220, 0.210, 0.200, 0.190, 0.180, 0.170, 0.160, 0.150, 0.140, 0.130, 0.120, 0.110, 0.100, 0.090, 0.080, 0.070, 0.060, 0.050, 0.040, 0.030, 0.020, or 0.010 is not or is less than 0.010. The aspect ratio of the surface structure (Str) is a measure of the uniformity of the surface texture. The value lies between 0 and 1, where 0 describes a perfectly uniform surface and 1 a perfectly non-uniform one. Determining the aspect ratio of the surface structure (Str) is known to those skilled in the art and can be done, for example, using laser scanning microscopy.This parameter is a measure of the uniformity of the surface texture, where the value is obtained by dividing the horizontal distance in the direction where the automatic correlation function decays most rapidly (according to Sal) to the value [s] (default: 0.2) by the horizontal distance in the direction where the automatic correlation function decays most slowly to the value [s]. 2023PF00113.

[0185] 28

[0186] In accordance with the invention, the cut portion of the intended separation point, i.e., the cross-section CSAcut, has an arithmetic mean value of the tip curvature (Spc) of not less than 1000,000 mm. -1 This means that the arithmetic mean of the tip curvature Spc is 1000,000 mm'. 1 , 1010,000 mm' 1 , 1020,000 mm' 1 , 1030,000 mm' 1 , 1040,000 mm' 1 , 1050,000 mm' 1 , 1060,000 mm' 1 , 1070,000 mm' 1, 1080,000 mm’ 1 , 1090,000 mm’ 1 oder 1100,000 mm’ 1 , 1110,000 mm’ 1 , 1120,000 mm’ 1 , 1130,000 mm’ 1 , 1140,000 mm’ 1 , 1150,000 mm’ 1 , 1160,000 mm’ 1 , 1170,000 mm’ 1 , 1180,000 mm’ 1 , 1190,000 mm’ 1 oder 1200,000 mm’ 1 , 1210,000 mm’ 1 , 1220,000 mm’ 1 , 1230,000 mm’ 1 , 1240,000 mm’ 1 , 1250,000 mm’ 1 , 1260,000 mm’ 1 , 1270,000 mm’ 1 , 1280,000 mm’ 1 , 1290,000 mm’ 1 oder 1300,000 mm’ 1 , 1310,000 mm’ 1 , 1320,000 mm’ 1 , 1330,000 mm’ 1 , 1340,000 mm’ 1 , 1350,000 mm’ 1 , 1360,000 mm’ 1 , 1370,000 mm’ 1 , 1380,000 mm’ 1 , 1390,000 mm’ 1 oder 1400,000 mm’ 1 , 1410,000 mm’ 1 , 1420,000 mm’ 1 , 1430,000 mm’ 1 , 1440,000 mm’1 , 1450,000 mm' 1 , 1460,000 mm' 1 , 1470,000 mm' 1 , 1480,000 mm' 1 , 1490,000 mm' 1 or 1500,000 mm' 1 , or even larger than 1500,000 mm' 1 The arithmetic mean value describes the principal curvature of the points on the surface, indicating whether the points are pointed or rounded. Determining the mean point curvature (Spc) is known to those skilled in the art and can be done, for example, using laser scanning microscopy. The mean point curvature (as the arithmetic mean) represents the arithmetic mean of the principal curvature of the points on the surface. A small value indicates that the contact points with other objects have a rounded shape. A larger value indicates that the contact points with other objects are pointed.

[0187] In accordance with the invention, the cut portion of the intended separation point, i.e., the cross-section CSAcut, has a developed surface area ratio (Sdr) of no more than 0.3000. The value is, for example, 0.3000, 0.2990, 0.2980, 0.2970, 0.2960, 0.2950, ​​0.2940, 0.2940, 0.2930, 0.2920, 0.2910, 0.2900, or 0.2890, 0.2880, 0.2870, 0.2860, 0.2850, 0.2840, 0.2840.

