Method for manufacturing preforms of antiresonant hollow optical fibers

Abstract

This invention relates to a method for manufacturing preforms of anti-resonant hollow optical fibers, the method comprising the following steps: a) providing a cladding tube having an inner bore and a longitudinal axis, the cladding tube wall extending along the longitudinal axis and defined by an inner side and an outer side; b) preparing a plurality of anti-resonant element preforms; c) arranging the anti-resonant element preforms on the inner side of the cladding tube wall; d) thermally fixing the anti-resonant element preforms to the cladding tube wall by means of a heat input; and e) introducing contact elements into at least one anti-resonant element preform in such a manner that the contact elements (in step d) increase the heat-absorbing mass of the anti-resonant element preforms to slow the heat flow from the cladding tube to the anti-resonant element preforms during the thermal fixing.

Description

Background Technology

[0001] This invention relates to a method for manufacturing preforms for anti-resonant hollow optical fibers.

[0002] Existing technology

[0003] Conventional single-mode optical fibers made of solid materials have a glass core region surrounded by a glass cladding region with a low refractive index. Light guidance is thus based on total internal reflection between the core and cladding regions. However, the interaction of guided light with the solid material is associated with increased delays during data transmission and a relatively low damage threshold (compared to high-energy radiation).

[0004] Hollow-core fiber avoids or reduces these drawbacks. In this case, the core comprises an evacuated cavity filled with gas or liquid. The interaction between light and glass in hollow-core fiber is less than that in solid-core fiber. The refractive index of the core is less than that of the cladding, making light guidance by total internal reflection impossible, and light typically escapes from the core into the cladding. Depending on the physical mechanism of light guidance, hollow-core fiber is classified into "photonic bandgap fiber" and "anti-resonant reflective fiber."

[0005] In the case of "photonic bandgap fiber," the hollow core region is surrounded by a cladding in which small hollow channels are periodically arranged. The periodic structure in the cladding causes an effect known in reference semiconductor technology as the "photonic bandgap," according to which light of a specific wavelength range scattered at the cladding structure undergoes constructive interference due to Bragg reflection in the central cavity and cannot propagate laterally within the cladding.

[0006] In an embodiment of hollow fiber known as “anti-resonant hollow fiber” (ARHCF), the hollow core region is surrounded by an inner cladding region in which so-called “anti-resonant elements” (or “anti-resonant elements”; abbreviated as “ARE”) are arranged. The walls surrounding the anti-resonant elements, which are uniformly distributed around the hollow core, can act as a Fabry-Perot cavity, which operates in anti-resonance and reflects and guides the incident light through the fiber core.

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

[0008] Potential applications of hollow-core optical fibers include: data transmission, high-performance beam guiding (e.g., for materials processing), modal filtering, and nonlinear optics (particularly for supercontinuum generation, from the ultraviolet to the infrared wavelength range).

[0009] One drawback of antiresonant hollow fiber is that higher-order modes are not necessarily suppressed, which means that they are usually not pure single-mode over long transmission lengths, and the quality of the output beam is degraded.

[0010] Francesco Poletti's paper, "Nested antiresonant nodeless hollow core fiber"; Optics Letters, Vol. 22, No. 20 (2014); DOI: 10.1364 / OE 22.023807, proposes a fiber design in which the antiresonant element is not formed as a simple single-structure element, but rather consists of several nested structural elements. The nested antiresonant elements are designed in such a way that higher-order core modes, rather than the fundamental core mode, are phase-fitted to the cladding mode and suppressed. Therefore, the propagation of the fundamental core mode is always ensured, and the hollow core fiber can be effectively made single-mode over a finite wavelength range.

[0011] Effective mode suppression is a function of the center wavelength of the transmitted light and the structural parameters of the fiber design (such as the radius of the hollow core and the diameter difference of the nested ring structure in the anti-resonant element).

[0012] An antiresonant hollow fiber (referred to herein as a "gapless hollow fiber") is known from EP 3136143 A1, in which the core can guide additional modes besides the fundamental mode. For this purpose, the core is surrounded by an inner cladding comprising "nonresonant elements" that provide phase adaptation between the antiresonant mode and the higher modes. The hollow fiber is manufactured using a so-called "stacked and drawn" technique, in which output elements are arranged to form an axially parallel monolith and fixed to form a preform, which is then drawn. This is achieved using a cladding tube comprising a hexagonal inner cross-section, and six so-called "ARE preforms" (antiresonant element preforms) are fixed within the inner edge of the cladding tube. This preform is drawn into a hollow fiber in two stages.

[0013] A method for manufacturing a preform of an antiresonant hollow optical fiber is known from WO 2018 / 169487 A1. In this method, a first cladding region comprises a plurality of rods, and a second cladding region comprises a plurality of tubes surrounded by an outer cladding tube. The rods, tubes, and cladding tubes are joined by means of a "stack and draw" technique to form the preform. Before the preform is elongated, the ends of the preform are sealed, which is done by applying a sealing compound. For example, a UV adhesive is used as the sealing compound.

[0014] Technical goals

[0015] Antiresonant hollow fibers, especially those including nested structural elements, have complex internal geometries, making their precise and reproducible fabrication more difficult. This is particularly true because small dimensional deviations in the magnitude of the operating wavelength of the light to be guided cannot be tolerated in order to follow the resonance or antiresonance conditions, respectively. Deviations from the target geometry can be caused by the configuration of the fiber preform, and they can also occur due to undesirable, disproportionate deformations during the fiber drawing process.

[0016] In the case of known "stacked and drawn" techniques, many components will be joined in a positionally precise manner. For example, in order to manufacture a known hollow fiber in the "NANF" design, six anti-resonant elements must be attached to the inner wall of the cladding tube, each consisting of a tube and a capillary welded to the inner tube wall on one side.

[0017] To achieve low attenuation and a wide transmission range, in addition to the uniform wall thickness of the anti-resonant element, the azimuth position of the anti-resonant element within the cladding tube is also crucial. This cannot be easily achieved using "stacking and pulling" techniques.

[0018] The purpose of this invention is to provide a method for cost-effectively manufacturing anti-resonant hollow optical fibers, which avoids the limitations of conventional manufacturing methods.

[0019] Another object of the present invention is to disclose a method for mass production of anti-resonant hollow optical fibers.

[0020] Specifically, the object of the present invention is to provide a method for manufacturing a preform of an anti-resonant hollow optical fiber, by means of which high precision of structural elements and accurate positioning of anti-resonant elements can be reproducibly obtained in a sufficiently stable and reproducible manner.

[0021] This avoids the drawbacks of the classic "stack and pull" technique, which cannot easily achieve the required structural accuracy, especially for precise positioning at a specified azimuth angle.

[0022] Preferred embodiments of the present invention

[0023] The features of the independent claim contribute to at least partially satisfying at least one of the foregoing objectives. The dependent claims provide preferred embodiments that contribute to at least partially satisfying at least one of these objectives.

[0024] / 1. / A method for manufacturing a preform of an anti-resonant hollow optical fiber, the method comprising the following steps:

[0025] a) Provide a cladding tube having an inner bore and a longitudinal axis, the cladding tube wall extending along the longitudinal axis and defined by an inner side and an outer side.

[0026] (b) Prepare multiple anti-resonant element preforms, each preform consisting of several nested tubular structural elements, each including an outer ARE tube and an inner ARE tube inserted therein, wherein each structural element has a longitudinal axis.

[0027] c) The anti-resonant element preform is arranged on the inner side of the cladding tube wall, and

[0028] d) The anti-resonant element preform is thermally fixed to the cladding tube wall by means of heat input, characterized in that the method comprises the following steps:

[0029] e) Introduce the contact elements into at least one anti-resonant element preform in such a manner that...

[0030] The contact element increases the heat-absorbing mass of the anti-resonant element preform in step d) in order to slow down the heat flow from the cladding tube to the anti-resonant element preform during the heat setting period.

[0031] / 2. / The method according to embodiment 1 is characterized in that step e) includes the following sequential steps:

[0032] / A-1. / Connect the contact element to the anti-resonant element preform.

[0033] / A-2. / Connect the anti-resonant element preform to the cladding tube.

[0034] / 3. / The method according to any one of the foregoing embodiments is characterized in that step e) comprises the following sequential steps:

[0035] / B-1. / to the thermal input of the assembly consisting of anti-resonant element preforms and contact elements,

[0036] / B-2. / The first connection between the contact element and the anti-resonant element preform is made by means of the first part of the heat input.

[0037] / B-3. / The second connection between the anti-resonant element preform and the cladding tube is made by means of the second part of the heat input.

[0038] / 4. / The method according to any one of the foregoing embodiments is characterized in that the contact element is designed in such a way that the following applies

[0039] C_cladding tube > C_contact element > C_anti-resonant element preform

[0040] in

[0041] • C_cladding tube is the average heat capacity of the solid material per unit volume of the cladding tube.

