Anti-resonant element preform for manufacturing anti-resonant hollow core fibers

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-resonance element preform for manufacturing an anti-resonance hollow core fiber, which includes a circular first circular element having a first circular radius and an arc-shaped first arc element having a first arc radius in an axial top view.

[0002] Furthermore, the present invention relates to a method for manufacturing an anti-resonance element preform, a preform for manufacturing an anti-resonance hollow core fiber including at least one anti-resonance element preform, and an anti-resonance hollow core fiber.

Background Art

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

[0004] "Hollow core fibers" with a vacuum cavity filled with gas or liquid avoid or reduce these drawbacks. In hollow core fibers, the interaction between light and glass is smaller than in solid core fibers. Since the refractive index of the core is smaller than that of the cladding, light guidance by total reflection is impossible, and light usually escapes from the core to the cladding. Depending on the physical mechanism of light guidance, hollow core fibers are divided into "photonic bandgap fibers" and "anti-resonance hollow core fibers".

[0005] In the case of a "photonic bandgap fiber," the hollow core region is surrounded by a covering with periodically arranged small hollow ducts. The periodic structure of the hollow ducts within the covering creates an effect known in semiconductor technology as the "photonic bandgap," which causes light in a specific wavelength range scattered by the covering structure to constructively interfere due to Bragg reflection within the central cavity, preventing it from propagating laterally within the covering.

[0006] In embodiments of hollow-core fibers referred to as "anti-resonant hollow-core fibers" (ARHCFs), the hollow core region is surrounded by an inner covering region containing so-called "anti-resonant elements" (or "anti-resonant elements"; abbreviated as "AREs"). The walls of the anti-resonant elements, uniformly distributed around the hollow core, can act as a Fabry-Perot cavity, which operates anti-resonantly, reflecting incident light and guiding it through the fiber core.

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

[0008] Potential applications for hollow core fibers include data transmission, high-performance beam guidance for material processing, mode filtering, and nonlinear optics, particularly 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, resulting in a degradation of output beam quality.

[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 so that higher-order core modes are suppressed by phase matching with the covering modes, but the fundamental core modes are not suppressed. This ensures that the propagation of the fundamental core modes is always guaranteed, and the hollow core fiber can be effectively single-mode within a limited wavelength range.

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

[0012] From European Patent Application Publication No. 3136143(A1), an anti-resonant hollow core fiber is known in which the core can induce additional modes in addition to the fundamental mode (referred to as a "bandgapless hollow core fiber" in the same document). For this purpose, the core is surrounded by an inner covering with "non-resonant elements" that provide phase matching of the anti-resonant modes with higher modes. The hollow core fiber is manufactured according to a so-called "stack-and-draw" technique, in which the output elements are arranged to form an axially parallel assembly and fixed to form a preform, which is then stretched. Thus, 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 fiber.

[0013] From International Publication No. 2015 / 185761(A1), an anti-resonant hollow core fiber is known in which further tubular, so-called "nested elements" are arranged inside the first tubular "non-resonant element," and these together form an anti-resonant element.

[0014] One drawback in the manufacture of this assembly is the relatively large contact points, which arise from the "nested" tube connections inside the first non-resonant element, and even slight deviations from the ideal structure already negatively impact the efficiency of optical induction of the fiber. A further drawback is that when only tubular elements are used, the range of variation in the design of the anti-resonant element is small.

[0015] Anti-resonant hollow core fibers are known from Chinese Patent Publication No. 111474627(A), in which the anti-resonant elements are formed from circular and arc-shaped elements in an axial top view. The circular and arc-shaped elements are not connected to each other, but are directly connected to the fiber sheathing in both cases. From a manufacturing standpoint, this has the disadvantage that it is impossible to pre-fabricate anti-resonant element preforms that will form the anti-resonant elements in the final stretched fiber, and all structural elements must be directly connected to the sheathing tube. This inevitably leads to the structural elements being highly prone to deviating significantly from their ideal arrangement, thus impairing the efficiency during optical induction.

[0016] From U.S. Patent Application Publication No. 2020 / 0241200(A1), an anti-resonant hollow core fiber is known in which the anti-resonant element comprises a circular element and a structural element formed in a straight line without curvature in the axial top view. The disadvantage of the straight structural element is that, in the case of an anti-resonant element, its optical induction is inferior compared to the curved structural element, which adversely affects optical properties such as optical attenuation of the fiber. [Overview of the Initiative] [Problems that the invention aims to solve]

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

[0018] Specifically, the present invention aims to provide an anti-resonant element preform that enables the easy and reproducible manufacture of anti-resonant hollow core fibers having good optical properties, such as low optical attenuation.

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

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

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

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

[0023] Preferred Embodiment of the Invention The features of the independent claim contribute to at least partially achieving at least one of the above-described objectives. The dependent claims provide preferred embodiments that contribute to at least partially achieving at least one of the above-described objectives.

