Smokeless manufacturing process for structured optical fiber preforms

Abstract

The present invention relates to a method for manufacturing a preform of an antiresonant hollow-core optical fiber. The method of the present invention uses a positioning template having at least one centering surface. The at least one centering surface cooperates with the first end of the cladding tube in a self-centering manner, so that the antiresonant element preform is arranged at a target position.

Description

Background Art

[0001] The present invention relates to a method for manufacturing a preform for an antiresonant hollow core optical fiber.

[0002] Existing technology

[0003] A hollow-core fiber has a core consisting of an evacuated cavity filled with a gas or liquid. The interaction of light with the glass in a hollow-core fiber is less than that in a solid-core fiber. The refractive index of the core is lower than that of the cladding, making light guidance by total internal reflection impossible. Depending on the physical mechanism of light guidance, hollow-core fibers are categorized as photonic bandgap fibers and antiresonant reflection fibers.

[0004] In the case of a "photonic bandgap fiber," a hollow core region is surrounded by a cladding in which small hollow tubes are periodically arranged. The periodic structure in the cladding induces an effect known in semiconductor technology as a "photonic bandgap," whereby light of a specific wavelength range scattered at the cladding structure constructively interferes due to Bragg reflection in the central cavity and cannot propagate laterally in the cladding.

[0005] In the case of an embodiment of a hollow-core fiber known as an "antiresonant hollow-core fiber" (ARHCF), the hollow-core region is surrounded by an inner cladding region in which a so-called "anti-resonance element" (also called "anti-resonant element" or "ARE") is arranged. The walls of the anti-resonant element, which are uniformly distributed around the hollow core, can act as a Fabry-Perot cavity, operating in antiresonance and reflecting incident light and guiding it through the fiber core.

[0006] This fiber optic technology guarantees low light attenuation, a very broad transmission spectrum (also in the UV or IR wavelength range) and small delays during data transmission.

[0007] EP 3 136 143 A11 discloses an antiresonant hollow-core fiber (referred to herein as a "gapless hollow-core fiber") in which, in addition to the fundamental mode, the core can also guide further modes. To this end, the core is surrounded by an inner cladding comprising a "non-resonant element" that provides phase matching of the antiresonant mode with the higher modes.

[0008] JP 2018 150184 A discloses a method for producing a preform for an antiresonant hollow-core optical fiber, in which the nonresonant element is positioned at the end of the cladding tube by welding on a perforated disk. However, it has proven disadvantageous that the required positioning accuracy of the nonresonant element (ARE) cannot be achieved using this type of perforated disk.

[0009] Further methods for connecting ARE and cladding tubes are described in the following documents: CN 105807363 B, WO 2015 185761 A1, WO 2017 108061 A1, WO 2018 169487 A1.

[0010] Technical goals

[0011] Antiresonant hollow-core fibers, particularly those comprising nested structural elements, possess complex internal geometries, making their precise and reproducible fabrication more difficult. This is particularly true because, in order to adhere to the resonant or antiresonant conditions, respectively, dimensional deviations can only be tolerated by an amount below the operating wavelength of the light to be guided. Deviations from the target geometry can be caused by the configuration of the fiber preform, and they can also occur due to undesirable, disproportionate deformations during the fiber drawing process.

[0012] It is an object of the present invention to specify a method for cost-effectively manufacturing a preform for an antiresonant hollow-core optical fiber, which avoids the limitations of conventional manufacturing methods.

[0013] In particular, it is an object of the present invention to provide a method for producing a preform for an antiresonant hollow-core optical fiber, by means of which method an exact positioning of the antiresonant element can be obtained reproducibly in a sufficiently stable manner.

[0014] Preferred embodiments of the present invention

[0015] The features of the independent claims contribute to at least partially satisfying at least one of the aforementioned objects. The dependent claims provide preferred embodiments which contribute to at least partially satisfying at least one of these objects.

[0016] / 1. / A method for manufacturing a preform of an antiresonant hollow-core optical fiber, the method comprising the following steps:

[0017] a) providing a cladding tube having a cladding tube inner bore and a cladding tube longitudinal axis, a cladding tube wall extending along the cladding tube longitudinal axis, the cladding tube wall being defined by an inner side and an outer side,

[0018] b) preparing a plurality of anti-resonance element preforms, each anti-resonance element preform comprising an ARE outer tube and an ARE inner tube inserted into the ARE outer tube,

[0019] c) preparing a positioning template having a plurality of passage openings therethrough, the plurality of passage openings being adapted to each longitudinally guide an anti-resonance element preform, wherein the positioning template and the cladding tube are made of the same material,

[0020] d) attaching the positioning template to the first end of the cladding tube,

[0021] e) inserting at least a portion of the anti-resonance element preform through the passage opening for arranging the anti-resonance element preform in the cladding tube inner bore,

[0022] f) treating an assembly comprising the cladding tube, the anti-resonance element preform and the positioning template by means of a thermoforming process selected from at least one of stretching and collapsing,

[0023] It is characterized by:

[0024] The positioning template has at least one centering surface which cooperates in a self-centering manner with the first end of the cladding tube so that the anti-resonance element preform is arranged at a target position in step e) “inserting”.

[0025] / 2. / The method according to embodiment 1 is characterized in that the cladding tube is at least partially cut away in the region of the first end in order to form a counter-centering surface which cooperates with the centering surface in a form-fitting manner.

[0026] / 3. / The method according to any of the preceding embodiments is characterized in that the positioning template is at least partially formed in a truncated cone-like manner, wherein the centering surface is at least partially formed in a cladding surface-like manner.

[0027] / 4. / The method according to any of the preceding embodiments, characterized in that the cladding tube is at least partially cut away in a truncated cone-shaped manner in the region of the first end.

[0028] / 5. / The method according to any one of the preceding embodiments, characterized in that in step f) "treating", the anti-resonance element preform is thermally fixed to the cladding tube wall in a flameless manner.

[0029] / 6. / The method according to any one of the preceding embodiments, characterized in that the cladding tube wall has a second end.

[0030] / 7. / The method according to embodiment 6 is characterized in that the method comprises the following steps:

[0031] (i) creating a second positioning template having a plurality of second passage openings therethrough, the plurality of second passage openings being adapted to each longitudinally guide an anti-resonance element preform, wherein the second positioning template and the cladding tube are made of the same material,

[0032] (ii) combining the second positioning template with the second end portion of the cladding tube.

[0033] / 8. / The method according to embodiment 7, characterized in that the method comprises the following steps:

[0034] (iii) inserting at least a portion of the anti-resonance element preform through the second passage opening of the second positioning template,

[0035] (iv) wherein the second positioning template has at least one second centering surface, which cooperates with the second end of the cladding tube in a self-centering manner so that the anti-resonance element preform is arranged at the target position during step (iii) "insertion".

[0036] / 9. / The method according to embodiment 8 is characterized in that the cladding tube is at least partially cut away in the region of the second end portion so as to form a second counter-centering surface which cooperates with the second centering surface in a form-fitting manner.

[0037] / 10. / The method according to any one of the aforementioned embodiments 7 to 9 is characterized in that the second positioning template is at least partially formed in a truncated cone manner, wherein the second centering surface is at least partially formed in a cladding surface manner.

[0038] / 11. / The method according to any one of the aforementioned embodiments 6 to 10 is characterized in that the cladding tube is at least partially cut away in a truncated cone-shaped manner in the region of the second end.

[0039] / 12. / The method according to any one of the preceding embodiments, characterized in that the method comprises the following steps:

[0040] A / Preparing a third positioning template having a plurality of third channel openings therethrough, each of the plurality of third channel openings being adapted to longitudinally guide the anti-resonance element preform, wherein the third positioning template has at least one third centering surface.

[0041] / 13. / The method according to embodiment 12, characterized in that the method comprises the following steps:

[0042] B / Manufacturing of tubular closure elements,

[0043] The closure element in the region of the first end region has an active surface in order to cooperate, in particular in a form-fitting manner, with the third centering surface.

[0044] / 14. / The method according to embodiment 13, characterized in that the method comprises the following steps:

[0045] C / connecting the third positioning template to the first end region,

[0046] D / connecting the closure element to the second end of the cladding tube,

[0047] E / pushing at least a portion of the anti-resonance element preform through the third passage opening to arrange the anti-resonance element preform in the cladding tube inner bore, wherein

[0048] The third centering surface cooperates with the active surface in a self-centering manner so that the anti-resonance element preform is arranged at a target location.

[0049] / 15. / The method according to any one of the aforementioned embodiments is characterized in that the following steps

[0050] At least one of the steps includes flameless thermal joining or flame-based thermal joining:

[0051] Step b) "Preparation",

[0052] Step d) "Attachment",

[0053] Step (ii) "combining",

[0054] Step C / "Link", and

[0055] • Step D / “Connect”.

[0056] / 16. / The method according to any one of the aforementioned embodiments is characterized in that the method comprises

[0057] Include at least one of the following steps:

[0058] heat fixing, in particular flameless heat fixing, at least some of the anti-resonance element preforms to the positioning template, and / or

[0059] • heat fixing, in particular flameless heat fixing, at least some of the anti-resonance element preforms to the second positioning template, and / or,

[0060] • heat fixing, in particular flameless heat fixing, at least some of the anti-resonance element pre-forms to the third positioning template.

[0061] / 17. / The method according to any of the preceding embodiments, characterized in that, before step f) "treating", the anti-resonance element preform is held in place only by means of

[0062] In the inner hole of the cladding tube:

[0063] The positioning template or

[0064] The positioning template and the second positioning template, or

[0065] The positioning template and the third positioning template

[0066] and other means in the absence of substance-to-substance bonding.

[0067] / 18. / The method according to any of the preceding embodiments is characterized in that, in some areas, preferably at the first ARE end, the ARE outer tube has an outer diameter widening portion, which is larger than the inner diameter of at least one of the channel opening, the second channel opening and the third channel opening.

[0068] / 19. / The method according to any one of the preceding embodiments is characterized in that, in some areas, preferably at the second ARE end, the ARE outer tube has an outer diameter tapering portion, which is smaller than the inner diameter of at least one of the channel opening, the second channel opening and the third channel opening.

[0069] / 20. / The method according to any one of the preceding embodiments is characterized in that the positioning template and / or the second positioning template and / or the third positioning template have at least one gas flow element, which connects the inner hole of the cladding tube to the surrounding area of ​​the preform in a fluid-conducting manner.

[0070] / 21. / The method according to any of the preceding embodiments, characterized in that the cladding tube inner bore is produced by means of mechanical processing, in particular by means of drilling, milling, grinding, honing and / or polishing.

