ANTI-RESONANT HOLLOW-CORE FIBER WITH OVAL BOTTOM ELEMENT

Description

Background of the invention

[0001] The invention relates to an antiresonant hollow core fiber. State of the art

[0002] Hollow-core fibers have a core that comprises an evacuated cavity filled with gas or liquid. In hollow-core fibers, the interaction of light with the core material is less pronounced than in solid-core fibers. The refractive index of the core is lower than that of the surrounding fiber cladding, so light transmission by total internal reflection is not possible. Depending on the physical mechanism of light transmission, hollow-core fibers are classified as "photonic bandgap fibers" and "antiresonant hollow-core fibers."

[0003] In the variant of the hollow-core fiber known as "antiresonant hollow-core fiber" (also "antiresonant hollow-core fiber" or "ARHCF"), the hollow core is surrounded by a fiber sheath containing so-called antiresonance units (also "antiresonant elements" or "AREs"). The walls of the antiresonance units, evenly distributed around the hollow core, can act as Fabry-Perot cavities operating in antiresonance, reflecting the incident light and thus enabling waveguiding within the fiber core.

[0004] This technology promises a hollow core fiber with low optical attenuation, a very broad transmission spectrum (also in the UV or IR wavelength range) and low latency in data transmission.

[0005] From patent application WO 2019 053412 A1, an antiresonant hollow-core fiber is known in which the hollow core is surrounded by a fiber sheath containing antiresonance units. These antiresonance units have three elements which are nested within each other: an outer ARE element, an NE element arranged in the ARE element, and a DNE element arranged in the NE element.

[0006] However, it has proven disadvantageous that this design exhibits an unfavorable correlation between the waveguide loss of the fundamental mode on the one hand and the difference in the effective mode index between higher core modes and lossy ARE modes on the other hand exhibiting this characteristic. This makes such antiresonant hollow core fibers unsuitable for applications, especially in the telecommunications sector. Technical task

[0007] For industrial applications, antiresonant hollow-core fibers with low waveguide losses are required. Furthermore, an antiresonant hollow-core fiber that is simple and can be manufactured on a large scale is needed. Only then can the costs for antiresonant hollow-core fibers be kept within a reasonable range. It should be noted that antiresonant hollow-core fibers that perform well on a laboratory scale are not necessarily suitable for large-scale applications.

[0008] One aim of the invention is to provide an antiresonant hollow core fiber that overcomes the aforementioned disadvantages.

[0009] One objective of the invention is to provide an antiresonant hollow core fiber that can be manufactured precisely and reproducibly and also has low damping.

[0010] In particular, an objective of the invention is to provide an antiresonant hollow core fiber that has particularly low waveguide losses.

[0011] In particular, an objective of the invention is to provide an antiresonant hollow core fiber that efficiently dampens higher-order modes in the fiber core.

[0012] In particular, an objective of the invention is to provide an antiresonant hollow core fiber that exhibits a favorable correlation between, on the one hand, low waveguide losses of the fundamental mode and, on the other hand, efficient attenuation of higher order modes in the core. Preferred embodiments of the invention

[0013] The features of the independent claims contribute to at least partially fulfilling at least one of the aforementioned tasks. The dependent claims provide preferred embodiments that contribute to at least partially fulfilling at least one of the tasks.

[0014] The following design variants of an antiresonant hollow core fiber contribute at least partially to fulfilling at least one of the aforementioned tasks: I1.I A first embodiment of an antiresonant hollow core fiber, comprising a fiber sheath having an inner bore, a fiber longitudinal axis and a fiber core radius R_fiber, a number of antiresonance units, each comprising an ARE element, a NE element, a DNE element, wherein the antiresonance units are spaced apart from each other and arranged without contact with each other at predetermined positions on an inner side of the inner bore, wherein in the antiresonance units the ARE element has a circular cross-section, the NE element is arranged in a first interior space of the ARE element, and the DNE element is arranged at least partially in a second interior space (3470) of the NE element.According to the invention, in this embodiment, the non-resonant element (NE) in at least one antiresonance unit has a circular arc-shaped cross-section and is connected to the hollow-core element (DNE) along two connecting seams. The DNE element has an oval cross-section, and the sum of the distances of any point on a DNE element wall from two focal points is less than 15% of the sum of the distances for all points. Another embodiment of an antiresonant hollow-core fiber, comprising the features of the first embodiment, is characterized in that the sum of the distances of any point on the DNE element wall from two focal points is less than 10%, and in particular less than 5%, of the sum of the distances for all points.I. Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous two embodiments, is characterized in that the DNE element has a longest cross-sectional axis AL and a shortest cross-sectional axis AK. I4. Another embodiment of an antiresonant hollow core fiber, comprising the features of the third embodiment, is characterized in that the DNE element is arranged such that the longest cross-sectional axis AL runs substantially parallel to the inner bore, and / or the shortest cross-sectional axis AK is oriented substantially perpendicular to the inner bore and to the fiber's longitudinal axis. I5. Another embodiment of an antiresonant hollow core fiber, comprising the features of the third or fourth embodiment, is characterized in that the following ratio of the longest cross-sectional axis AL to the shortest cross-sectional axis AK holds: . AL AK = 1 1 4 0 I6.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the preceding embodiments 3 to 5, is characterized in that the ratio of the longest cross-sectional axis AL to the shortest cross-sectional axis AK is: greater than or equal to 1.15, in particular greater than or equal to 1.20, in particular greater than or equal to 1.25, in particular greater than or equal to 1.50; and less than or equal to 3.80, in particular less than or equal to 3.60, in particular less than or equal to 3.50. I7.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the preceding embodiments, is characterized in that the following ratio of an NE internal height H_NE, multiplied by twice the NE circular radius NE_R, divided by a fiber core area A_Fiber, is: H_NE ∗ 2 ∗ NE_R A _ Faser = 0 35 0 7 I8.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the ratio of the NE internal height H_NE, multiplied by twice the NE circular radius NE_R, divided by the fiber core area A_Fiber, is: greater than or equal to 0.4, in particular greater than or equal to 0.50, in particular greater than or equal to 0.56; and less than or equal to 0.65, in particular less than or equal to 0.62, in particular less than or equal to 0.6. I9.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the ratio of an ARE internal height H_ARE divided by a core radius R_Fiber is: H_ARE R _ Faser = 0 85 1 25 I10.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the ratio of the ARE internal height H_ARE divided by the core radius R_Fiber is: greater than or equal to 0.9, in particular greater than or equal to 0.95, in particular greater than or equal to 1.0; and less than or equal to 1.2, in particular less than or equal to 1.15, in particular less than or equal to 1.1. 111.1 Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the ratio of the ARE internal height H_ARE, multiplied by twice the NE circular radius NE_R, divided by an NE internal surface A_NE is: H_ARE ∗ 2 ∗ NE_R A_NE = 0 2 1 0 I12.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the ratio of the ARE internal height H_ARE, multiplied by twice the NE circular radius NE_R, divided by the NE internal surface area A_NE is: greater than or equal to 0.25, in particular greater than or equal to 0.3; and less than or equal to 0.95, in particular less than or equal to 0.8. I13.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the ARE element has a first circular radius R_ARE, and the NE element has a second circular radius R_NE and a central angle MW_NE. I14.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in thatthat the antiresonant hollow core fiber has three, four, five, six, seven, or eight antiresonance units. I15.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the preceding embodiments, is characterized in that at least one of the antiresonance units has at least one of the following features: the ARE element and / or the NE element and / or the DNE element comprises an amorphous solid, in particular a glass, in particular fused silica; the ARE element and / or the NE element and / or the DNE element consists of an amorphous solid, in particular a glass, in particular fused silica; at least two of the ARE element, NE element, and DNE element are of the same material, in particular comprising or consisting of a glass with a refractive index of at least 1.4, in particular 1.4 to 3, in particular 1.4 to 2.8, and a wall thickness of at least two of the ARE element.NE element and DNE element are essentially the same. I16.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the preceding embodiments, is characterized in that the antiresonant hollow core fiber has at least one of the following features: a fundamental attenuation of less than 1.0 dB / km, in particular less than 0.25 dB / km, in particular less than 0.1 dB / km at a transported wavelength between 0.3 µm and 3.0 µm, in particular between 1.0 µm and 2.5 µm, and a fundamental attenuation of less than 1 dB / km at a transported wavelength of up to 0.8 µm. I17.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the preceding embodiments, is characterized in thatthat the antiresonance unit has at least one of the following features: a wall thickness of an ARE element wall of the ARE element and / or an NE element wall of the NE element and / or a DNE element wall of the DNE element is between 0.1 µm and 2.5 µm, in particular between 0.15 µm and 1.5 µm, in particular between 0.25 µm and 0.75 µm, in particular between 0.35 µm and 0.65 µm, in particular 0.5 µm; a wall thickness of an ARE element wall of the ARE element and / or an NE element wall of the NE element and / or a DNE element wall of the DNE element is between 0.35 µm and 0.65 µm at a signal wavelength of 1550 nm in the first transmission window, in particular between 0.4 µm and 0.6 µm, in particular 0.5 µm, a wall thickness of an ARE element wall of the ARE element and / or a NE element wall of the NE element and / or a DNE element wall of the DNE element is at a signal wavelength of 1550 nm in the second transmission window between 0,75 µm and 1.25 µm, in particular between 0.9 µm and 1.1 µm, in particular 1 µm. I18.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the core radius R_fiber has at least one of the following features: less than or equal to 26 µm, in particular less than or equal to 23 µm, in particular less than or equal to 20 µm; and greater than or equal to 10 µm, in particular greater than or equal to 12 µm, in particular greater than or equal to 14 µm. I19.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the ARE element has at least one of the following features: a first circular radius R_ARE less than or equal to 30 µm, in particular less than or equal to 25 µm, in particular less than or equal to 22.5 µm,in particular less than or equal to 16 µm; and the first circle radius R_ARE greater than or equal to 5 µm, in particular greater than or equal to 7 µm, in particular greater than or equal to 11.5 µm, in particular greater than or equal to 12.25 µm, in particular greater than or equal to 14.5 µm. I20.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the NE element has at least one of the following features: a second circular radius R_NE less than or equal to 25 µm, in particular less than or equal to 19 µm, in particular less than or equal to 17 µm; the second circular radius R_NE greater than or equal to 1.5 µm, in particular greater than 2.5 µm, in particular greater than or equal to 3.5 µm; a central angle MW_NE less than 340°, in particular less than 330°, in particular less than 320°; and the central angle MW_NE greater than 180°, in particular greater than 200°.in particular greater than 220°. I21.I Another embodiment of an antiresonant hollow core fiber, comprising the features of at least one of the previous embodiments, is characterized in that the DNE element has at least one of the following features: the longest cross-sectional axis AL is less than or equal to 20 µm, in particular less than or equal to 16.5 µm, in particular less than or equal to 14.6 µm; the longest cross-sectional axis AL is greater than or equal to 4 µm, in particular greater than or equal to 6.5 µm, in particular greater than or equal to 8 µm; the shortest cross-sectional axis AK is less than or equal to 12 µm, in particular less than or equal to 9.5 µm, in particular less than or equal to 8 µm; and the shortest cross-sectional axis AK is greater than or equal to 1.5 µm, in particular greater than or equal to 2.5 µm, in particular greater than or equal to 4 µm. I22.I Another variant of an antiresonant hollow core fiber,comprising the features of at least one of the preceding embodiments, is characterized in that all antiresonance units have a configuration according to one of the preceding claims. Detailed description