[0024] / 1 / An anti-resonant element preform for manufacturing an anti-resonant hollow core fiber, in an axial top view, It comprises a first circular element having a first circular radius and a first arc-shaped element having a first arc radius, The first circular element and the first circular arc element are connected to each other at two points of contact, Anti-resonance element preform.

[0025] / 2 / The anti-resonant element preform according to Embodiment 1, wherein the first circular element and the first arc element are made of glass, particularly quartz glass, particularly quartz glass having a refractive index of at least 1.4, particularly 1.4 to 3, particularly 1.4 to 2.8, or particularly glass, particularly quartz glass, particularly quartz glass having a refractive index of at least 1.4, particularly 1.4 to 3, particularly 1.4 to 2.8, or a polymer, and includes a polymer.

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

[0027] / 4 / The anti-resonant element preform according to any one of the foregoing embodiments, characterized in that the anti-resonant element preform includes an arc-shaped second arc element having a second arc radius.

[0028] / 5 / The anti-resonant element preform according to any one of the foregoing embodiments, characterized in that the size of the first circular radius is smaller than the first arc radius.

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

[0030] / 7 / The 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 manufacturing the anti-resonant element preform according to any one of Embodiments 1 to 7, (a) A method step of providing a first circular element that is circular in an axial top view and has a first circular radius, (b) A method step of providing a first arc element that is arc-shaped in an axial top view and has a first arc radius, (c1) A method step of positioning a first arc element inside a first circular element such that the first and second arc ends are positioned inside the first circular element, or (c2) The step of positioning the first arc element outside the first circle element so that the first arc end and the second arc end are positioned outside the first circle element, (d) A method of connecting the first arc end and the second arc end to the first circular element by forming a second contact point, Methods that include...

[0032] The method according to Embodiment 8, characterized in that the connection in step (d) is made by thermal input.

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

[0034] / 11 / A preform for manufacturing an anti-resonant hollow core fiber according to Embodiment 10, characterized in that at least one anti-resonant element preform is connected to the inner surface of a cladding tube.

[0035] A preform for manufacturing an anti-resonant hollow core fiber according to Embodiment 10 or 11, characterized in that 3 to 10 anti-resonant element preforms are arranged inside a cladding tube.

[0036] / 13 / An anti-resonant hollow core fiber comprising, in an axial top view, a covering region, at least one anti-resonant element disposed in the covering region, and a circular first circular structure having a first circular structure radius, and an arc-shaped first arc structure having a first arc structure radius, wherein 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 according to claim 13, manufactured by stretching a preform according to any one of embodiments 10 to 12.

[0038] General matters In this specification, a range specification includes values ​​referred to as limits. Therefore, a specification of the type "within the range of X to Y" for a variable A means that A can take values ​​X, Y, and values ​​between X and Y. Thus, a one-sided range of the type "up to Y" for a variable A means values ​​between Y and less than Y.

[0039] Some of the described features are associated with the term “essentially.” The term “essentially” should be understood as meaning that, under actual conditions and manufacturing techniques, it is not possible to precisely interpret terms such as “overlapping,” “perpendicular,” “diameter,” or “parallelism,” and that such interpretations are only possible within specific manufacturing tolerances. For example, “essentially perpendicular axes” means drawing an angle of 85 to 95 degrees relative to each other, and “essentially identical volumes” means including deviations of up to 5 volume percent. For example, “a device essentially made of quartz glass” means including a portion of quartz glass between 95% and 100% by weight. For example, “essentially complete filling of volume B” means filling of the total volume of B between 95% and 100% by volume. [Modes for carrying out the invention]

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

[0041] To overcome the aforementioned drawbacks of the prior art, according to the present invention, a first circular element and a first arc element are connected to each other at two points of contact, the arc element being connected in particular to a circular element having a first arc end and a second arc end opposite to the first arc end. The first and second arc ends should be understood as corner points of the first arc element, which can be seen in the axial top view of the anti-resonance element preform, and the first arc element extends in an arc shape between these corner points.

[0042] The anti-resonant element preforms constructed in this manner can be manufactured separately from other components for producing anti-resonant hollow core fibers, which is advantageous from a manufacturing standpoint. Therefore, for example, anti-resonant element preforms that do not conform to the ideal structure during manufacturing can be discarded in a relatively inexpensive manner, and there is no need to discard further components for producing the anti-resonant hollow core fibers. Pre-manufacturing of anti-resonant element preforms further enhances uniformity across the entire manufacturing batch, which has a favorable effect on the symmetry of preforms manufactured using the anti-resonant element preforms, and ultimately on the symmetry of the anti-resonant hollow core fibers. Increasing symmetry positively impacts the optical properties of the hollow core fibers.