[0071] / 22. / The method according to any of the preceding embodiments, characterized in that the cladding tube has an outer diameter in the range of 65 nm to 300 mm, in particular in the range of 90 nm to 250 mm, and in particular has a length of at least 1 m.

[0072] / 23. / A method for producing a secondary preform from a preform produced according to any one of the preceding embodiments 1 to 22, from which an antiresonant hollow-core optical fiber can be drawn, the method comprising the following steps:

[0073] further processing the preform into the secondary preform,

[0074] The further processing comprises one or more of the following thermoforming processes:

[0075] i.) stretch,

[0076] ii.) collapse,

[0077] iii.) collapse and stretch simultaneously,

[0078] iv.) adding additional cladding material,

[0079] v.) adding additional cladding material and subsequent elongation,

[0080] vi.) Adding additional cladding material and stretching it simultaneously.

[0081] / 24. / A method for manufacturing an antiresonant hollow-core optical fiber from a preform manufactured according to any one of the aforementioned embodiments 1 to 22, the method comprising the following steps:

[0082] Further processing the preform into the antiresonant hollow-core optical fiber, wherein the further processing comprises one or more of the following thermoforming processes:

[0083] i.) stretch,

[0084] ii.) collapse,

[0085] iii.) collapse and stretch simultaneously,

[0086] iv.) adding additional cladding material,

[0087] v.) adding additional cladding material and subsequent elongation,

[0088] vi.) Adding additional cladding material and stretching it simultaneously.

[0089] / 25. / The method according to any of the preceding embodiments, characterized in that, in step f) "treating", a relative internal pressure between -25 mbar and -300 mbar, in particular in the range of -100 mbar to -250 mbar, is set as part of the elongation and / or the collapse in the inner bore of the cladding tube.

[0090] Some of the described features are associated with the term "substantially." The term "substantially" should be understood such that, under practical conditions and manufacturing techniques, mathematically exact interpretations of terms such as "overlap," "perpendicular," "diameter," or "parallelism" are never provided, but rather apply only within certain manufacturing-related error tolerances. For example, "substantially parallel axes" define an angle of -5 to 5 degrees relative to one another, and "substantially equal volumes" encompass deviations of up to 5% by volume. "Device consisting essentially of quartz glass" encompasses, for example, a quartz glass portion of ≥95% by weight to ≤100% by weight. Furthermore, "substantially at right angles" encompasses angles of 85 to 95 degrees. DETAILED DESCRIPTION

[0091] The present invention relates to a method for manufacturing a preform of an antiresonant hollow-core optical fiber, the method comprising the following steps:

[0092] a) providing a cladding tube having a cladding tube inner bore and a cladding tube longitudinal axis, a cladding tube wall extending along the cladding tube longitudinal axis, the cladding tube wall being defined by an inner side and an outer side,

[0093] b) preparing a plurality of anti-resonance element preforms, each anti-resonance element preform comprising an ARE outer tube and an ARE inner tube inserted into the ARE outer tube,

[0094] c) preparing a positioning template having a plurality of passage openings therethrough, the plurality of passage openings being adapted to each longitudinally guide an anti-resonance element preform, wherein the positioning template and the cladding tube are made of the same material,

[0095] d) attaching the positioning template to the first end of the cladding tube,

[0096] e) inserting at least a portion of the anti-resonance element preform through the passage opening for arranging the anti-resonance element preform in the cladding tube inner bore,

[0097] f) treating an assembly comprising the cladding tube, the anti-resonant element preform and the positioning template by means of a thermoforming process selected from at least one of stretching and collapsing.

[0098] In order to overcome the above-mentioned shortcomings in the prior art, according to the present invention, it is provided that the positioning template has at least one centering surface, which cooperates with the first end of the cladding tube in a self-centering manner, so that the anti-resonance element preform is arranged at the target position in step e) "insertion".

[0099] By using a positioning template, the method for manufacturing a preform provides a reproducible and precise placement of the antiresonant element preform in the inner bore of the cladding tube. Thus, the preform is a component from which an antiresonant hollow-core fiber can be drawn. In an alternative embodiment, the preform can be further processed into a secondary preform, from which a hollow-core fiber is drawn. The method thus comprises the following steps:

[0100] Step a)

[0101] A cladding tube is prepared as part of step a) "providing." The cladding tube has a hollow core extending along the longitudinal axis of the cladding tube. In one embodiment, the cladding tube has an outer diameter in the range of 65 mm to 300 mm, preferably 90 mm to 250 mm, and preferably 120 mm to 200 mm. Specifically, the cladding tube may have a length of at least 1 m. In one embodiment, the cladding tube comprises or consists of a material transparent to the optical fiber's operating light (e.g., glass, specifically doped or undoped quartz glass (SiO2)). Doping allows for adaptation of physical properties (e.g., coefficient of thermal expansion). Fluorine, chlorine, and / or hydroxyl groups are preferably used as dopants, which reduce the viscosity of the quartz glass.

[0102] Step b)

[0103] As part of step b), "preparing," a plurality of antiresonance element preforms are produced. A component or component of a preform, referred to as an antiresonance element preform, essentially becomes an antiresonance element in a hollow-core optical fiber by simple stretching during the fiber drawing process. Individual antiresonance element preforms are composed of a tubular structural element, at least a portion of which may have a wall thickness in the range of 0.1 mm to 2 mm, preferably 0.2 mm to 1.5 mm. The antiresonance element preforms may be simple or nested components, wherein each antiresonance element preform comprises an outer ARE tube and an inner ARE tube inserted into the outer ARE tube. The antiresonance element preform has at least two walls that, viewed in the direction of the hollow core, have a negative curvature (convex) or no curvature (flat, straight). Further processing of the preform, particularly by means of a thermoforming step, may produce an intermediate product in which the initial antiresonance element preform has a modified shape compared to its initial shape.

[0104] In one embodiment, the antiresonant element preform comprises or consists of a material that is transparent to the optical fiber's operating light (e.g., glass, specifically doped or undoped silica glass (SiO 2 )). Doping provides for adaptation of physical properties (e.g., thermal expansion coefficient). Fluorine, chlorine, and / or hydroxyl groups are preferably used as dopants, which reduce the viscosity of the silica glass.

[0105] In one embodiment, the antiresonance element preform and the cladding tube are made of the same material. In another embodiment, the antiresonance element preform and the cladding tube are composed of the same material, specifically undoped or doped quartz glass (SiO2), wherein the doping amount does not exceed 0.1 wt%.

[0106] The term "made of the same material" describes the material properties of the two parts. Thus, the two parts have essentially the same chemical composition. The total mass of the different chemical elements in the two parts can thus be less than 1% by weight, in particular less than 0.5% by weight, and in particular less than 0.1% by weight. The chemical compositions of the two parts differ, in particular, by a contaminant content of less than 500 ppm by weight, in particular less than 100 ppm by weight, and / or a dopant content of less than 10,000 ppm by weight, in particular less than 5,000 ppm by weight.

[0107] Step c)

[0108] A positioning template is produced as part of step c), "Preparation." The positioning template has a cylindrical, cap-shaped, or disk-shaped shape. In one embodiment, the positioning template has a lateral extension of 5 mm to 200 mm, particularly 15 mm to 80 mm. In one embodiment, the positioning template and the cladding tube consist of the same material, particularly undoped or doped quartz glass (SiO2), with the doping amount not exceeding 0.1% by weight.

[0109] The positioning template has a plurality of passage openings extending through the positioning template. Each passage opening is configured to establish at least one fluid-conducting connection between the cladding tube inner bore and the exterior space through the base of the positioning template. Furthermore, the inner diameter of the passage opening is designed such that the anti-resonance element preform can be pushed longitudinally therethrough to a significant extent. This statement does not limit the use of the widened portion of the ARE outer tube, which is used to position the anti-resonance element preform and will be described in more detail later.

[0110] Furthermore, the passage openings are adapted to each longitudinally guide the anti-resonance element preform. In step f), the "processing", the passage openings support the anti-resonance element preform, so that their design may affect the accuracy during positioning of the anti-resonance element preform in the inner bore of the cladding tube. In order to achieve the desired accuracy during positioning of the anti-resonance element preform at the target position, the passage openings may have one or more of the following features:

[0111] The difference between the inner diameter of the channel opening and the outer diameter of the anti-resonance element preform may be less than 5%, in particular less than 3.5%, preferably less than 2% of the outer diameter of the anti-resonance element preform.

[0112] At least 95%, preferably at least 97%, preferably at least 99.7% of the surfaces of the passage openings have a roughness Ra of [0.01; 0.4] μm, preferably [0.02; 0.2] μm.

[0113] The surface of the passage opening has less than 1000 microcracks / cm2, preferably less than 500 microcracks / cm2.

[0114] In one embodiment, the positioning template and the cladding tube consist of the same material, in particular of undoped or doped quartz glass (SiO 2 ), wherein the doping amount does not exceed 0.1% by weight.

[0115] The positioning template and the cladding tube are made of the same material. The term made of the same material as defined above describes the material properties of the two parts of the positioning template and the cladding tube.

[0116] Step d)

[0117] As part of step d) "Attaching," a positioning template is attached to the first end of the cladding tube. In the method according to the present invention, the positioning template is used to position the antiresonance element preform within the inner bore of the cladding tube. To this end, a bond between the positioning template and the cladding tube is required.

[0118] Step e)

[0119] As part of step d) "inserting", the anti-resonance element preform is inserted at least partially through the passage opening. Thereby, the aim is to arrange the anti-resonance element preform in the cladding tube inner bore.

[0120] Step f)

[0121] As part of step d) "processing", the assembly comprising the cladding tube, the anti-resonant element preform and the positioning template is further processed by means of at least one of a thermal process including elongation and collapse.

[0122] In the context of the present invention, the term "stretching" is understood to mean an increase in the longitudinal expansion of the body. This increase in longitudinal expansion can be coupled with a reduction in the lateral expansion of the body. Stretching can be performed proportionally, such that, for example, the shape and arrangement of a component or component parts are reflected in the stretched final product.

[0123] In the context of the present invention, the term "collapse" is understood to be a reduction in the transverse expansion of the body. This reduction in the transverse expansion of the body may occur as part of a temperature increase of the body and may in particular result in an increase in the longitudinal expansion of the body.

[0124] The term thermal process is understood to mean a method step during which the temperature of a component is increased by means of heat input. Examples of thermal processes are:

[0125] - Flame-based thermal processes based on the oxidation of exothermic reaction gases. An example is the use of hydrogen (also called "H2") as the combustion gas (flame hydrolysis). It reacts with oxygen (also called "O2") in the air.