[0015] Some of the described characteristics are linked to the term "essentially." The term "essentially" means that, under real-world conditions and manufacturing techniques, a mathematically exact interpretation of terms such as "elliptical," "perpendicular," "parallel," "diameter," or "oval" can never be exact, but only within certain manufacturing tolerances. For example, "essentially parallel axes" include an angle of -10 degrees to 10 degrees, and in particular, -5 degrees to 5 degrees, between them. A "device consisting essentially of quartz glass" includes, for example, a quartz glass content of ≥95 to ≤100% by weight. Furthermore, "essentially right-angled" includes an angle of 85 degrees to 95 degrees. Further clarification of the term "essentially" for some characteristics follows below.

[0016] The above-mentioned tasks are at least partially solved by an antiresonant hollow-core fiber comprising a fiber sheath (also referred to as a cladding) which has an internal bore, a fiber longitudinal axis and a fiber core radius R_fiber, and a number of antiresonant units, each comprising an ARE element, an NE element, and a DNE element, wherein the anti-resonance units are spaced apart from each other and arranged without contact with each other at predetermined positions on an inner side of the inner bore, wherein in the anti-resonance units the ARE element has a circular cross-section, the NE element is arranged in a first interior space of the ARE element, and the DNE element is arranged at least partially in a second interior space of the NE element.

[0017] It is provided that in at least one antiresonance unit the NE element has a circular arc-shaped cross-section and is connected to the DNE element along two connecting seams, the DNE element has an oval cross-section, and in the cross-section the sum of the distances of any point on a DNE element wall from two foci is less than 15% of the sum of the distances for all points.

[0018] Surprisingly, it was found that the oval geometry of the DNE element, in combination with the circular arc-like cross-section of the NE element, is advantageous for the waveguide losses of the fundamental mode.

[0019] The following fashions are considered: Fundamental modes in the core, also referred to as core fundamental modes, which propagate within a fiber core; higher-order modes in the core, also referred to as higher-order nuclear modes (HOM); modes in the ARE element, also referred to as ARE modes, which propagate within a first interior space of the ARE element; modes in the NE element, also referred to as NE modes, which propagate within a second interior space of the NE element; modes in the DNE element, also referred to as DNE modes, which propagate within a third interior space of the DNE element.

[0020] Confinement loss (also known as waveguide loss or wave transmission loss) refers to the attenuation of the respective mode.

[0021] The effective mode index n eff gives, via the relation v phase = c / n eff, the phase velocity of the respective mode in the direction of propagation along the longitudinal axis of the fiber, where c denotes the speed of light in a vacuum.

[0022] The mode index difference Δn eff (ARE) denotes the difference between the effective mode index of the higher-order modes in the kernel and the effective mode index of the ARE modes: Δn eff ARE = n eff , core − HOM − n eff , ARE Mode .

[0023] Equivalently, the mode index difference Δn eff (NE) is the difference between the effective mode index of the higher-order modes in the kernel and the effective mode index of the NE mode: Δn eff NE = n eff , core - HOM − n eff , NE Mode .

[0024] If the mode index difference Δneff is close to zero, the two modes under consideration propagate with essentially the same phase propagation velocity and can therefore couple coherently (in phase), leading to effective energy coupling. In this case, the energy of the higher-order nuclear mode couples into highly lossy ARE or NE modes. Thus, energy migrates from the higher-order nuclear modes into the modes of the antiresonant elements, resulting in an improvement of the fundamental mode.

[0025] In the simulations described in more detail below, the effective mode index neff was extracted from the propagation constant β of the respective mode. A mode "j" is a solution to the physical system of equations: E j x y z t = Amplitude j x y * exp i * β j * z − ω * t .

[0026] This describes E j (x,y,z,t) is the electric field distribution in the three spatial dimensions x,y,z at time t, and Amplitude j (x,y) is the transverse electric field distribution.

[0027] Consequently, the propagation constant β describes the phase properties of wave propagation along the fiber axis z. Based on the wavelength of the light λ, the effective mode index neff for mode "j" is directly derived from β: β j = 2 * pi / λ * n eff , j

[0028] The propagation constant of the j-th mode – βj – is generally a complex parameter as a solution to the simulation. While the real part yields n_eff,j, the waveguide loss can be derived from the imaginary part.

[0029] As will be explained in more detail below, the design of the DNE element leads to an effective coupling of the higher-order modes in the core with the modes in the DNE element, so that after a short propagation distance only the fundamental mode in the core is propagated. Ideally, the DNE element of the described antiresonant hollow-core fiber has an ellipsoidal cross-section. An ellipse is defined as a closed oval curve where the sum of the distances of a point on the ellipse from any two points—the foci—is the same for all points. However, due to manufacturing tolerances, the cross-section of the DNE element of the disclosed antiresonant hollow-core fiber will never be mathematically exactly ellipsoidal. Rather, the cross-section of the DNE element will ideally approximate an ellipsoidal shape.Therefore, the DNE element is designed to have an oval cross-section, and the sum of the distances from any point on a DNE element wall to any two foci is less than 15% of the total distance for all points on the DNE element wall. This deviation from the optimal ellipsoidal cross-section is, on the one hand, realistic from a manufacturing perspective and, on the other hand, continues to produce excellent waveguide results.

[0030] Another embodiment variant is characterized by the fact that in the cross-section the sum of the distances of any point on the DNE element wall from two focal points on the DNE element wall is less than 10%, in particular less than 5%, of the sum of the distances for all points.

[0031] Another embodiment is characterized by the fact that the DNE element has a longest cross-sectional axis AL and / or a shortest cross-sectional axis AK. The longest cross-sectional axis AL is the axis that passes through two points on the DNE element wall that are at their maximum distance from each other. The shortest cross-sectional axis AK is the axis that passes through two points on the DNE element wall that are at their minimum distance from each other. In particular, one or both cross-sectional axes are axes of symmetry of the DNE element.

