Antiresonance element preform for manufacturing antiresonance hollow core fiber

Abstract

To provide an antiresonance element preform capable of easily and reproducibly manufacturing an antiresonance hollow core fiber having a good optical characteristic, for example, low optical attenuation.SOLUTION: An antiresonance element preform (100) for manufacturing an antiresonance hollow core fiber comprises a first circular element (200) having a first circle radius (250), and a first arc-like element (300) having a first arc radius (350) on an axial top view. Furthermore, the present invention relates to a method for manufacturing an antiresonance preform, a preform for manufacturing an antiresonance hollow core fiber having at least one antiresonance element preform, and an antiresonance hollow core fiber. According to the present invention, the first circular element (200) and the first arc-like element (300) are connected to each other with two contact points (400).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an anti-resonant element preform for producing an anti-resonant hollow-core fiber, comprising, in a top axial view, a circular first circular element having a first circular radius and a circular first arc element having a first arc radius.

[0002] Furthermore, the invention relates to a method for manufacturing an antiresonant element preform, a preform for manufacturing an antiresonant hollow-core fiber comprising at least one antiresonant element preform, and an antiresonant hollow-core fiber. [Background technology]

[0003] Conventional single-mode optical fibers of solid material have a core region of glass surrounded by a cladding region of glass with a lower refractive index, whereby light guiding is based on total internal reflection between the core region and the cladding region, however, the interaction of the guided light with the solid material is associated with increased latency during data transmission and a relatively low damage threshold compared to high energy radiation.

[0004] "Hollow-core fibers", in which the core comprises a vacuum cavity filled with a gas or liquid, avoid or reduce these drawbacks. In hollow-core fibers, the interaction of light with the glass is smaller than in solid-core fibers. Since the refractive index of the core is smaller than that of the cladding, light guiding by total internal reflection is not possible and light usually escapes from the core to the cladding. Depending on the physical mechanism of light guiding, hollow-core fibers are divided into "photonic band-gap fibers" and "anti-resonant hollow-core fibers".

[0005] In the case of a "photonic bandgap fiber", the hollow core region is surrounded by a cladding that contains a periodic arrangement of small hollow ducts. The periodic structure of the hollow ducts in the cladding causes an effect known in semiconductor technology as "photonic bandgap", according to which light in a certain wavelength range scattered in the cladding structure constructively interferes due to Bragg reflection in the central cavity and cannot propagate laterally in the cladding.

[0006] In the case of an embodiment of a hollow-core fiber referred to as an "anti-resonant hollow-core fiber" (ARHCF), the hollow core region is surrounded by an inner cladding region, inside which so-called "anti-resonant elements" (or "anti-resonant elements"; "AREs" for short) are located. The walls of the anti-resonant elements, which are uniformly distributed around the hollow core, can act as a Fabry-Perot cavity, which operates in anti-resonance, reflecting the incident light and guiding it through the fiber core.

[0007] This fiber technology promises low optical attenuation, a very wide transmission spectrum (even in the UV or IR wavelength range), and low latency during data transmission.

[0008] Potential applications of hollow-core fibers are in the fields of data transmission, high-performance beam guidance, e.g. for material processing, mode filtering, and nonlinear optics, especially for supercontinuum generation in the ultraviolet to infrared wavelength range.

[0009] prior art One drawback of anti-resonant hollow-core fibers is that higher order modes are not necessarily suppressed and therefore they are often not purely single mode over long transmission lengths, degrading the quality of the output beam.

[0010] In the paper "Nested antiresonant nodeless hollow core fiber" by Francesco Poletti; Optics Express, Vol. 22, No. 20 (2014); DOI: 10.1364 / OE 22.023807, a fiber design is proposed where the antiresonant element is not formed as a simple single structural element, but consists of several nested structural elements. The nested antiresonant element is designed in such a way that the higher-order core modes are phase-matched to the cladding modes and suppressed, but the fundamental core mode is not suppressed. This ensures that the fundamental core mode always propagates, and the hollow core fiber can be effectively single-mode over a limited wavelength range.

[0011] Effective modal suppression depends on the central wavelength of the transmitted light and the structural parameters of the fiber design, such as the radius of the hollow core and the diameter difference of the nested ring structures within the anti-resonant element.

[0012] From EP 3136143 A1 an anti-resonant hollow-core fibre is known in which the core is capable of guiding further modes in addition to the fundamental mode (in which it is referred to as a "hollow-core fibre without band gap"). For this purpose, the core is surrounded by an inner cladding comprising "non-resonant elements" which provide a phase match of the anti-resonant mode with the higher modes. The manufacture of the hollow-core fibre is carried out according to the so-called "stack-and-draw" technique, in which the output elements are arranged to form an axially parallel assembly and are fixed to form a preform, which is subsequently stretched. Thereby, a cladding tube with a hexagonal inner cross section is used and six so-called "ARE preforms" (anti-resonant element preforms) are fixed to the inner edge of the cladding tube. This preform is stretched in two stages to form the hollow-core fibre.

[0013] From WO 2015 / 185761 A1 an anti-resonant hollow-core fiber is known in which a further tubular, so-called "nested element" is arranged inside a first tubular "non-resonant element", which together form an anti-resonant element.

[0014] One drawback of the manufacture of this assembly is the relatively large contacts, which arise from the connection of the "nested" tube inside the first non-resonant element, and even small deviations from the ideal structure already have a negative effect on the efficiency of the light guidance of the fiber. A further drawback is that when using only tubular elements, the range of variation in the design of the anti-resonant element is small.

[0015] An anti-resonant hollow core fiber is known from CN 111474627(A), in which the anti-resonant element is formed from a circle element and a circular arc element in the axial top view. The circle element and the circular arc element are not connected to each other, but in each case directly to the fiber cladding. From the manufacturing point of view, this has the disadvantage that it is not possible to pre-manufacture the anti-resonant element preform that forms the anti-resonant element in the final drawn fiber, and all structural elements have to be directly connected to the cladding. This ensures that the structural elements are very prone to deviate from the ideal arrangement with respect to each other, which impairs efficiency during light guiding.