[0188] 0.2830, 0.2820, 0.2810, 0.2800 or 0.2790, 0.2780, 0.2770, 0.2760, 0.2750, 0.2740, 0.2740,

[0189] 0.2730, 0.2720, 0.2710, 0.2700 or 0.2690, 0.2680, 0.2670, 0.2660, 0.2650, 0.2640, 0.2640,

[0190] 0.2630, 0.2620, 0.2610, 0.2600 or 0.2590, 0.2580, 0.2570, 0.2560, 0.2550, 0.2540, 0.2540,

[0191] 0.2530, 0.2520, 0.2510, 0.2500 or 0.2490, 0.2480, 0.2470, 0.2460, 0.2450, 0.2440, 0.2440,

[0192] 0.2430, 0.2420, 0.2410, 0.2400 or 0.2390, 0.2380, 0.2370, 0.2360, 0.2350, 0.2340, 0.2340,

[0193] 0.2330, 0.2320, 0.2310, 0.2300 or 0.2290, 0.2280, 0.2270, 0.2260, 0.2250, 0.2240, 0.2240,

[0194] 0.2230, 0.2220, 0.2210, 0.2200 or 0.2190, 0.2180, 0.2170, 0.2160, 0.2150, 0.2140, 0.2140,

[0195] 0.2130, 0.2120, 0.2110, 0.2100 or 0.2090, 0.2080, 0.2070, 0.2060, 0.2050, 0.2040, 0.2040,

[0196] 0.2030, 0.2020, 0.2010, 0.2000 or 0.1900, 0.1800, 0.1700, 0.1600, 0.1500 or it is still 2023PF00113

[0197] 29 less than 1,500. The developed interfacial ratio describes the percentage of the additional area of ​​the definition domain attributable to the texture, compared to the perfectly flat definition domain. If the surface in the definition domain has a slope, Sdr increases. Determining the developed interfacial ratio (Sdr) is known to those skilled in the art and can be done, for example, using laser scanning microscopy. The developed interfacial ratio represents the percentage of the additional area of ​​the definition domain attributable to the texture, compared to the perfectly flat definition domain.

[0198] In accordance with the invention, a cross-sectional surface CSA is thus created by means of the circumferential incision according to the invention. cut with a quantifiably flat surface is obtained. If the inventive method is carried out comprising step ii), the antiresonance element preforms located in the cavities of the glass body and the cross-sectional area CSAASC are also separated by the force-induced break at the stub separation point.

[0199] This results in a preform whose end surface comprises three areas corresponding to the separation process steps according to the invention. The end surface has a cross-sectional area of ​​the circumferential incision CSA. cuThe glass body is characterized by a cross-sectional area that was cut before the preform was completely separated. Furthermore, it features a cross-sectional area of ​​the remaining CSAASC glass body that was not cut but rather separated by means of a fracture. Finally, it includes the end face of the broken-off antiresonance element preforms, which are centrally fixed within the hollow structures of the glass body.

[0200] According to the invention, the breakage of the antiresonance element preforms does not lead to an excessive protrusion of the antiresonance element preforms beyond the remaining end surface, nor does it lead to the broken-off end surface of the antiresonance element preforms being hidden far below the remaining end surface in the inner cavity of the glass body.

[0201] In accordance with the invention, the broken end surface of the antiresonance element preforms projects beyond the cross-sectional area of ​​the circumferential incision CSA to a maximum of the cutting width of the circumferential incision, preferably 0.00 mm. cu t of the glass body. This means that the end surface of the antiresonance element preforms can, if necessary, project as far beyond the plane defined by the cross-sectional area of ​​the circumferential incision CSA. cu t is formed, such as the width of the cutting element, 2023PF00113

[0202] 30 with which the circumferential incision was induced. However, it is preferred if the end surfaces of the antiresonance element preforms lie exactly in one plane with the cross-sectional area of ​​the circumferential incision CSA. cu t of the glass body are.