[0043] Furthermore, anti-resonant elements manufactured from this type of anti-resonant element preform have been proven to be components with improved optical properties in the final hollow core fiber, resulting in reduced light propagation loss (i.e., including scattering, diffraction, absorption, and inclusion of light), and thus increasing the data transmission capacity of the final hollow core fiber.

[0044] It has been shown that arc elements connected to circular elements at two points of contact allow for advanced control of the structural parameters of the anti-resonant element preform, and thus enable the provision of anti-resonant hollow core fibers with improved optical properties.

[0045] For example, the improved optical properties of this type of anti-resonant hollow core fiber reveal 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 intensity of a propagated signal without affecting its shape is called optical attenuation.

[0046] Components or parts that essentially become anti-resonant elements within a hollow core fiber through simple elongation (also called stretching) during the fiber drawing process are referred to as anti-resonant element preforms.

[0047] In an axial top view, i.e., a two-dimensional view with respect to the longitudinal axis, the anti-resonance element preform comprises a first circular element corresponding to a tubular structural element in a three-dimensional view. The first circular element is essentially designed to be circular, having an essentially uniform first circular radius, and the radius at a first point deviates from the radius at further points by 5% or less, preferably 3% or less, more preferably 1% or less, and most preferably 0.5% or less. Thus, the first circular element has an essentially uniform diameter, and the diameter at a first point deviates from the diameter at further points of the anti-resonance element preform by 5% or less, preferably 3% or less, more preferably 1% or less, and most preferably 0.5% or less. As a result, for example, the first circular radius can be in the range of 2 to 18 mm, preferably 3 to 16 mm, and more preferably 4 to 12 mm. The wall thickness of the first circular element is in the range of 0.1 mm to 3 mm, preferably 0.1 mm to 2 mm, and more preferably 0.2 to 1.5 mm.

[0048] In an axial top view, i.e., a two-dimensional view along the longitudinal axis, the anti-resonance 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, to a curved disk. The first arc element has an essentially uniform first arc. Thus, in a three-dimensional view, the first arc element represents a segment of an essentially circular tubular structural element cut parallel to the longitudinal axis, having a radius corresponding to the arc radius, and the radius at a first point deviates from the radius at further points by 5% or less, preferably 3% or less, more preferably 1% or less, and most preferably 0.5% or less. As a result, 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, and more preferably in the range of 3 to 20 mm. The wall thickness of the first arc element is in the 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 radius of a circle and the radius of an arc should both be understood as the outer diameter of the corresponding element. The corresponding inner diameter is obtained by subtracting the individual wall thickness from the individual outer diameter. The same applies to the corresponding diameter.

[0050] A contact point is the position where the first circular element and the first arc element are connected to each other, particularly by intermaterial bonding. 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 to the first arc end. The first circular element and the first arc element are connected to each other at exactly two contact points.

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

[0052] To provide an anti-resonant element preform with high structural precision and improved optical properties, the first arc element includes an arc element circumference corresponding to 10% to 85%, preferably 20% to 80%, more preferably 20% to 75%, and even more preferably 20% to 70%, of the circumference of the complete circular element, corresponding to the radius of the first arc. The advantage of this is that the contacts are not coalesced with each other, but are spatially arranged at a distance from each other such that the first arc element and the first arc are connected to each other, resulting in one large contact rather than two separate contacts. A large contact can negatively affect the optical light guide property of the final glass fiber, for example, due to a localized increase in the glass material portion at the large contact, which can lead to ellipticization of the anti-resonant element.

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

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

[0055] Embodiments of the anti-resonance element preform are characterized in that the first circular element and the first arc element comprise at least glass, particularly doped or undoped quartz glass, particularly quartz glass having a refractive index of at least 1.4, particularly 1.4 to 3, or a polymer, such as polymethyl methacrylate, cyclic olefin copolymer, polycarbonate, or fluoropolymer. Further designs comprise the first circular element and the first arc element comprise glass, particularly doped or undoped quartz glass, particularly quartz glass having a refractive index of at least 1.4, particularly 1.4 to 3, or a polymer such as polymethyl methacrylate, cyclic olefin copolymer, polycarbonate, or fluoropolymer.

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

[0057] The term "identical material" describes the material properties of two components. Thus, the two components have essentially the same chemical substances. Therefore, the total mass of different chemical elements in both parts may be less than 1% by weight, particularly less than 0.5% by weight, particularly less than 0.1% by weight. The chemical composition of the two parts differs, in particular, by the content of contaminants less than 500 ppm by weight, particularly less than 100 ppm by weight, and / or by the content of doping agents less than 10,000 ppm by weight, particularly less than 5,000 ppm by weight.

[0058] In one embodiment, the anti-resonance element preform consists of a first circular element and a first arc element.