[0032] Another design variant is characterized by the fact that the focal points are arranged on the longest cross-sectional axis AL. In this variant, the oval cross-section of the DNE element more closely approximates an ellipsoidal shape, which positively influences the waveguide losses.

[0033] Another embodiment is characterized in that, for the at least one antiresonance unit, the longest cross-sectional axis AL runs parallel to a circle tangent within an angular interval of [-10 degrees; 10 degrees], with the circle tangent being perpendicular to the inner radius of the casing. In other words, the longest cross-sectional axis AL runs essentially parallel to the inner bore. In this embodiment, the oval cross-section of the DNE element more closely approximates an ellipsoidal shape, which has a positive effect on waveguide losses.

[0034] Another embodiment is characterized by the fact that the shortest cross-sectional axis AK is used for the at least one anti-resonance unit. within an angular interval of [-10 degrees; 10 degrees] parallel to the inner radius of the shell, and / or within [-2 µm; 2 µm] past the longitudinal axis of the fiber runs. In other words, the shortest cross-sectional axis AK is essentially perpendicular to the inner bore.

[0035] Another design variant is characterized by the fact that the following ratio applies to the longest cross-sectional axis AL to the shortest cross-sectional axis AK: AL AK = 1 1 4 0

[0036] This design variant leads to a further optimization of waveguide losses.

[0037] Another design variant is characterized by the fact that the following applies to the ratio of the longest cross-sectional axis AL to the shortest cross-sectional axis AK: greater than or equal to 1.15, in particular greater than or equal to 1.20, in particular greater than or equal to 1.25, in particular greater than or equal to 1.50; and less than or equal to 3.80, in particular less than or equal to 3.60, in particular less than or equal to 3.50.

[0038] By using a DNE element which has an oval cross-section and possesses the cross-sectional axis ratios described above, waveguide losses can be further reduced.

[0039] Another embodiment variant is characterized by the fact that for a ratio of the NE interior height H_NE, multiplied by twice the NE circle radius NE_R, divided by a fiber core area A_Fiber, the following applies: H_NE ∗ 2 ∗ NE_R A_Faser = 0 35 0 7 .

[0040] This design variant is characterized by a small mode index difference Δn eff (NE), which means that the fundamental modeness in the fiber is reached after a short transmission distance and that waveguide losses are also low.

[0041] Another embodiment variant is characterized by the fact that the following applies to the ratio of the NE interior height H_NE, multiplied by twice the NE circle radius NE_R, divided by the fiber core area A_Fiber: greater than or equal to 0.4, in particular greater than or equal to 0.50, in particular greater than or equal to 0.56; and less than or equal to 0.65, in particular less than or equal to 0.62, in particular less than or equal to 0.6.

[0042] Designing the antiresonant hollow-core fiber based on these parameters results in a further reduction of the mode index difference Δn eff (NE). This leads to a further reduction in the transmission distance required to achieve the fundamental mode.

[0043] Another variant is characterized by the fact that for a ratio of an ARE interior height H_ARE, divided by a core radius R_Fiber, the following applies: H_ARE R_Faser = 0 , 85 ; 1 , 25 .

[0044] This design variant is characterized by a small mode index difference Δn eff (ARE). As a result, the basic modeness in the fiber is reached after only a short running distance.

[0045] Another variant is characterized by the fact that the following applies to the ratio of the ARE interior height H_ARE, divided by the core radius R_Fiber: greater than or equal to 0.9, in particular greater than or equal to 0.95, in particular greater than or equal to 1.0; and less than or equal to 1.2, in particular less than or equal to 1.15, in particular less than or equal to 1.1.

[0046] Designing the antiresonant hollow-core fiber based on these parameters results in a further reduction of the mode index difference Δn eff (ARE). This leads to a further reduction in the transmission distance required to achieve the fundamental mode.

[0047] Another variant is characterized by the fact that for a ratio of the ARE interior height H_ARE, multiplied by twice the NE circle radius NE_R, divided by the NE interior surface A_NE, the following applies: H_ARE ∗ 2 ∗ NE_R A_NE = 0 , 2 ; 1 , 0

[0048] This design of at least one antiresonance unit results in an antiresonant hollow core fiber that exhibits low waveguide loss.

[0049] Another variant is characterized by the fact that the following applies to the ratio of the ARE interior height H_ARE, multiplied by twice the NE circle radius NE_R, divided by the NE interior surface A_NE: greater than or equal to 0.25, in particular greater than or equal to 0.3; and less than or equal to 0.95, in particular less than or equal to 0.8.

[0050] The listed parameters for the design of the antiresonant hollow core fiber lead to a further reduction in waveguide losses.

[0051] Another embodiment variant is characterized by the fact that the following applies to the ratio of the NE interior height H_NE, multiplied by twice the NE circle radius NE_R, divided by the fiber core area A_Fiber: H_NE ∗ 2 ∗ NE_R A_Faser = 0 , 35 ; 0 , 7 and additionally for a ratio of the ARE interior height H_ARE, multiplied by twice the NE circle radius NE_R, divided by the NE interior surface A_NE, the following applies: H_ARE ∗ 2 ∗ NE_R A_NE = 0 , 2 ; 1 , 0

[0052] This version is characterized by the fact that the mode index difference Δn eff (NE) between the fundamental mode and the NE mode is close to zero, and the waveguide losses of the fundamental mode are minimized.

[0053] A process for producing a preform from which an antiresonant hollow core fiber can be elongated may include the following steps: Providing a fiber sheath preform, preparing a number of antiresonance unit preforms, inserting the antiresonance unit preforms into an internal bore of the fiber sheath preform, and processing an arrangement comprising the fiber sheath preform and the number of antiresonance unit preforms, by a hot forming process selected from at least one of elongation and collapse.

[0054] The term hot forming refers to a process step in which the temperature of an element is increased by the input of heat. Well-known hot forming processes include flame-based hot forming processes, which are based on the oxidation of an exothermic gas. The hot forming process results in a metallurgical bond between the antiresonance unit preforms and the inner bore of the fiber sheath preform. In the finished antiresonance hollow core fiber, this bond is reflected, for example, in the metallurgical connection between the antiresonance units and the inner bore of the sheath.

[0055] Another embodiment is characterized by the fact that the antiresonant hollow core fiber has three, four, five, six, seven, or eight antiresonance units, in particular that the antiresonant hollow core fiber has an odd number of antiresonance units. This embodiment allows for further optimization of the fundamental mode attenuation.

[0056] Another design variant is characterized by the asymmetrical arrangement of the antiresonance units on the inner surface of the sheath. This dampens higher-order modes in the core and renders the hollow-core fiber fundamental-mode over a shorter distance.

[0057] Another embodiment is characterized by the fact that at least one of the antiresonance units has at least one of the following features: the ARE element and / or the NE element and / or the DNE element comprises an amorphous solid, in particular a glass, in particular quartz glass, the ARE element and / or the NE element and / or the DNE element consists of an amorphous solid, in particular a glass, in particular quartz glass, that at least two of the ARE element, NE element and DNE element are of the same material, in particular comprise or consist of a glass with a refractive index of at least 1.4, in particular 1.4 to 3, in particular 1.4 to 2.8, and that an element wall of at least two of the ARE element, NE element and DNE element is substantially the same.

[0058] These variants of the antiresonance units are optimized for low-loss signal transmission at wavelengths between 0.3 µm and 3.0 µm, especially between 1.0 µm and 2.5 µm.

[0059] Another embodiment is characterized by the fact that the antiresonant hollow core fiber has at least one of the following features: a fundamental attenuation of less than 1.0 dB / km, in particular less than 0.25 dB / km, in particular less than 0.1 dB / km at a transported wavelength between 0.3 µm and 3.0 µm, in particular between 1.0 µm and 2.5 µm, and a fundamental attenuation of less than 1 dB / km at a transported wavelength of up to 0.8 µm.

[0060] This variant of the antiresonant hollow core fiber is particularly suitable for use in data centers due to the low attenuation of the fundamental mode.

[0061] Another embodiment is characterized by the fact that the at least one antiresonance unit has at least one of the following features: The wall thickness of an ARE element wall of the ARE element and / or an NE element wall of the NE element and / or a DNE element wall of the DNE element is between 0.1 µm and 2.5 µm, in particular between 0.15 µm and 1.5 µm, in particular between 0.25 µm and 0.75 µm, in particular between 0.35 µm and 0.65 µm, in particular 0.5 µm. At a signal wavelength of 1550 nm in the first transmission window, the wall thickness of an ARE element wall of the ARE element and / or an NE element wall of the NE element and / or a DNE element wall of the DNE element is between 0.35 µm and 0.65 µm, in particular between 0.4 µm and 0.6 µm. µm, in particular 0.5 µm, a wall thickness of an ARE element wall of the ARE element and / or an NE element wall of the NE element and / or a DNE element wall of the DNE element is between 0.75 µm and 1.25 µm, in particular between 0.9 µm and 1.1 µm, in particular 1 µm, at a signal wavelength of 1550 nm in the second transmission window..