[0203] In accordance with the invention, it is also preferred if the cross-sectional area of ​​the circumferential incision CSA cu The glass body protrudes at most 1.00 mm, but preferably 0.00 mm, beyond the separated end surface of the antiresonance element preforms. This means that the cross-sectional area of ​​the circumferential incision CSA cu t protrudes 1.00 mm, 0.95 mm, 0.90 mm, 0.85 mm, 0.80 mm, 0.75 mm, 0.70 mm, 0.65 mm, 0.60 mm, 0.55 mm, 0.50 mm, 0.45 mm, 0.40 mm, 0.35 mm, 0.30 mm, 0.25 mm, 0.20 mm, 0.15 mm, 0.10 mm, 0.05 mm, but preferably 0.00 mm, beyond the end surface of the antiresonance element preforms.

[0204] According to the invention, the fracture of the cross-sectional area CSAASC results in a flat end surface for the preform at the specified length. This means that the CSAASC cross-sectional area does not extend excessively far beyond the cross-sectional area of ​​the circumferential cut CSA. cuFurthermore, the cross-sectional area of ​​CSAASC is significantly larger than the cross-sectional area of ​​the circumferential cut CSA. cu t lies far below in the inner cavity of the glass body.

[0205] In accordance with the invention, the cross-sectional area CSA projects cu t protrudes at most 1.00 mm, but preferably 0.00 mm, beyond the cross-sectional area of ​​the remaining glass body CSAASC. This means that the cross-sectional area of ​​the circumferential incision CSA cu t protrudes 1.00 mm, 0.95 mm, 0.90 mm, 0.85 mm, 0.80 mm, 0.75 mm, 0.70 mm, 0.65 mm, 0.60 mm, 0.55 mm, 0.50 mm, 0.45 mm, 0.40 mm, 0.35 mm, 0.30 mm, 0.25 mm, 0.20 mm, 0.15 mm, 0.10 mm, 0.05 mm, but preferably 0.00 mm, beyond the cross-sectional area of ​​the remaining glass body CSAASC.

[0206] In accordance with the invention, the cross-sectional area CSAASC is located above the cross-sectional area of ​​the circumferential incision CSA, up to a maximum of the cutting width of the circumferential incision, but preferably 0.00 mm. cu t. This means that the cross-sectional area CSAASC can, if necessary, extend as far beyond the plane defined by the cross-sectional area of ​​the circumferential cut CSA. cu t is formed, such as the width of the cutting element with which the circumferential incision was induced. Preferably, however, the cross-sectional area of ​​the residual glass body CSAASC lies exactly in one plane with the cross-sectional area of ​​the circumferential incision CSA. cu t of the vitreous body. 2023PF00113

[0207] 31

[0208] In accordance with the inventive method, a terminal end piece with a length of at least 15 mm can first be cut off from a glass body by means of the inventive method steps i) and ii). The glass body thus prepared is then characterized by an end surface with the properties described above and can optionally already be used as a preform for the production of an antiresonant hollow core fiber. However, the glass body can also be further cut into one or more additional preforms of the desired length, which then have two end surfaces with the properties of the inventive method. This step can be advantageous according to the inventive method if the glass body, which is processed into one or more preforms, was initially cut off by means of other cutting methods and does not have an end surface with the properties of the inventive method, and is therefore possibly inaccessible for required pressure connections.

[0209] The removed terminal edge piece has a length of at least 15 mm, as it must be long enough to be removed from the glass body or preform; that is, it must be large enough to exert a force according to the invention upon it. However, it can also be longer than 15 mm.

[0210] The method according to the invention thus makes it possible to produce preforms for the manufacture of antiresonant hollow core fibers in a target length, obtaining high-quality end faces that are accessible for pressure connection. At the same time, the method enables the cutting of preforms to the target length without the risk of contaminating the internal cavities of the glass body or the antiresonant element preforms.In a particularly preferred embodiment, the method according to the invention comprises the steps: i) sealing the end surface watertight, and ii) circumferentially cutting a predetermined separation point on the outer surface of the glass body without completely penetrating the glass body wall and without completely separating the preform, using a saw, and optionally iii) making at least one additional notch along the predetermined separation point by sawing out a section with the rotating saw blade that is 0.10 to 2.00 times deeper than the predetermined separation point and has a length of 0.2 to 1.7 times the radius of the glass body, and iv) applying a force to the glass body until a preform of predetermined length breaks off along the predetermined separation point by means of a tensile stress. 2023PF00113.