[0016] From US 2020 / 0241200 A1, an anti-resonant hollow core fiber is known, in which the anti-resonant element comprises a circular element and a linearly shaped structural element without curvature in an axial top view. A disadvantage of the linearly shaped structural element is that the anti-resonant element has poorer light guidance compared to curved structural elements, which has a negative effect on the optical properties, such as the optical attenuation of the fiber. Summary of the Invention [Problem to be solved by the invention]

[0017] The object of the present invention is to at least partially overcome one or several of the drawbacks arising from the prior art.

[0018] In particular, the invention is based on the object of providing an anti-resonant element preform that allows for the easy and reproducible production of anti-resonant hollow-core fibers with good optical properties, such as low optical attenuation.

[0019] It is a further object of the present invention to provide a method for reproducibly manufacturing anti-resonant element preforms with high precision and good optical properties, such as low optical attenuation.

[0020] It is a further object of the present invention to identify a cost-effective method for manufacturing preforms for anti-resonant hollow-core fibers that avoids the limitations of conventional manufacturing methods.

[0021] It is a further object of the present invention to provide a preform for producing anti-resonant hollow-core fiber that avoids the limitations of conventional preforms.

[0022] It is a further object of the present invention to provide an anti-resonant hollow core that avoids the limitations of conventional hollow core fibers.

[0023] Preferred embodiments of the invention The features of the independent claims contribute to at least partially achieving at least one of the above-mentioned objects. The dependent claims provide preferred embodiments which contribute to at least partially achieving at least one of the objects.

[0024] / 1 / An antiresonant element preform for producing an antiresonant hollow-core fiber, comprising, in axial top view: A first circular element having a first circular radius and a first arc element having an arc shape and a first arc radius, The first circular element and the first arc element are connected to each other at two contact points. Anti-resonant element preform.

[0025] / 2 / An anti-resonant element preform according to embodiment 1, characterized in that the first circular element and the first circular arc element comprise glass, in particular quartz glass, in particular quartz glass having a refractive index of at least 1.4, in particular 1.4 to 3, in particular 1.4 to 2.8, or a polymer, in particular made of glass, in particular quartz glass, in particular quartz glass having a refractive index of at least 1.4, in particular 1.4 to 3, in particular 1.4 to 2.8, or a polymer.

[0026] / 3 / An anti-resonant element preform according to embodiment 1 or 2, characterized in that the anti-resonant element preform comprises a circular second circular element having a second circular radius.

[0027] / 4 / An anti-resonant element preform according to any one of the preceding embodiments, characterized in that the anti-resonant element preform comprises a second arc element having an arc shape with a second arc radius.

[0028] / 5 / An anti-resonant element preform according to any one of the preceding embodiments, characterized in that the first circle radius is smaller in magnitude than the first circle arc radius.

[0029] / 6 / An anti-resonant element preform according to any one of the preceding embodiments, characterized in that a first arc element is disposed inside a first circular element.

[0030] / 7 / An anti-resonant element preform according to any one of embodiments 1 to 5, characterized in that the first arc element is disposed outside the first circular element.

[0031] / 8 / A method for producing an anti-resonant element preform according to any one of claims 1 to 7, comprising: (a) providing a first circular element that is circular in axial top view and has a first circular radius; (b) providing a first arc element having an arc shape in a top axial view and a first arc radius; (c1) disposing a first arc element inside a first circular element such that the first arc end and the second arc end are disposed inside the first circular element; or (c2) arranging the first arc element outside the first circle element such that the first arc end and the second arc end are arranged outside the first circle element; (d) the method step of connecting the first circular arc end and the second circular arc end to the first circular element by forming a second tangent point; A method comprising:

[0032] / 9 / The method according to embodiment 8, characterized in that the connection in method step (d) is effected by heat input.

[0033] / 10 / A preform for manufacturing an anti-resonant hollow-core fiber with a cladding tube, characterized in that at least one anti-resonant element preform according to any one of embodiments 1 to 7 is disposed within the cladding tube.

[0034] / 11 / A preform for manufacturing an antiresonant hollow-core fiber as described in embodiment 10, characterized in that at least one antiresonant element preform is connected to the inner surface of the cladding tube.

[0035] / 12 / A preform for producing an antiresonant hollow-core fiber according to embodiment 10 or 11, characterized in that 3 to 10 antiresonant element preforms are arranged in a covering tube.

[0036] / 13 / An anti-resonant hollow-core fiber comprising, in an axial top view, a coating region, at least one anti-resonant element arranged on the coating region, a circular first circular structure having a first circular structure radius, and an arc-shaped first arc structure having a first arc structure radius, characterized in that the first circular structure and the first arc structure are connected to each other at two contact points.

[0037] / 14 / An anti-resonant hollow-core fiber as claimed in claim 13, produced by drawing a preform as claimed in any one of claims 10 to 12.

[0038] General matters In this specification, range designations also include values ​​that are mentioned as limits. Thus, a designation of the type "in the range from X to Y" for a variable A means that A can take on values ​​X, Y, and values ​​between X and Y. Thus, a unilaterally limited range of the type "up to Y" for a variable A means values ​​Y and less than Y.

[0039] Some of the described features are associated with the term "essentially". The term "essentially" should be understood to mean that under practical conditions and manufacturing techniques, a mathematically precise interpretation of terms such as "overlapping", "perpendicular", "diameter" or "parallelism" cannot be precisely performed, but only within certain manufacturing-related error tolerances. For example, "essentially perpendicular axes" describe angles of 85 degrees to 95 degrees with respect to each other, and "essentially the same volume" includes deviations of up to 5% by volume. For example, a "device consisting essentially of quartz glass" includes a quartz glass portion of more than 95% by weight and less than 100% by weight. For example, "essentially complete filling of volume B" includes a filling of more than 95% by volume and less than 100% by volume of the total volume of B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The present invention relates to an anti-resonant element preform for producing an anti-resonant hollow-core fiber, comprising, in a top axial view, a circular first circular element having a first circular radius and a circular first arc element having a first arc radius.

[0041] In order to overcome the above-mentioned shortcomings in the prior art, according to the present invention, a first circular element and a first arc element are connected to each other at two contact points, and the arc element is in particular connected to a circular element having a first arc end and a second arc end opposite to the first arc end. The first arc end and the second arc end should be understood as corner points of the first arc element, which are visible in an axial top view of the anti-resonance element preform, and between which the first arc element extends in an arc shape.