[0126] - Flameless thermal processes that use other systems that can be preheated and do not require an open flame. An example is the use of resistors that convert electrical energy into thermal energy (heat).

[0127] According to the invention, the positioning template has at least one centering surface which cooperates in a self-centering manner with the first end of the cladding tube so that the antiresonance element preform is arranged at the target position during step e) “insertion”.

[0128] In the context of the present invention, the term self-centering describes the cooperation of two bodies having an outer shape that is designed such that the two bodies assume a predefined position relative to each other without external influences.

[0129] Fulfillment of at least one of the following conditions is necessary for compliance with the resonance or antiresonance conditions, respectively, in the subsequent hollow-core fiber or for further reduction of the attenuation in the subsequent hollow-core fiber:

[0130] - The anti-resonance element preform must be placed at the pre-calculated target position in the cladding tube.

[0131] - The anti-resonance element preform must be placed at the pre-calculated target position in the assembly.

[0132] - The anti-resonance element preform must be arranged at the pre-calculated target position in the preform.

[0133] The present invention provides for a reduction in the deviation of the actual position of the anti-resonance element preform from the target position in the cladding tube and / or assembly and / or preform.

[0134] To achieve this reduction, the positioning template has at least one centering surface which, due to self-centering, enables reproducible positioning relative to the cladding tube and, therefore, reproducible positioning of the passage opening relative to the inner bore of the cladding tube. This reproducible positioning of the passage opening relative to the inner bore of the cladding tube then leads to reproducible positioning of the anti-resonance element preform at a target position in the cladding tube and / or the assembly and / or the preform.

[0135] After step d) "attachment", the longitudinal axis of the passage opening may be aligned substantially parallel to the longitudinal axis of the cladding tube. In one embodiment, the longitudinal axis of the passage opening and the longitudinal axis of the cladding tube are designed to be parallel so that after step d) "attachment" and step e) "insertion", the longitudinal axis of the anti-resonance element preform and the longitudinal axis of the cladding tube have an angle of -1.5 to 1.5 degrees, preferably -0.85 to 0.85 degrees, preferably -0.42 to 0.42 degrees with respect to each other. This parallelism ensures that the anti-resonance element preform is arranged at the target position in the cladding tube and / or assembly and / or preform, and thus ensures that the resonance or anti-resonance conditions, respectively, are observed in the subsequent hollow-core optical fiber.

[0136] In particular, the positioning template may have a first positioning element, such as a cutout, which cooperates with a first counter-positioning element at the first end of the cladding tube and thus in this way prevents the positioning template from rotating about its longitudinal axis.

[0137] As part of one embodiment, the positioning template can have at least one cylindrically designed passage opening. Thus, the inner diameter of the at least one passage opening has a diameter that is 0.15% to 7%, in particular 0.35% to 6%, in particular 0.55% to 3.5% greater than the outer diameter of the anti-resonance element preform. With this type of design, the anti-resonance element preform can be pushed directly through the passage opening and can rest against the inner wall of the passage opening in a form-fitting and / or force-fitting manner, in particular over the entire length of the positioning template.

[0138] One embodiment is characterized in that the cladding tube is at least partially cut away in the region of the first end in order to form a counter-centering surface that cooperates with the centering surface in a form-fitting manner. This type of cooperation facilitates self-centering of the centering surface and the first end of the cladding tube and can occur in particular as part of step e) "insertion." This allows the working load to act normally, i.e., at right angles to the surfaces of the two connection partners.

[0139] One embodiment is characterized in that the counter-centering surface and the centering surface cooperate in a force-fitting manner. This type of cooperation can take place as part of step f) "processing".

[0140] In one embodiment, the edge of the inner protrusion of the cladding tube is provided with a border at the first end. The resulting surface acts as a centering surface.

[0141] One embodiment is characterized in that the positioning template is at least partially shaped in a frustoconical manner, wherein the centering surface is at least partially formed in a cladding surface-like manner.

[0142] A frustum is a special solid of revolution created by cutting a smaller cone from a right circular cone parallel to the base surface. This smaller cone is called the supplementary cone of the actual frustum. The base surface is the larger of the two parallel circular surfaces, and the cap surface is the smaller one. The third surface, which limits the frustum, is called the cladding surface. The height of a frustum is defined as the distance from the base and cap surfaces.

[0143] The truncated cone (also called tapered) configuration is produced by bending the side surfaces relative to the longitudinal axis of the positioning template. This type of treatment increases the geometric surface area of ​​the cladding's centering surface relative to the circumferential surface of the positioning template. This larger surface area allows the positioning template to achieve greater positioning accuracy.

[0144] One embodiment is characterized in that, in the region of the first end, the cladding tube is at least partially cut away in a truncated cone-like manner. This type of design provides a simple self-centering fit of the centering surface and the counter-centering surface. As part of step d) "attachment", the cladding surface-like centering surface rests in a force-fit and / or form-fit manner in the region of the first end of the cladding tube, which region is cut away in a truncated cone-like manner. By means of the matching design of the centering surface and the counter-centering surface, a positioning template can be introduced into the first end of the tube. During the insertion of the anti-resonance element preform through the channel opening (as part of step e) "insertion"), the positioning template remains in its position and ensures that the anti-resonance element preform is arranged at the target position.

[0145] One embodiment is characterized in that the attachment (as part of step d) "attachment") is performed using a flame-based process. In the case of flame-based processes (such as flame hydrolysis), hydrogen (also referred to as "H2") is preferably used as the combustion gas. This reacts with oxygen (also referred to as "O2") in the air. This exothermic reaction generates the energy required in step d).

[0146] Heat is thus applied to the cladding tube (particularly with the aid of a welding torch). In one embodiment, the heat is applied to the front surface of the cladding tube near the positioning template. This heat application can be performed particularly with the aid of a focused flame. The heat thus flows through the front surface of the cladding tube and enters the tube wall there. The heat escapes, in particular, at the inner bore of the cladding tube. There, the heat then acts on the positioning template, which can lead to material-to-material bonding.

[0147] In the context of the present invention, the term substance-to-substance bonding is understood to mean the connection of two parts to one another by means of melting and by means of intermolecular or chemical bonding forces (optionally via additives). These bonds specifically include welding and soldering connections. At the same time, these connections are non-releasable and can only be separated by destroying the connecting means.

[0148] One embodiment is characterized in that in step f) "processing", the anti-resonance element preform is thermally fixed to the cladding tube wall in a flameless manner. The position of the anti-resonance element preform in the cladding tube, which is determined by the design of the passage opening in the positioning template, can be as follows:

[0149] After step e) "insertion", the anti-resonance element preform may contact the inside of the cladding tube bore, or

[0150] • After step e) "insertion", in particular a gap that was closed during step f) "processing" may still exist between the anti-resonance element preform and the inside of the cladding tube bore.

[0151] In the known method, the anti-resonance element preform is thermally fixed to the cladding tube wall using a flame with the aid of a welding torch. Elongation and / or collapse only occurs thereafter. The formation of soot (the name for SiO2 particles) and burnouts is therefore disadvantageous. These combustion byproducts can have different starting points: the combustion of the combustion gases in the welding torch can occur by forming a flame with an excess of combustible material or with an excess of oxidant. For example, a known byproduct of this type of combustion is soot. Furthermore, the heat input from the welding torch to the cladding tube can lead to localized evaporation of the quartz glass. The soot generated in this way can then be deposited on various parts of the preform, particularly on the anti-resonance element preform. This then leads to a reduction in the quality of the final preform, which is particularly evident in higher attenuation or fiber breakage.

[0152] In particular, burnout deposits or soot are formed on the front surface of the cladding tube and on the inner surface of the cladding tube. Furthermore, the surface of the antiresonance element preform is particularly affected. Due to the resulting complex geometry, thorough cleaning, for example with hydrofluoric acid, is virtually impossible. Thanks to the use of the positioning template according to the invention, the antiresonance element preforms can now be positioned in their target position and then connected to the cladding tube wall by means of a flameless process (as part of step f), the "treatment") by means of material-to-material bonding, without depositing soot or burnout in the assembly.

[0153] Only by using the positioning template according to the present invention, which provides for precise positioning of the antiresonant element preform at the target location due to a self-centering mechanism, can the flame-based attachment or complete connection of the antiresonant element preform to the cladding tube prior to step f) "processing" be dispensed with. In currently known methods for manufacturing preforms for antiresonant hollow-core optical fibers, a flame-based thermoforming process is used to weld the antiresonant element preform to the cladding tube so that it remains in position during elongation and / or collapse. The present invention overcomes the disadvantage of preforms produced in this manner being contaminated with soot or burnt-out products.

[0154] An embodiment of the method is characterized in that the cladding tube has a second end portion.The first end portion and the second end portion are located oppositely at respective outermost end points of the cladding tube.

[0155] An embodiment of the method is characterized in that the method comprises the following steps:

[0156] (i) creating a second positioning template having a plurality of second passage openings therethrough, the plurality of second passage openings being adapted to each longitudinally guide an anti-resonance element preform, wherein the second positioning template and the cladding tube are made of the same material,

[0157] (ii) combining the second positioning template with the second end portion of the cladding tube.

[0158] All properties described for the first positioning template also apply to the second positioning template and vice versa.

[0159] In particular, the second positioning template may have a second positioning element, such as a cutout, which cooperates with a second counter-positioning element at the second end of the cladding tube and thus in this way prevents the second positioning template from rotating about its longitudinal axis.

[0160] An embodiment of the method is characterized in that the method comprises the following steps:

[0161] (iii) inserting at least a portion of the anti-resonance element preform through the passage opening of the second positioning template,

[0162] (iv) wherein the second positioning template has at least one second centering surface, which cooperates with the second end of the cladding tube in a self-centering manner so that the anti-resonance element preform is arranged at the target position during step (iii) "insertion".

[0163] As part of this embodiment, the anti-resonance element preform is held in the target position not only by means of a positioning template, but also by means of a combination of a positioning template and a second positioning template. Both positioning templates have a passage opening through which at least a portion of the anti-resonance element preform can be guided. Thus, the anti-resonance element preform can be held in the cladding tube at two opposing ends thereof by means of the positioning template and the second positioning template. According to the present invention, this type of embodiment alternative further improves the precision with which the anti-resonance element preform is positioned in the target position.

[0164] As part of one embodiment, the second positioning template can have at least one second passage opening of cylindrical design. Thus, the inner diameter of the at least one second passage opening has a diameter that is 0.15% to 7%, in particular 0.35% to 6%, in particular 0.55% to 3.5% greater than the outer diameter of the anti-resonance element preform. With this type of design, the anti-resonance element preform can be pushed directly through the passage opening and can rest against the inner wall of the passage opening in a form-fitting and / or force-fitting manner, in particular over the entire length of the positioning template.