[0211] 32

[0212] The resulting preform has an end surface which possesses the surface roughness parameters described above.

[0213] III. Products

[0214] The preform obtained in the desired length using the inventive method is compatible with a conventional pressure connection due to its flat surface. It is extremely advantageous for the production of antiresonant hollow core fibers if a pressure connection can be gas-tightly attached to an end surface of a preform for the production of an antiresonant hollow core fiber.

[0215] A gas-tight connection places high demands on the surface to which the pressure connection is attached. The surface must be as flat as possible so that the pressure connection can be flush with the preform, ensuring that overpressure or underpressure can be maintained constantly.

[0216] The inventive method, comprising a circumferential incision in the glass body without completely penetrating it, enables the production of preforms with quantifiable roughness parameters on the end surfaces. This ensures optimal access for a pressure connection, while simultaneously the preforms exhibit high quality, as they cannot be internally contaminated by the inventive method.

[0217] The end surfaces of the preforms according to the invention in nominal length comprise a cross-sectional area of ​​the circumferentially circumferential cut (CSA). cut), which was separated by the circumferential cut, and a cross-sectional area of ​​the remaining glass body (CSAASC), which was separated by the force. Furthermore, antiresonance element preforms of the specified length are located in the hollow interior of the preform; these were also separated by the force. The end surface of the antiresonance element preforms separated by fracture is therefore also part of the end surface of the preform.

[0218] Deformations according to the invention are characterized in particular by the fact that the cross-sectional area of ​​the circumferential incision (CSA) cu t) and the cross-sectional area of ​​the residual glass body (CSAASC) exhibit different surface properties. In particular, 2023PF00113

[0219] 33 other roughness parameters, since CSA cu t is obtained by making a cut, while CSAASC is obtained by breaking off the preform at the target length from the remaining glass body.

[0220] In accordance with the invention, the cross-sectional areas of the circumferential cut (CSAcut), which have a proportion of the end surface of the preforms in nominal length, have the roughness parameters Sa, Sz, Str Spc and Sdr as described above.

[0221] This means that the mean arithmetic height Sa, the maximum height Sz, the aspect ratio of the surface texture Str, the arithmetic mean of the tip curvature Spc, and the developed interface ratio Sdr of the cross-sectional area of ​​the circumferential cut (CSAcut) preferably have the same values ​​as previously determined according to the inventive method for the cross-sectional area of ​​the circumferential cut (CSA). cu t) shown. These roughness parameters are determined according to the invention using 3D laser scanning microscopy.

[0222] After the preform has been cut to the desired length in step ii) of the inventive method, a preform of the desired length is obtained with an end surface that is defined by a cut area of ​​the glass body (cross-sectional area of ​​the circumferential cut (CSA)). cu t)), a fractured area of ​​the glass body (cross-sectional area of ​​the residual glass body (CSAASC)) and a fractured end surface of the antiresonance element preforms. According to the invention, none of these three surfaces projects significantly beyond the other surfaces.

[0223] In accordance with the invention, the broken end surface of the antiresonance element preforms projects beyond the cross-sectional area of ​​the circumferential incision CSA to a maximum of the cutting width of the circumferential incision, preferably 0.00 mm. cu t of the glass body beyond, as previously described for the method according to the invention.

[0224] In accordance with the invention, it is also preferred if the cross-sectional area of ​​the circumferential incision CSA cu t of the glass body projects at most 1.00 mm, but preferably 0.00 mm, beyond the separated end surface of the antiresonance element preforms, as previously described for the method according to the invention.

[0225] In accordance with the invention, the cross-sectional area CSA projects cu t protrudes at most 1.00 mm, but preferably 0.00 mm, beyond the cross-sectional area of ​​the residual glass body CSAASC, as previously described for 2023PF00113

[0226] 34 describes the method according to the invention.

[0227] In accordance with the invention, the cross-sectional area CSAASC is located above the cross-sectional area of ​​the circumferential incision CSA, up to a maximum of the cutting width of the circumferential incision, but preferably 0.00 mm. cu t, as previously described for the method according to the invention.