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

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

[0061] In one embodiment, the second circular element is positioned inside the first circular element. In another embodiment, the first and second circular elements are connected to each other at a point of contact, particularly by intermaterial bonding. In a further design, the first arc element and the second circular element are connected to each other, particularly by intermaterial bonding. In a further design, the second circular element is connected to the first circular element and the first arc element, particularly by intermaterial bonding.

[0062] In further embodiments, the first circular element is positioned inside the second circular element, and the first and second circular elements are preferably connected to each other at a contact point, particularly by intermaterial bonding.

[0063] In further embodiments, the second circular element is located within the space enclosed by the first circular element and the first arc element, and the second circular element is connected to the first circular element, the first arc element, or the first circular element and the first arc element, particularly by intermaterial bonding.

[0064] An embodiment of the anti-resonance element preform is characterized in that the anti-resonance element preform comprises a second arc-shaped element having a second arc radius.

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

[0066] In one embodiment, the second arc element is positioned inside the first circular element, and the first circular element and the second arc element are preferably connected to each other at two points of contact, particularly by intermaterial bonding.

[0067] In a further embodiment, the second arc element is positioned within the space enclosed by the first circle element and the first arc element, and the second arc element is connected to the first circle element at two contact points, to the first arc element at two contact points, or to the first circle element at one contact point and to the first arc element at one contact point, particularly by intermaterial bonding.

[0068] Furthermore, because the anti-resonance element preform has a first circular element and a first arc element as structural elements, the degree of 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 one embodiment, the first circle radius and the first arc radius have essentially the same value. When an anti-resonance element preform is formed using only circular elements, the corresponding structural components cannot be accessed.

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

[0071] An embodiment of the anti-resonance element preform is characterized in that the first circle radius is smaller than the first arc radius. When the anti-resonance element preform is formed using only circular elements, the corresponding structural part cannot be accessed.

[0072] The first circular element and the first arc element can be arranged differently from each other, insofar as they are connected to each other at at least two, preferably exactly two, points of contact, particularly by intermaterial bonding.

[0073] Embodiments of the anti-resonance element preform are characterized by the placement of a first arc element inside a first circular element. This means that the first arc element is connected to the inside of the first circular element at two points of contact, particularly by intermaterial bonding. Thus, the first arc element is located inside the first circular element. This makes it possible to provide a circular, or tubular in three-dimensional diagram, anti-resonance element preform with improved optical properties, and therefore the anti-resonance element preform can be easily handled. Such an anti-resonance element preform can be easily and with high structural precision connected to further components of the preform to manufacture an anti-resonance hollow core fiber.

[0074] Embodiments of the anti-resonance element preform are characterized in that the first arc element is positioned outside the first circular element. This means that the first arc element is connected to the outside of the first circular element at two points of contact, particularly by intermaterial bonding. Thus, the first arc element is positioned outside the first circular element. This makes it possible to manufacture anti-resonance element preforms having eight contours in the axial top view, or anti-resonance element preforms having irregular eight contours depending on the individual radii of the first circular element and the first arc element.

[0075] Furthermore, the present invention relates to a method for manufacturing the above-described anti-resonance element preform.

[0076] Depending on the desired design of the anti-resonance element preform, this method can be carried out in different ways.

[0077] A first embodiment of a method for manufacturing an anti-resonance element preform using any one of the above designs is, at least, (a) A method step of providing a first circular element that is circular in an axial top view and has a first circular radius, (b) A method step of providing a first arc element having a first arc radius and being arc-shaped in an axial top view, (c1) A method step of positioning the first arc element (300) inside the first circular element (200), and positioning the first arc end (305) and the second arc end (306) inside the first circular element (200) (205), (d) The step of connecting the first arc end and the second arc end by forming a second contact point, particularly by intermaterial bonding, Includes.

[0078] A first embodiment of the method for manufacturing an anti-resonance element preform is useful for manufacturing the above-described anti-resonance element preform, in which a first arc element is positioned inside a first circular element. The first embodiment of the method can be useful for manufacturing an essentially circular anti-resonance element preform.

[0079] A second embodiment of a method for manufacturing an anti-resonance element preform using any one of the above designs is at least: (a) A method step of providing a first circular element that is circular in an axial top view and has a first circular radius, (b) A method step of providing a first arc element having a first arc radius and being arc-shaped in an axial top view, (c2) A method step of positioning the first arc element outside the first circle element such that the first arc end and the second arc end are positioned outside the first circle element, (d) A method of connecting the first arc end and the second arc end, particularly by intermaterial bonding, by forming a second contact point, Includes.

[0080] A second embodiment of the method for manufacturing an anti-resonant element preform is useful for manufacturing the above-described anti-resonant element preform, in which the first arc element is positioned outside the first circular element. The second embodiment of the method can be useful for manufacturing an anti-resonant element having an 8-shaped contour in an axial top view, or an anti-resonant element having an irregular 8-shaped contour depending on the corresponding radii of the first circular element and the first arc element.