[0062] In the case of an antiresonant hollow core fiber, which in particular has a DNE element with one of the specified wall thicknesses and in particular at a transported wavelength between 0.3 µm and 3.0 µm, especially between 1.0 µm and 2.5 µm, a broad spectral range with low waveguide losses is obtained.

[0063] Another variant is characterized by the fact that the core radius R_Fiber has at least one of the following features: less than or equal to 26 µm, in particular less than or equal to 23 µm, in particular less than or equal to 20 µm; and greater than or equal to 10 µm, in particular greater than or equal to 12 µm, in particular greater than or equal to 14 µm.

[0064] Another variant is characterized by the fact that the ARE element has at least one of the following features: the first circle radius R_ARE is less than or equal to 30 µm, in particular less than or equal to 25 µm, in particular less than or equal to 22.5 µm, in particular less than or equal to 16 µm; and the first circle radius R_ARE is greater than or equal to 5 µm, in particular greater than or equal to 7 µm, in particular greater than or equal to 11.5 µm, in particular greater than or equal to 12.25 µm, in particular greater than or equal to 14.5 µm.

[0065] In antiresonant hollow-core fibers exhibiting one of the first circular radii R_ARE listed above, a particularly effective interaction of the higher-order modes in the core with those in the ARE element can be observed, resulting in a small absolute difference in the effective mode index Δneff(ARE). This is especially true if the antiresonant hollow-core fiber has one of the core radii R_Fiber listed above.

[0066] Another embodiment variant is characterized by the fact that the non-renewable element has at least one of the following features: the second circle radius R_NE is less than or equal to 25 µm, in particular less than or equal to 19 µm, in particular less than or equal to 17 µm; the second circle radius R_NE is greater than or equal to 1.5 µm, in particular greater than 2.5 µm, in particular greater than or equal to 3.5 µm; a central angle MW_NE is less than 340°, in particular less than 330°, in particular less than 320°; and a central angle MW_NE is greater than 180°, in particular greater than 200°, in particular greater than 230°.

[0067] In antiresonant hollow-core fibers exhibiting one of the second circular radii R_NE and / or central angle MW_NE listed above, a particularly effective interaction of the higher-order modes in the core with those in the NE element can be observed, resulting in a small absolute difference in the effective mode index Δneff(NE). This is especially true if the antiresonant hollow-core fiber has one of the core radii R_Fiber and / or one of the first circular radii R_ARE listed above.

[0068] Another variant is characterized by the fact that the DNE element has at least one of the following features: the longest cross-sectional axis AL is less than or equal to 20 µm, in particular less than or equal to 16.5 µm, in particular less than or equal to 14.6 µm; the longest cross-sectional axis AL is greater than or equal to 4 µm, in particular greater than or equal to 6.5 µm, in particular greater than or equal to 8 µm; the shortest cross-sectional axis AK is less than or equal to 12 µm, in particular less than or equal to 9.5 µm, in particular less than or equal to 8 µm; and the shortest cross-sectional axis AK is greater than or equal to 1.5 µm, in particular greater than or equal to 2.5 µm, in particular greater than or equal to 4 µm.

[0069] In antiresonant hollow-core fibers that have at least one antiresonance unit with an ARE element exhibiting at least one of the listed features, a particularly effective interaction of the higher-order modes in the core with those in the ARE element can be observed, resulting in a small absolute difference in the effective mode index Δneff(ARE). This is especially true if the antiresonant hollow-core fiber has one of the core radii R_fiber and / or one of the first circle radii R_ARE listed above.

[0070] Another embodiment is characterized in that more than 70% of the antiresonance units, in particular all antiresonance units, have a design according to one of the described embodiments. The antiresonance units can all be designed uniformly or according to different embodiments. Properties and features of different embodiments can be combined separately or in any combination.

[0071] The properties and features disclosed in the description can be essential for various embodiments of the claimed invention, both separately and in any combination with one another.

[0072] The invention is further illustrated below by means of figures. The invention is not limited to the figures. Figures

[0073] They show Fig. 1 a tubular ARE element, Fig. 2 a circular arc NE element, Fig. 3 an oval DNE element, Fig. 4 the oval DNE element made of Fig. 3 , Fig. 5a an antiresonance unit, comprising the ARE element made of Fig. 1 , the NE element from Fig. 2 and the DNE element from Fig. 3 , Fig. 5 legged close-up of the antiresonance unit from Fig. 5a , Fig. 5 shows a further enlarged section of the antiresonance unit from Fig. 5a , Fig. 6 a cross-section through a part of an antiresonant hollow core fiber with the antiresonant unit made of Fig. 5Fig. 7 a cross-section through the antiresonant hollow core fiber with a plurality of antiresonance units, Fig. 8 a diagram of a difference of an effective mode index Δneff (NE), plotted as a function of a ratio of an NE internal height H_NE, multiplied by twice the NE circular radius NE_R, divided by a fiber core area A_fiber, Fig. 9 a diagram of a waveguide loss of a fundamental mode (FM), plotted as a function of a ratio of the NE internal height H_NE, multiplied by twice the NE circular radius NE_R, divided by the fiber core area A_fiber, Fig. 10 a diagram of a difference of the effective mode index Δneff (ARE), plotted as a function of a ratio of an ARE internal height H_ARE, divided by a core radius R_fiber11 A diagram of a waveguide loss of the fundamental mode, plotted as a function of the ratio of the ARE interior height H_ARE, multiplied by twice the NE circle radius NE_R, divided by an NE interior surface area A_NE.

[0074] The Figure 1 Figure 3 shows a cross-section through an ARE element 3100. The ARE element 3100 is a tubular structure with a circular cross-section. The ARE element 3100 extends along a first longitudinal axis 3110. Figure 1 The ARE element 3100 therefore extends into the drawing plane. Due to its circular cross-section, the ARE element 3100 has a first circular radius R_ARE 3200.

[0075] The ARE element 3100 has an ARE element wall 3150. The ARE element wall 3150 encloses a first interior space 3170. The first interior space 3170 has an ARE interior surface 3180. The ARE interior surface 3180 is proportional to the square of the first circle radius R_ARE 3200.

[0076] A manufacturing-related variation in the first circle radius R_ARE 3200 is in particular not more than 10%, preferably not more than 5%, and more preferably not more than 3%, based on the length of the first circle radius R_ARE 3200.

[0077] The Figure 2 Figure 3 shows a cross-section through a non-renewable element (NE element) 3400. The NE element 3400 is a tubular structure with a circular arc-shaped cross-section. The NE element 3400 extends along a second longitudinal axis 3410. Figure 2 The NE element 3400 extends into the drawing plane.

[0078] As the in Figure 2As the cross-section shown illustrates, the NE element 3400 has a circular arc-like cross-section. Within the scope of the invention, the term "circular arc" is understood to mean a segment of a circle. Two points on a circle divide the circle into two circular arcs. Within the scope of this invention, an element is described as "circular arc-like" if its outer shape follows the course of one of the aforementioned two circular arcs. For clarification, the following is shown in Figure 2 A circle 2990 is drawn. This circle 2990 is divided into two arcs by the two intersection lines HH and II. The cross-section of the NE element 3400 follows one of these two arcs.

[0079] Furthermore, a section line GG is drawn, which runs through the two points where the two section lines HH and II intersect circle 2990. The segment lying on section line GG and bounded by section lines HH and II is designated as the chord of the NE inner unit 3400. The length of the chord is designated as chord length 3590.

[0080] The NE element 3400 has a NE element wall 3450. The NE element 3400 has a second circular radius R_NE 3500. This second circular radius R_NE 3500 describes the distance of the NE element wall 3450 to the second longitudinal axis of the body 3410.

[0081] A manufacturing-related variation in the second circle radius R_NE 3500 is in particular not more than 10%, preferably not more than 5%, and more preferably not more than 3%, based on the length of the second circle radius R_NE 3500.

[0082] The NE element 3400 has a segment height SH_NE 3580. This segment height SH_NE 3580 describes the length of a straight line that is perpendicular to the chord and runs to the vertex of the NE element wall 3450.