[0042] • C_Contact element is the average heat capacity of the contact element and the ambient air per unit volume.

[0043] •C_Anti-resonant element preform is the average heat capacity of the anti-resonant element preform and the ambient air per unit volume.

[0044] Furthermore, the unit volume is 25% larger than the volume of the contact element.

[0045] / 5. / The method according to any one of the foregoing embodiments is characterized in that the heat fixation in step d) is carried out by means of a flame-based process.

[0046] / 6. / The method according to any one of the foregoing embodiments is characterized in that the contact element is designed in a rod-like manner, specifically the contact element

[0047] It has lengths of [5; 50] mm, specifically [10; 40] mm, specifically [12; 30] mm, and...

[0048] It has a diameter of [0.5; 10] mm, specifically [0.7; 7] mm, specifically [1; 5] mm.

[0049] / 7. / The method according to any one of the foregoing embodiments is characterized in that the contact element is introduced into the outer tube of the at least one anti-resonant element preform of the ARE.

[0050] / 8. / The method according to any one of the foregoing embodiments is characterized in that the contact element is introduced into the inner tube of the at least one anti-resonant element preform of the ARE.

[0051] / 9. / The method according to any one of the foregoing embodiments is characterized in that the arrangement of the anti-resonant element preform on the inner side of the cladding tube bore includes the arrangement of the anti-resonant element preform at a target position on the inner side of the cladding tube wall, wherein the arrangement of the anti-resonant element preform is carried out by means of a positioning template, which is inserted into the cladding tube bore and has a holding element for positioning the anti-resonant element preform at the target position.

[0052] / 10. / The method according to any one of the foregoing embodiments is characterized in that the inner hole of the cladding tube is produced by means of machining, specifically by means of drilling, milling, grinding, honing and / or polishing.

[0053] / 11. / The method according to any one of the foregoing embodiments is characterized in that the cladding tube has an outer diameter in the range of 65 nm to 300 mm, specifically in the range of 90 nm to 250 mm, and specifically has a length of at least 1 m.

[0054] / 12. / The method according to any one of the foregoing embodiments is characterized in that the method comprises the following steps:

[0055] • A cladding tube closure is created by at least partial closure of the front end of the cladding tube bore.

[0056] / 13. / A method for manufacturing a secondary preform from a preform manufactured according to any one of claims 1 to 12, wherein hollow optical fibers can be drawn from the secondary preform, the method comprising the following steps:

[0057] • Further process the preform into the secondary preform.

[0058] This further processing includes one or more of the following thermoforming processes being performed once or repeatedly:

[0059] i.) elongate,

[0060] ii.) collapse,

[0061] iii.) Collapse and elongation simultaneously

[0062] iv.) Add additional cladding material,

[0063] v.) Add additional cladding material and then stretch it.

[0064] vi.) Add additional cladding material and stretch it at the same time.

[0065] / 14. / A method for manufacturing anti-resonant hollow optical fiber from a preform manufactured according to any one of the foregoing embodiments 1 to 12, the method comprising the following steps:

[0066] • The preform is further processed into the anti-resonant hollow fiber, wherein the further processing includes one or more of the following thermoforming processes being performed once or repeatedly:

[0067] i.) elongate,

[0068] ii.) collapse,

[0069] iii.) Collapse and elongation simultaneously

[0070] iv.) Add additional cladding material,

[0071] v.) Add additional cladding material and then stretch it.

[0072] vi.) Add additional cladding material and stretch it at the same time.

[0073] / 15. / The method according to any one of the foregoing embodiments 13 or 14 is characterized in that the elongation period in the core region is set at a relative internal pressure in the range of 0.05 mbar to 20 mbar.

[0074] / 16. / The method according to any one of the foregoing embodiments is characterized in that the method has at least one of the following points:

[0075] The contact element is between 40mm and 60mm in length, specifically 50mm.

[0076] The radius of the contact element is between 0.25 mm and 5 mm, specifically between 0.35 mm and 3.5 mm, specifically between 0.8 mm and 1.5 mm, and specifically between 1 mm and 1.1 mm.

[0077] • The outer surface of this contact element is 2.8 mm. 2 and 4.5mm 2 Between, specifically 3.80mm 2 ,

[0078] The mass of the cladding tube per unit volume is between 0.49g and 0.55g, specifically between 0.50g and 0.54g, and specifically 0.52g.

[0079] The mass of the contact element and the ambient air per unit volume is between 0.34g and 0.48g, specifically between 0.40g and 0.44g, and more specifically 0.42g.

[0080] The mass of the anti-resonant element preform and the ambient air per unit volume is between 0.14g and 0.26g, specifically between 0.17g and 0.23g, and specifically 0.2g.

[0081] • Average heat capacity C_contact element = [68%; 92%]C_cladding tube and C_anti-resonant element preform = [21%; 51%]C_cladding tube, specifically C_contact element = [72%; 88%]C_cladding tube and C_anti-resonant element preform = [24%; 47%]C_cladding tube, specifically C_contact element = [76%; 85%]C_cladding tube and C_anti-resonant element preform = [28%; 44%]C_cladding tube.

[0082] • The C-clad tube temperature range is less than 0.70 J / (K), specifically less than 0.67 J / (K), specifically less than 0.62 J / (K), and specifically less than 0.59 J / (K) within the temperature range [200℃; 450℃].

[0083] • Within the temperature range [200℃; 450℃], the C-clad tube exhibits a flux density greater than 0.35 J / (K), specifically greater than 0.42 J / (K), specifically greater than 0.47 J / (K), and specifically greater than 0.51 J / (K).

[0084] • Within the temperature range [200℃; 450℃], the C-contact element transistor has a capacitance of less than 0.55 J / (K), specifically less than 0.51 J / (K), specifically less than 0.48 J / (K), and specifically less than 0.46 J / (K).

[0085] • Within the temperature range [200℃; 450℃], the C-contact element is greater than 0.31 J / (K), specifically greater than 0.33 J / (K), specifically greater than 0.39 J / (K), specifically greater than 0.41 J / (K).

[0086] • The C-type anti-resonant element preform has a power consumption of less than 0.3 J / (K), specifically less than 0.27 J / (K), specifically less than 0.23 J / (K), and specifically less than 0.21 J / (K) within the temperature range [200℃; 450℃].

[0087] • The C-type anti-resonant element preform within the temperature range [200℃; 450℃] exhibits a power density greater than 0.11 J / (K), specifically greater than 0.13 J / (K), specifically greater than 0.14 J / (K), and specifically greater than 0.17 J / (K).

[0088] Specifically, the heat capacity of quartz glass is 1052 [J / kg K], the heat capacity of air is 1005 [J / kg K], and the density of quartz glass is 0.0022 [g / mm³]. 3 (or 2.2 g / cm³ respectively) 3 The density of air is 0.0000012 g / mm³. 3 (or 1.2 kg / m)3 (Measured under normal conditions).

[0089] In this specification, the range specification also includes values ​​referred to as limits. The specification of the type of variable A as "within the range of X to Y" means that A can take the values ​​of X, Y, and values ​​between X and Y. Therefore, the range of variable A's type limited on one side as "up to Y" thus means Y and values ​​less than Y.

[0090] Some of the characteristics described relate to the term "substantially". The term "substantially" should be understood in such a way that, under actual conditions and manufacturing techniques, the precise mathematical interpretation of terms such as "overlap," "perpendicular," "diameter," or "parallelism" may never be provided precisely, but can only be applied within certain manufacturing-related error tolerances. For example, "substantially parallel axes" refers to angles between each other from -5 degrees to 5 degrees, and "substantially equal volumes" includes deviations of up to 5% by volume. "A device substantially composed of quartz glass" includes, for example... > 95% to ≤100% by weight of quartz glass portion. In addition, "substantially right angle" includes angles of 85 to 95 degrees. Detailed Implementation

[0091] This invention relates to a method for manufacturing a preform for anti-resonant hollow optical fiber. As part of step a), a cladding tube is provided having an inner cladding tube bore and a longitudinal axis of the cladding tube, the cladding tube wall extending along the longitudinal axis of the cladding tube being defined by an inner side and an outer side.

[0092] Step b) includes preparing a plurality of anti-resonant element preforms, each preform consisting of a plurality of nested tubular structural elements, each including an outer ARE tube and an inner ARE tube inserted therein, wherein each structural element has a longitudinal axis. Step c) includes arranging the anti-resonant element preform on the inner side of the cladding tube wall. Step d) includes thermally fixing the anti-resonant element preform to the cladding tube wall by means of a heat input.

[0093] A solution to this objective is obtained, wherein the method includes introducing contact elements into at least one anti-resonant element preform in step e) in such a manner that the contact elements increase the heat-absorbing mass of the anti-resonant element preform in step d) so as to slow down the heat flow from the cladding tube to the anti-resonant element preform during the heat setting.