[0165] In another design, at least one of the second channel openings may have a retaining region for end-side support of the anti-resonance element preform. This retaining region can be achieved by reducing the inner diameter of the second channel opening. The retaining region arranged in the second channel opening can be used to limit the longitudinal movement of the anti-resonance element preform in the inner bore of the cladding tube. As part of the component preparation, at least a portion of the anti-resonance element preform is inserted into the inner bore of the cladding tube through the channel opening of the positioning template. In this embodiment, the second positioning template attached to the second end of the cladding tube is used, on the one hand, to ensure that the anti-resonance element preform is positioned at the target position. In addition, as part of step f) "processing", longitudinal movement of the anti-resonance element preform can be prevented.

[0166] An embodiment of the method is characterized in that the cladding tube is at least partially cut away in the region of the second end in order to form a second counter-centering surface which cooperates in a form-fitting manner with the second centering surface.

[0167] An embodiment of the method is characterized in that the second positioning template is at least partially shaped in a frustoconical manner, wherein the second centering surface is formed at least partially in a cladding surface-like manner.

[0168] An embodiment of the method is characterized in that the cladding tube is at least partially cut away in a frustoconical manner in the region of the second end.

[0169] One embodiment of the method is characterized in that the method has the following steps:

[0170] A / preparing a third positioning template having a plurality of third passage openings therethrough, each of the plurality of third passage openings being adapted to longitudinally guide the anti-resonance element preform,

[0171] The third positioning template has at least one third centering surface.

[0172] As part of step A / "preparation", a third positioning template is produced. The third positioning template can have a cylindrical, cap-shaped or disc-shaped shape. In one embodiment, the third positioning template has a lateral extension of 5 mm to 200 mm, specifically 15 mm to 80 mm.

[0173] The third positioning template and the cladding tube can be designed to be made of the same material. In one embodiment, the third positioning template and the cladding tube are composed of the same material, specifically composed of undoped or doped quartz glass (SiO2), wherein the doping amount does not exceed 0.1 weight%.

[0174] The third positioning template has a plurality of third passage openings extending therethrough. Each third passage opening is configured to establish at least one fluid-conducting connection between the cladding tube inner bore and the exterior space through the base of the third positioning template. Furthermore, the inner diameter of the third passage openings is designed to allow the anti-resonance element preform to be pushed longitudinally therethrough to a significant extent. This statement does not limit the use of the widened portion of the ARE outer tube, which is used to position the anti-resonance element preform and will be described in greater detail later.

[0175] As part of one embodiment, the third positioning template may have at least one third passage opening of cylindrical design, wherein the inner diameter of the at least one third passage opening has a diameter that is 0.15% to 7%, particularly 0.35% to 6%, particularly 0.55% to 3.5% greater than the outer diameter of the anti-resonance element preform.

[0176] All properties described for the positioning template and / or the second positioning template also apply to the third positioning template, and vice versa.

[0177] All properties described for the passage opening and / or the second passage opening also apply to the third passage opening and vice versa.

[0178] An embodiment of the method is characterized in that the method comprises the following steps:

[0179] B / Manufacturing of tubular closure elements,

[0180] The closure element in the region of the first end region has an active surface in order to cooperate, in particular in a form-fitting manner, with the third centering surface.

[0181] As part of step B / "manufacturing," a closure element is produced that is designed to cooperate with the third positioning template. Furthermore, a tubular closure element is designed to be connected to the cladding tube. The closure element can be designed in a tubular, particularly partially funnel-shaped, manner and typically has a maximum outer diameter that corresponds to the outer diameter of the cladding tube.

[0182] The third positioning template and the closing element can be designed to be made of the same material. In one embodiment, the positioning template and the cladding tube are composed of the same material, specifically composed of undoped or doped quartz glass (SiO2), wherein the doping amount does not exceed 0.1 weight %.

[0183] In one embodiment, the closing element and the cladding tube can be designed to be made of the same material. In one embodiment, the closing element and the cladding tube consist of the same material, in particular of undoped or doped quartz glass (SiO2), wherein the doping amount does not exceed 0.1% by weight.

[0184] An embodiment of the method is characterized in that the method comprises the following steps:

[0185] C / connecting the third positioning template to the first end region,

[0186] D / connecting the closure element to the second end of the cladding tube,

[0187] E / pushing at least a portion of the anti-resonance element preform through the third passage opening to arrange the anti-resonance element preform in the cladding tube inner bore, wherein

[0188] The third centering surface cooperates with the active surface in a self-centering manner so that the anti-resonance element preform is arranged at a target location.

[0189] As part of step C / "joining", form-fitting bonding of the third positioning template to the first end region of the closure element is performed. According to the invention, the third positioning template thus centers itself due to the cooperation of the active surface with the third centering surface.

[0190] As part of a further step, a force fit and / or a material-to-material bond can be formed between the closing element and the third positioning template. The cooperation of the third centering surface and the movable surface thereby ensures that the relative position of the third positioning template with respect to the closing element does not change.

[0191] In particular, the third positioning template can have third positioning elements, such as cutouts, which cooperate with third counter-positioning elements at the closing element in order in this way to prevent the third positioning template from rotating about its longitudinal axis.

[0192] As part of step D / "connecting," a closure element is connected to the second end of the cladding tube. Specifically, step D / "connecting" can result in a material-to-material bond between the closure element and the cladding tube. The third positioning template, as well as the positioning template and / or the second positioning template, are used to ensure that the antiresonance element preform is positioned at a target location within the cladding tube and / or assembly and / or preform. To this end, the third positioning template has a third passage opening for positioning the antiresonance element preform. The third passage opening is designed to retain the antiresonance element preform. After at least a portion of the antiresonance element preform has been pushed through the third passage opening of the third positioning template (step E / ), the portion is retained in the target location within the inner bore of the cladding tube using the two positioning templates (the positioning template and the third positioning template). Due to the fact that the closure element is positioned at the second end of the cladding tube and the first positioning template is positioned at the first end of the tube, corresponding end-side support of the antiresonance element preform is achieved. As part of step f) "processing," the assembly can be processed into a preform using a thermoforming process.

[0193] One embodiment is characterized in that a closing element (also called a blowpipe) is used to set a negative or positive pressure in the cladding tube. The closing element can be attached thermally. The first end region of the closing element can thus be positioned at a distance of 0.5 mm to 20 mm, in particular 1 mm to 5 mm, from the second end of the cladding tube. The first end region and the second end are heated and subsequently pressed against each other. This creates a positive connection between the two elements.

[0194] In the event of excessive forces, local deformations may occur in the first end region of the closing element and / or in the second end of the cladding tube as part of step D / "connecting". If such deformations occur in the area of ​​the positioning template, such deformations may have a negative impact on the anti-resonance element preform and / or its positioning. In order to reduce the risk of potential local deformations in the first end region of the closing element and / or in the second end of the cladding tube as part of step D / "connecting", one embodiment is characterized in that the preform has a first connecting element. The first connecting element can be designed in a tubular manner and can have a connecting element inner bore and a connecting element longitudinal axis, along which a connecting element wall extends, which is defined by an inner side and an outer side. The first connecting element and the cladding tube can be designed to be made of the same material. The first connecting element acts as a kind of buffer between the cladding tube and the closing element. The two are not directly connected and potential deformations in the area of ​​the positioning template are prevented. Thus,

[0195] The first end of the first connecting element may be attached to the second end of the cladding tube and / or

[0196] • The second end section of the first connecting element may be attached to the first end region of the closure element.

[0197] The first connecting element can also be used to maintain the cladding tube and / or to set a negative or positive pressure in the cladding tube.

[0198] One embodiment is characterized in that the preform has a second connecting element. The second connecting element can be designed in a tubular manner and can have a connecting element inner bore and a connecting element longitudinal axis, along which a connecting element wall extends, the connecting element wall being defined by an inner side and an outer side. Like the first connecting element, the second connecting element can be used to maintain the cladding tube and / or to establish a negative or positive pressure in the cladding tube. Thus, the first end of the second connecting element is attached to the first end of the cladding tube. The second connecting element and the cladding tube can be designed to be made of the same material.

[0199] One embodiment is characterized in that the diameter of the connecting element inner bore of the first and / or second connecting element is 2%-15% larger, in particular 5%-10% larger, than the diameter of the inner bore of the cladding tube. The larger inner diameter of the first and / or second connecting element makes it possible to guide the corresponding positioning template through the connecting element and position it in the cladding tube. The first and / or second connecting element can have a length of 50 mm to 150 mm to effectively prevent potential deformation in the area of ​​at least one of the first, second, or third positioning templates.

[0200] Step f) "processing" can be designed in a flameless manner, resulting in no soot or burnt-out deposits on the antiresonant element preform. By using a positioning template, specifically by combining the positioning template with a second positioning template and / or a third positioning template, the antiresonant element preform can be precisely supported at a target location within the cladding tube and / or assembly, eliminating the need for flame-based bonding of the antiresonant element preform to the cladding tube prior to heat treatment as part of step f) "processing." This option not only improves efficiency but also reduces attenuation in the finished preform and finished antiresonant hollow-core fiber compared to known manufacturing methods.

[0201] An embodiment of the method is characterized in that at least one of the following steps comprises flameless thermal joining or flame-based thermal joining:

[0202] Step b) "Preparation",

[0203] Step d) "Attachment",

[0204] Step (ii) "combining",

[0205] Step C / "Link", and

[0206] • Step D / “Connect”.

[0207] To achieve a process that can be carried out technically quickly, it may be advantageous to produce certain components of the assembly as part of a flame-based thermal process. These components are specifically those of the assembly that can also undergo a cleaning step prior to the processing step f) "processing." In particular, steps b) "preparation" and d) "attachment" can thus be carried out cost-effectively as part of a flame-based thermal process. However, both the anti-resonance element preform and the combination of cladding tube and positioning template must subsequently be cleaned to remove any deposits of soot or burnt products. The same applies to steps (ii) "combining" and at least one of C / "joining" and D / "connecting."

[0208] In contrast, if the emphasis is on precision of assembly of the anti-resonance element preform into the preform and / or reduction of attenuation, it may be advantageous to perform the above steps as part of flameless thermal joining.