[0228] The flat surface achieved by the inventive method makes it possible to connect a pressure connection to the preform in the desired length in such a way that the connection is gas-tight.

[0229] EXAMPLES

[0230] Example 1 - Cutting glass objects of different thicknesses

[0231] The following table lists a series of cutting parameters that have been used for the production of preforms of the target length. In the examples shown, the blanks were always circular. However, it is also in accordance with the invention if the blanks have polygonal shapes or shapes of polygons with rounded edges.

[0232] Table 1. Outer and inner diameters of the processed preforms (ODpre, IDpre), outer diameter of the residual glass body (0ASC), residual glass body wall thickness (dAsc) and cut depth (deut), cross-sectional area of ​​the residual glass body (CSAASC), the cross-sectional area of ​​the circumferential cut (CSAcut) and the cut depth of a possible notch (dKerbe). 2023PF00113

[0233] 35

[0234] Table 2. Outer and inner diameters of the processed preforms (ODpre, IDpre), outer diameter of the residual glass body (0ASC), residual glass body wall thickness (dAsc) and cut depth (deut), cross-sectional area of ​​the residual glass body (CSAASC) and the cross-sectional area of ​​the circumferential cut (CSAcut). The examples were produced without a notch.

[0235] Table 1 and Figure 2 show a series of glass body geometries that were cut to the target length for further processing into antiresonant hollow core fibers according to the inventive method. It is illustrated that the inventive process- 2023PF00113

[0236] 36 is suitable for narrower as well as particularly wide glass bodies.

[0237] A possible combination of the areas d according to the invention cu t / dAsc and dxerbe / dcut are given by 1.0 to 8.7 (d cu t / dAsc ) and 0.2 to 6 (d Ke rbe / dcut).

[0238] Example 2 - Roughness determination on the cut surfaces of 7 samples

[0239] Using 3D laser microscopy, the roughness parameters Sa, Sz, Str, Spc, and Sdr were determined for seven selected preforms of nominal length. The following table presents the results.

[0240] Table 32. Roughness parameters determined for 7 cross-sectional areas: the mean arithmetic height Sa, the maximum height Sz, the aspect ratio of the surface texture Str, the arithmetic mean of the tip curvature Spc, and the developed interface ratio Sdr.

[0241] The samples correspond to glass bodies that have been cut with a rotating saw blade.

[0242] Example 3 - Qualitative description of possible work steps of a process according to the invention

[0243] A glass body suitable for processing into preforms for the production of antiresonant hollow-core fibers was presented. The end surface of the glass body was sealed watertight, preventing contamination of the preform's interior by liquid and / or cutting dust.

[0244] A suitable saw with a rotating blade was selected as the cutting device. The stationary cutting device was adjusted so that it could make the cut according to the selected cutting depth for the preform. Then the 2023PF00113

[0245] 37

[0246] The glass body was positioned in a suitable holding device so that it could be continuously moved at target length intervals to the cutting position for applying the target separation point.

[0247] Once the glass object was positioned, the rotating saw blade was slowly moved towards the desired cutting point. Simultaneously, the glass object was slowly moved in the opposite direction to the saw blade's rotation. The saw blade was lowered to the previously set cutting depth, and the glass object was rotated several times around its own axis.

[0248] The glass body, onto which a circular predetermined parting line had now been applied, was removed from the holder, and the predetermined parting line was cleaned of impurities using an aqueous alcohol solution and compressed air / nitrogen rinsing. Applying force to the preform at its predetermined length caused it to break away from the remaining glass body.

[0249] FIGURE DESCRIPTION

[0250] FIGURE 1 Schematic cross-section of the end surface of a preform according to the invention, wherein the circumferential incision is a circular incision. The surfaces CSA cu t and CSAASC have been designated. These are cutting depths d. cu The diagram shows the t and the residual glass body wall thickness dAsc. A schematic arrangement of antiresonance element preforms is located centrally; their cavity and the remaining cavity are colorless.