[0094] Anti-resonant elements can be simple or nested structural elements of hollow optical fibers. They have at least two walls that, when viewed from the hollow direction, have negative curvature (convex) or no curvature (flat, straight). They are typically composed of materials transparent to the working light (e.g., glass, especially doped or undoped silica glass (SiO2), plastics, especially polymers, composites, or crystalline materials).

[0095] A component or constituent part of a preform is called an anti-resonant element preform, which is essentially transformed into an anti-resonant element in a hollow fiber by simple elongation during the fiber drawing process. The anti-resonant element preform can be a simple or nested component, to which positioning aids can be additionally fixed. The anti-resonant element preform has at least two walls that, when viewed from the hollow direction, have negative curvature (convex) or no curvature (flat, straight). Through further processing of the preform, particularly by means of a thermoforming step, intermediate products can be produced, in which the initial anti-resonant element preform exists with a shape altered compared to its initial shape.

[0096] The preform is a component from which antiresonant hollow optical fiber can be drawn. Alternatively, the preform can be further processed into a secondary preform from which hollow optical fiber can be drawn. This further processing may include one or repeated thermoforming processes (e.g., elongation, collapse, or addition of additional cladding material).

[0097] During the heat-setting of at least one anti-resonant element preform, heat is applied from the outside onto the cladding wall. This heat application can be performed using a torch (such as, for example, a hydrogen torch). The purpose of heat-setting in step d) is to achieve material-to-material bonding between the anti-resonant element preform and the cladding wall. The introduced heat application must therefore make material-to-material bonding between the materials of the two elements possible. This effect is achieved when the cladding wall and the anti-resonant element preform change at least partially from a solid to a liquid state (particularly a viscous state). It is therefore disadvantageous that the heat application necessary for heat-setting can lead to the destruction of at least one anti-resonant element preform.

[0098] The anti-resonant element preform is composed of a tubular structural element, at least a portion of which has a wall thickness in the range of 0.1 mm to 2 mm, preferably 0.2 mm to 1.5 mm. The heat input required to partially and / or completely melt the anti-resonant element preform is less than the heat input required to change the state of the cladding tube in a manner that makes it possible to fix the anti-resonant element preform. Heat introduced from the outside onto the cladding tube can specifically cause an increase in temperature within the cladding tube bore, such an increase being so rapid that thermal deformation and / or thermal failure of at least one anti-resonant element preform occurs. To prevent this and thus ensure precise positioning of the anti-resonant element preform within the preform, the present invention discloses the use of contact elements that increase the heat-absorbing mass of the anti-resonant element preform. The contact elements can slow the temperature rise during heat setting.

[0099] This concept is also suitable for reproducible and precise manufacturing methods of antiresonant hollow optical fibers on an industrial scale. It is particularly suitable for the precise manufacturing of antiresonant hollow optical fibers including nested antiresonant elements with substantially different inner diameters from each other.

[0100] The accuracy of positioning at least one anti-resonant element preform in the cladding tube is improved because a tubular structural element is provided, at least a portion of which has a wall thickness in the range of 0.2 mm to 2 mm, preferably in the range of 0.25 mm to 1 mm, and wherein a cladding tube with an outer diameter in the range of 65 mm to 300 mm, preferably in the range of 90 mm to 250 mm, preferably in the range of 120 mm to 200 mm is provided. These components can thus each specifically have a length of at least 1 m.

[0101] One embodiment of the method is characterized in that step e) includes the following sequential steps:

[0102] / A-1. / Connect the contact element to the anti-resonant element preform.

[0103] / A-2. / Connect the anti-resonant element preform to the cladding tube.

[0104] As part of this method, the connection between the contact element and the anti-resonant element preform is first performed. Heat flow through the cladding tube wall heats both the anti-resonant element preform and the contact element, forming a material-to-material bond. Subsequently, the system of the anti-resonant element preform and contact element is bonded to the cladding tube (specifically, a material-to-material bond). This sequence of steps ensures an increase in the heat-absorbing mass of the anti-resonant element preform when it is thermally fixed at the cladding tube bore.

[0105] One embodiment of the method is characterized in that step e) includes the following sequential steps:

[0106] / B-1. / to the thermal input of the assembly consisting of anti-resonant element preforms and contact elements,

[0107] / B-2. / The first connection between the contact element and the anti-resonant element preform is made by means of the first part of the heat input.

[0108] / B-3. / The second connection between the anti-resonant element preform and the cladding tube is made by means of the second part of the heat input.

[0109] In an embodiment of this method, the components of the preform are sequentially connected. As part of the first connection, a material-to-material bond is formed between the contact element and at least one anti-resonant element preform. This bond is generated by means of a first portion of thermal input.

[0110] As part of the heat fixation in step d), heat input to the cladding tube is specifically performed by means of a torch. In an alternative embodiment, heat input to the cladding tube wall is performed from the outside, specifically at approximately right angles to the cladding tube wall. Heat thus flows through the tube wall and impacts the contact elements at the cladding tube bore and at least one anti-resonant element preform. In another alternative embodiment, heat input is performed on the front surface of the cladding tube near the anti-resonant element preform. This heat input can be specifically performed by means of a focused flame. Heat thus flows through the front surface of the cladding tube and enters the tube wall there. Heat escape occurs particularly at the cladding tube bore. There, the heat then acts on the contact elements and at least one anti-resonant element preform.

[0111] In an alternative embodiment, the heat-fixing in step d) is performed using a wire-like connecting element made of glass (specifically quartz glass). As part of the heat-fixing in step d), this connecting element (also called a welding wire or welding additive) is heated by means of a heat flow. Due to the localized low mass of the connecting element, it can be slightly and / or completely melted, and thus acts as a type of adhesive that facilitates material-to-material bonding between the cladding tube bore to be joined and the elements of the anti-resonant element preform.

[0112] In both embodiments, the first portion of the heat input heats the contact element and the anti-resonant element preform in such a way that a first material-to-material bond is formed. This material-to-material bond causes an increase in the heat-absorbing mass of the anti-resonant element preform in that region, wherein the temperature increase is achieved by means of the heat input as part of step d).

[0113] By increasing the heat-absorbing mass, the rate of temperature increase and / or maximum achievable temperature of the anti-resonant element preform decreases with constant heat input. This also reduces the risk of thermal damage and / or thermal changes to the anti-resonant element preform. In subsequent step / B-3 / , the cladding tube (specifically, the cladding tube bore) is heated by a second portion of the heat input in such a way that a material-to-material bond is achieved between the cladding tube and the anti-resonant element preform. This second bond is the practical objective of the method according to the invention. By using the contact element according to the invention, it is ensured that the temperature on the cladding tube bore and the temperature on the anti-resonant element preform with the contact element are not significantly different. The temperature difference in the localized region of heat input between the cladding tube bore and the anti-resonant element preform is preferably less than 300°C, specifically less than 200°C, and specifically less than 50°C.

[0114] When designing contact elements, two opposing aspects should be considered:

[0115] • If the contact element is designed to be too large, as part of step e), it absorbs too much heat and thus prevents rapid material-to-material bonding between the anti-resonant element preform and the cladding wall. Consequently, the heat source may act on the cladding wall for too long and damage it. Damage may thus result primarily in the complete melting of portions of the cladding wall or in deformation of the cladding wall caused by flame pressure. Alternatively or additionally, in the case of a contact element that is selected to be too large, there is a risk that the anti-resonant preform may close during heat setting. During further processing, pressure may therefore accumulate in the anti-resonant preform, leading to undesirable deformation and / or expansion of the anti-resonant preform.

[0116] If the contact element is designed to be too small, it cannot achieve the goal of sufficiently increasing the heat absorption mass of the anti-resonant element preform according to the invention. Therefore, precise positioning of the anti-resonant element preform will not be possible, or in the worst case, even destruction of the anti-resonant element preform may occur.

[0117] One embodiment of this method is characterized in that the contact element is designed in such a way that the following applies

[0118] C_cladding tube > C_contact element > C_anti-resonant element preform

[0119] in

[0120] • C_cladding tube is the average heat capacity of the solid material per unit volume of the cladding tube.

[0121] • C_Contact element is the average heat capacity of the contact element and the ambient air per unit volume.

[0122] •C_Anti-resonant element preform is the average heat capacity of the anti-resonant element preform and the ambient air per unit volume.

[0123] Furthermore, the unit volume is 25% larger than the volume of the contact element.

[0124] The specific heat capacity (C) of a substance characterizes its mass-based heat capacity. The specific heat capacity of a substance in a specific state is the heat supplied to or removed from a given quantity of the substance divided by the corresponding temperature increase or decrease and the mass of the substance.

[0125]

[0126] thus

[0127] ΔQ is the heat supplied to or removed from a substance.

[0128] ·m is the mass of the substance.

[0129] ΔT = T2 - T1 is the difference between the final temperature and the initial temperature.

[0130] In the case of a homogeneous object, the heat capacity can be calculated as the product of the object's specific heat capacity C and its mass m.