[0209] An embodiment of the method is characterized in that the method comprises at least one of the following steps:

[0210] heat fixing, in particular flameless heat fixing, at least some of the anti-resonance element preforms to the positioning template, and / or

[0211] • heat fixing, in particular flameless heat fixing, at least some of the anti-resonance element preforms to the second positioning template, and / or,

[0212] • heat fixing, in particular flameless heat fixing, at least some of the anti-resonance element pre-forms to the third positioning template.

[0213] One embodiment of the method is characterized in that, before step f) "treating", the antiresonance element preform is held in the cladding tube inner bore only by means of:

[0214] The positioning template or

[0215] The positioning template and the second positioning template, or

[0216] The positioning template and the third positioning template

[0217] and other means in the absence of substance-to-substance bonding.

[0218] By using a positioning template, in particular by using the positioning template in combination with a second positioning template and / or a third positioning template, the anti-resonance element preform can be positioned at a target position in the inner bore of the cladding tube with such precision that no thermal connection of the anti-resonance element preform to the inner bore of the cladding tube is required before stretching and / or collapsing as part of step f) "processing".

[0219] The self-centering design of the positioning template and the second or third positioning template ensures that the anti-resonance element preform remains in the corresponding target position even during assembly processing. Therefore, no material-to-material bonding between the anti-resonance element preform and the inner bore of the cladding tube is required.

[0220] An embodiment of the method is characterized in that in some areas, preferably at the first end of the anti-resonance element preform, the ARE outer tube has an outer diameter widening, which is larger than the inner diameter of at least one of the passage opening, the second passage opening and the third passage opening.

[0221] The outer diameter widening serves to provide a defined holding point on the anti-resonance element preform when the anti-resonance element preform is guided through at least one of the passage opening, the second passage opening, and the third passage opening. Arranging the widening on the anti-resonance element preform allows its longitudinal position in the cladding tube to be controlled.

[0222] An embodiment of the method is characterized in that in some areas, preferably at the second end of the anti-resonance element preform, the ARE has an outer diameter taper that is smaller than the inner diameter of at least one of the channel opening, the second channel opening and the third channel opening.

[0223] The tapered portion is configured to facilitate insertion of the anti-resonance element preform into at least one of the passage opening, the second passage opening, and the third passage opening. Another advantage is that the number of edges is reduced, and the risk of the anti-resonance element preform breaking during insertion and / or positioning of the anti-resonance element preform in the passage opening is significantly reduced.

[0224] An embodiment of the method is characterized in that the positioning template and / or the second positioning template and / or the third positioning template have at least one gas flow element, which connects the inner hole of the cladding tube to the surrounding area of ​​the preform in a fluid-conducting manner.

[0225] The gas flow element may be a hole extending completely through the positioning template and / or the second positioning template and / or the third positioning template. Its purpose is to establish a fluid-conducting connection between the inner bore of the cladding tube and the surrounding area of ​​the preform. This connection is used to control the internal pressure in the inner bore of the cladding tube.

[0226] An embodiment is characterized in that the cladding tube inner bore is produced by means of mechanical processing, in particular by means of drilling, milling, grinding, honing and / or polishing. Compared to other known forming techniques, these mechanical processing techniques provide a more accurate and precise structure by using heat and pressure and avoid contamination of the surface caused by the forming tool.

[0227] One embodiment is characterized in that the cladding tube has an outer diameter in the range of 65 mm to 300 mm, in particular 90 mm to 250 mm, and in particular has a length of at least 1 m. The accuracy of the positioning of the at least one antiresonance element preform in the cladding tube is improved in that a tubular structural element is provided, at least a portion of which has a wall thickness in the range of 0.2 mm to 2 mm, preferably in the range of 0.25 mm to 1 mm, and in that a cladding tube is provided with an outer diameter in the range of 65 mm to 300 mm, preferably in the range of 90 mm to 250 mm, preferably in the range of 120 mm to 200 mm. These components can thus each additionally have a length of at least 1 m.

[0228] This type of bulky structural element (anti-resonance element preform, ARE inner tube or ARE outer tube) simplifies handling. In the case of a vertical arrangement of the cladding tube and the structural element, gravity additionally supports the parallelism and vertical alignment of the longitudinal axis of the anti-resonance element preform when the anti-resonance element preform is positioned in each case at the target position on its upper front end.

[0229] The above object is also solved by a method for producing a secondary preform from a preform produced according to any of the preceding embodiments, from which an antiresonant hollow-core optical fiber can be drawn, the method comprising the following steps:

[0230] further processing the preform into the secondary preform,

[0231] The further processing comprises one or more of the following thermoforming processes:

[0232] i.) stretch,

[0233] ii.) collapse,

[0234] iii.) collapse and stretch simultaneously,

[0235] iv.) adding additional cladding material,

[0236] v.) adding additional cladding material and subsequent elongation,

[0237] vi.) Adding additional cladding material and stretching it simultaneously.

[0238] The preform is the starting point for the manufacture of antiresonant hollow core optical fibers. In the method according to the invention, the preform is further processed into a secondary preform by performing one or several thermoforming processes.

[0239] During elongation, the preform is lengthened. The elongation can be carried out without collapsing simultaneously. The elongation can be carried out proportionally, so that, for example, the shape and arrangement of the parts or components of the primary preform are reflected in the elongated final product. However, during elongation, the primary preform can also be drawn non-proportionally and its geometry can be changed. During collapse, the inner bore narrows or the annular gaps between the tubular parts close or narrow. Collapse is usually associated with elongation. The secondary preform produced in this way can already be designed and suitable for drawing hollow-core optical fibers. The secondary preform can optionally be further processed, for example, by elongating it or adding additional cladding material to it.

[0240] The above object is also solved by a method for producing an antiresonant hollow-core optical fiber from a preform produced according to any of the preceding embodiments, the method comprising the following steps:

[0241] Further processing the preform into the antiresonant hollow-core optical fiber, wherein the further processing comprises one or more of the following thermoforming processes:

[0242] i.) stretch,

[0243] ii.) collapse,

[0244] iii.) collapse and stretch simultaneously,

[0245] iv.) adding additional cladding material,

[0246] v.) adding additional cladding material and subsequent elongation,

[0247] vi.) Adding additional cladding material and stretching it simultaneously.

[0248] The preform is the starting point for the manufacture of an antiresonant hollow core fiber. The antiresonant hollow core fiber is produced by means of a thermal process, specifically by elongating the preform.

[0249] During elongation, the preform is lengthened. This elongation can be proportional, so that, for example, the shape and arrangement of the components or parts of the nascent preform are reflected in the elongated final product. However, during elongation, the nascent preform can also be drawn out of proportion and its geometry can be altered. During collapse, the inner bore narrows, or the annular gaps between the tubular components close or narrow.

[0250] To elongate and produce an antiresonant hollow-core fiber from a preform, the preform is guided vertically through a furnace. The lower end of the preform is thereby heated to a drawing temperature, from which an antiresonant hollow-core fiber is drawn in a tapered form. The drawn fiber is then cooled from the drawing temperature by means of a gas flow directed opposite to the drawing direction.

[0251] In one embodiment, an antiresonant hollow-core fiber is coated with an adhesion promoter, wherein this step is performed during the drawing process during glass fiber manufacturing, and the antiresonant hollow-core fiber is subsequently coated with a plastic in a second, subsequent step. This second step can be performed so as to be decoupled from the drawing process of glass fiber manufacturing in terms of time. The plastic used for the coating can be one or more of the following: urethane acrylate, acrylate, polyolefin, polyamide (nylon), polyether, urethane methacrylate, fluoroalkyl methacrylate, or polyimide.

[0252] One embodiment is characterized in that, during at least one of steps f) "treating" and "further treating" of the assembly as part of the elongation and / or collapse, a relative internal pressure (negative pressure compared to the ambient atmospheric pressure) is set in the bore of the cladding tube in the range of -10 mbar to -300 mbar, in particular -50 mbar to -250 mbar. This pressure window ensures that the OD / ID ratio (ratio of the outer diameter to the inner diameter of the cladding tube) does not become too small as part of the elongation and / or collapse.

[0253] One embodiment is characterized in that, during the "further processing" of the preform (as part of the elongation) into an antiresonant hollow-core fiber, a relative internal pressure (positive pressure compared to the ambient atmospheric pressure) is set in the core region in the range of 0.05 mbar to 20 mbar. In the case of a relative internal pressure of less than 0.05 mbar, it may happen that the antiresonant element preform expands excessively. Vice versa, a relative internal pressure of more than 20 mbar in the core region may have the following consequence: insufficient gas pressure within the hollow ducts of the antiresonant element preform, so that they widen sufficiently during the thermoforming process.

[0254] The temperature of the heating zone during the thermoforming process should be as constant as possible. Advantageously, temperature-controlled heating elements are used during the thermoforming process, whose target temperature is precisely maintained within + / - 0.1°C. Thus, temperature fluctuations during the thermoforming process can be limited to less than + / - 0.5°C.

[0255] All properties and features described for the passage opening also apply to the second passage opening and / or the third passage opening, and vice versa.

[0256] All properties and features described for the positioning template also apply to the second positioning template and / or the third positioning template, and vice versa.

[0257] The properties and features disclosed in the description may be important for various designs of the claimed invention (alone and in any combination with one another). Properties and features disclosed for the preform or antiresonant hollow core fiber are also disclosed for the method, and vice versa.

[0258] The present invention will be further described below in an exemplary manner with the aid of the accompanying drawings. The present invention is not limited to the accompanying drawings.