[0251] FIGURE 2 Schematic cross-section of the end surface of a preform according to the invention, wherein the circumferential cut is not uniform. The surfaces CSAcut and CSAASC have been labelled. The cut depth d is shown. cu The t and the residual glass body wall thickness dAsc are shown. They differ at various points on their corresponding surfaces. Centrally located is a schematic arrangement of antiresonance element preforms, whose cavity and the remaining cavity are colorless.

[0252] FIGURE 3 shows an exemplary pressure connection with which a preform according to the invention can be connected gas-tight, so that pressure can be built up in the hollow interiors of the preform when the second end surface of the 2023PF00113

[0253] 38

[0254] The preform is closed, or if, during fiber drawing, the hollow interiors in the capillaries become so small that pressure equalization through the capillaries can only occur very slowly. The figure shows a pressure inlet 1, a push button 2, a seal 3, an annular saw cut 4, and an internal structure with ARE 5 in the preform 6.

[0255] Figure 4a shows, by way of example, the mean arithmetic height value of the surface relative to the mean plane, using the data from the following table (parameter Sa):

[0256] Position Height

[0257] 1 0.2

[0258] 2 -0.1

[0259] 3 0.3

[0260] 4 -0.2

[0261] 5 0.1

[0262] 6 -0.3

[0263] 7 0.2

[0264] 8 -0.1

[0265] 9 0.3

[0266] 10 -0.2

[0267] Figure 4b shows an example of the maximum height between the highest and lowest points of the surface, using the data from the following table (parameter Sz): 2023PF00113

[0268] 39

[0269] Figure 4c shows an example of the directional dependence of the texture, where a low value indicates a directional structure, using the data from the following table (parameter Str) as an example:

[0270] Figure 4d shows an example of the mean curvature value of the roughness peaks and describes their sharpness, using the data in the following table (parameter Spc) as an example:

[0271] Figure 4e shows, by way of example, the percentage increase in surface area due to microstructure compared to the ideal area, using the data from the following table (parameter Sdr) as an example: 2023PF00113

[0272] 40

Claims

2023PF00113 41 REQUIREMENTS 1. A method for producing preforms for antiresonant hollow-core fibers comprising a) a glass body with hollow structures, with an internal glass body bore and a longitudinal glass body axis along which a glass body wall bounded by an inner glass body surface and an outer glass body surface extends, and b) antiresonant element preforms, and wherein The glass body and the antiresonance element preform are partially or completely fixed to one another, corresponding to a target length, comprising the following process steps, performed at least once: i) circumferential cutting of a target separation point on the outer glass body surface without completely penetrating the glass body wall and without completely separating the preform, by means of a suitable cutting device, and ii) exerting a force on the glass body until a preform of target length breaks off at the target separation point.

2. Method according to claim 1, characterized in that the glass body is rotated during cutting, or that rotation and cutting are performed successively.

3. Method according to claims 1 and 2, characterized in that cutting devices comprise mechanical and high-energy cutting devices and mechanical cutting devices are preferred.

4. Method according to claims 1 to 3, characterized in that the circumferential incision is made at an angle of 85° to 95°, preferably at an angle of 90° to the longitudinal axis of the glass body.

5. Method according to claims 1 to 4, characterized in that the circumferential incision results in a residual glass body, which is defined by a residual glass body wall thickness (dAsc distance annular-saw-cut [mm]) and a incision depth of the circumferential incision (d cu t distance cut [mm]) is characterized and characterized in that the ratio between the cutting depth of the circumferential cut d cu t and the residual glass body wall thickness dAsc between 15.0 and 0.1, preferably between 13.0 and 0.2, more preferably between 12.0 and 0.3, further be- 2023PF00113 42 preferably between 11.0 and 0.4, further preferably between 10.0 and 0.5, further preferably between 9.0 and 0.8, further preferably between 8.0 and 1.0, further preferably between 7.0 and 1.5, further preferably between 6.0 and 2.5, further preferably between 5.0 and 2.0, further preferably between 4.0 and 2.

5.