[0131] Unit volume refers to a volume V_unit volume that is 25% larger than the volume V_contact element. Therefore:

[0132] V_unit volume = V_contact element + 25% volume % * V_contact element

[0133] Average heat capacity identifies the arithmetic mean of the specific heat capacity of a material per unit volume.

[0134] C_cladding tube therefore identifies the average heat capacity of the solid material of the cladding tube per unit volume. Therefore, the average heat capacity C_cladding tube is the same as the specific heat capacity of the solid material of the cladding tube.

[0135] Furthermore, the C_contact element identifies the average heat capacity of the contact element and the ambient air per unit volume. Therefore, the specific heat capacity of the contact element accounts for 75% of the average heat capacity C_contact element, and the heat capacity of the ambient air accounts for 25% of the average heat capacity C_contact element.

[0136] The average heat capacity C_of the anti-resonant element preform is calculated based on the average heat capacity per unit volume of the anti-resonant element preform and ambient air. In this calculation, contact elements are not considered. Therefore, the average heat capacity of the anti-resonant element preform is obtained over the non-contact portion of the anti-resonant element preform and ambient air.

[0137] Since the anti-resonant element preform can be a tubular structural element (preferably made of or composed of quartz glass) with a wall thickness in the range of 0.2 mm to 2 mm, the embodiment is characterized by:

[0138] C_anti-resonant element preform = [15%; 55%]C_cladding tube.

[0139] The implementation scheme is characterized in that the average heat capacities per unit volume of the components (cladding tube, contact element, anti-resonant element preform) that are thermally fixed as part of step f are adapted to each other. By means of the corresponding design and adaptation of the average heat capacities, material-to-material bonding between the anti-resonant element preform and the cladding tube wall is ensured with high precision. Three average heat capacities...

[0140] • C_Contact element = [68%; 92%]C_cladding tube

[0141] • C_anti-resonant element preform = [21%; 51%]C_cladding tube

[0142] The gradation balances two effects, which will be described below and are opposite to each other.

[0143] Specifically, according to

[0144] • C_Contact element = [72%; 88%%]C_cladding tube

[0145] • C_anti-resonant element preform = [24%; 47%]C_cladding tube

[0146] The three average heat capacities are graded to balance two effects, which will be described below and are opposite to each other. Specifically, according to

[0147] • C_Contact element = [76%; 85%]C_cladding tube

[0148] • C_anti-resonant element preform = [28%; 44%]C_cladding tube

[0149] The three average heat capacities are graded to balance two effects, which will be described below and are opposite to each other.

[0150] The implementation scheme is characterized in that the C-cladding tube has a strength of less than 0.70 J / (K), specifically less than 0.67 J / (K), specifically less than 0.62 J / (K), and specifically less than 0.59 J / (K) within the temperature range [200℃; 450℃].

[0151] The implementation scheme is characterized in that the C-clad tube has a capacitance greater than 0.35 J / (K), specifically greater than 0.42 J / (K), specifically greater than 0.47 J / (K), and specifically greater than 0.51 J / (K) within the temperature range [200℃; 450℃].

[0152] The implementation scheme is characterized in that the C_ contact element is less than 0.55 J / (K), specifically less than 0.51 J / (K), specifically less than 0.48 J / (K), and specifically less than 0.46 J / (K) within the temperature range [200℃; 450℃].

[0153] The implementation scheme is characterized in that the C_contact element is greater than 0.31 J / (K), specifically greater than 0.33 J / (K), specifically greater than 0.39 J / (K), and specifically greater than 0.41 J / (K) within the temperature range [200℃; 450℃].

[0154] The implementation scheme is characterized in that the C-anti-resonant element preform has a power consumption of less than 0.3 J / (K), specifically less than 0.27 J / (K), specifically less than 0.23 J / (K), and specifically less than 0.21 J / (K) within the temperature range [200℃; 450℃].

[0155] The implementation scheme is characterized in that the C-anti-resonant element preform has a power greater than 0.11 J / (K), specifically greater than 0.13 J / (K), specifically greater than 0.14 J / (K), and specifically greater than 0.17 J / (K) within the temperature range [200℃; 450℃].

[0156] The implementation scheme is characterized in that the method has at least one of the following:

[0157] The contact element is between 40mm and 60mm in length, specifically 50mm.

[0158] The radius of the contact element is between 0.25 mm and 5 mm, specifically between 0.35 mm and 3.5 mm, specifically between 0.8 mm and 1.5 mm, and specifically between 1 mm and 1.1 mm.

[0159] • The outer surface of this contact element is 2.8 mm. 2 and 4.5mm 2 Between, specifically 3.80mm 2 ,

[0160] The mass of the cladding tube per unit volume is between 0.49g and 0.55g, specifically between 0.50g and 0.54g, and specifically 0.52g.

[0161] The mass of the contact element and the ambient air per unit volume is between 0.34g and 0.48g, specifically between 0.40g and 0.44g, and more specifically 0.42g.

[0162] The mass of the anti-resonant element preform and the ambient air per unit volume is between 0.14g and 0.26g, specifically between 0.17g and 0.23g, specifically 0.2g.

[0163] One implementation of this method is characterized in that the contact element is designed in a rod-like manner.

[0164] One embodiment of the method is characterized in that the contact element has a material (e.g., glass, specifically doped or undoped silica glass (SiO2)) that is transparent to the working light of the optical fiber. Furthermore, only a portion of the contact element may have silica glass, and / or the contact element may be composed of doped or undoped silica glass.

[0165] The implementation scheme is characterized in that the heat fixation in step e) is carried out by means of a flame-based process. In the case of a flame-based process (such as flame hydrolysis), hydrogen (also known as "H2") is preferably used as the combustion gas. It reacts with oxygen (also known as "O2") in the air. This exothermic reaction produces the energy required in step e).

[0166] One embodiment is characterized in that the contact element has a length of less than 15 cm, specifically less than 10 cm, specifically less than 8 cm, specifically less than 5 cm. In another embodiment, the contact element has a length greater than 0.5 cm, specifically greater than 1 cm, specifically greater than 1 cm. Another embodiment is characterized in that the contact element is designed in a rod-like manner, specifically having a length of [5; 50] mm, specifically [10; 40] mm, specifically [12; 30] mm, and a diameter of [0.5; 10] mm, specifically [0.7; 7] mm, specifically [1; 5] mm. The contact element is preferably designed in a cylindrical manner. In another embodiment, the contact element is designed to be made of the same or substantially the same material as the anti-resonant element preform and / or the cladding tube.

[0167] Two opposing requirements can be imposed on the size and geometry of the contact element. In one embodiment, the contact element is designed such that, due to the action of the contact element, the areas to be joined in the anti-resonant element preform and the areas to be joined in the cladding tube reach substantially the same temperature or substantially the same state of aggregation at substantially the same point in time. This allows for particularly high precision during joining. This embodiment results in a longer and heavier contact element.

[0168] In another embodiment, the contact element is designed to be as small as possible so that the area of ​​the preform that must receive the contact element is geometrically as small as possible. If, as part of step e), the contact element is also formed material-to-material bonded to the anti-resonant element preform, the contact element remains within the completed preform. If it is drawn into an anti-resonant hollow fiber, the contact element may cause blockage of the ARE outer tube and / or ARE inner tube in at least some areas. This area, which cannot be drawn into a usable anti-resonant hollow fiber, should be kept as small as possible.

[0169] Therefore, there are two opposing requirements for the dimensions of the contact elements. The geometry specified above optimally combines these two requirements and thus provides high precision for the structural elements and accurate positioning of the anti-resonant elements during stabilization.

[0170] The embodiment is characterized in that the contact element is introduced into the outer ARE tube of the at least one anti-resonant element preform. In this case, the contact element is arranged inside the outer ARE tube close to the inner ARE tube. To ensure compliance with the purpose of the invention, the contact element can be designed in a crescent shape and thus at least partially surround the inner ARE tube. Alternatively, a cylindrical design of the contact element is also possible.

[0171] The embodiment is characterized in that the contact element is introduced into the ARE inner tube of the at least one anti-resonant element preform. The advantage of this embodiment is that the contact element can be easily inserted into the ARE inner tube, which simplifies the manufacturing process. Furthermore, the contact element may have an outer diameter smaller than the inner diameter of the ARE inner tube. Advantageously, the outer diameter of the contact element is at most 95%, specifically 93%, specifically 90% of the inner diameter of the ARE inner tube. Advantageously, the outer diameter of the contact element is at least 30%, specifically 35%, specifically 40% of the inner diameter of the ARE inner tube. In one embodiment, the ARE inner tube and the contact element are made of the same material or substantially the same material. The advantage of this embodiment is that, as part of step e), contamination of the ARE inner tube does not occur by means of the contact element.