[0042] The antiresonant element preform constructed in this way can be manufactured separately from the other components for manufacturing the antiresonant hollow-core fiber, which is advantageous from a manufacturing-related point of view. Antiresonant element preforms that differ from the ideal structure, for example during manufacturing, can therefore be discarded in a relatively inexpensive manner and without the need to discard further components for manufacturing the antiresonant hollow-core fiber. Through the pre-manufacturing of the antiresonant element preforms, further uniformity can be achieved over the entire manufacturing batch, which has an advantageous effect on the symmetry of the preforms manufactured with the antiresonant element preforms and ultimately on the symmetry of the antiresonant hollow-core fiber. Increasing the symmetry has a positive effect on the optical properties of the hollow-core fiber.

[0043] Furthermore, anti-resonant elements fabricated from this type of anti-resonant element preform have proven to be components with improved optical properties in the final hollow-core fiber, which results in lower light propagation losses (i.e., including light scattering, diffraction, absorption, and containment) and therefore higher data transmission capacity of the final hollow-core fiber.

[0044] It has been shown that a circular arc element connected to a circular element at two junctions allows for a high degree of control over the structural parameters of the antiresonant element preform, and therefore allows for the provision of an antiresonant hollow-core fiber with improved optical properties.

[0045] For example, the improved optical properties of this type of antiresonant hollow-core fiber manifest themselves in optical attenuation of less than 0.15 dB / km at wavelengths between 1.0 μm and 2.5 μm, or less than 1 dB / km at wavelengths up to 0.8 μm. Any type of phenomenon that causes a decrease in the strength of a propagating signal, without thereby affecting its shape, is referred to as optical attenuation.

[0046] The component or component that essentially becomes the anti-resonant element within the hollow-core fiber by simple length forming (also called stretching) during the fiber drawing process is referred to as an anti-resonant element preform.

[0047] In an axial top view, i.e. in a two-dimensional view relative to the longitudinal axis, the anti-resonant element preform comprises a first circular element, which in a three-dimensional view corresponds to a tubular structural element. The first circular element is designed essentially circular, having an essentially uniform first circular radius, the radius at the first point deviating from the radius at the further point by no more than 5%, preferably no more than 3%, more preferably no more than 1%, most preferably no more than 0.5%. The first circular element thus has an essentially uniform diameter, the diameter at the first point deviating from the diameter at the further point of the anti-resonant element preform by no more than 5%, preferably no more than 3%, more preferably no more than 1%, most preferably no more than 0.5%. Thereby, for example, the first circular radius can be in the range of 2 to 18 mm, preferably in the range of 3 to 16 mm, more preferably in the range of 4 to 12 mm. The wall thickness of the first circular element is in the range of 0.1 mm to 3 mm, preferably in the range of 0.1 mm to 2 mm, more preferably in the range of 0.2 to 1.5 mm.

[0048] In an axial top view, i.e. in a two-dimensional view on the longitudinal axis, the anti-resonant element preform comprises a first arc element which in a three-dimensional view corresponds to a segment of a tubular, essentially circular structural element cut parallel to the longitudinal axis, or in other words corresponds to a curved disk. The first arc element has an essentially uniform first arc. In a three-dimensional view, the first arc element thus represents a segment cut parallel to the longitudinal axis of an essentially circular tubular structural element having a radius corresponding to the arc radius, the radius at the first point deviating from the radius at the further point by no more than 5%, preferably no more than 3%, more preferably no more than 1% and most preferably no more than 0.5%. Thereby, the first arc radius can be, for example, in the range of 1 to 30 mm, preferably in the range of 2 to 25 mm, more preferably in the range of 3 to 20 mm. The wall thickness of the first arc element is within a range of 0.1 mm to 3 mm, preferably 0.1 mm to 2 mm, and more preferably 0.2 mm to 1.5 mm.

[0049] The circle radius and the arc radius are in each case to be understood as the outer diameter of the corresponding element. The corresponding inner diameter is determined by subtracting the respective wall thickness from the respective outer diameter. The same applies to the corresponding diameter.

[0050] The tangent points are locations where the first circular element and the first arc element are connected to each other, in particular by a material bond. In one embodiment, the first arc element is connected to a first circular element having a first arc end and a second arc end opposite the first arc end. The first circular element and the first arc element are connected to each other at exactly two tangent points.

[0051] The contact points can be designed differently. In one embodiment, the first circular element and the first circular arc element are connected to each other at least at one contact point via fastening means such as, for example, adhesives, rivets, screws or nails. In a preferred design, the first circular element and the first circular arc element are connected to each other by a material bond at least at one contact point, preferably at both contact points.

[0052] In order to provide an anti-resonant element preform with high structural accuracy and improved optical properties, the first arc element comprises an arc element circumference corresponding to 10%-85%, preferably 20%-80%, more preferably 20%-75%, even more preferably 20%-70% of the circumference of the full circular element corresponding to the first arc radius. The advantage of this is that the contacts are spatially arranged at a distance from each other such that the first arc element and the first arc are connected to each other without the contacts merging with each other, and there is one large contact instead of two separate contacts. The large contact will adversely affect the optical light guide properties of the final glass fiber, for example due to a local increase in the material portion of, for example, glass at the large contact, which may result in ovalization of the anti-resonant element.

[0053] At the tangency point, the first circular element and the first circular arc element describe an exterior angle in each case greater than 10°, preferably greater than 15°, more preferably greater than 20°, most preferably greater than 25°. The exterior angle is less than or equal to 160°, preferably less than or equal to 150°, more preferably less than or equal to 130°. The exterior angle is to be understood as the angle described at the tangency point between the first circular element and the convex side of the first circular arc element in an axial top view. This makes it possible to provide an anti-resonant element preform with high structural precision and improved optical properties.

[0054] In an embodiment, the entire anti-resonant element preform comprises or consists of a material transparent to the work light of the optical fiber, for example glass, in particular doped or undoped quartz glass (SiO2). Doping allows for the adaptation of physical properties, for example the thermal expansion coefficient. Fluorine, chlorine and / or hydroxyl groups are preferably used as doping agents to reduce the viscosity of the quartz glass.