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

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

[0083] Thermal input is particularly useful for the intermaterial bonding between the first circular element and the first arc element at the point of contact. The thermal input must be applied in such a way that intermaterial bonding 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 state, especially a viscous state, at least at the point of contact.

[0084] Thermal input can be achieved in the following 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 the exothermic reaction combustion gas (flame hydrolysis). It reacts with oxygen (also called "O2") in the air, or - Flameless process: Use a heating system that does not require an open flame. One example is the use of resistors, which can convert electrical energy into thermal energy (heat).

[0085] Furthermore, the present invention relates to a preform for manufacturing an anti-resonant hollow core fiber comprising a cladding tube, characterized in that at least one of the above-mentioned anti-resonant element preforms is disposed within the cladding tube.

[0086] A preform is a component from which anti-resonant hollow core fibers can be drawn. Alternatively, the preform can be further processed into a secondary preform from which anti-resonant hollow core fibers are drawn. This further processing may include a one-time or repeated execution of a hot forming process, such as stretching, crushing, or adding additional coating material.

[0087] The cladding tube is a tubular element essentially made of quartz glass, in which at least one of the anti-resonance element preforms described above is placed. When the final preform is stretched to form the final fiber, the cladding tube surrounds the hollow core of the anti-resonance hollow core fiber. In some embodiments, the inner diameter of the cladding tube is in the range of 10 to 60 mm. In embodiments, the outer diameter of the cladding tube is in the range of 25 to 250 mm, preferably 30 to 200 mm. In embodiments, the length of the cladding tube is in the range of 500 to 1200 mm.

[0088] At least one anti-resonance element preform can be arranged inside the cladding tube in different ways.

[0089] Embodiments of the preform are characterized in that at least one anti-resonance element preform is connected to the inner surface of the cladding tube, particularly by an intermaterial joint. In one embodiment, the anti-resonance element preform is connected to the cladding tube via a first circular element. In a further design, the anti-resonance element preform is connected to the cladding tube via a first arc element, in the case of these anti-resonance elements, thereby the first arc element is positioned outside the first circular element.

[0090] To construct the preform, a different number of anti-resonance elements can be placed inside the cladding tube.

[0091] The preform embodiment is characterized by having 3 to 10, preferably 3 to 8, and more preferably 4 to 6, anti-resonance element preforms arranged inside the cladding tube.

[0092] In one embodiment, only anti-resonant element preforms having the characteristics and features of the above-described anti-resonant element preforms are placed inside the cladding tube. In a further design, at least one anti-resonant element preform placed inside the cladding tube has characteristics and features other than those of the above-described anti-resonant element preforms.

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

[0094] The anti-resonant hollow core fiber can be manufactured from the above-mentioned preform, particularly by stretching, with at least a portion of the covering area of ​​the anti-resonant hollow core fiber formed from the covering tube of the preform, and at least one anti-resonant element of the anti-resonant hollow core fiber formed from at least one anti-resonant element preform of the preform. Thus, the first circular structure is constructed from the first circular element, and the first arc structure is constructed from the first arc element. The respective contact points are maintained.

[0095] The preform is stretched during the stretching process. Preferably, the stretching is carried out to scale so that, for example, the shape and arrangement of the preform's components or parts, particularly the first circular element and the first arc element, are reflected in the stretched final product.

[0096] In one embodiment of an anti-resonant hollow core fiber, the covering region corresponds to an extended cladding tube. In a further design, the covering region corresponds to a cladding tube and an overlay tube, the overlay tube being added to the cladding tube before or during extension. "Addition" should be understood as connecting the cladding tube and the overlay tube, particularly by intermaterial bonding, which is done by using negative pressure applied between the cladding tube and the overlay tube, particularly by thermal input.

[0097] To produce anti-resonant hollow core fibers from a preform, the preform can be guided vertically through a furnace. The lower end of the preform, from which the anti-resonant hollow core fibers are drawn in a conical shape, is thereby heated to a drawing temperature, and the drawn fibers are then cooled from the drawing temperature by a gas flow directed opposite to the drawing direction.

[0098] The properties and features disclosed herein may be important separately and in combination with each other for the various embodiments of the invention described in the claims. The properties and features disclosed with respect to anti-resonant element preforms, preforms, or anti-resonant hollow core fibers are also disclosed with respect to methods, and vice versa.

[0099] The present invention will be further illustrated below with reference to the drawings. The present invention is not limited to the drawings. [Brief explanation of the drawing]

[0100] [Figure 1] This is an axial top view of an anti-resonance element preform comprising a first circular element and a first circular arc element. [Figure 2] Further embodiments of the anti-resonance element preform are shown. [Figure 3] Further embodiments of the anti-resonance element preform are shown. [Figure 4] Further embodiments of the anti-resonance element preform are shown. [Figure 5] Further embodiments of the anti-resonance element preform are shown. [Figure 6] Further embodiments of the anti-resonance element preform are shown. [Figure 7] Further embodiments of the anti-resonance element preform are shown. [Figure 8] Further embodiments of the anti-resonance element preform are shown. [Figure 9] Further embodiments of the anti-resonance element preform are shown. [Figure 10]This is an axial top view of the preform for an anti-resonant hollow core fiber. [Figure 11] This shows an axial top view of an anti-resonant hollow core fiber. [Figure 12] This document describes a method for manufacturing anti-resonance element preforms.