[0172] The embodiment is characterized in that the arrangement of the anti-resonant element preform on the inner side of the cladding tube bore includes its arrangement at a target position on the inner side of the cladding tube wall. This arrangement is achieved by means of a positioning template, which is inserted into the cladding tube bore and has retaining elements for positioning the anti-resonant element preform at the target position. The positioning template, for example, has a shaft protruding into the cladding tube bore and is provided with retaining elements radially outward in the form of several retaining arms. A structurally specific star-shaped arrangement of the retaining elements facilitates precise positioning and fixation of the anti-resonant element preform at the corresponding target position.

[0173] The retaining element may be in non-positive and / or positive contact with the ARE anti-resonant element preform. In one embodiment, the retaining element partially has an external shape that at least partially reflects the external shape of the anti-resonant element preform. In one embodiment, the retaining element of the positioning template may be graphite, specifically composed of graphite. In one embodiment, the positioning template may be composed of graphite.

[0174] The implementation scheme is characterized by using machining, specifically drilling, milling, grinding, honing, and / or polishing, to produce the inner bore of the cladding tube. Compared to other known forming techniques, these machining techniques provide more precise and refined structures by using heat and pressure, and avoid surface contamination caused by forming tools.

[0175] The accuracy of positioning the preform within the cladding tube is improved because a tubular structural element is provided, at least a portion of which has a wall thickness ranging from 0.2 mm to 2 mm, preferably from 0.25 mm to 1 mm, and wherein a cladding tube with an outer diameter ranging from 65 mm to 300 mm, preferably from 90 mm to 250 mm, and preferably from 120 mm to 200 mm is provided. Furthermore, these components can thus have a length of at least 1 m in each case.

[0176] These are relatively large structural elements used to form anti-resonant elements. This simplifies the handling. In the case of a vertical arrangement of the cladding tube and structural elements, gravity additionally supports the parallelism and vertical alignment of the longitudinal axis of the structural elements when the structural elements are positioned at the target location on their upper front end in each case.

[0177] The implementation scheme is characterized by the anti-resonant elements being arranged around the hollow core with odd-numbered symmetry.

[0178] The implementation scheme is characterized by the following steps:

[0179] • A cladding tube closure is created by at least partial closure of the front end of the cladding tube bore.

[0180] As part of the method steps, at least one of the front ends of the anti-resonant element preforms is partially closed to create a cladding tube closure. The preform according to the invention is characterized by a large outer diameter. Since the absolute geometric errors are more significantly reduced during fiber drawing with increasing preform outer diameter, it generally makes more precise fabrication of hollow fibers possible. However, it has been shown that any increase in the preform outer diameter does not automatically lead to more precise hollow fibers, but rather helps maintain a maximum relative geometric error of 3.5% in the wall thickness of the hollow fiber. All anti-resonant element preforms, or at least a portion thereof, form hollow tubes and are typically open on both sides. The free inner diameter of the hollow tube is small and typically in the range of a few millimeters within the preform. During the thermoforming process, the preform is heated from the outside, resulting in a radial temperature gradient within the preform volume. Under otherwise identical process conditions, the greater the temperature difference and thus the resulting viscosity difference, the thicker the preform. There is a risk that the hollow tube will shrink due to surface tension and varying degrees of shrinkage depending on local temperature. The higher the radial temperature gradient and the thicker the preform, the greater this risk. In contrast, the temperature gradient has no significant effect on the central hollow core. To address this effect in the case of a relatively thick preform according to the invention, the core region (hollow core) remains open in a vertical orientation along the longitudinal axis during the fiber drawing process, and in the case of at least a portion of the anti-resonant element preform, the upper end of the opening is at least partially closed by means of a cladding tube closure.

[0181] The above objective is also achieved by a method for manufacturing a secondary preform from a preform manufactured according to any of the foregoing embodiments, from which hollow optical fibers can be drawn, the method comprising the following steps:

[0182] • Further process the preform into the secondary preform.

[0183] This further processing includes one or more of the following thermoforming processes being performed once or repeatedly:

[0184] i.) elongate,

[0185] ii.) collapse,

[0186] iii.) Collapse and elongation simultaneously

[0187] iv.) Add additional cladding material,

[0188] v.) Add additional cladding material and then stretch it.

[0189] vi.) Add additional cladding material and stretch it at the same time.

[0190] The preform is the starting point for the manufacture of anti-resonant hollow optical fiber. In the method according to the invention, the preform is further processed into a secondary preform by performing one or more thermoforming processes.

[0191] During elongation, the preform is stretched. Elongation can occur without simultaneous collapse. Elongation can be scaled up so that the shape and arrangement of components or constituent parts of the nascent preform are reflected in the stretched final product. However, the nascent preform can also be drawn non-scaled during elongation, and its geometry can be altered. During collapse, the bore narrows, or the annular gaps between tubular components close or narrow. Collapse is typically associated with elongation. Secondary preforms manufactured in this manner may have been designed and are suitable for drawing hollow optical fibers. The secondary preform may optionally be further processed, such as elongating it or adding additional cladding material.

[0192] The above objective is also achieved by a method for manufacturing anti-resonant hollow optical fiber from a preform manufactured according to any of the foregoing embodiments, the method comprising the following steps:

[0193] • The preform is further processed into the anti-resonant hollow fiber, wherein the further processing includes one or more of the following thermoforming processes being performed once or repeatedly:

[0194] i.) elongate,

[0195] ii.) collapse,

[0196] iii.) Collapse and elongation simultaneously

[0197] iv.) Add additional cladding material,

[0198] v.) Add additional cladding material and then stretch it.

[0199] vi.) Add additional cladding material and stretch it at the same time.

[0200] The preform is the starting point for the manufacture of antiresonant hollow fiber. The antiresonant hollow fiber is produced by means of a thermal process (specifically by elongating the preform).

[0201] During stretching, the preform is elongated. Stretching can be done proportionally, such that the shape and arrangement of components or constituent parts of the nascent preform are reflected in the stretched final product. However, the nascent preform can also be stretched disproportionately during stretching, and its geometry can be altered. During collapse, the bore narrows, or the annular gaps between tubular components close or narrow.

[0202] To draw and produce anti-resonant hollow optical fibers from the preform, the preform is guided vertically through a furnace. The lower end of the preform is heated to a drawing temperature, from which the anti-resonant hollow optical fiber is drawn in a tapered shape. The drawn fiber is then cooled from the drawing temperature by means of an airflow directed in the opposite direction to the drawing direction.

[0203] In one embodiment, the antiresonant hollow fiber is coated with an adhesion promoter, wherein this step is performed during the drawing process during glass fiber manufacturing, and the antiresonant hollow fiber is subsequently coated with plastic in a second follow-up step. This second step can be performed to decouple it from the drawing process of glass fiber manufacturing in terms of time. The plastic used for the coating can be one or more of the following substances: polyurethane acrylate, acrylate, polyolefin, polyamide (nylon), polyether, polyurethane methacrylate, fluoroalkyl methacrylate, or polyimide.

[0204] The preform comprises a cladding tube and an anti-resonant element preform disposed therein, as well as an additional cladding material, which is provided, for example, in the form of a covering cylinder or several covering cylinders, and which collapses onto the preform. Doping provides adaptation of the coefficient of thermal expansion of adjacent preform components to avoid or reduce stress. Fluorine, chlorine, and / or hydroxyl groups are preferably used as dopants, which reduce the viscosity of the quartz glass. Doping can also be used to reduce the thermal stability of the components, thereby benefiting the stability of adjacent components.

[0205] The implementation scheme is characterized by setting a relative internal pressure (negative pressure compared to ambient atmospheric pressure) in the core region during the elongation of the individual component parts into the finished preform. This pressure window ensures that the OD / ID ratio (the ratio of the outer diameter to the inner diameter of the cladding tube) does not become too small as part of the elongation process.

[0206] The implementation scheme is characterized by setting a relative internal pressure (positive pressure compared to ambient atmospheric pressure) in the core region within the range of 0.05 mbar to 20 mbar during the elongation of the preform into an antiresonant hollow fiber. At relative internal pressures less than 0.05 mbar, excessive expansion of the antiresonant element preform may occur. Conversely, a relative internal pressure greater than 20 mbar in the core region may result in insufficient gas pressure within the hollow channels of the antiresonant element preform, allowing them to widen sufficiently during thermoforming.

[0207] The temperature of the heating zone during the thermoforming process should be kept as constant as possible. Advantageously, a temperature-controlled heating element is therefore used during the thermoforming process, with the target temperature precisely maintained at + / -0.1°C. Thus, temperature fluctuations during the thermoforming process can be limited to less than + / -0.5°C.