[0055] An embodiment of the anti-resonant element preform is characterized in that the first circular element and the first circular arc element comprise at least glass, in particular doped or undoped quartz glass, in particular quartz glass having a refractive index of at least 1.4, in particular 1.4 to 3, or a polymer, for example polymethylmethacrylate, cyclic olefin copolymer, polycarbonate or fluoropolymer. In a further design, the first circular element and the first circular arc element consist of glass, in particular doped or undoped quartz glass, in particular quartz glass having a refractive index of at least 1.4, in particular 1.4 to 3, or a polymer, for example polymethylmethacrylate, cyclic olefin copolymer, polycarbonate or fluoropolymer.

[0056] In an embodiment, the first circular element and the circular arc element are made of the same material. In a further design, the first circular element and the first circular arc element are made of the same material, in particular undoped or doped quartz glass, in particular glass having a refractive index of at least 1.4, in particular 1.4 to 3, in particular 1.4 to 2.8, and the amount of doping does not exceed 0.1% by weight.

[0057] The term identical material refers to the material properties of the two components, whereby the two components have essentially the same chemical properties. Thus, the total mass of different chemical elements in both parts may be less than 1% by weight, in particular less than 0.5% by weight, in particular less than 0.1% by weight. The chemical composition of the two parts differs in particular by a contaminant content of less than 500 ppm by weight, in particular less than 100 ppm by weight, and / or by a doping agent content of less than 10,000 ppm by weight, in particular less than 5,000 ppm by weight.

[0058] In one embodiment, the anti-resonant element preform comprises a first circular element and a first arc element.

[0059] An embodiment of the anti-resonant element preform is characterized in that the anti-resonant element preform comprises a circular second circular element having a second circular radius.

[0060] The second circular element can have the same features and characteristics as the first circular element above, and the second circular radius can be designed to be larger, smaller, or the same as the first circular radius.

[0061] In one embodiment, the second circle element is arranged inside the first circle element. In one embodiment, the first circle element and the second circle element are connected to each other at the contact points, in particular by material bonds. In a further design, the first circle element and the second circle element are connected to each other, in particular by material bonds. In a further design, the second circle element is connected to the first circle element as well as to the first circle element, in particular by material bonds.

[0062] In a further embodiment, the first circular element is arranged inside the second circular element, and the first and second circular elements are preferably connected to each other at a contact point, in particular by a material bond.

[0063] In a further embodiment, the second circular element is arranged within the space enclosed by the first circular element and the first arc element, and the second circular element is connected to either the first circular element, the first arc element, or the first circular element and the first arc element, in particular by a material bond.

[0064] An embodiment of the anti-resonant element preform is characterized in that the anti-resonant element preform comprises a second arc element having an arc shape with a second arc radius.

[0065] The second arc element can have the same features and characteristics as the first arc element described above, and the second arc radius can be larger than, smaller than, or the same as the first arc radius.

[0066] In one embodiment, the second circular arc element is disposed inside the first circular element, and the first circular element and the second circular arc element are preferably connected to each other at two contact points, in particular by a material bond.

[0067] In a further embodiment, the second arc element is arranged in the space enclosed by the first circular element and the first arc element, and the second arc element is connected, in particular by a material bond, to the first circular element at two junctions, to the first arc element at two junctions, or to the first circular element at one junction and to the first arc element at one junction.

[0068] Furthermore, since the anti-resonance element preform has a first circular element and a first arc element as structural elements, the freedom in selecting the first circular radius and the first arc radius is greater than when the anti-resonance element preform is formed using only circular elements as structural elements.

[0069] In some embodiments, the first circle radius and the first arc radius have essentially the same value. When using only circle elements to form the anti-resonant element preform, the corresponding features are not accessible.

[0070] In a further design, the first circle radius has a greater value than the first arc radius.

[0071] An embodiment of the anti-resonant element preform is characterized in that the first circle radius has a value smaller than the first circle arc radius. If only circle elements are used to form the anti-resonant element preform, the corresponding structure cannot be accessed.

[0072] The first circle element and the first arc element may be arranged differently from each other, as long as they are connected to each other at least two, preferably exactly two, contact points, in particular by material bonds.

[0073] An embodiment of the antiresonant element preform is characterized in that the first arc element is arranged inside the first circle element. This means that the first arc element is connected to the inside of the first circle element at two contact points, in particular by material bonding. The first arc element is therefore arranged inside the first circle element. This makes it possible to provide a circular, or in a three-dimensional view tubular, antiresonant element preform with improved optical properties and therefore easier handling of the antiresonant element preform. Such an antiresonant element preform can be easily and with high structural precision connected to further components of the preform in order to produce an antiresonant hollow core fiber.

[0074] An embodiment of the anti-resonant element preform is characterized in that the first circular arc element is arranged outside the first circular element. This means that the first circular arc element is connected to the outside of the first circular element at two contact points, in particular by a material bond. The first circular arc element is therefore arranged outside the first circular element. This allows the production of anti-resonant element preforms with an eight-point profile in the axial top view or with an irregular eight-point profile depending on the individual radii of the first circular element and the first circular arc element.

[0075] The present invention further relates to a method for manufacturing the above-described anti-resonant element preform.

[0076] Depending on the desired design of the anti-resonant element preform, the method can be performed in different ways.

[0077] A first embodiment of a method for manufacturing an anti-resonant element preform according to any one of the above designs comprises at least: (a) providing a first circular element that is circular in axial top view and has a first circular radius; (b) providing a first arc element having a first arc radius and being arc-shaped in axial top view; (c1) a method step of arranging a first arc element (300) inside a first circular element (200) such that a first arc end (305) and a second arc end (306) are arranged inside (205) of the first circular element (200); (d) connecting the first and second arc ends by forming a second junction, in particular by a material bond; Includes.

[0078] A first embodiment of a method for manufacturing an antiresonant element preform is useful for manufacturing the above-mentioned antiresonant element preform, where a first circular arc element is disposed inside a first circular element. The first embodiment of the method can be useful for manufacturing an essentially circular antiresonant element preform.

[0079] A second embodiment of a method for manufacturing an anti-resonant element preform according to any one of the above designs comprises at least: (a) providing a first circular element that is circular in axial top view and has a first circular radius; (b) providing a first arc element having a first arc radius and being arc-shaped in axial top view; (c2) a method step of locating the first arc element outside the first circle element such that the first arc end and the second arc end are located outside the first circle element; (d) a method step of connecting said first and second arcuate ends by forming a second contact, in particular by a material bond; Includes.