[0259] Attached photos

[0260] Figure 1 shows a partial longitudinal section through an antiresonant hollow-core fiber,

[0261] Figure 2 shows a partial cross section through an antiresonant hollow core fiber,

[0262] Figure 3 shows a partial longitudinal section through an element of a first embodiment of an assembly,

[0263] Figure 4 Shown according to Figure 3 Components,

[0264] Figure 5 Shown according to Figure 3 and Figure 4 preforms,

[0265] Figure 6 shows a partial longitudinal section through an element of another embodiment of the assembly,

[0266] Figure 7 Shown according to Figure 6 Components,

[0267] Figure 8 Shown according to Figure 7 and Figure 8 preforms,

[0268] Figure 9Another embodiment of the assembly is shown,

[0269] Figure 10 Shown according to Figure 9 Assembled preforms,

[0270] Figure 11 Shown Figure 9 The embodiment shown is supplemented with connecting elements,

[0271] Figure 12 Shown according to Figure 11 Assembled preforms,

[0272] Figure 13 A first embodiment of the positioning template is shown,

[0273] Figure 14 Another embodiment of the positioning template is shown,

[0274] Figure 15 Another embodiment of the positioning template is shown,

[0275] Figure 16 Shown including according to Figure 13 The partially assembled preform of the positioning template,

[0276] Figure 17 shows the preform in step f) "processing",

[0277] Figure 18 A flow chart showing a method for manufacturing a preform is shown, and

[0278] Figure 19 A flow chart showing a method for fabricating an antiresonant hollow-core fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0279] Figure 1 A longitudinal section through an antiresonant hollow core fiber 2400 is shown. Shown is a section of the antiresonant hollow core fiber 2400 between two section lines AA and BB. The antiresonant hollow core fiber 2400 has a cladding 2450. In the illustrated embodiment of the antiresonant hollow core fiber 2400, the cladding 2450 is composed of an elongated cladding tube 200 and an elongated cladding material 2452. Due to the fact that the cladding material 2452 and the cladding tube material 200 are designed to have the same material in the illustrated embodiment, Figure 2The transition between the two materials in the cladding 2450 is marked by a dashed line. Antiresonant hollow-core fiber 2400 has a hollow core 2470. Electromagnetic waves can propagate through hollow core 2470. In the illustrated embodiment, two antiresonant elements 2410 are disposed within hollow core 2470. They are connected to an inner surface 2480 of cladding 2450 via a material-to-material bond. Antiresonant element 2410 has an ARE fiber outer tube 2420 and an ARE fiber inner tube 2430. ARE fiber inner tube 2430 is disposed within ARE fiber outer tube 2420. Antiresonant element 2410 is arranged parallel to longitudinal axis 2460 of antiresonant hollow-core fiber 2400.

[0280] Figure 2 Shown Figure 1 The cross section of the antiresonant hollow core fiber 2400 is shown. Figure 2 The arrangement of the antiresonant element 2410 on the inner surface 2480 of the confining hollow core 2470 is illustrated. The antiresonant element 2410 is constructed in a tubular manner, wherein an ARE fiber inner tube 2430 is connected to an ARE fiber outer tube 2420 by means of a material-to-material bond. The illustrated ARE fiber inner tube 2430 and / or ARE fiber outer tube 2420 may partially have a wall thickness in the range of 0.2 μm to 2 μm. The illustrated cladding tube 2450 may have an outer diameter in the range of 90 mm to 250 mm and a length of at least 1 m. The inner diameter of the hollow core 2470 is preferably 10 mm to 50 mm.

[0281] The antiresonant hollow core fiber 2400 shown is manufactured from the preform 100, which will be described in more detail below. The antiresonant hollow core fiber 2400 is manufactured from the preform 100 by one or more of the following thermoforming processes: stretching 2300, collapsing 2100, adding 2200 additional cladding material.

[0282] Figure 3 A separate section of a first embodiment of an assembly 110 of a preform 100 according to the present invention for an antiresonant hollow-core fiber 2400 is shown. The assembly 110 comprises a cladding tube 200. The cladding tube 200 is tubular and comprises a cladding tube wall 210 having a thickness 211 ranging from 20 mm to 90 mm. As part of the method, antiresonant element preforms 300 are to be arranged on the inner side 215 of the cladding tube 200. Antiresonant elements 2410 are produced from these antiresonant element preforms 300 using a corresponding process.

[0283] In the known method, antiresonance element preforms 300 are individually placed into the cladding tube 200. Graphite elements can be used to position the antiresonance element preforms 300. Due to the geometry and tolerances of the tube, these graphite elements are manufactured with gap dimensions, which, however, result in play in the graphite elements and the antiresonance element preforms 300. For example, if six antiresonance element preforms 300 are inserted, it is not possible to ensure that the precise angular distance of 60° is always maintained. Furthermore, the described technique allows the antiresonance element preforms to be rotated radially along the length of the tube.

[0284] In the known method, the anti-resonance element preform 300 is then fixed to the two front surfaces of the cladding tube 200. This is achieved by melting the glass at specific points using a manual torch. This results in soot or burnt-out deposits on the glass surface. This typically affects the front surface of the cladding tube, as well as the inner surface of the cladding tube and the surface of the anti-resonance element preform. Due to the resulting complex geometry, thorough cleaning of the assembly is almost impossible.

[0285] In order to overcome these drawbacks, the following method 2000 for manufacturing a preform 100 of an antiresonant hollow core optical fiber 2400 is disclosed, comprising the following method steps:

[0286] a) providing 1000 a cladding tube 200 having a cladding tube inner bore 220 and a cladding tube longitudinal axis 230 , along which a cladding tube wall 210 extends, the cladding tube wall being defined by an inner side 215 and an outer side 216 ,

[0287] b) preparing more than 1,100 anti-resonance element preforms 300, each anti-resonance element preform comprising an ARE outer tube 310 and an ARE inner tube 320 inserted into the ARE outer tube;

[0288] c) preparing 1200 a positioning template 400 having a plurality of passage openings 410 through the positioning template 400 , the plurality of passage openings being adapted to each longitudinally guide an anti-resonance element preform 300 , wherein the positioning template 400 and the cladding tube 200 are made of the same material,

[0289] d) attaching 1300 the positioning template 400 to the first end 250 of the cladding tube 200,

[0290] e) inserting 1400 at least part of the anti-resonance element preform 300 through the passage opening 410 for arranging the anti-resonance element preform in the cladding tube inner bore 220 ,

[0291] f) Processing 1500 the assembly 100 comprising the cladding tube 200, the anti-resonant element preform 300 and the positioning template 400 by means of a thermoforming process selected from at least one of stretching and collapsing.

[0292] It is thus provided that the method is designed such that the positioning template 400 has at least one centering surface 420 which cooperates in a self-centering manner with the first end 250 of the cladding tube 200 so that the anti-resonance element preform 300 is arranged at the target position in step e) “insertion” 1400 .

[0293] In step c) "Preparation" 1200, a positioning template 400 is produced, which has a plurality of passage openings 410 through the positioning template 400, which are suitable for longitudinally guiding the anti-resonance element preform 300 respectively, wherein the positioning template 400 and the cladding tube 200 are made of the same material.

[0294] exist Figure 4 In the embodiment of the present invention, a portion of the anti-resonance element preform is guided through the passage opening 410 and extends into the cladding tube inner bore 220 (step e) "insertion" 1400). The positioning template 400 is lowered in the direction of the cladding tube 200 as part of step d) "attachment" 1300. After the positioning template 400 is attached to the cladding tube 200 with a force fit and / or a form fit, the assembly 110 (which includes the cladding tube 200, the anti-resonance element preform 300, and the positioning template 400) is further processed into the preform 100 by means of a thermoforming process selected from at least one of elongation and collapse.

[0295] The positioning template 400 to be used is designed so that the passage openings 410 for the anti-resonance element preform 300 are always positioned at the same angular distance from one another, thus automatically achieving symmetry. Furthermore, a gas flow element for gas flow is provided in the center of the disk. Subsequent processes, such as flushing or cleaning with gas, and the application of negative pressure within the entire tube arrangement are thus possible. The size of the holes may affect the gas flow through the core area and the anti-resonance element preform.

[0296] Figure 5 The preform 100 is shown. Due to the self-centering cooperation of the centering surface 420 of the positioning template 400 with the first end 250 of the cladding tube 200, the anti-resonance element preform is maintained at the predetermined target position during step e) "insertion" 1400 and in particular also during step f) "processing" 1500.

[0297] One aspect of this method is that the precise joining of the cladding tube 200 and the anti-resonance element preform 300 can be achieved directly in the processing apparatus (typically a vertical glass lathe), thus requiring only one process step for assembly and stretching of the entire preform.

[0298] One embodiment of the method 2000 is characterized in that, in step f) "processing" 1500, the anti-resonance element preform 300 is flamelessly thermally fixed to the cladding tube wall 210. A preliminary spot-by-point partial melting of the anti-resonance element preform 300 and the cladding tube 200, in particular of the cladding tube wall 210, in particular by means of a manual welding torch, can be omitted.

[0299] Figure 6 、 Figure 7 and Figure 8 Another embodiment of an assembly 110' and a preform 100' manufactured by means of the disclosed method is shown. Figure 6 、 Figure 7 and Figure 8 The embodiments correspond largely to those described above and Figure 3 、 Figure 4 、 Figure 5 and Figure 6 The embodiment shown is such that reference is made to the above description in order to avoid repetitions. Figure 3 、 Figure 4 、 Figure 5 and Figure 6 Repeated structures in the description have the same reference numerals. Figure 3 、 Figure 4 、 Figure 5 and Figure 6 Modifications of the structure have the same reference numerals with a prime (') compared to the structure shown.

[0300] and Figure 3 and Figure 4 In contrast, the cladding tube 200' shown has not only a centering surface 251 on the first end 250. In addition, the cladding tube 200' has a second centering surface 261 on the second end 260. As part of the method, the following steps are provided:

[0301] (i) producing a second positioning template 500 having a plurality of second passage openings 510 therethrough, the plurality of second passage openings being adapted to each longitudinally guide the anti-resonance element preform 300, wherein the second positioning template 500 and the cladding tube 200 are made of the same material,

[0302] (ii) The second positioning template 500 is coupled to the second end portion 260 of the cladding tube 200 .

[0303] In the embodiment shown, the positioning template 500 is at least partially shaped in a frustoconical manner. The second centering surface 520 is thereby partially formed in a cladding surface-like manner.

[0304] The cladding tube 200' is at least partially cut away in the region of the second end 260 in order to form a second centering surface 261 which can cooperate in a form-fitting manner with the second centering surface 520. Figure 6 In the embodiment shown, the cladding tube 200 ′ is at least partially cut away in a truncated cone-like manner in the region of the second end 260 .

[0305] Figure 7 1 . Step (iii) is shown, i.e., "inserting" at least part of the anti-resonance element preform 300 through the second passage opening 510 of the second positioning template 500. Subsequently, step f), i.e., "processing" 1500 the assembly comprising the cladding tube 200', the anti-resonance element preform 300, and the positioning templates 400 and the second positioning template 500, is carried out by means of a thermoforming process selected from at least one of stretching and collapsing. The second centering surface 520 cooperates in a self-centering manner with the second end 260 of the cladding tube 200', so that in step (iii) "insertion" and in particular in step f) "processing" 1500, the anti-resonance element preform is arranged at the target position, as shown in FIG. Figure 8 As explained in .

[0306] Figure 9 and Figure 10 An embodiment of a component 110" and a preform 100" manufactured by means of the disclosed method is shown. Figure 9 and Figure 10 The embodiments correspond largely to those described above and Figure 3 、 Figure 4 、 Figure 5 and Figure 6 The embodiment shown is such that reference is made to the above description in order to avoid repetitions. Figure 3 、 Figure 4 、 Figure 5 and Figure 6 Repeated structures in the description have the same reference numerals. Figure 3 、 Figure 4 、 Figure 5 and Figure 6 Modifications of the structure have the same reference numeral with two primes (") compared to the structure shown.