[0083] The NE element 3400 has a central angle MW_NE 3550. This central angle MW_NE 3550 describes the angle whose vertex lies at the center of circle 2990 and whose sides intersect the boundary points of the circular arc (here, the points of intersection of circle 2990 with the lines of intersection HH and II). A full circle has a degree value of 360°. Since the NE element 3400 is designed as a circular arc, the central angle MW_NE 3550 is less than 360°.

[0084] The NE element 3400 has a second interior space 3470 bounded by the NE element wall 3450 and the chord.

[0085] One design variant is characterized by the fact that the NE element 3400 has at least one of the following features: the second circle radius R_NE 3500 is less than or equal to 25 µm, in particular less than or equal to 19 µm, in particular less than or equal to 17 µm; the second circle radius R_NE 3500 is greater than or equal to 1.5 µm, in particular greater than 2.5 µm, in particular greater than or equal to 3.5 µm; the central angle MW_NE 3550 is less than 340°, in particular less than 330°, in particular less than 320°; and the central angle MW_NE 3550 is greater than 180°, in particular greater than 200°, in particular greater than 230°.

[0086] The Figure 3 Figure 3 shows a cross-section through a DNE element 3900. The DNE element 3900 is a tubular structure with an oval cross-section. Figure 2 The DNE element 3900 therefore extends into the drawing plane.

[0087] The DNE element 3900 has a DNE element wall 3950. The DNE element wall 3950 encloses a third interior space 3970. The third interior space 3970 has a DNE interior surface 3980.

[0088] The DNE element 3900 has an oval cross-section. Within the scope of the invention, the term "oval" is understood to mean a planar, rounded, convex shape, which includes ellipses as a special case, whereby, unlike the ellipse, any oval shape does not necessarily have an axis of symmetry.

[0089] The DNE element 3900 has a longest cross-sectional axis AL 4010 and a shortest cross-sectional axis AK 4020. Here, the longest cross-sectional axis AL 4010 the longest straight extension between two points on the DNE element wall 3950, and the shortest cross-sectional axis AK 4020 the shortest straight extension between two points on the DNE element wall 3950.

[0090] In another variant, the longest cross-sectional axis AL 4010 and / or the shortest cross-sectional axis AK 4020 are axes of symmetry of the DNE element 3900.

[0091] The Figure 4 This serves to clarify the understanding of the term "oval" and shows the in Figure 3 The cross-section shown is through the DNE element 3900. The oval cross-section of the DNE element 3900 is limited such that the sum of the distances 4001, 4001' from any point on the DNE element wall 3950 to any two foci 4000, 4000' is less than 15% of the sum of the distances 4001, 4001' for all points. The foci 4000, 4000' are disjoint and not identical. Consequently, an elliptical cross-section is targeted for the DNE element 3900, but for manufacturing reasons, this is only achieved within the range of the specified variation. Figure 4The illustrated version of the DNE element 3900 is characterized by the fact that the focal points 4000,4000' lie on the longest cross-sectional axis AL 4010.

[0092] Another embodiment of the DNE element 3900 is characterized by the fact that in the cross-section the sum of the distances 4001, 4001' of any point on the DNE element wall 3950 from two focal points 4000, 4000', which lie in particular on the longest cross-sectional axis AL 4010, is less than 10%, in particular less than 5%, of the sum of the distances 4001, 4001' for all points.

[0093] Surprisingly, it has been found that a DNE element 3900 with an oval cross-section positively influences the transmission properties of an antiresonant hollow core fiber 1000. One variant of the DNE element 3900 is characterized by the following ratio of the longest cross-sectional axis AL 4010 to the shortest cross-sectional axis AK 4020: AL / AK = 1 , 1 ; 4,0

[0094] This design variant leads to an optimization of waveguide losses.

[0095] Another design variant is characterized by the fact that the following applies to the ratio of the longest cross-sectional axis AL 4010 to the shortest cross-sectional axis AK 4020: greater than or equal to 1.15, in particular greater than or equal to 1.20, in particular greater than or equal to 1.25, in particular greater than or equal to 1.50; and less than or equal to 3.80, in particular less than or equal to 3.60, in particular less than or equal to 3.50.

[0096] By using a DNE element 3900, which has an oval cross-section and possesses the conditions described above, waveguide losses can be reduced.

[0097] Another embodiment is characterized by the fact that the DNE element 3900 has at least one of the following features: the longest cross-sectional axis AL 4010 is less than or equal to 20 µm, in particular less than or equal to 16.5 µm, in particular less than or equal to 14.6 µm; the longest cross-sectional axis AL 4010 is greater than or equal to 4 µm, in particular greater than or equal to 6.5 µm, in particular greater than or equal to 8 µm; the shortest cross-sectional axis AK 4020 is less than or equal to 12 µm, in particular less than or equal to 9.5 µm, in particular less than or equal to 8 µm; and the shortest cross-sectional axis AK 4020 is greater than or equal to 1.5 µm, in particular greater than or equal to 2.5 µm, in particular greater than or equal to 4 µm.

[0098] The Figure 5aFigure 3 shows a cross-section through an antiresonance unit 3000, which comprises the ARE element 3100, the NE element 3400, and the DNE element 3900. The NE element 3400 and the DNE element 3900 are arranged within the first interior space 3170 of the ARE element 3100. The oval-shaped DNE element 3900 projects at least partially into the second interior space 3470 of the arc-shaped NE element 3400. This means that, in cross-section, the DNE element 3900 extends at least partially above the chord of the NE element 3400.

[0099] The NE element 3400 has an NE inner surface A_NE 3480. This is bounded by the NE element wall 3450 and the DNE element wall 3950. Consequently, the NE inner surface A_NE 3480 and the second inner surface 3470 are not exactly congruent.

[0100] The arc-shaped NE element 3400 and the oval-shaped DNE element 3900 are connected to each other along two connecting seams 3700, 3700' which are arranged essentially parallel to the first longitudinal axis 3110 of the body. This connection can be made in particular by a hot process.

[0101] To illustrate, in Figure 5b An area around the connecting seam 3700 is shown enlarged. This reveals that the connecting seams 3700 as a connection between a first endpoint of the NE element wall 3450 and a first point on the DNE element wall 3950, and the connecting seams 3700' as a connection between a second endpoint of the NE element wall 3450 and a second point on the DNE element wall 3950.

[0102] Analogous to Figure 5b shows Figure 5ca part of the arc-shaped NE element 3400 and the oval-shaped DNE element 3900, bounded by the section lines C and D. Shown are three exemplary positions A1, A2, A3 of the respective first endpoint of the NE element wall 3450 on the DNE element wall 3950.

[0103] Each of the three positions A1, A2, A3 has a connection height of 3705, 3705', 3705". The connection height 3705, 3705', 3705" results from a distance from a top edge of the DNE element 3900 to the respective circle 2990, 2990', 2990".

[0104] To clarify, the connection height of 3705" for position A3 is described in more detail. The connection height of 3705" results from the distance between the following two elements: The top edge of the DNE element 3900: The top edge can be the intersection point of the shortest cross-sectional axis AK 4020 with the DNE element wall 3950 (see also Figure 3). The circle 2990" of the respective NE element 3400: To illustrate the arc-shaped cross-section of the NE element 3400, in Figure 2 A circle 2990 is drawn. This circle 2990 is divided into two arcs by the two intersection lines HH and II. The cross-section of the NE element 3400 follows one of these two arcs.

[0105] The connection height 3705" for position A3 therefore does not correspond to the distance between a plane spanned by the connection seams 3700,3700' and the top edge of the DNE element 3900. Rather, the connection height 3705" is greater than said distance to the plane spanned by the connection seams 3700,3700'.

[0106] With a connection height of zero (3705, 3705', 3705"), the NE element 3400 and the DNE element 3900 would touch at only one point, and the NE element would essentially form a circle. Therefore, to ensure the arc-shaped cross-section of the NE element 3400, the connection height (3705, 3705', 3705") for the hollow core fiber 1000 is greater than zero. The connection height (3705, 3705', 3705") can vary between 1.25 µm and 5.75 µm in one design variant.

[0107] Since in Figure 5a,b , c In a three-dimensional representation of the hollow core fiber 1000, where a cross-section of the antiresonance unit 3000 is shown, the two connecting seams 3700, 3700' extend into the plane of the drawing.

[0108] The Figures 1 to 5a , b , cThe figures show the antiresonance unit 3000, the ARE element 3100, the NE element 3400, and the DNE element 3900, each in a cross-sectional view, i.e., an axial view. In a three-dimensional view, the antiresonance unit 3000, the ARE element 3100, the NE element 3400, and the DNE element 3900 are therefore each represented as an elongated and / or tubular structure.