[0208] In one embodiment, the provision according to step a) includes the arrangement of an anti-resonant element preform at a target location on the inner bore of the cladding tube, wherein the arrangement of the anti-resonant element preform includes fixation and / or sealing measures using a sealing or bonding compound containing amorphous SiO2 particles. The sealing or bonding compound used for sealing or fixation contains SiO2 particles, specifically at least 60% by weight, which are, for example, contained in a dispersion liquid. The compound is applied between the surfaces to be joined or sealed, and is typically in a paste form upon use. During drying at a low temperature, the dispersion liquid is partially or completely removed, and the compound is cured. The sealing or bonding compound (and specifically, the cured SiO2-containing sealing or bonding compound obtained after drying) satisfies the requirements for fixation and sealing. The low temperature of below 300°C required for this purpose promotes the maintenance of dimensional stability of the preform and avoids negative thermal effects.

[0209] Sealing or bonding compounds are also suitable for forming opaque or transparent glass by heating them to higher temperatures, for example, during the stretching of a preform into a hollow optical fiber. This is achieved by means of sintering or glazing, where sintering into opaque glass requires relatively lower temperatures and / or shorter heating periods than glazing is used to achieve complete transparency. Thus, during the thermoforming process, sealing or bonding compounds can be compacted by means of heating and can be glazed by means of heating.

[0210] During the thermoforming process, the sealing or bonding compound does not decompose and releases very few contaminants. Therefore, it is characterized by thermal stability and purity during the thermoforming process, and it avoids deformation due to different coefficients of thermal expansion.

[0211] The features disclosed in the specification may be important for various designs of the claimed invention (individually and in any combination of each other). Features disclosed for preforms or anti-resonant hollow optical fibers are also disclosed for methods, and vice versa.

[0212] The invention will now be further described by way of example with the aid of the accompanying drawings. The invention is not limited to the drawings.

[0213] Attached Figure

[0214] Figure 1 A partial longitudinal section passing through an anti-resonant hollow fiber is shown.

[0215] Figure 2 A partial cross-section through an anti-resonant hollow fiber is shown.

[0216] Figure 3 A partial longitudinal section through a first embodiment of the preform according to the invention is shown.

[0217] Figure 4 A partial cross-section through a first embodiment of the preform according to the invention is shown.

[0218] Figure 5 A partial longitudinal section through a second embodiment of the preform according to the invention is shown.

[0219] Figure 6 A partial cross-section through a second embodiment of the preform according to the invention is shown.

[0220] Figure 7 An illustration of a preform comprising a unit volume according to the present invention is shown.

[0221] Figure 8 A flowchart of a method for manufacturing preforms is shown, and

[0222] Figure 9 A flowchart is shown for a method of manufacturing antiresonant hollow optical fibers. Attached Figure Description

[0223] Figure 1 The longitudinal section passing through the anti-resonant hollow fiber 2400 is shown. Figure 2 It shows Figure 1 The cross-section of the anti-resonant hollow fiber 2400 is shown. The cross-section of the anti-resonant hollow fiber 2400 between two cross-section lines AA and BB is shown. The anti-resonant hollow fiber 2400 has a cladding 2450. In the illustrated embodiment of the anti-resonant hollow fiber 2400, the cladding 2450 consists of an elongated cladding tube 200 and an elongated cladding material 2452. Because the cladding material 2452 and the cladding tube material 200 are designed to have the same material in the illustrated embodiment, therefore... Figure 2The transition between the two materials is indicated only by dashed lines. The antiresonant hollow fiber 2400 has a hollow core 2470. Electromagnetic waves can propagate through the hollow core 2470. In the illustrated embodiment, two antiresonant elements 2410 are arranged within the hollow core 2470. They are attached to the inner surface 2480 of the cladding 2450 by means of material-to-material bonding. The antiresonant element 2410 has an ARE fiber outer tube 2420 and an ARE fiber inner tube 2430. The ARE fiber inner tube 2430 is arranged within the ARE fiber outer tube 2420. The antiresonant element 2410 is arranged parallel to the longitudinal axis 2460 of the antiresonant hollow fiber 2400.

[0224] Figure 2 It shows Figure 1 The cross-section of the anti-resonant hollow fiber 2400 is shown. Figure 2 The arrangement of the anti-resonant element 2410 on the inner surface 2480 of the confining hollow core 2470 is illustrated. The anti-resonant element 2410 is constructed in a tubular manner, wherein the ARE fiber inner tube 2430 is connected to the ARE fiber outer tube 2420 by means of material-to-material bonding.

[0225] The ARE fiber inner tube 2430 and / or ARE fiber outer tube 2420 shown may have a wall thickness in the range of 0.2 μm to 2 μm. The cladding tube 2450 shown may have an outer diameter in the range of 90 mm to 250 mm and a length of at least 1 m. The inner diameter of the hollow core 2470 is preferably 10 mm to 50 mm.

[0226] The antiresonant hollow fiber 2400 shown is manufactured from a preform 100, which will be described in more detail below. The manufacture of the antiresonant hollow fiber 2400 from the preform 100 is specifically carried out by one or more of the following thermoforming processes, either once or repeatedly: elongation 2300, collapse 2100, and addition 2200 of additional cladding material.

[0227] Figure 3 and Figure 4 A cross-section of a preform 100 according to the invention for an anti-resonant hollow fiber 2400 is shown, representing a first embodiment of the invention. The preform 100 has a cladding tube 200. The cladding tube 200 is designed in a tubular manner and includes a cladding tube wall 210 having a thickness 211 ranging from 20 mm to 150 mm, specifically from 30 mm to 130 mm. An anti-resonant element preform 300 is disposed on the inner side 215 of the cladding tube 200. At least one anti-resonant element preform 300 thereby ensures that the core mode can propagate in the central hollow core 2470 of the final hollow fiber 2400.

[0228] The anti-resonant element preform 300 includes an outer ARE tube 310 and an inner ARE tube 320, both designed in a tubular manner. The outer ARE tube 310 and / or the inner ARE tube 320 may have a wall thickness in the range of 0.1 mm to 2 mm. The inner ARE tube 320 may be attached to the outer ARE tube 310 by means of material-to-material bonding. This bonding is performed by means of thermal attachment, which may be specifically performed as part of the preparation 1200 of multiple anti-resonant element preforms 300. As part of this preparation step 1200, several nested tubular structural elements, such as the outer ARE tube 310 and the inner ARE tube 320, may be assembled.

[0229] The thermal attachment, as part of the preparation of 1200, can be performed on the outside of the cladding tube 200 and / or also inside the cladding tube. Specifically, as follows Figure 4 As illustrated, the anti-resonant element preform includes an outer ARE tube 310 and an inner ARE tube 320 inserted therein. Thermal attachment can cause material-to-material bonding between the inner ARE tube 320 and the inner side of the outer ARE tube 310. The longitudinal axis of the inner ARE tube 320, specified by its tubular shape, is thus positioned parallel to the longitudinal axis of the outer ARE tube 310, specified by its shape. Therefore, the combination of the outer ARE tube 310 and the inner ARE tube 320 forms a nested tubular structural element having its own longitudinal axis.

[0230] The cladding tube 200 is tubular and / or cylindrical in shape and has a longitudinal axis 230. On its inner side, the cladding tube 200 has an inner bore 220. A cladding tube wall 210, defined by an inner side 215 and an outer side 216, extends along the longitudinal axis 230. The cladding tube 200 can be at least partially closed at its end by means of a cladding tube closure 214.

[0231] In another step, at least one anti-resonant element preform 300 is arranged 1300 within the cladding tube 200 provided 1100 in the first step. Subsequently, at least one anti-resonant element preform 300 is thermally fixed to the cladding tube wall 210 1500 by means of a heat input. A heat source 850 (such as, for example, a hydrogen torch that heats region 851 of the cladding tube wall 210 thermally) can be used to generate this heat input. The purpose of heating is to bond the anti-resonant element preform 300 to the material-to-material bond of the inner side 215. In one embodiment, only localized material-to-material bonding of the anti-resonant element preform 300 to the cladding tube 200 is performed in the heated region 851. Therefore, at least one anti-resonant element preform 300 is connected to the cladding tube 200 only point-by-point. This point-by-point bonding can be performed at five, specifically three, or specifically two locations along the length of the anti-resonant element preform 300.

[0232] In the illustrated embodiment, the cladding tube 200 and at least one anti-resonant element preform 300 have a material that is transparent to the working light of the optical fiber, such as glass, specifically doped or undoped silica glass (SiO2). In one embodiment, the cladding tube 200 and the anti-resonant element preform 300 are composed of doped or undoped silica glass (SiO2).

[0233] The disclosed method includes introducing contact elements 400 into at least one anti-resonant element preform 300 at 1400 in such a manner that the contact elements 400 increase the heat-absorbing mass of the anti-resonant element preform 300 in step d) in order to slow the heat flow from the cladding tube 200 to the anti-resonant element preform 300 during heat setting 1500 and / or to slow the temperature rise of the anti-resonant element preform 300 triggered by the heat flow.