[0101] Description of the drawing Figure 1 shows an anti-resonance element preform 100 in an axial top view. The anti-resonance element preform 100 comprises a circular first circular element 200 having a first circular radius 250. A first arc element 300 having a first arc radius 350 is positioned inside the first circular element 200. In the illustrated embodiment of the anti-resonance element preform 100, the first circular radius 250 and the first arc radius 350 have the same value. The first circular element 200 and the first arc element 300 are connected to each other at two contact points 400, in particular by intermaterial bonding. At the contact points 400, the convex side of the first arc element 300 and the inside of the first arc both form an exterior angle 150, which has the same value in the illustrated embodiment due to the symmetrical setting of the anti-resonance element preform 100. In further embodiments not shown, the two exterior angles 150 are not identical. In the illustrated embodiment, the first circular element 200 and the first arc element 300 are formed from the same material, in particular from doped or undoped quartz glass.

[0102] Figure 2 shows a further embodiment of the anti-resonance element preform 100a. The embodiment in Figure 2 largely corresponds to the embodiment shown in Figure 1, which is described above; therefore, please refer to the above description to avoid repetition. Structures that are repeated from the description of Figure 1 have the same reference numerals. Modifications of structures compared to the structure shown in Figure 1 have the same reference numerals with the additional letter 'a'.

[0103] In the illustrated embodiment, the first circle radius 250 is greater than the first arc radius 350a, and thereafter, the exterior angle 150a is greater than the exterior angle 150 in Figure 1. Due to the smaller first arc radius 350a compared to Figure 1, the contact points 400a are also located closer to each other compared to the contact points 400 in Figure 1.

[0104] Figure 3 shows a further embodiment of the anti-resonance element preform 100b. The embodiment according to Figure 3 is described above and largely corresponds to the embodiment shown in the figures above; therefore, refer to the above description to avoid repetition. Structures that are repeated from the description of the figures above have the same reference numerals. Modifications of structures compared to the structures shown in the figures above have the same reference numerals with the additional letter b. Compared with embodiment 100a in Figure 2, a further embodiment of the anti-resonance element preform 100b has an arc-shaped second arc element 310 having a second arc radius 360. Similar to the first arc element 300a, the second arc element 310 is positioned inside the first circular element 200 and is connected to the first circular element 200 by two contact points 330. In the illustrated embodiment, the first arc radius 350a and the second arc radius 360 have the same value. In further embodiments not shown, the first arc radius 350a and the second arc radius 360 may have different values. In the illustrated embodiment, the first arc element 300a and the second arc element 360 are positioned opposite each other inside the first circular element 200, so that the corresponding convex sides of the first arc element 300a and the second arc element 310 face each other. In further embodiments not shown, the first arc element 300a and the second arc element 310 are positioned more spatially close to each other inside the first circular element 200.

[0105] Figure 4 shows a further embodiment of the anti-resonance element preform 100c. The embodiment shown in Figure 4 largely corresponds to the embodiment described above and shown in the figures above; therefore, please refer to the above description to avoid repetition. Structures that are repeated from the description of the figures above have the same reference numerals. Modifications of structures compared to the structures shown in the figures above have the same reference numerals with the additional letter c.

[0106] In the illustrated embodiment, the second arc element 310c is located inside the first arc element 200 and on the same side 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 positioned 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 further embodiments not shown, the first arc element 350 and the second arc element 310c are positioned 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] Figure 5 shows a further embodiment of the anti-resonance element preform 100d. The embodiment shown in Figure 5 largely corresponds to the embodiment described above and shown in the figures above; therefore, please refer to the above description to avoid repetition. Structures that are repeated from the description of the figures above have the same reference numerals. Modifications of structures compared to the structures shown in the figures above have the same reference numerals with the additional letter 'd'.

[0108] In the illustrated embodiment of the anti-resonance element preform 100d, the second arc element 310d is positioned inside the first arc element 200 and on the same side as the first arc element 300, as shown in Figure 4, and the radius of the first arc 350 is smaller than the radius of the second arc 360d. The first arc element 300 and the second arc element 360 are positioned at the same point on the first arc element 400, and the contact point 400 of the first arc element 400 and the contact 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 positioned 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 further embodiments not shown, the first arc element 350 and the second arc element 310d are arranged relative to each other such that the concave side of the second arc element 310d faces the concave side of the first arc element 350.