[0109] The ARE element 3100 and / or the NE element 3400 and / or the DNE element 3900 can comprise and / or consist of an amorphous solid, in particular a glass, especially quartz glass. The in Figure 5 The depicted antiresonance unit 3000 can have at least one of the following features: a wall thickness of the ARE element wall 3150 of the ARE element 3100 and / or the NE element wall 3450 of the NE element 3400 and / or the DNE element wall 3950 of the DNE element 3900 is between 0.1 µm and 2.5 µm, in particular between 0.15 µm and 1.5 µm, in particular between 0.25 µm and 0.75 µm, in particular between 0.35 µm and 0.65 µm, in particular 0.5 µm, a wall thickness of the ARE element wall 3150 of the ARE element 3100 and / or the NE element wall 3450 of the NE element 3400 and / or the DNE element wall 3950 of the DNE element 3900, at a signal wavelength of 1550 nm in the first transmission window between 0.35 µm and 0.65 µm, in particular between 0.4 µm and 0.6 µm, in particular 0.5 µm, is a wall thickness of the ARE element wall 3150 of the ARE element 3100 and / or the NE element wall 3450 of the NE element 3400 and / or the DNE element wall 3950 of the DNE element 3900, at a signal wavelength of 1550 nm in the second transmission window between 0,75 µm and 1.25 µm, in particular between 0.9 µm and 1.1 µm, in particular 1 µm.

[0110] The Figure 6Figure 1 shows a cross-section through a portion of an antiresonant hollow core fiber 1000. The section of the antiresonant hollow core fiber 1000 between two sections AA and BB is depicted. The antiresonant hollow core fiber 1000 has a fiber sheath 2000 (also referred to as sheath). The fiber sheath 2000 can be constructed in one piece from an elongated sheath material or from an elongated cladding tube in combination with an elongated sheath material. The fiber sheath 2000 has an inner radius 2170, which is determined by the distance between a fiber longitudinal axis 2300 of the antiresonant hollow core fiber 1000 and an inner surface 2150 of the sheath 2000. An antiresonance unit 3000 is arranged on the inner surface 2150. The antiresonance unit 3000 is metallurgically bonded to the fiber sheath 2000. The antiresonance unit 3000 corresponds in particular to that in Figure 5a shown.

[0111] The ARE element 3100 is circular in shape. Deviations of the ARE element wall 3150 and / or the first circular radius R_ARE 3200 from the ideal circular shape are primarily due to manufacturing variations. In particular, the first circular radius R_ARE 3200 may not deviate by more than 15%, in particular by more than 10%, in particular by more than 3% from the mean first circular radius R_ARE 3200 of the ARE element 3100, especially both azimuthally over a circle – resulting in an oval shape – and at axially different locations of the antiresonant hollow core fiber 1000.

[0112] The NE element 3400 has a circular arc shape. Deviations of the NE element wall 3450 and / or the second circular radius R_NE 3500 from the ideal circular arc shape are primarily due to manufacturing variations. In particular, the second circular radius R_NE 3500 may not deviate by more than 15%, in particular by more than 10%, in particular by more than 3% from a mean second circular radius R_NE 3500, especially both azimuthally over a circular arc – resulting in an oval shape – and at axially different locations of the antiresonant hollow core fiber 1000.

[0113] The antiresonance unit 3000 comprises the ARE element 3100, the NE element 3400, and the DNE element 3900. One value of the inner mantle radius 2170 corresponds to the sum of: a core radius R_Fiber 2310, which results from the shortest distance between the fiber longitudinal axis 2300 and the antiresonance unit 3000, an ARE internal height H_ARE 3190, which results from the distance between the ARE element wall 3150 and the NE element wall 3450 in the line to the fiber longitudinal axis 2300, an NE internal height H_NE 3490, which results from the distance between the NE element wall 3450 and the DNE element wall 3950 in the line to the fiber longitudinal axis 2300, and the length of the shortest cross-sectional axis AK 4090, and the sum of the wall thicknesses of the ARE element wall 3150, the NE element wall 3450 and the DNE element wall 3950.

[0114] The Figure 7Figure 1 shows a cross-section through the antiresonant hollow core fiber 1000. The antiresonant hollow core fiber 1000 has a hollow core through which an electromagnetic wave can propagate. The hollow core has a core radius of 2310 and a fiber core area A_fiber 2320. The fiber sheath 2000 has a circular cross-section and is tubular in design. The fiber sheath 2000 encloses an inner bore 2200 in which the antiresonance units 3000 are arranged.

[0115] One implementation variant is characterized by the fact that the core radius R_Fiber 2310 has at least one of the following features: less than or equal to 26 µm, in particular less than or equal to 23 µm, in particular less than or equal to 20 µm; and greater than or equal to 10 µm, in particular greater than or equal to 12 µm, in particular greater than or equal to 14 µm.

[0116] The Figure 7The arrangement of the majority of antiresonance units 3000 on the inner surface 2150 is illustrated. In one version, the antiresonant hollow core fiber 1000 can have three, four, five, six, seven, or eight antiresonance units 3000. Figure 7 The antiresonant hollow core fiber 1000 has five antiresonance units 3000. In this version, the antiresonance units 3000 are arranged asymmetrically on the inner side 2150 of the sheath 2000.

[0117] The Figures 8 to 11The results of simulations of the antiresonant hollow-core fiber 1000 are shown. A finite element mode solver in the COMSOL Multiphysics program was used for the numerical calculations. A perfectly matched layer (PML) with a thickness of 10 µm was implemented at the outer interface of the optical fiber to investigate the emission characteristics of the waveguide structure by absorbing the radially emitted light energy.

[0118] The starting point for the simulations was an antiresonant hollow core fiber 1000. This antiresonant hollow core fiber 1000 comprises the fiber longitudinal axis 2300, the fiber core radius R_Fiber 2310, and the fiber sheath 2000, which has the inner bore 2200. Furthermore, the antiresonant hollow core fiber 1000 comprises five antiresonance units 3000, each comprising an ARE element 3100, an NE element 3400, a DNE element 3900,

[0119] The antiresonance units 3000 are spaced apart from each other and arranged without contact with each other at designated positions on an inner side 2150 of the inner bore 2200.

[0120] Whereupon each antiresonance unit contains 3000 the ARE element 3100 has a circular cross-section, the NE element 3400 is arranged in a first interior space 3170 of the ARE element 3100, and the DNE element 3900 is arranged at least partially in a second interior space 3470 of the NE element 3400.

[0121] The antiresonance units 3000 in the antiresonant hollow core fiber 1000 are characterized by the fact that the DNE element 3900 has an oval cross-section, the NE element 3400 has a circular arc-shaped cross-section and is connected to the DNE element 3400 along two connecting seams 3700, 3700', and in the cross-section a sum of the distances of any point on a DNE element wall 3950 from two focal points 4000, 4000' is equal to less than 15% of the sum of the distances for all points.

[0122] The simulated antiresonant hollow core fibers 1000 exhibited the following properties: a wall thickness of 500 nm, which in particular corresponds to a wide transmission range (1st transmission band) around the signal wavelength of 1550 nm, five antiresonance units 3000 each, and the DNE elements had the contour of an ideal ellipse.

[0123] Table 1 lists further parameters of the seven different designs of the simulated antiresonant hollow core fiber 1000.

[0124] Multiple calculations were performed for each of the seven designs. The following parameters were varied: 1. second circle radius R_NE 3500, and 2. the connection height 3705, 3705', 3705", i.e. the position of the NE element on the DNE element. Regarding point 1:

[0125] For the otherwise fixed design, the second circle radius R_NE 3500 was varied in 500 nm steps (except for Design 5). For example, the interval [3.5; 11.0] listed for Design 1 describes how, during the simulation, the second circle radius R_NE 3500 was varied in 0.5 µm steps within the interval [3.5 µm; 11.0 µm]. Regarding point 2:

[0126] For the otherwise fixed design, the position of the NE element on the DNE element was varied (see below). Fig 5c). For example, the interval [1.25; 5.75] step 0.50 listed for Design 1 describes that the connection height 3705, 3705', 3705" was varied in 0.5 µm steps from 1.25 µm to 5.75 µm during the simulation.

[0127] Further parameters are defined as follows: The value "Diameter Oval" is calculated from the arithmetic mean of the longest cross-sectional axis AL and the shortest cross-sectional axis AK: ( (AL 4010 + AK 4020) / 2 ). The value "Ovality" is calculated from the ratio of the longest cross-sectional axis AL to the shortest cross-sectional axis AK (AL 4010 / AK 4020). The penetration depth of the ARE element into the shell describes the penetration of the ARE element to a depth of 1 µm into the shell during the hot process. The penetration depth of the DNE element into the shell describes the penetration of the DNE element to a depth of 0.25 µm into the shell during the hot process.