[0234] Contact element 400 is used to increase the heat absorption of the anti-resonant element preform 300. For example... Figure 3 As shown, heat flow originates from the heat source 850 in the direction of the wall 210 of the cladding tube 200. Figure 3 In this configuration, heat source 850 is arranged substantially perpendicular to the cladding tube wall. Alternatively, heat source 850 may also heat the front surface of the cladding tube near the anti-resonant element preform 300. This heat flow causes the temperature of the cladding tube wall 200 to rise, eventually reaching the anti-resonant element preform 300 as well. There is a risk that the temperature reached on the inner side 215 may become so high and / or the rate of temperature rise may be so high that thermal damage to at least one anti-resonant element preform 300 may occur, and / or at least one anti-resonant element preform 300 may not be precisely and / or tension-free secured to the inner side 215 of the cladding tube wall 210. However, non-tension-free and / or non-precise securing of the anti-resonant element preform 300 results in the resulting anti-resonant hollow fiber 2400 not possessing the desired attenuation characteristics.

[0235] To ensure reliable and reproducible fixation of the anti-resonant element preform 300 to the cladding wall 210 during industrial processes, a contact element 400 is provided, which increases the heat absorption capacity of the anti-resonant element preform 300. With the aid of the contact element 400, the anti-resonant element preform 300 becomes more thermally inert in the region where material-to-material bonding between the anti-resonant element preform 300 and the cladding wall 210 occurs.

[0236] In the design of contact element 400, it is necessary to balance two opposing characteristics.

[0237] i.) On the one hand, the heavier the contact element 400 is, the more significant the heat-absorbing mass of the anti-resonant element preform 300 is, and thus the risk of thermal damage or deformation of the anti-resonant element preform 300 is reduced. Therefore, it appears advantageous to have the largest and heaviest contact element 400 possible.

[0238] ii.) On the other hand, in the case of a contact element 400 that is too heavy, the material of the anti-resonant element preform 300 cannot be sufficiently heated to ensure material-to-material bonding with the cladding wall 210. Material-to-material bonding can be ensured in an emergency by a corresponding increase in heat input via heat source 850. However, the heat input required by heat source 850 at that time may be so great that it causes damage to the cladding wall 210 in region 851. Therefore, it appears advantageous for the contact element 400 to be as small as possible and have the smallest possible mass. In the case of a contact element that is too large, there is an additional or alternative danger that the anti-resonant preform 300 closes during heat setting 1500. During further processing, pressure can therefore accumulate in the anti-resonant preform 300, leading to undesirable deformation and / or expansion of the anti-resonant preform 300.

[0239] Therefore, it is necessary to set the balance dimension of the contact element 400.

[0240] As part of step d), at least one anti-resonant element preform 300 is arranged 1300 on the inner side 215 of the cladding tube wall 210. In one embodiment, this arrangement 1300 may be performed by means of non-positive and / or positive clamping elements. The clamping elements thereby hold the anti-resonant element preform 300 in the cladding tube 200 (specifically on the end side). In another embodiment, a positioning template 800 is arranged in the cladding tube 200, which holds at least one anti-resonant element preform 300 in a designated position in a non-positive and / or positive manner. The arrangement 1300 of the anti-resonant element preform 300 on the inner side 215 of the cladding tube bore 220 can therefore include the arrangement of the anti-resonant element preform 300 at a target position on the inner side of the cladding tube wall 210, wherein the arrangement 1300 of the anti-resonant element preform 300 is carried out by means of a positioning template 800, which is introduced into the cladding tube bore and has holding elements for positioning the anti-resonant element preform 300 at the target position. With the help of an attractive selection of geometry and materials, a reproducible accuracy of + / -5 mm can be obtained during the positioning of the anti-resonant element preform 300 by means of the positioning template 800. The positioning template 800, composed of graphite, has proven advantageous.

[0241] In one embodiment, the heat-fixing 1500 in step d) may be characterized in that step e) includes the following sequential steps:

[0242] / A-1. / Connect the contact element 400 to the anti-resonance element preform 300.

[0243] / A-2. / Connect the anti-resonant element preform 300 to the cladding tube 200.

[0244] Alternatively or otherwise, the heat-fixing 1500 in step d) may be characterized in that step e) includes the following sequential steps:

[0245] / B-1. / to the heat input of the assembly consisting of the anti-resonant element preform 300 and the contact element 400,

[0246] / B-2. / The first connection between the contact element 400 and the anti-resonant element preform 300 is made by means of the first part of the heat input.

[0247] / B-3. / The second connection between the anti-resonant element preform 300 and the cladding tube 200 is made by means of the second part of the heat input.

[0248] Figure 5 and Figure 6 An embodiment of a preform 100' manufactured by means of the disclosed method is shown. According to... Figure 5 and Figure 6 The implementation plan largely corresponds to the above and Figure 3 and Figure 4 The illustrated implementation scheme, to avoid repetition, refers to the above description. From Figure 3 and Figure 4 The descriptions of repeated structures have the same reference numerals. (And...) Figure 3 and Figure 4 Compared to the structure shown, the modified structure has the same reference numeral with an apostrophe (').

[0249] Figure 5 and Figure 6 The preform 100' shown is Figure 3 and Figure 4 The difference in the illustrated embodiment lies in the arrangement of the contact element 400. The preform 100' has contact elements 400 arranged within the ARE outer tube 310. In contrast, in... Figure 4 and Figure 5 In the illustrated embodiment, the contact element 400 is arranged within the ARE inner tube 320. Specifically, as shown... Figure 6As illustrated, the contact element 400 may have a crescent-shaped structure and may surround the ARE inner tube 320 at least in some areas. This type of design ensures optimal heat flow from the inner side 215 of the cladding wall 210 to the contact element 400. However, sufficient heat simultaneously reaches the contact point between the outer side of the anti-resonant element preform 300 and the inner side 215 of the cladding wall 210 to achieve material-to-material bonding.

[0250] By using the corresponding dimensional settings of the contact element 400, it is ensured that the geometrical change of the anti-resonance element preform 300, as part of the thermal fastener 1500, is less than 10%, specifically less than 5%, specifically less than 2%, and specifically less than 1%. The geometrical change is understood to be at least one of the following variables: the radius of the inner ARE tube 320, the radius of the outer ARE tube 310, the wall thickness of the inner ARE tube 320, the wall thickness of the outer ARE tube 310, the deviation from the ideal circular geometry of the inner ARE tube, the deviation from the ideal circular geometry of the outer ARE tube 310, the circular surface of the inner ARE tube 320, and the circular surface of the outer ARE tube 310.

[0251] Figure 7 An embodiment of a preform 100” manufactured by means of the disclosed method is shown. According to Figure 7 The implementation plan largely corresponds to the above and Figure 3 and Figure 4 The illustrated implementation scheme, to avoid repetition, refers to the above description. From Figure 3 and Figure 4 The descriptions of repeated structures have the same reference numerals. (And...) Figure 3 and Figure 4 Compared to the structure shown, the modified structure has the same reference numeral with two apostrophes (”).

[0252] Figure 7 The embodiment of the preform 100 shown is characterized in that the contact element 400 is designed in such a way that the following applicable

[0253] C_cladding tube > C_contact element > C_anti-resonant element preform

[0254] in

[0255] • C_cladding tube is the average heat capacity of the solid material of the cladding tube 200 per unit volume 410.

[0256] • The C-contact element is the average heat capacity of the contact element 400 and the ambient air per unit volume of 410".

[0257] • The C-type anti-resonant element preform is the average heat capacity of the anti-resonant element preform 300 and ambient air per unit volume of 410".

[0258] Furthermore, its unit volume is 25% larger than that of contact element 400.

[0259] The average heat capacity "C_cladding tube" of the cladding tube 200 is derived from the average heat capacity of the solid material of the cladding tube 200 per unit volume 410. Therefore, the average heat capacity corresponds to the specific heat capacity of the material used to manufacture the cladding tube 200. The volume that is 25% larger than the volume of the contact element 400 is thus referred to as the unit volume.

[0260] The average heat capacity of contact element 400, “C_contact element”, is derived by averaging over a unit volume 410' that is 25% larger than the volume of contact element 400. Therefore, it is averaged over the specific heat capacity of the material used to manufacture contact element 400 and the air surrounding it (under normal conditions according to DIN 1343).

[0261] To determine the average heat capacity "C_anti-resonant element preform" of the anti-resonant element preform 300, the unit volume "410" should be designed in such a way that it includes the portion attached to the inner wall of the cladding tube 200 by means of material-to-material bonding. This is in Figure 7 The diagram illustrates a configuration in which the unit volume 410” is cylindrical and encloses the portion of the inner ARE tube 320 and the outer ARE tube 310. Consequently, the longitudinal axis of the unit volume 410” is aligned parallel to the imaginary longitudinal axis of the anti-resonant element preform 300. The average heat capacity of the preform 300 is derived from the average heat capacity of the tubular structures 310, 320 forming the anti-resonant element preform 300 and also from the air contained within the unit volume 410” (under normal conditions according to DIN 1343).