[0080] A second embodiment of the method for manufacturing an anti-resonant element preform is useful for manufacturing the above-mentioned anti-resonant element preform, in which the first circular arc element is arranged outside the first circular element. The second embodiment of the method can be useful for manufacturing an anti-resonant element having a contour in the shape of an eight in an axial top view, or an anti-resonant element having an irregular contour in the shape of an eight depending on the corresponding radii of the first circular element and the first circular arc element.

[0081] The connection in method step (d) can be made in different ways in all embodiments of the method, for example by gluing, screwing, riveting, welding, nailing or jamming.

[0082] An embodiment of the method for manufacturing an anti-resonant element preform described above is characterized in that the connection in method step (d) is performed by heat input.

[0083] The heat input serves in particular for the inter-material bond between the first circle element and the first arc element at the junction. The heat input must be performed in such a way that an inter-material bond between the materials of the two elements is possible. This can be achieved in such a way that the surfaces of the elements, at least at the junction, at least partially change from a solid state to a liquid, in particular a viscous state.

[0084] The heat input can be realized in different ways, for example: - Flame-based processes: based on the oxidation of exothermic reaction gases. One example is the use of hydrogen (also called "H2") as an exothermic reaction combustion gas (flame hydrolysis), which reacts with oxygen (also called "O2") in the air, or -Flameless process: Using other systems that heat and do not require an open flame. One example is the use of resistors that can convert electrical energy into thermal energy (heat).

[0085] Furthermore, the invention relates to a preform for manufacturing an antiresonant hollow-core fiber with a cladding tube, characterized in that at least one antiresonant element preform as described above is arranged in the cladding tube.

[0086] The preform is the component from which an anti-resonant hollow-core fiber can be drawn. Alternatively, the preform can be further processed into a secondary preform from which an anti-resonant hollow-core fiber is drawn. This further processing can include, for example, a single or repeated run of a hot forming process, such as stretching, collapsing, or adding additional coating material.

[0087] The cladding tube is a tubular element made essentially of quartz glass in which at least one of the anti-resonant element preforms described above is disposed. When the final preform is drawn into the final fiber, the cladding tube surrounds the hollow core of the anti-resonant hollow core fiber. In an embodiment, the inner diameter of the cladding tube is in the range of 10-60 mm. In an embodiment, the outer diameter of the cladding tube is in the range of 25-250 mm, preferably 30-200 mm. In an embodiment, the length of the cladding tube is in the range of 500-1200 mm.

[0088] The at least one anti-resonant element preform may be arranged in different ways inside the cladding tube.

[0089] An embodiment of the preform is characterized in that at least one anti-resonant element preform is connected to the inner surface of the cladding tube, in particular by a material bond. In one embodiment, the anti-resonant element preform is connected to the cladding tube via a first circular element. In a further design, the anti-resonant element preform is connected to the cladding tube via a first circular arc element, whereby in the case of these anti-resonant elements, the first circular arc element is arranged outside the first circular element.

[0090] To build a preform, different numbers of anti-resonant elements can be placed inside the cladding tube.

[0091] An embodiment of the preform is characterized in that 3 to 10, preferably 3 to 8, more preferably 4 to 6 anti-resonant element preforms are arranged in the cladding tube.

[0092] In some embodiments, only anti-resonant element preforms having the properties and characteristics of the anti-resonant element preforms described above are disposed inside the cladding tube. In further designs, at least one anti-resonant element preform disposed inside the cladding tube has properties and characteristics other than those of the anti-resonant element preforms described above.

[0093] Furthermore, the present invention relates to an anti-resonant hollow-core fiber comprising, in an axial top view, a coating region and at least one anti-resonant element arranged in the coating region, the anti-resonant element comprising a circular first circular structure having a first circular structure radius and an arc-shaped first arc structure having a first arc structure radius, characterized in that the first circular structure and the first arc structure are connected to each other at two contact points.

[0094] An anti-resonant hollow core fiber can be manufactured from the above preform, in particular by drawing, where at least a part of the cladding region of the anti-resonant hollow core fiber is formed from the cladding tube of the preform and at least one anti-resonant element of the anti-resonant hollow core fiber is formed from at least one anti-resonant element preform of the preform. Thus, a first circle structure is constructed from the first circle element and a first arc structure is constructed from the first arc element. The respective contact points are maintained.

[0095] The preform is stretched during stretching, which is preferably performed to scale, such that the shape and arrangement of the components or parts of the preform, in particular the first circular element and the first circular arc element, are reflected in the stretched final product.

[0096] In certain anti-resonant hollow-core fiber embodiments, the coating region corresponds to a stretched cladding tube. In further designs, the coating region corresponds to a cladding tube and an overlay tube, the overlay tube being added to the cladding tube before or during stretching. By "adding" it is to be understood connecting the cladding tube and the overlay tube, in particular by material bonding, which is done in particular by heat input, preferably by using a negative pressure applied between the cladding tube and the overlay tube.

[0097] To elongate and produce an anti-resonant hollow-core fiber from the preform, the preform can be guided vertically through a furnace, whereby the lower end of the preform, from which the anti-resonant hollow-core fiber is drawn in the form of a cone, is warmed to the draw temperature, and the drawn fiber is then cooled from the draw temperature by a gas flow directed opposite the draw direction.

[0098] The properties and features disclosed herein may be important both separately and in combination with one another for the various embodiments of the invention as claimed. Properties and features disclosed with respect to the antiresonant element preform, the preform, or the antiresonant hollow-core fiber are also disclosed with respect to the method, and vice versa.

[0099] The invention will now be further described, by way of example only, with reference to the drawings, in which the invention is not limited thereto. [Brief description of the drawings]

[0100] [Figure 1] FIG. 2 is a top axial view of an anti-resonance element preform comprising a first circular element and a first arcuate element. [Diagram 2] 1 illustrates a further embodiment of an anti-resonant element preform. [Diagram 3] 1 illustrates a further embodiment of an anti-resonant element preform. [Figure 4] 1 illustrates a further embodiment of an anti-resonant element preform. [Diagram 5] 1 illustrates a further embodiment of an anti-resonant element preform. [Figure 6] 1 illustrates a further embodiment of an anti-resonant element preform. [Figure 7] 1 illustrates a further embodiment of an anti-resonant element preform. [Figure 8] 1 illustrates a further embodiment of an anti-resonant element preform. [Figure 9] 1 illustrates a further embodiment of an anti-resonant element preform. [Figure 10]FIG. 2 is an axial top view of an anti-resonant hollow-core fiber preform. [Figure 11] FIG. 1 shows an axial top view of an anti-resonant hollow-core fiber. [Figure 12] A method for manufacturing an anti-resonant element preform is presented.