[0109] Figure 6 shows a further embodiment of the anti-resonance element preform 100e. The embodiment shown in Figure 6 largely corresponds to the embodiment described above and shown in the figures above; therefore, please refer to the above description to avoid repetition. Structures that are repeated from the description of the figures above have the same reference number. Modifications of structures compared to the structures shown in the figures above have the same reference number with the additional letter e.

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

[0111] Figure 7 shows a further embodiment of the anti-resonance element preform 100f. The embodiment shown in Figure 7 largely corresponds to the embodiment described above and shown in the figures above; therefore, please refer to the above description to avoid repetition. Structures that are repeated from the description of the figures above have the same reference number. Modifications of structures compared to the structures shown in the figures above have the same reference number with the additional letter f.

[0112] In the illustrated embodiment, the second circular element 210 is positioned within the space formed by the concave side of the second arc element 210d and the inside of the first circular element 200. This connects the second circular element 210 to the first circular element 200. In further embodiments not shown, the second circular element 210 is connected to the second arc element 210, or to the first circular element 200 and the second arc element 310d. In further embodiments not shown, the second circular element 210 is positioned within the space formed by the convex side of the first arc element 300 and the inside of the first circular element 200. In a further embodiment, the second circular element 210 is positioned within the space formed by the first arc element 300 and the second arc element 310d, and the second circular element 210 is connected to either the first arc element 300, the second arc element 310d, or both the first and second arc elements 300 and 310d.

[0113] Figure 8 shows a further embodiment of the anti-resonance element preform 100g. The embodiment shown in Figure 8 largely corresponds to the embodiment described above and shown in the figure above; therefore, please refer to the description above to avoid repetition. Structures that are repeated from the description of the figure above have the same reference number. Modifications of the structure compared to the structure shown in the figure above have the same reference number with the additional letter g.

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

[0115] Figure 9 shows a further embodiment of the anti-resonance element preform 100h. The embodiment shown in Figure 9 largely corresponds to the embodiment described above and shown in the figures above; therefore, please refer to the above description to avoid repetition. Structures that are repeated from the description of the figures above have the same reference number. Modifications of the structure compared to the structure shown in the figures above have the same reference number with the additional letter h.

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

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

[0118] In the illustrated example, four anti-resonant element preforms 100 are connected to the inside of a cladding tube 550. The distribution of the anti-resonant elements 100 inside the cladding tube 500 is symmetrical, and as a result, by extending the preforms 500, a symmetrical anti-resonant hollow core fiber can be manufactured from the preforms 500, thereby improving the optical properties. The four anti-resonant element preforms 100 are positioned 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 further embodiments 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 toward the center 510 with their respective convex sides and some first arc elements 300 can be aligned toward the center 510 with their respective concave sides. The arrangement of the arc elements 300 is preferably designed symmetrically with respect to the center 510.

[0119] Figure 11 shows an anti-resonant hollow core fiber 600 that can be manufactured by stretching a preform 500 according to Figure 10, which comprises, for example, a covering region 550' and four anti-resonant elements 100' arranged within the covering region 550'. In further embodiments not shown, the anti-resonant hollow core fiber 600 comprises a different number, for example, 2 to 10 anti-resonant elements 100'. The anti-resonant elements 100' have a circular first circular structure 200' and an arc-shaped first arc structure 300'. The first arc structures 300' are connected to each other by two contacts 400'. In the illustrated embodiment, the anti-resonant hollow core fiber 600 has a structure that can be obtained by stretching a preform 500 according to Figure 10. In further embodiments not shown, the anti-resonant hollow core fiber has anti-resonant elements 100' of different shapes, which can be obtained by stretching different anti-resonant element preforms according to the present invention, for example, as shown in Figures 2 to 9. Four anti-resonant elements 100' are arranged in the covering region 550' such that the convex side of each first arc structure 300' is aligned toward the hollow core fiber center 610 of the anti-resonant hollow core fiber 600. In further embodiments not shown, the concave side of the first arc structure 300' can be aligned toward the hollow core fiber center 610, or several arc structures 300' can be aligned toward the hollow core fiber center 610 with their respective convex sides, and several first arc structures 300' can be aligned toward 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] Figure 12 shows a method 700 for manufacturing an anti-resonance element preform 100. In the first embodiment, method 700 includes method steps 710, 720, 730, and 740. In the second embodiment, method 700 includes method steps 710, 720, 740, and 750.

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

[0122] The first circular element 200 and the first circular arc elements 300, 300a, and 300g can be arranged differently from one another.

[0123] In the first embodiment of Method 700, the first arc elements 300, 300a and the first circular element 200 are arranged in step 730 of Method such that the first arc elements 300, 300a are positioned inside the first circular element 200, which has a first arc end and a second arc end opposite to the first arc end. Thus, the first arc elements 300, 300a are positioned inside the first circular element 200.