[0307] Figure 9 An assembly 110" is shown which can be formed into a preform 100" by stretching and / or collapsing as part of step f) "processing". The method required for this comprises the following steps:

[0308] A / Preparing a third positioning template 600 having a plurality of third channel openings 610 through the third positioning template 600 , the plurality of third channel openings being adapted to each longitudinally guide the anti-resonance element preform 300 , wherein the third positioning template 600 has at least one third centering surface 620 .

[0309] To produce the preform 100" shown, the following steps are required:

[0310] B / Production of a tubular closure element 700 , wherein the closure element 700 has an active surface 710 in the region of the first end region 730 in order to cooperate with the third centering surface 620 , in particular in a form-fitting manner.

[0311] The illustrated assembly 110″ has a funnel-shaped closing element 700. The outer diameter of the closing element 700 in a first end region 730 corresponds substantially to the outer diameter of the cladding tube 200. At an opposite second end region 740, the diameter of the closing element 700 decreases in order to form an outlet 790. This outlet 790 can be used, in particular, to adjust the pressure ratio in the cladding tube inner bore 220 or in the at least one anti-resonance element preform 300 inside the cladding tube inner bore, respectively.

[0312] Figure 10 The completed preform 100 is shown. Figure 9 Produced after the following steps:

[0313] C / attaching the third positioning template 600 to the first end region 730,

[0314] D / connecting the closing element 700 to the second end 260 of the cladding tube 200,

[0315] E / Pushing at least a portion of the anti-resonance element preform 300 through the third passage opening 610 so as to arrange the anti-resonance element preform 300 in the cladding tube inner bore 220, wherein the third centering surface 620 cooperates with the active surface 710 in a self-centering manner so that the anti-resonance element preform 300 is arranged at the target position.

[0316] In the exemplary embodiment shown, the anti-resonance element preform 300 is held at two locations on the end side. On the one hand, the anti-resonance element preform 300 is held at the first end 250 of the cladding tube 200 by means of a positioning template 400. In addition, a third positioning template 600 ensures that the other end side of the anti-resonance element preform 300 is held. Together, the positioning template 400 and the third positioning template 600 ensure that the anti-resonance element preform 300 is held at the target position within the cladding tube inner bore 220.

[0317] In step f) "processing", the anti-resonance element preform 300 can be thermally fixed to the inner hole of the cladding tube in a flameless manner. Specifically, Figure 17 (which shows the assembly passing through an electric furnace 800 as part of step f) "processing") illustrates this step. Reference is therefore made to the description made there.

[0318] Figure 11 and Figure 12 An embodiment of an assembly 110" and a preform 100" is shown, the outer shape of which is similar to Figure 9 and Figure 10 To avoid repetition, reference is made to the above description. In contrast, the assembly 110 ″ has a first connecting element 900 and a second connecting element 910 . The first connecting element 900 is thus arranged at the first end 250 of the cladding tube 200 , and the second connecting element 910 is arranged at the second end 260 of the cladding tube.

[0319] Figures 13 to 15 Different embodiments of positioning templates 400 , 400 ′, 400 ″ are shown.

[0320] Figure 13 4 shows a disk-shaped positioning template 400. This positioning template is shaped in a frustoconical manner so that the side surface completely forms the centering surface 420. The passage opening 410 is designed in a tubular manner and has a uniform inner diameter 411 over its longitudinal extension.

[0321] The difference between the inner diameter of the channel opening 410 and the outer diameter of the anti-resonance element preform 300 should be between 0.15% and 7%, specifically between 0.35% and 6%, specifically between 0.55% and 3.5%.

[0322] Figure 14 The positioning template 400' in the embodiment has side surfaces which are more strongly inclined and form the centering surface 420. The collar region 422 is arranged above the centering surface 420. The first end 250 of the cladding tube 200 can be designed such that

[0323] Only the counter-centering surface 251 cooperates with the centering surface 420, or

[0324] On the one hand, the counter-centering surface 251 cooperates with the centering surface 420 and, on the other hand, the collar region 422 cooperates, in particular in a form-fitting and / or force-fitting manner, with the counter-collar region at the cladding tube 200. This cooperation enhances the self-centering effect.

[0325] The passage opening 410 is shaped in a tubular manner.

[0326] Figure 15An embodiment of a positioning template 400" is shown, the outer shape of which is similar to Figure 14 In contrast, the positioning template 400 ″ does not have any tubular passage openings 410 having a uniform inner diameter. Instead, the passage openings 410 ′ are designed in sections in a tubular manner, wherein the two sections have different inner diameters. The passage openings 410 ′ have

[0327] a receiving region 430 , which is designed in a tubular manner and whose inner diameter is adapted to the outer diameter of the anti-resonance element preforms 300 , in order to be able to guide these anti-resonance element preforms at least partially,

[0328] a holding region 434 which is designed in a tubular manner and has an inner diameter which is smaller than the outer diameter of the anti-resonance element preform 300 and which is designed to hold the anti-resonance element preform 300 , and

[0329] A funnel-shaped transition region 432 , which connects the receiving region 430 and the retaining region 434 .

[0330] This type of design of the channel 410 serves two purposes. Specifically, the receiving region 430 serves to position the anti-resonance element preform 300 within the cladding tube bore 220. Thus, the primary purpose of the receiving region 430 is to prevent lateral movement of the anti-resonance element preform 300. In contrast, the retaining region 434 serves primarily to prevent longitudinal movement of the corresponding anti-resonance element preform 300.

[0331] Figures 13 to 15 All shown features and described characteristics of the positioning templates 400 , 400 ′, 400 ″ also apply to the second positioning template 500 and / or the third positioning template 600 .

[0332] Figure 16 The illustrated preform assembly 110' corresponds to Figure 9 The two embodiments differ only in that the preform 100" is an assembly 100". Figure 16 The assembly 110'' is shown with a third positioning template 600', which is designed to correspond in structure to Figure 15 The positioning template 400 ″ prevents longitudinal movement of the anti-resonance element preform 300 . The anti-resonance element preform is positioned transversely through the tubular receiving area 430 and longitudinally through the holding area 434 . This prevents the anti-resonance element preform 300 from deviating from the target position.

[0333] As described, the anti-resonance element preform 300 is fixed to both front surfaces of the cladding tube 200 using known methods. This is achieved by point-by-point melting using a manual torch. This produces soot or burnout that deposits on the glass surface and thus reduces the quality of the preform. To overcome this drawback, one embodiment of the method described herein is characterized in that, in step f) "processing" 1500, the anti-resonance element preform 300 is thermally fixed to the cladding tube wall 210 in a flameless manner.

[0334] Figure 17 Shown Figure 8 The creation of a preform 100' is shown (as part of step f) "Preparation" 1500. Movement arrow 810 illustrates the direction in which assembly 110' is moved into an electric furnace 800 (non-flame heat source) to create preform 100'.

[0335] The illustrated assembly 110 ′ includes a cladding tube 200 ′. The positioning template 400 and the second positioning template 500 are shaped in a frustoconical manner. The centering surface 420 and the second centering surface 520 are thereby partially formed in a cladding surface-like manner. Therefore, the cladding tube 200 and the positioning template 400 and the second positioning template 500 are designed so that they can each fit together in a form-fitting manner. These elements are combined to form the assembly 110 ′ as part of the following steps:

[0336] Attaching the positioning template 400 to the first end 250 of the cladding tube 200',

[0337] · Combine the second positioning template 500 with the second end portion 160 of the cladding tube 200 ′,

[0338] inserting at least part of the anti-resonance element preform 300 through the passage opening 410 for arranging the anti-resonance element preform in the cladding tube bore, and

[0339] Inserting at least part of the anti-resonance element preform 300 through the second passage opening 510 of the second positioning template 500 .

[0340] Figure 17 An electric furnace 800 is listed as the flameless heat source. In the hot zone of the furnace, the assembly is heated to a temperature at which the viscosity of the quartz glass is significantly reduced, allowing deformation. Simultaneously, one of the two working heads in which the assembly is clamped is displaced, causing the cladding tube 200 to taper to a thinner cross-section and thereby collapse. The connection between the antiresonance element preform 300 and the cladding tube 200 is precisely established at the point where the tube is heated and tapers, i.e., continuously tapering over its entire length as the process progresses.

[0341] The use of the electric furnace 800 eliminates the need for a manual torch process for securing the anti-resonance element preform 300. The manual torch process poses issues with burnout and soot formation associated with the use of the torch. Condensate cannot be completely removed, leaving the preform further processed and carrying contaminants. In particular, this can lead to blistering, inclusions, and subsequent fiber breakage during drawing. Using a furnace eliminates these issues, resulting in the production of a clean preform.

[0342] As part of step f) "processing" 1500, the anti-resonant element preform 300 may be retained within the cladding tube bore 220 solely by:

[0343] Positioning template 400, 400', 400", or

[0344] Positioning templates 400, 400', 400", and a second positioning template 500, or

[0345] Positioning templates 400, 400', 400" and third positioning templates 600, 600'

[0346] and other means in the absence of substance-to-substance bonding.

[0347] One aspect of this method is that the precise joining of the cladding tube 200 can be achieved directly in a processing device, such as, for example, a vertical glass lathe, and thus only one process step is required for the assembly and stretching of the entire preform.

[0348] exist Figure 17 In FIG. 1 , the anti-resonance element preform 300 is shown held in the cladding tube bore 220 solely by means of the positioning templates 400 , 400 ′, 400 ″ and the second positioning template 500 and other means without substance-to-substance bonding.

[0349] Figure 18 An embodiment of a method 2000 for manufacturing a preform 100 for an antiresonant hollow core optical fiber 2400 is shown, the method comprising the following steps:

[0350] a) providing 1000 a cladding tube 200 having a cladding tube inner bore 220 and a cladding tube longitudinal axis 230 , along which a cladding tube wall 210 extends, the cladding tube wall being defined by an inner side 215 and an outer side 216 ,

[0351] b) preparing more than 1,100 anti-resonance element preforms 300, each anti-resonance element preform comprising an ARE outer tube 310 and an ARE inner tube 320 inserted into the ARE outer tube;

[0352] c) preparing 1200 a positioning template 400, 400', 400", which has a plurality of passage openings 410, 410' passing through the positioning template 400, 400', 400", each of which is suitable for longitudinally guiding the anti-resonance element preform 300, wherein the positioning template 400, 400', 400" and the cladding tube 200 are made of the same material,

[0353] d) attaching 1300 the positioning template 400, 400', 400" to the first end 250 of the cladding tube 200,

[0354] e) inserting 1400 at least part of the anti-resonance element preform 300 through the passage openings 410 , 410 ′ for arranging the anti-resonance element preform in the cladding tube inner bore 220 ,

[0355] f) processing 1500 the assembly 110 comprising the cladding tube 200, the anti-resonance element preform 300 and the positioning templates 400, 400', 400" by means of a thermoforming process selected from at least one of stretching and collapsing.