[0128] In the Figures 8 to 11 The results of the simulations are entered as follows: Results marked with a dot based on design 1, results marked with a cross based on design 2, results marked with an x ​​based on design 3, results marked with a circle based on design 4, results marked with a star based on design 5, results marked with a triangle based on design 6, and results marked with a rectangle based on design 7.

[0129] In addition to the definitions given above, the following modes were considered in the simulation: In the simulations, only second-order modes (i.e., first-order modes above the fundamental mode) were considered for higher-order modes in the core, since third- and higher-order modes typically exhibit even higher waveguide losses and are therefore less relevant for considering the fundamental mode, which is predominantly determined by the power and waveguide losses in the second-order modes; in the simulations, only the fundamental mode in the ARE element was considered for modes; in the simulations, only the fundamental mode in the NE element was considered for modes.

[0130] In the simulation, the effective mode index neff was extracted from the propagation constant β of the respective mode. A mode "j" is a solution to the physical system of equations: E j x y z t = Amplitude j x y * exp i * β j * z − ω * t .

[0131] This describes E j (x,y,z,t) is the electric field distribution in the three spatial dimensions x,y,z at time t, Amplitude j (x,y) is the transverse electric field distribution.

[0132] Consequently, the propagation constant β describes the phase properties of wave propagation along the fiber axis z. Based on the wavelength of the light λ, neff for mode "j" is directly derived from β: β j = 2 * pi / λ * n eff , j

[0133] The propagation constant of the j-th mode – βj – is generally a complex parameter as a solution to the simulation. While the real part yields n_eff,j, the waveguide losses, which were determined for the nuclear modes, can be derived from the imaginary part. The parameter βj thus encompasses all the essential properties here.

[0134] The aforementioned disadvantages of known antiresonant hollow-core fibers are overcome, in particular, when a rapid fundamental mode is achieved. This means that higher-order modes are attenuated in the core, and the antiresonant hollow-core fiber effectively exhibits fundamental mode behavior after a shorter propagation distance. The shorter this propagation distance, the higher the fundamental mode. The physical basis for this is that the energy of the higher-order modes couples into the ARE modes and / or DNE modes in the core, which are more lossy. Thus, the higher-order modes no longer contribute to the disruptive transmission of the light signal in the core. Surprisingly, the simulation of the antiresonant hollow-core fiber 1000 revealed that the oval geometry of the DNE element 3900 influences the fundamental mode.

[0135] In Figure 8For the simulated designs, the difference of the effective mode index Δ neff (NE) is plotted against the ratio of the NE interior height H_NE 3490, multiplied by twice the NE circle radius NE_R 3500, divided by the fiber core area A_Fiber 2320.

[0136] The desired coupling between the fundamental mode and the NE modes—and thus good fundamental mode characteristics—is achieved when the magnitude of the mode index Δneff(NE) is small, particularly zero. It has proven advantageous if the following ratio holds for the NE internal height H_NE 3490, multiplied by twice the NE circular radius NE_R 3500, divided by the fiber core area A_Fiber 2320: H_NE ∗ 2 ∗ NE_R A_Faser = 0 , 35 ; 0 , 7

[0137] A further positive influence on the basic modeness can be achieved if the following applies to the ratio of the NE interior height H_NE 3490, multiplied by twice the NE circle radius NE_R 3500, divided by the fiber core area A_Fiber 2320: greater than or equal to 0.4, in particular greater than or equal to 0.50, in particular greater than or equal to 0.56; and less than or equal to 0.65, in particular less than or equal to 0.62, in particular less than or equal to 0.6.

[0138] In Figure 9 For the simulated designs of the antiresonant hollow core fiber 1000, the waveguide losses are plotted against the - in Figure 8 Also recorded - ratio of the NE internal height H_NE 3490, multiplied by twice the NE circular radius NE_R 3500, divided by the fiber core area A_Fiber 2320. The aim is to achieve the lowest possible waveguide loss. This is achieved for the simulated designs if the following applies: H_NE ∗ 2 ∗ NE_R A_Faser = 0 , 35 ; 0 , 7

[0139] This interval coincides with the optimal interval for the fundamental modeness.

[0140] The Figure 8 and 9illustrates the special feature of the described antiresonant hollow core fiber 1000. A geometric design of the antiresonant hollow core fiber 1000 according to H_NE ∗ 2 ∗ NE_R A_Faser = 0 , 35 ; 0 , 7 This results in the following advantages: This geometric design of the antiresonant hollow-core fiber 1000 results in the difference in the effective mode index Δneff (NE) being close to or equal to zero. Consequently, higher-order modes in the core and the modes in the NE element propagate with approximately the same phase propagation velocity and can thus couple coherently (in phase), leading to effective energy coupling. Energy migrates from the higher-order core modes into the ARE modes and / or DNE modes, resulting in an improvement of the fundamental mode. Furthermore, this geometric design of the antiresonant hollow-core fiber 1000 enables low waveguide loss. The fundamental mode of the antiresonant hollow-core fiber 1000 is subject to low attenuation. Therefore, in commercial applications of the antiresonant hollow-core fiber 1000, only a small number of amplifiers are required to bridge large distances.

[0141] In Figure 10The difference in the effective mode index Δneff (ARE) is plotted against the ratio of the ARE interior height H_ARE 3190 divided by the core radius R_Fiber 2310. It has proven advantageous if the following holds for the ratio of the ARE interior height H_ARE 3190 divided by the core radius R_Fiber 2310: H _ ARE R _ Faser = 0 85 1 25

[0142] This geometric design of the antiresonant hollow core fiber 1000 results in the difference of the effective mode index Δ neff (ARE) being close to or equal to zero.

[0143] A further positive influence on the basic modeness can be achieved if the ratio of the ARE interior height H_ARE 3190 divided by the core radius R_Fiber 2310 holds true: greater than or equal to 0.9, in particular greater than or equal to 0.95, in particular greater than or equal to 1.0; and less than or equal to 1.2, in particular less than or equal to 1.15, in particular less than or equal to 1.1.

[0144] In Figure 11For the designs of the antiresonant hollow core fiber 1000, the waveguide losses are plotted against the ratio of the ARE internal height H_ARE 3190, multiplied by twice the NE circular radius NE_R 3500, divided by the NE internal area A_NE 3480. It has proven advantageous if the following holds for the ratio of the ARE internal height H_ARE 3190, multiplied by twice the NE circular radius NE_R 3500, divided by the NE internal area A_NE 3480: H _ ARE ∗ 2 ∗ NE _ R A _ NE = 0 2 1 0

[0145] A further positive influence on waveguide losses can be achieved if the following applies to the ratio of the ARE interior height H_ARE 3190, multiplied by twice the NE circle radius NE_R 3500, divided by the NE interior surface A_NE 3480: greater than or equal to 0.25, in particular greater than or equal to 0.3; and less than or equal to 0.95, in particular less than or equal to 0.8.

[0146] Another positive influence 1. the coupling of the higher-order modes in the core with the modes in the antiresonance units 3000, and 2. the waveguide losses of the fundamental mode This can be achieved if at least two of the following apply to the antiresonant hollow core fiber 1000: The ratio of the longest cross-sectional axis AL 4010 to the shortest cross-sectional axis AK 4020 is AL AK = 1 1 4 0 The ratio of the NE interior height H_NE 3490, multiplied by twice the NE circle radius NE_R 3500, divided by the fiber core area A_Fiber 2320 is H _ NE * 2 * NE _ R A _ Faser = 0 35 0 7 The ratio of the ARE interior height H_ARE 3190, divided by the core radius R_Fiber 2310 is H _ ARE R _ Faser = 0 85 1 25 The ratio of the ARE interior height H_ARE 3190, multiplied by twice the NE circle radius NE_R 3500, divided by the NE interior surface area A_NE 3480 is H _ ARE ∗ 2 ∗ NE _ R A _ NE = 0 2 1 0 Reference sign

[0147] 1000 anti-resonant hollow core fiber 2000Mantle or fiber mantle 2150Inside of the mantle 2170Mantle inner radius 2300 Fiber longitudinal axis 2310 Core radius R_Fiber 2320 Fiber core area A_Fiber 2990 district 3000 antiresonance unit, also known as ARE unit 3100ARE element 3110 first longitudinal axis of the body 3150ARE element wall 3170 first interior space of the ARE element 3180ARE interior surface 3190ARE interior height H_ARE 3200 first radius of circle R_ARE 3400NE element 3410 second longitudinal axis of the body 3450NE element wall 3470 second interior of the NE element 3480NE interior surface A_NE 3490NE interior height H_NE 3500 second radius of circle R_NE 3550 center angle MW_NE 3580 segment height SH_NE 3590 chord length 3700, 3700' connection seam 3705, 3705', 3705" connection height 3900DNE element of the antiresonant hollow core fiber 3950DNE element wall 3970third interior space of the DNE element 3980DNE inner surface A_DNE 4000, 4000'two focal points 4010longest cross-sectional axis AL 4020shortest cross-sectional axis AK 4080length of the longest cross-sectional axis AL 4090length of the shortest cross-sectional axis AK