[0101] Description of the drawings FIG. 1 shows an anti-resonant element preform 100 in an axial top view. The anti-resonant element preform 100 comprises a circular first circle element 200 with a first circle radius 250. A first circle arc element 300 with a first circle arc radius 350 is arranged inside the first circle element 200. In the illustrated embodiment of the anti-resonant element preform 100, the first circle radius 250 and the first circle arc radius 350 have the same value. The first circle element 200 and the first circle arc element 300 are connected to each other at two contact points 400, in particular by material bonding. At the contact points 400, the convex side of the first circle arc element 300 and the inside of the first circle arc in each case describe an exterior angle 150, which in the illustrated embodiment has the same value due to the symmetrical setting of the anti-resonant element preform 100. In a further embodiment not illustrated, the two exterior angles 150 are not identical. In the illustrated embodiment, the first circle element 200 and the first arc element 300 are made from the same material, in particular doped or undoped fused silica.

[0102] Figure 2 shows a further embodiment of an anti-resonant element preform 100a. The embodiment according to Figure 2 largely corresponds to the embodiment shown in Figure 1 described above, and therefore, to avoid repetition, reference is made to said description. Structures repeated from the description of Figure 1 bear the same reference numbers. Structural modifications compared to the structure shown in Figure 1 bear the same reference numbers with the additional letter a.

[0103] In the illustrated embodiment, the first circle radius 250 has a larger value than the first circle arc radius 350a, whereby the exterior angle 150a is larger than the exterior angle 150 according to Figure 1. Due to the smaller first circle arc radius 350a compared to Figure 1, the tangent points 400a are also located closer to each other compared to the tangent points 400 of Figure 1.

[0104] FIG. 3 shows a further embodiment of the anti-resonant element preform 100b. The embodiment according to FIG. 3 corresponds largely to the embodiment described above and shown in the figures above, therefore, to avoid repetition, reference is made to the above description. Structures repeated from the description of the figures above bear the same reference numbers. Modifications of the structure compared to the structures shown in the figures above bear the same reference numbers with the additional letter b. Compared to the embodiment 100a of FIG. 2, the further embodiment of the anti-resonant element preform 100b has a second arc-shaped arc element 310 with a second arc radius 360. Like the first arc element 300a, the second arc element 310 is arranged inside the first circle element 200 and is connected to the first circle element 200 at two contact points 330. In the illustrated embodiment, the first arc radius 350a and the second arc radius 360 have the same value. In a further embodiment not shown, the first arc radius 350a and the second arc radius 360 can have different values. In the illustrated embodiment, the first arc element 300a and the second arc element 360 are disposed on opposite inner sides of the first circular element 200, such that the corresponding convex sides of the first arc element 300a and the second arc element 310 face each other. In a further embodiment not shown, the first arc element 300a and the second arc element 310 are disposed closer in space to each other on the inner side of the first circular element 200.

[0105] Fig. 4 shows a further embodiment of an anti-resonant element preform 100c. The embodiment according to Fig. 4 corresponds largely to the embodiment described above and shown in the figures above, therefore, to avoid repetition, reference is made to the above description. Structures repeated from the description of the figures above bear the same reference numbers. Modifications of the structure compared to the structures shown in the figures above bear the same reference numbers with the additional letter c.

[0106] In the illustrated embodiment, the second arc element 310c is disposed on the same side of the first arc element 200 as the first arc element 300, and the first arc radius 350 and the second arc element 360c have the same value. The first arc element 350 and the second arc element 310c are disposed relative to each other such that the convex side of the second arc element 310c faces the concave side of the first arc element 300. In a further embodiment not shown, the first arc element 350 and the second arc element 310c are disposed relative to each other such that the concave side of the second arc element 310c faces the concave side of the first arc element 350.

[0107] Fig. 5 shows a further embodiment of an anti-resonant element preform 100d. The embodiment according to Fig. 5 corresponds largely to the embodiment described above and shown in the figures above, therefore, to avoid repetition, reference is made to the above description. Structures repeated from the description of the figures above bear the same reference numbers. Modifications of the structure compared to the structures shown in the figures above bear the same reference numbers with the additional letter d.

[0108] In the illustrated embodiment of the anti-resonant element preform 100d, the second arc element 310d is disposed on the same side of the first arc element 200 as the first arc element 300, and the first arc radius 350 has a smaller value than the second arc radius 360d, as shown in Figure 4. The first arc element 300 and the second arc element 360 are disposed at the same point of the first arc element 400, and the tangent point 400 of the first arc element 400 and the tangent point 330d of the second arc element 330 coincide with the first arc 200. The first arc element 350 and the second arc element 310d are disposed relative to each other such that the convex side of the second arc element 310d faces the concave side of the first arc element 300. In a further embodiment not shown, the first arc element 350 and the second arc element 310d are positioned relative to one another such that the concave side of the second arc element 310d faces the concave side of the first arc element 350.

[0109] Fig. 6 shows a further embodiment of an anti-resonant element preform 100e. The embodiment according to Fig. 6 corresponds largely to the embodiment described above and shown in the figures above, therefore, to avoid repetition, reference is made to the above description. Structures repeated from the description of the figures above bear the same reference numbers. Modifications of the structure compared to the structure shown in the figures above bear the same reference numbers with the additional letter e.

[0110] The illustrated embodiment of the anti-resonant element preform 100e has a second circular element 210 with a second circular radius 260. The second circular element 210 is disposed in a space formed by the inside of the first circular element 200 and the concave side of the first circular arc element 300. This connects the second circular element 210 to the first circular element 200. In a further embodiment not illustrated, the second circular element 210 is connected to the first circular arc element 300 or to the first circular element 200 and the first circular arc element 300. In a further embodiment not illustrated, the second circular element 210 is disposed in a space formed by the inside of the first circular element 200 and the convex side of the first circular arc element 300, and the second circular element 210 is connected to the first circular arc element 300 and / or the first circular element 200.