6. Method according to claims 1 to 5, characterized in that the circumferential incision results in a residual glass body defined by a cross-sectional area of ​​the residual glass body CSAASC (Cross-Section-Area Annular-Saw-Cut [mm²]). 2 ]) and a cross-sectional area of ​​the circumferential cut CSA cu t (Cross-Section-Area cut [mm 2 ]) is characterized and characterized in that the ratio between the cross-sectional area of ​​the circumferential cut CSA cu t (Cross-Section-Area cut [mm 2]) and the cross-sectional area of ​​the residual glass body CSAASC (Cross-Section-Area Annular-Saw-Cut [mm²] 2 ]) between 35.0 and 0.5, preferably between 19.0 and 1.0, preferably between 18.0 and 1.5, preferably between 17.0 and 1.5, preferably between 16.0 and 2.0, preferably between 15.0 and 2.5, preferably between 14.0 and 3.0, preferably between 13.0 and 3.5, preferably between 12.0 and 4.0, preferably between 11.0 and 4.5, preferably between 10.0 and 5.

0.

7. Method according to claims 1 to 6, characterized in that a terminal edge piece with a length of at least 15 mm is removed from the glass body by applying method steps i) and ii).

8. Method according to claims 1 to 7, characterized in that the following method steps are carried out at least once: i) sealing the end surface in a watertight and / or dustproof manner, and ii) circumferentially cutting a predetermined separation point on the outer surface of the glass body without completely penetrating the glass body wall and without completely separating the preform, by means of a saw, and optionally iii) making at least one additional notch along the predetermined separation point by sawing out with the rotating saw blade a piece that is 0.01 to 1.50 times deeper than the predetermined separation point and corresponds to 0.2 to 1.7 times the radius of the glass body, and iv) applying a force to the glass body until a preform of predetermined length breaks off along the predetermined separation point by means of a tensile stress or a torsional force.

9. Preform of nominal length for the production of an antiresonant hollow core fiber, characterized in that it has at least one end surface compatible with a pressure connection, which has a cross-sectional area of ​​a circumferential incision. 2023PF00113 43 CSAcut (Cross-Section-Area cut [mm 2 ]), a cross-sectional area of ​​a residual glass body CSAASC (Cross-Section-Area Annular-Saw-Cut [mm²] 2 ]) and comprises an end surface of antiresonance element preforms.

10. Preform according to claim 9, characterized in that the surface properties of the cross-sectional area of ​​the circumferential incision CSA cu t and the surface texture of the cross-sectional area of ​​the residual glass body CSAASC are different.

11. Preform according to claims 9 and 10, characterized in that it has at least one of the following features: a cross-sectional area CSA cut with a mean arithmetic height Sa not exceeding 2,000 pm; a maximum height Sz not exceeding 25,000 pm; a surface texture aspect ratio Str not exceeding 0.400; a mean arithmetic tip curvature Spc not less than 1,000,000 mm -1 is; a developed interface ratio Sdr which is not more than 0.3000.

12. Preform according to claims 9 to 11, characterized in that it has at least one of the following features: the end surface of the antiresonance element preforms projects at most to the cutting width of the circumferential incision, but preferably 0.00 mm beyond the cross-sectional area of ​​the circumferential incision CSA. cu t of the glass body; the cross-sectional area of ​​the circumferential incision CSA cuThe t of the glass body protrudes at most 1.00 mm, but preferably 0.00 mm, beyond the end surface of the antiresonance element preforms.

13. Preform according to claims 9 to 12, characterized in that it has at least one of the following features: the cross-sectional area of ​​the circumferential incision CSA cu t projects at most 1.00 mm, but preferably 0.00 mm, beyond the cross-sectional area of ​​the residual glass body CSAASC; the cross-sectional area of ​​the residual glass body CSAASC projects at most up to the cutting width of the circumferential incision, but preferably 0.00 mm, beyond the cross-sectional area of ​​the circumferential incision CSA cu out. 2023PF00113 44 14. Preform according to claims 9 to 13, obtainable by a method according to any one of claims 1 to 8.

15. Preform according to claim 14, obtainable by a method according to any one of claims 1 to 8, wherein the circumferential cutting of the predetermined separation point is carried out by mechanical cutting devices.

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