Claims

1. An anti-resonant hollow-core fiber (1000), comprising a fiber cladding (2000) which comprises an inner bore (2200), a fiber longitudinal axis (2300) and a fiber core radius R_Faser (2310), a number of anti-resonance units (3000), each comprising • an ARE element (3100), • an NE element (3400), • a DNE element (3900), wherein the anti-resonance units (3000) are mutually spaced and are arranged so as to have no contact with one another at desired positions on an inner side (2150) of the inner bore (2200), wherein in the anti-resonance units (3000) • the ARE element (3100) has a circular cross section, • the NE element (3400) is arranged in a first interior (3170) of the ARE element (3100), and • the DNE element (3900) is arranged at least partially in a second interior (3470) of the NE element (3400), wherein in at least one anti-resonance unit (3000) • the NE element (3400) has a circular-arc-like cross section, characterized in that in the anti-resonance unit, the NE element is connected, along two connection seams (3700, 3700'), to the DNE element (3400), • the DNE element (3900) has an oval cross section, and • in cross section, a sum of the distances of any point on a DNE element wall (3950) from two focal points (4000,4000') is the same for all points to less than 15% of the sum of the distances.

2. The anti-resonant hollow-core fiber (1000) according to claim 1, characterized in that, in cross section, the sum of the distances of any point on the DNE element wall (3950) from two focal points (4000,4000') is the same for all points to less than 10%, in particular less than 5% of the sum of the distances.

3. The anti-resonant hollow-core fiber (1000) according to either of the preceding claims, characterized in that the DNE element (3900) comprises a longest cross-sectional axis AL (4010) and a shortest cross-sectional axis AK (4020) and, for a ratio of the longest cross-sectional axis AL (4010) to the shortest cross-sectional axis AK (4020), the following applies: AL AK = 1.1 4.0 4. The anti-resonant hollow-core fiber (1000) according to claim 3, characterized in that, for the ratio of the longest cross-sectional axis AL (4010) to the shortest cross-sectional axis AK (4020), the following applies: • it is greater than or equal to 1.15, in particular greater than or equal to 1.20, in particular greater than or equal to 1.25, in particular greater than or equal to 1.50; and • it is less than or equal to 3.80, in particular less than or equal to 3.60, in particular less than or equal to 3.50.

5. The anti-resonant hollow-core fiber (1000) according to any of the preceding claims, characterized in that, for a ratio of an NE interior height H_NE (3490), multiplied by a doubled NE circle radius NE_R (3500), divided by a fiber core surface area A_Faser (2320), the following applies: H _ NE ∗ 2 ∗ NE _ R A _ Faser = 0.35 0.7 6. The anti-resonant hollow-core fiber (1000) according to claim 5, characterized in that, for the ratio of the NE interior height H_NE (3490), multiplied by the doubled NE circle radius NE_R (3500), divided by the fiber core surface area A_Faser (2320), the following applies: • it is greater than or equal to 0.4, in particular greater than or equal to 0.50, in particular greater than or equal to 0.56; and • it is less than or equal to 0.65, in particular less than or equal to 0.62, in particular less than or equal to 0.6.

7. The anti-resonant hollow-core fiber (1000) according to any of the preceding claims, characterized in that, for a ratio of an ARE interior height H_ARE (3190) divided by a core radius R_Faser (2310), the following applies: H _ ARE R _ Faser = 0.85 1.25 8. The anti-resonant hollow-core fiber (1000) according to claim 7, characterized in that, for the ratio of the ARE interior height H_ARE (3190) divided by the core radius R_Faser (2310), the following applies: • it is greater than or equal to 0.9, in particular greater than or equal to 0.95, in particular greater than or equal to 1.0; and • it is less than or equal to 1.2, in particular less than or equal to 1.15, in particular less than or equal to 1.1.

9. The anti-resonant hollow-core fiber (1000) according to any of the preceding claims, characterized in that, for a ratio of the ARE interior height H_ARE (3190), multiplied by the doubled NE circle radius NE_R (3500), divided by an NE internal surface area A_NE (3480), the following applies: H _ ARE ∗ 2 ∗ NE _ R A _ NE = 0.2 1.0 10. The anti-resonant hollow-core fiber (1000) according to claim 9, characterized in that, for the ratio of the ARE interior height H_ARE (3190), multiplied by the doubled NE circle radius NE_R (3500), divided by the NE internal surface area A_NE (3480), the following applies: • it is greater than or equal to 0.25, in particular greater than or equal to 0.3; and • it is less than or equal to 0.95, in particular less than or equal to 0.8.

11. The anti-resonant hollow-core fiber (1000) according to any of the preceding claims, characterized in that the at least one anti-resonance unit (3000) comprises at least one of the following features: • a wall thickness of an ARE element wall (3150) of the ARE element (3100) and / or an NE element wall (3450) of the NE element (3400) and / or a DNE element wall (3950) of the DNE element (3900) is between 0.1 µm and 2.5 µm, in particular between 0.15 µm and 1.5 µm, in particular between 0.25 µm and 0.75 µm, in particular between 0.35 µm and 0.65 µm, in particular 0.5 µm, • a wall thickness of an ARE element wall (3150) of the ARE element (3100) and / or an NE element wall (3450) of the NE element (3400) and / or a DNE element wall (3950) of the DNE element (3900) is, at a signal wavelength of 1550 nm in the first transmission window, between 0.35 µm and 0.65 µm, in particular between 0.4 µm and 0.6 µm, in particular 0.5 µm, • a wall thickness of an ARE element wall (3150) of the ARE element (3100) and / or an NE element wall (3450) of the NE element (3400) and / or a DNE element wall (3950) of the DNE element (3900) is, at a signal wavelength of 1550 nm in the second transmission window, between 0.75 µm and 1.25 µm, in particular between 0.9 µm and 1.1 µm, in particular 1 µm.

12. The anti-resonant hollow-core fiber (1000) according to any of the preceding claims, characterized in that the core radius R_Faser (2310) comprises at least one of the following features: • it is less than or equal to 26 µm, in particular less than or equal to 23 µm, in particular less than or equal to 20 µm; and • it is greater than or equal to 10 µm, in particular greater than or equal to 12 µm, in particular greater than or equal to 14 µm.

13. The anti-resonant hollow-core fiber (1000) according to any of the preceding claims, characterized in that the ARE element (3100) comprises at least one of the following features: • a first circle radius R_ARE (3200) is less than or equal to 30 µm, in particular less than or equal to 25 µm, in particular less than or equal to 22.5 µm, in particular less than or equal to 16 µm; and • the first circle radius R_ARE (3200) is greater than or equal to 5 µm, in particular greater than or equal to 7 µm, in particular greater than or equal to 11.5 µm, in particular greater than or equal to 12.25 µm, in particular greater than or equal to 14.5 µm.

14. The anti-resonant hollow-core fiber (1000) according to any of the preceding claims, characterized in that the NE element (3400) comprises at least one of the following features: • a second circle radius R_NE (3500) is less than or equal to 25 µm, in particular less than or equal to 19 µm, in particular less than or equal to 17 µm, • the second circle radius R_NE (3500) is greater than or equal to 1.5 µm, in particular greater than 2.5 µm, in particular greater than or equal to 3.5 µm, • a center point angle MW_NE (3550) is less than 340°, in particular less than 330°, in particular less than 320°; and • the center point angle MW_NE (3550) is greater than 180°, in particular greater than 200°, in particular greater than 220°.

15. The anti-resonant hollow-core fiber (1000) according to any of the preceding claims 3 to 14, characterized in that the DNE element (3900) comprises at least one of the following features: • the longest cross-sectional axis AL (4010) is less than or equal to 20 µm, in particular less than or equal to 16.5 µm, in particular less than or equal to 14.6 µm; • the longest cross-sectional axis AL (4010) is greater than or equal to 4 µm, in particular greater than or equal to 6.5 µm, in particular greater than or equal to 8 µm; • the shortest cross-sectional axis AK (4020) is less than or equal to 12 µm, in particular less than or equal to 9.5 µm, in particular less than or equal to 8 µm; and • the shortest cross-sectional axis AK (4020) is greater than or equal to 1.5 µm, in particular greater than or equal to 2.5 µm, in particular greater than or equal to 4 µm.