[0124] In a second embodiment of Method 700, the first arc element 300g and the first circular element 200 are positioned relative to each other in Method step 740 such that the first arc element is positioned outside the first circular element 200, which has a first arc end and a second arc end. Thus, the first arc element 300g is positioned outside the first circular element 200.

[0125] In step 750 of the method, the first arc end and the second arc end, and therefore the first arc elements 300, 300a, and 300g, are connected to the first circular element 200. The connection in step 750 can be achieved in different ways, for example by adhesive, clamping, or by fastening means such as screws, rivets, or nails. In a preferred embodiment, the connection in step 750 is achieved by heat input.

[0126] The thermal input is particularly useful in connecting the first circular element 200 and the first arc elements 300, 300a, and 300g via intermaterial bonding at the contact points 400, 400a, and 400g of these two elements. The thermal input is performed in such a way that intermaterial bonding between the materials of the two elements is possible. This can be achieved such that the surfaces of the elements change from a solid state to a liquid state, particularly a viscous state, at least at the contact points 400, 400a, and 400g.

[0127] Thermal input can be achieved in the following 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). Thereafter, hydrogen reacts with oxygen (also called "O2") in the air, or - Flameless process: Use a heating system that does not require an open flame. One example is the use of resistors, which can convert electrical energy into thermal energy (heat). [Explanation of Symbols]

[0128] 100, 100a, 100b, 100c, 100d Anti-resonance element preforms 100e, 100f, 100g, 100h 100' anti-resonance element 150, 150a, 150g outside corner 200 First circular element 200' First circular structure 210, 210h Second circular element 250 First circle radius 260, 260h Second circular element radius 300, 300a, 300g First circular arc element 300' First arc structure 310, 310c, 310d Second arc element 330, 330c, 330d: Point of contact between the first circular element and the second circular arc element. 350, 350a, 350g First arc radius 360, 360c, 360d Second arc radius 400, 400a, 400g: Point of tangency 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' Covered area 600 Anti-resonant hollow core fiber 610 Center of anti-resonant hollow core fiber 700 methods 710 Provides the first circular element 720 Provides 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. Anti-resonant element preforms (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 arc-shaped first arc elements (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 by two contact points (400, 400a, 400g), and The anti-resonance element preforms (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) each comprises a second arc-shaped element (310) having a second arc radius (360), The first circular element (200) is a circular tubular structural element, The first arc element (300, 300a, 300g) is a segment of a circular tubular structural element having a radius corresponding to the first arc radius (350, 350a, 350g), The second arc element (310) is a segment of a circular tubular structural element having a radius corresponding to the second arc radius (360), The second arc element (310) is connected to at least one of the first circular element (200) and the first arc elements (300, 300a, 300g). Anti-resonance element preforms (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h).

2. The anti-resonance 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 arc elements (300, 300a, 300g) include glass, particularly quartz glass, or a polymer, and are in particular made of glass, particularly quartz glass, or a polymer.

3. The anti-resonance element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to claim 1 or 2, characterized in that the first circular radius (250) is smaller than the first circular arc radius (350, 350a, 350g).

4. The anti-resonance element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to claim 1 or 2, characterized in that the first arc element (300, 300a) is arranged inside the first circular element (200).

5. A method (700) for producing an anti-resonance element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) according to claim 1 or 2, (a) A method step (710) to provide a first circular element (200) which is circular in an axial top view, (b) A method step (720) to provide a first arc element (300, 300a, 300g) which is arc-shaped in an axial top view, (c1) A method (730) of positioning the first arc element (300, 300a) inside the first circular element (200) such that the first arc end and the second arc end are positioned inside the first circular element (200), or (c2) A method step (740) of positioning the first arc element (300g) outside the first circular element (200) such that the first arc end and the second arc end are positioned outside the first circular element (200), (d) A method step (750) of connecting the first arc end and the second arc end to the first circular element (200) by forming a second contact point (400, 400a, 400g), Methods that include...

6. The method (700) of claim 5, characterized in that the connection (750) in step (d) is made by thermal input.

7. 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 claim 1 or 2 is disposed within the cladding tube (550).

8. A preform (500) for manufacturing an anti-resonant hollow core fiber (600) according to claim 7, characterized in that at least one anti-resonant element preform (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) is connected to the inner surface of the cladding tube (550).

9. A preform (500) for manufacturing an anti-resonant hollow core fiber according to claim 7, characterized in that 3 to 10 anti-resonant element preforms (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h) are arranged inside the coating tube (550).

10. An anti-resonant hollow core fiber (600) manufactured by stretching a preform (500) according to claim 7, comprising, in an axial top view, a covering region (550') and at least one anti-resonant element (100') disposed within the covering region (550'), the covering 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 by two contact points (400'). An anti-resonant hollow core fiber (600) characterized by the above.

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