[0356] It is thus provided that the method is designed such that the positioning template 400, 400', 400" has at least one centering surface 420 which cooperates in a self-centering manner with the first end 250 of the cladding tube 200, so that the anti-resonance element preform 300 is arranged at the target position in step e) "insertion" 1400.

[0357] Figure 19 An embodiment of a method for producing an antiresonant hollow-core fiber 2400 from a preform 100 produced in particular according to any of the aforementioned method steps 1000 to 1500 is shown, the method having the following steps:

[0358] The preform 100 is further processed into the antiresonant hollow core fiber 2400,

[0359] The further processing comprises one or more of the following thermoforming processes:

[0360] · Collapse 2100,

[0361] Added 2200 additional cladding materials, and

[0362] · Lengthened 2300.

[0363] All properties and features described for the passage opening also apply to the second passage opening and / or the third passage opening, and vice versa.

[0364] All properties and features described for the positioning template also apply to the second positioning template and / or the third positioning template, and vice versa.

[0365] All properties and features described for the method also apply to the preform and / or antiresonant hollow-core fiber, and vice versa.

[0366] Unless otherwise stated, all physical variables specified in the claims, description, and drawings are determined under normal conditions according to DIN 1343. The expression "under normal conditions" refers to measurements under conditions according to DIN 1343. The features disclosed in the claims, description, and drawings may be important for various designs of the claimed invention (individually and in any combination with one another). Features disclosed for the device (in particular, the preform, the secondary preform, or the antiresonant hollow-core fiber) are also disclosed for the method, and vice versa.

[0367] Figure Numbers

[0368] 100, 100', 100" Antiresonant Hollow-Core Fiber Preforms

[0369] 110, 110', 110", 110'' components

[0370] 200, 200' cladding pipe

[0371] 210 cladding tube wall

[0372] 211 Cladding tube wall thickness

[0373] 215 Inside of cladding tube wall

[0374] 216 The outside of the cladding tube wall

[0375] 220 cladding tube inner hole

[0376] 230 Longitudinal axis of cladding tube

[0377] 250 First end of cladding tube

[0378] 251 Anti-centering surface

[0379] 260 Second end of cladding tube

[0380] 261 Second anti-centering surface

[0381] 300 Anti-resonance element preform

[0382] 400, 400', 400" Positioning Templates

[0383] 410, 410' channel opening

[0384] 420, 420' centering surface

[0385] 422 Ring Area

[0386] 430 Reception Area

[0387] 432 Transition Zone

[0388] 434 Keep Area

[0389] 500 Second Positioning Template

[0390] 510 Second channel opening

[0391] 520 Second centering surface

[0392] 600, 600' third positioning template

[0393] 610, 610' Third channel opening

[0394] 620 Third centering surface

[0395] 700 Closing element

[0396] 710 Active Surface

[0397] 730 first end region

[0398] 740 Second end region

[0399] 750 Exit

[0400] 800 heat source

[0401] 810 Move Arrow

[0402] 900 first connecting element

[0403] 910 Second connecting element

[0404] 1000 Provide cladding tube

[0405] 1100 Preparation of multiple anti-resonance element preforms

[0406] 1200 Preparation of positioning template

[0407] 1300 Attachment

[0408] 1400 Insert

[0409] 1500 processing

[0410] 2000 Method steps 1000 to 1500

[0411] 2100 Collapse

[0412] 2200 Addition of additional cladding material

[0413] 2300 Lengthened

[0414] 2400 Antiresonant Hollow Core Fiber

[0415] 2410 Anti-resonance Element

[0416] 2420 ARE outer tube of optical fiber

[0417] 2430 ARE inner tube of optical fiber

[0418] 2450 Cladding of Antiresonant Hollow-Core Fiber

[0419] 2452 A portion of the cladding material formed at the cladding of an antiresonant hollow-core fiber

[0420] 2460 Longitudinal axis of antiresonant hollow-core fiber

[0421] 2470 Hollow core of antiresonant hollow core fiber

[0422] 2480 inner surface

Claims

1. A method for manufacturing a preform (100, 100', 100") for an antiresonant hollow core optical fiber, the method comprising the following steps: a) providing (1000) a cladding tube (200), the cladding tube having a cladding tube inner bore and a cladding tube longitudinal axis, a cladding tube wall extending along the cladding tube longitudinal axis, the cladding tube wall being defined by an inner side and an outer side, b) preparing (1100) a plurality of anti-resonance element preforms (300), each anti-resonance element preform comprising an ARE outer tube and an ARE inner tube inserted into the ARE outer tube, c) preparing (1200) a positioning template (400, 400', 400") having a plurality of passage openings therethrough, the plurality of passage openings being adapted to each longitudinally guide an anti-resonance element preform (300), wherein the positioning template (400, 400', 400") and the cladding tube (200) are made of the same material, d) attaching (1300) the positioning template (400, 400', 400") to the first end of the cladding tube (200), e) inserting (1400) at least a portion of the anti-resonance element preform (300) through the passage opening for arranging the anti-resonance element preform (300) in the cladding tube inner bore, f) processing (1500) an assembly (110, 110', 110", 110'") comprising the cladding tube (200), the anti-resonance element preform (300) and the positioning template (400, 400', 400") by means of a thermoforming process selected from at least one of stretching and collapsing, It is characterized in that The positioning template (400, 400', 400") has at least one centering surface that cooperates with the first end of the cladding tube (200) in a self-centering manner so that the anti-resonance element preform (300) is arranged at a target position in step e) "insertion".

2. The method according to claim 1, characterized in that The cladding tube (200) is at least partially cut away in the region of the first end (250) in order to form a counter-centering surface (251) which cooperates with the centering surface in a form-fitting manner.

3. The method according to claim 1 or 2, characterized in that In step f) "processing", the anti-resonance element preform (300) is thermally fixed to the cladding tube wall (210) in a flameless manner.

4. The method according to claim 1 or 2, characterized in that The cladding tube (200) has a second end (260).

5. The method according to claim 4, characterized in that The method comprises the following steps: (i) producing a second positioning template (500) having a plurality of second passage openings (510) therethrough, the plurality of second passage openings being adapted to each longitudinally guide an anti-resonance element preform (300), wherein the second positioning template (500) and the cladding tube (200) are made of the same material, (ii) combining the second positioning template (500) with the second end portion (260) of the cladding tube (200).

6. The method according to claim 5, characterized in that The method comprises the following steps: (iii) inserting at least a portion of the anti-resonance element preform (300) through the second passage opening (510) of the second positioning template (500), (iv) wherein the second positioning template (500) has at least one second centering surface (520), and the at least one second centering surface (520) cooperates with the second end (260) of the cladding tube (200) in a self-centering manner, so that the anti-resonance element preform (300) is arranged at a target position in the step (iii) "insertion".

7. The method according to claim 6, characterized in that The cladding tube (200) is at least partially cut away in the region of the second end (260) in order to form a second counter-centering surface (261) which cooperates in a form-fitting manner with the at least one second centering surface (520).

8. The method according to claim 5, characterized in that The method comprises the following steps: A / preparing a third positioning template (600, 600') having a plurality of third channel openings (610, 610') through the third positioning template (600, 600'), each of the plurality of third channel openings being adapted to longitudinally guide the anti-resonance element preform (300), The third positioning template (600, 600') has at least one third centering surface (620).

9. The method according to claim 8, characterized in that The method comprises the following steps: B / Manufacturing of a tubular closure element (700), The closure element (700) has an active surface (710) in the region of the first end region (730) in order to cooperate with the third centering surface (620), in particular in a form-fitting manner.

10. The method according to claim 9, characterized in that The method comprises the following steps: C / connecting the third positioning template (600, 600') to the first end region (730), D / connecting the closure element (700) to the second end (260) of the cladding tube (200), E / Pushing at least a portion of the anti-resonance element preform (300) through the third passage opening (610, 610') to arrange the anti-resonance element preform (300) in the cladding tube inner bore (220), wherein the third centering surface (620) cooperates with the active surface (710) in a self-centering manner so that the anti-resonance element preform (300) is arranged at a target position.

11. The method according to claim 10, characterized in that At least one of the following steps comprises flameless thermal joining or flame-based thermal joining: Step b) "Preparation", Step d) "Attach", Step (ii) "combining", Step C / "Link", and Step D / "Connect".

12. The method according to claim 8, characterized in that Prior to step f) "treating", the anti-resonance element preform (300) is held in the cladding tube bore only by: The positioning template (400, 400', 400"), or The positioning template (400, 400', 400") and the second positioning template (500), or The positioning template (400, 400', 400") and the third positioning template (600, 600') and other methods without material-to-material bonding.

13. The method according to claim 8, characterized in that The positioning template (400, 400', 400") and / or the second positioning template (500) and / or the third positioning template (600, 600') have at least one gas flow element, which connects the inner hole of the cladding tube to the surrounding area of ​​the preform in a fluid-conducting manner.

14. A method for producing a secondary preform, the method being for producing the secondary preform from the preform (100, 100', 100") manufactured according to the method of any one of claims 1 to 13, the secondary preform being capable of being used for drawing an antiresonant hollow-core optical fiber, the method comprising the following steps: further processing said preform (100, 100', 100") into said secondary preform, The further processing comprises one or more of the following thermoforming processes: vii.) Lengthen, viii.) collapse, ix.) collapse and stretch simultaneously, x.) adding additional cladding material, xi.) adding additional cladding material and subsequent elongation, xii.)Addition of additional cladding material and simultaneous elongation.

15. A production method for producing an antiresonant hollow-core optical fiber from a preform (100, 100', 100") produced by the method according to any one of claims 1 to 13, the production method comprising the following steps: further processing the preform (100, 100', 100") into the antiresonant hollow core optical fiber, The further processing comprises one or more of the following thermoforming processes: vii.) Lengthen, viii.) collapse, ix.) collapse and stretch simultaneously, x.) adding additional cladding material, xi.) adding additional cladding material and subsequently stretching, xii.) adding additional cladding material and simultaneously stretching.

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