[0111] Fig. 7 shows a further embodiment of an anti-resonant element preform 100f. The embodiment according to Fig. 7 corresponds largely to the embodiment described above and shown in the figures above, therefore, to avoid repetition, reference is made to the above description. Structures repeated from the description of the figures above bear the same reference numbers. Modifications of the structure compared to the structure shown in the figures above bear the same reference numbers with the additional letter f.

[0112] In the illustrated embodiment, the second circle element 210 is disposed in the space formed by the concave side of the second circle element 210d and the inside of the first circle element 200. This connects the second circle element 210 to the first circle element 200. In a further embodiment not illustrated, the second circle element 210 is connected to the second circle element 210 or to the first circle element 200 and the second circle element 310d. In a further embodiment not illustrated, the second circle element 210 is disposed in the space formed by the convex side of the first circle element 300 and the inside of the first circle element 200. In a further embodiment, the second circle element 210 is disposed within the space formed by the first circle element 300 and the second circle element 310d, and the second circle element 210 is connected to either the first circle element 300, the second circle element 310d, or the first circle element 300 and the second circle element 310d.

[0113] Figure 8 shows a further embodiment of an anti-resonant element preform 100g. The embodiment according to Figure 8 corresponds largely to the embodiment described above and shown in the figures above, therefore, to avoid repetition, reference is made to the above description. Structures repeated from the description of the figures above bear the same reference numbers. Modifications of the structure compared to the structure shown in the figures above bear the same reference numbers with the additional letter g.

[0114] The first circular arc element 300g is disposed outside the first circular element 200 and is connected to the first circular element at two contact points 400g, the first circular element 200 and the first circular arc element 300g each having an exterior angle 150g at the two contact points 400. The anti-resonant element preform 100g has a contour that essentially corresponds to the contour of an 8. In the illustrated embodiment, the first circular arc radius 350g has a value greater than the first circular radius 250. In a further embodiment not illustrated, the first circular arc radius 350g has a value equal to or less than the first circular radius 250.

[0115] Figure 9 shows a further embodiment of an anti-resonant element preform 100h. The embodiment according to Figure 9 corresponds largely to the embodiment described above and shown in the figures above, therefore, to avoid repetition, reference is made to the above description. Structures repeated from the description of the figures above bear the same reference numbers. Modifications of the structure compared to the structure shown in the figures above bear the same reference numbers with the additional letter h.

[0116] The illustrated embodiment has a first circular arc element 300g arranged outside the first circular element 200 and a second circular element 210h arranged inside the first circular element 200 and having a second circular element radius 260h, the second circular element 210h and the first circular arc element 300g being arranged on opposite sides of the first circular element 200. In a further embodiment not shown, the first circular arc element 300g and the second circular element 210h are arranged on the same side of the first circular element 200. In a further embodiment not shown, the second circular element 210h is arranged in the space formed by the concave side of the first circular element 300g and the first circular element 200, and the second circular element 210g can be connected to the first circular element 200 and / or the first circular arc element 300g.

[0117] Fig. 10 shows a preform 500 comprising a covering tube 550 and four anti-resonant element preforms 100 according to Fig. 1 arranged inside the covering tube 550. In further embodiments not shown, the preform 500 comprises a different number, e.g. 2-10, of anti-resonant element preforms 100 and / or different shapes of anti-resonant element preforms according to the invention, e.g. according to one of Figs. 2-9, or the preform 500 comprises two or more different embodiments according to the invention of anti-resonant element preforms, e.g. according to Figs. 1-9.

[0118] In the illustrated example, four anti-resonant element preforms 100 are connected inside the cladding tube 550. The distribution of the anti-resonant elements 100 inside the cladding tube 500 is symmetric, so that a symmetric anti-resonant hollow-core fiber can be manufactured from the preform 500 by stretching the preform 500, which improves the optical properties. The four anti-resonant element preforms 100 are arranged in the cladding tube 550 such that the convex side of each first arc element 300 is aligned toward the center 510 of the preform 500. In a further embodiment not shown, the concave side of the first arc element 300 can be aligned toward the center 510, or some arc elements 300 can be aligned with their respective convex sides toward the center 510 and some first arc elements 300 can be aligned with their respective concave sides. The arrangement of the arc elements 300 is preferably designed symmetrically with respect to the center 510.

[0119] FIG. 11 shows an anti-resonant hollow-core fiber 600 that can be manufactured, for example, by stretching the preform 500 according to FIG. 10, comprising a coating region 550′ and four anti-resonant elements 100′ arranged in the coating region 550′. In a further embodiment not shown, the anti-resonant hollow-core fiber 600 comprises a different number of anti-resonant elements 100′, for example between 2 and 10. The anti-resonant elements 100′ have a circular first circular structure 200′ and an arc-shaped first circular arc structure 300′. The first circular arc structures 300′ are each connected to the respective first circular structure 200′ by two contacts 400′. In the illustrated embodiment, the anti-resonant hollow-core fiber 600 has a structure that can be obtained by stretching the preform 500 according to FIG. 10. In a further embodiment not shown, the anti-resonant hollow core fiber has anti-resonant elements 100' of different shapes, which can be obtained by stretching using different anti-resonant element preforms according to the invention, for example according to Figs. 2-9. Four anti-resonant elements 100' are arranged in the coating region 550' such that the convex side of each first arc structure 300' is aligned in the direction of the hollow core fiber center 610 of the anti-resonant hollow core fiber 600. In a further embodiment not shown, the concave side of the first arc structure 300' can be aligned in the direction of the hollow core fiber center 610, or several arc structures 300' can be aligned with their respective convex sides in the direction of the hollow core fiber center 610 and several first arc structures 300' can be aligned with their respective concave sides. The arrangement of the arc structures 300' is preferably designed symmetrically with respect to the hollow core fiber center 610.

[0120] 12 illustrates a method 700 for manufacturing the anti-resonant element preform 100. In a first embodiment, the method 700 includes method steps 710, 720, 730, and 740. In a second embodiment, the method 700 includes method steps 710, 720, 740, and 750.

[0121] Method step 710 includes providing a first circular element 200 that is circular in axial top view, and method step 720 includes providing a first arc element 300, 300a, 300g that is arc-shaped in axial top view.

[0122] The first circle element 200 and the first arc elements 300, 300a, 300g may be arranged differently from each other.

[0123] In a first embodiment of the method 700, the first arc element 300, 300a and the first circle element 200 are positioned relative to one another in a method step 730 such that the first arc element 300, 300a is positioned inside the first circle element 200, which has a first arc end and a second arc end opposite the first arc end. Thus, the first arc element 300, 300a is positioned inside the first circle element 200.

[0124] In a second embodiment of method 700, the first arc element 300g and the first circle element 200 are positioned relative to one another such that the first arc element is positioned outside the first circle element 200 having a first arc end and a second arc end in method step 740. In this manner, the first arc element 300g is positioned outside the first circle element 200.

[0125] In method step 750, the first and second arc ends, and thus the first arc element 300, 300a, 300g, are connected to the first circle element 200. The connection in method step 750 can be realized in different ways, for example by gluing, clamping or fastening means such as screws, rivets or nails. In a preferred embodiment, the connection in method step 750 is performed by heat input.

[0126] The heat input serves in particular to connect the first circle element 200 and the first arc element 300, 300a, 300g via a material bond at the contact points 400, 400a, 400g of these two elements. The heat input is performed in such a way that a material bond between the materials of the two elements is possible. This can be achieved in such a way that the surfaces of the elements change at least partially from a solid state to a liquid, in particular viscous state, at least at the contact points 400, 400a, 400g.

[0127] The heat input can be realized in different ways, for example: - Flame-based processes: based on the oxidation of exothermic reaction gases. One example is the use of hydrogen (also called "H2") as a combustion gas (flame hydrolysis), whereby hydrogen reacts with oxygen (also called "O2") in the air, or -Flameless process: Using other systems that heat and do not require an open flame. One example is the use of resistors that can convert electrical energy into thermal energy (heat). [Explanation of symbols]

[0128] 100, 100a, 100b, 100c, 100d Anti-resonant element preform 100e, 100f, 100g, 100h 100' anti-resonance element 150, 150a, 150g Outside angle 200 First circle element 200' First circular structure 210, 210h Second circular element 250 First circle radius 260, 260h Radius of the second circular element 300, 300a, 300g First circular arc element 300' First Arc Structure 310, 310c, 310d Second arc element 330, 330c, 330d: points of contact between a first circular element and a second circular arc element 350, 350a, 350g First arc radius 360, 360c, 360d Second arc radius 400, 400a, 400g: Point of contact between the first circular element and the first circular arc element 400' Point of contact between the first circular structure and the first circular arc structure 500 preforms 510 Preform center 550 Cladding tube 550' Coverage Area 600 Anti-resonant hollow core fiber 610 Center of antiresonant hollow-core fiber 700 methods 710 Provide the first circle element 720 Provide the first arc element 730 Place the first arc element inside the first circle element 740 Place the first arc element inside the first circle element 750 Connect

Claims

1. An anti-resonant element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) for manufacturing an anti-resonant hollow-core fiber (600), comprising, in an axial top view, a circular first circular element (200) having a first circular radius (250) and an arc-shaped first arc element (300, 300a, 300g) having a first arc radius (350, 350a, 350g); The first circular element (200) and the first arc element (300, 300a, 300g) are connected to each other at two contact points (400, 400a, 400g). Anti-resonant element preforms (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h).

2. The anti-resonant element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to claim 1, characterized in that the first circular element (200) and the first arcuate element (300, 300a, 300g) comprise glass, in particular quartz glass, or a polymer, in particular consist of glass, in particular quartz glass, or a polymer.

3. The anti-resonant element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to claim 1 or 2, characterized in that it comprises a circular second circular element (210) having a second circular radius (260).

4. The anti-resonant element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to any one of claims 1 to 3, characterized in that it comprises a second arc element (310) having an arc shape with a second arc radius (360).

5. The anti-resonance element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to any one of claims 1 to 4, characterized in that the first circle radius (250) has a value smaller than the first circle arc radius (350, 350a, 350g).

6. The anti-resonance element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to any one of claims 1 to 5, characterized in that the first arc element (300, 300a) is arranged inside the first circular element (200).

7. The anti-resonance element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to any one of claims 1 to 5, characterized in that the first arc element (300g) is arranged outside the first circular element (200).

8. A method (700) for manufacturing an anti-resonant element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to any one of claims 1 to 7, comprising the steps of: (a) a method step (710) of providing a first circular element (200) that is circular in axial top view; (b) a method step (720) of providing a first arc element (300, 300a, 300g) that is arc-shaped in an axial top view; (c1) a method step (730) of positioning the first circular arc element (300, 300a) inside the first circular element (200) such that a first circular arc end and a second circular arc end are located inside the first circular element (200); or (c2) a method step (740) of placing the first circular arc element (300g) outside the first circular element (200) such that a first circular arc end and a second circular arc end are located outside the first circular element (200); (d) a method step (750) of connecting said first and second circular arc ends to said first circular element (200) by forming second contact points (400, 400a, 400g); A method comprising:

9. 9. The method (700) of claim 8, wherein the connecting (750) in method step (d) is performed by heat input.

10. A preform (500) for manufacturing an anti-resonant hollow-core fiber (600) comprising a cladding tube (550), characterized in that at least one anti-resonant element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to any one of claims 1 to 7 is disposed within the cladding tube (550).

11. 11. A preform (500) for manufacturing an antiresonant hollow-core fiber (600) according to claim 10, characterized in that the at least one antiresonant element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) is connected to an inner surface of the cladding tube (550).

12. 12. A preform (500) for manufacturing an antiresonant hollow-core fiber according to claim 10 or 11, characterized in that 3 to 10 antiresonant element preforms (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) are arranged in the cladding tube (550).

13. 1. An anti-resonant hollow-core fiber (600) comprising, in an axial top view, a coating region (550') and at least one anti-resonant element (100') disposed within the coating region (550') comprising a circular first circular structure (200') having a first circular structure radius and an arc-shaped first arc structure (300') having a first arc structure radius, The first circular structure (200') and the first arc structure (300') are connected to each other at two contact points (400').

1. An anti-resonant hollow-core fiber (600).

14. 14. An anti-resonant hollow-core fibre (600) according to claim 13, produced by drawing a preform (500) according to any one of claims 10 to 12.

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