[0262] The unit volumes 410, 410', and 410" can be selected in such a way that their shape substantially reflects the external shape of the contact element 400, and their size is increased only by making them 25% larger in volume than the contact element 400. In the case of a contact element 400 designed in a cylindrical manner, the unit volumes 410, 410', and 410" can also be designed in a cylindrical manner. The increased diameter and greater length compared to the contact element 400 result in a 25% larger volume.

[0263] In one embodiment, the contact element 400 has a material (e.g., glass, specifically doped or undoped silica glass (SiO2)) that is transparent to the working light of the optical fiber. In one embodiment, the contact element 400 is composed of a material (e.g., glass, specifically doped or undoped silica glass (SiO2)) that is transparent to the working light of the optical fiber.

[0264] Figure 8 An embodiment of a method 2000 for manufacturing a preform 100 of an anti-resonant hollow optical fiber 2400 is shown, the method comprising the following steps:

[0265] A provides a 1000-layer cladding tube 200, the cladding tube having a cladding tube inner hole 220 and a cladding tube longitudinal axis 230, the cladding tube wall 210 extending along the longitudinal axis of the cladding tube, the cladding tube wall being defined by an inner side 215 and an outer side 216.

[0266] b. Prepare more than 1200 anti-resonant element preforms 300. Each preform consists of several nested tubular structural elements, including an outer ARE tube 310 and an inner ARE tube 320 inserted therein. Each structural element has a longitudinal axis.

[0267] c. Arrange the anti-resonant element preform 300 on the inner side of the cladding tube wall 210, and

[0268] d. The anti-resonant element preform 300 is thermally fixed 1500 to the cladding tube wall 210 by means of heat input.

[0269] This defines the method as having the following steps:

[0270] e introduces contact elements 400 into at least one anti-resonant element preform 300 in such a manner that the contact elements 400 increase the heat-absorbing mass of the anti-resonant element preform 300 in step d) so as to slow down the temperature rise of the heat flow from the cladding tube 200 to the anti-resonant element preform 300 during the heat fixation 1500.

[0271] Figure 9 An embodiment of a method for manufacturing an anti-resonant hollow optical fiber 2400 from a preform 100 specifically manufactured according to any one of the aforementioned method steps 1000 to 1500 is shown, the method comprising the following steps:

[0272] • The preform 100 is further processed into the anti-resonant hollow optical fiber 2400.

[0273] This further processing includes one or more of the following thermoforming processes being performed once or repeatedly:

[0274] • Collapse 2100,

[0275] • Add 2200 additional cladding materials, and

[0276] • Lengthen by 2300.

[0277] Unless otherwise stated, all physical variables specified in the claims, specification, and drawings are determined under normal conditions according to DIN 1343. The expression "under normal conditions" means measurement under conditions according to DIN 1343. Features disclosed in the claims, specification, and drawings may be important for various embodiments of the claimed invention (individually and in any combination thereof). Features disclosed for the apparatus (specifically, preforms, secondary preforms, or anti-resonant hollow optical fibers) are also disclosed for the method, and vice versa.

[0278] Attached icon number

[0279] Preform of 100 anti-resonant hollow optical fiber

[0280] 200 cladding tube

[0281] 210 cladding wall

[0282] 211. Thickness of the cladding wall

[0283] 215 Inner side of the cladding wall

[0284] 216 The outer side of the cladding wall

[0285] 220 cladding tube inner bore

[0286] 230 Longitudinal axis of cladding tube

[0287] 240 Cladding tube closure

[0288] 300 Anti-resonant element preform

[0289] 310 ARE Foreign Management

[0290] 320 ARE Internal Management

[0291] 400 contact element

[0292] 410, 410', 410” unit volume

[0293] 800 Positioning Template

[0294] 850 heat source

[0295] 851 Heating Zone

[0296] 1000 provides cladding tubes

[0297] 1100 generates cladding tube closure.

[0298] 1200 Fabrication of multiple anti-resonant element preforms

[0299] 1300 Preform for Arranging Anti-Resonant Elements

[0300] 1400 respectively introduce contact elements

[0301] Thermosetting of 1500 anti-resonant element preform

[0302] 2000 Method steps 1000 to 1500

[0303] 2100 Collapse

[0304] 2200 Add additional cladding material

[0305] 2300 elongated

[0306] 2400 anti-resonant hollow fiber

[0307] 2410 Anti-resonant element

[0308] 2420 fiber optic ARE outer tube

[0309] 2430 Fiber Optic ARE Inner Tube

[0310] Cladding of 2450 anti-resonant hollow fiber

[0311] 2452 A portion of the cladding material formed at the cladding of an anti-resonant hollow fiber.

[0312] The longitudinal axis of the 2460 anti-resonant hollow fiber

[0313] 2470 Hollow core of anti-resonant hollow fiber

[0314] 2480 inner surface

Claims

1. A method for manufacturing a preform of an anti-resonant hollow optical fiber (2400), the method comprising the following steps: a) Provide a cladding tube (200) having a cladding tube bore (220) and a cladding tube longitudinal axis (230), a cladding tube wall (210) extending along the cladding tube longitudinal axis, the cladding tube wall being defined by an inner side (215) and an outer side (216). b) Prepare (1200) a plurality of anti-resonant element preforms (300), the plurality of anti-resonant element preforms being composed of several nested tubular structural elements, the nested tubular structural elements including an ARE outer tube (310) and an ARE inner tube (320) inserted into the ARE outer tube, wherein the structural element has a longitudinal axis. c) Arranging the anti-resonant element preform (300) (1300) on the inner side of the cladding tube wall (210), and d) The anti-resonant element preform (300) is thermally fixed (1500) to the cladding tube wall (210) by means of heat input. Its features are, The method comprises the following steps: e) The contact elements (400) are respectively introduced (1400) into at least one anti-resonant element preform (300) in such a manner that... The contact element (400) increases the heat-absorbing mass of the anti-resonant element preform (300) in step d) in order to slow down the heat flow from the cladding tube (200) to the anti-resonant element preform (300) during the heat setting (1500); The contact element is designed in a rod-like manner. The length of the contact element is less than 15 centimeters. When the preform is drawn into an anti-resonant hollow fiber, the contact element can cause blockage of the ARE outer tube and / or ARE inner tube in at least some areas, thereby preventing that area from being drawn into a usable anti-resonant hollow fiber.

2. The method according to claim 1, characterized in that, Step e) includes the following sequential steps: / A-1. / Connect the contact element (400) to the anti-resonant element preform (300), / A-2. / Connect the anti-resonant element preform (300) to the cladding tube (200).

3. The method according to claim 1 or 2, characterized in that, Step e) includes the following sequential steps: / B-1. / to the heat input of the assembly consisting of the anti-resonant element preform (300) and the contact element (400), / B-2. / The contact element (400) is operated by means of the first part of the heat input. The first connection to the anti-resonant element preform (300) / B-3. / The second connection between the anti-resonant element preform (300) and the cladding tube (200) is made by means of the second part of the heat input.

4. The method according to claim 1 or 2, characterized in that, The contact element (400) is designed in such a way that the following applies: C_cladding tube > C_contact element > C_anti-resonant element preform in • C_cladding tube is the average heat capacity of the solid material of the cladding tube (200) per unit volume (410, 410', 410"), • C_Contact element is the average heat capacity of the contact element (400) and ambient air per unit volume (410, 410', 410”). • The C-type anti-resonant element preform is the average heat capacity of the anti-resonant element preform (300) and the ambient air over the unit volume (410, 410', 410"), and the unit volume is 25% larger than the volume of the contact element (400).

5. The method according to claim 1 or 2, characterized in that, The heat fixation in step d) is performed by means of a flame-based process.

6. The method according to claim 1 or 2, characterized in that, The contact element (400) It has a length of [5; 50] mm, and It has a diameter of [0.5; 10] mm.

7. The method according to claim 6, characterized in that, The contact element (400) has a length of [10; 40] mm.

8. The method according to claim 6, characterized in that, The contact element (400) has a length of [12; 30] mm.

9. The method according to claim 6, characterized in that, The contact element (400) has a diameter of [0.7; 7] mm.

10. The method according to claim 6, characterized in that, The contact element (400) has a diameter of [1; 5] mm.

11. The method according to claim 1 or 2, characterized in that, The contact element (400) is introduced into the outer tube (310) of the at least one anti-resonant element preform (300).

12. The method according to claim 1 or 2, characterized in that, The contact element (400) is introduced into the ARE inner tube (320) of the at least one anti-resonant element preform (300).

13. The method according to claim 1 or 2, characterized in that, The arrangement of the anti-resonant element preform (300) on the inner side of the cladding tube bore includes the arrangement of the anti-resonant element preform (300) at a target position on the inner side of the cladding tube wall, wherein the arrangement of the anti-resonant element preform (300) is carried out by means of a positioning template, which is inserted into the cladding tube bore and has a holding element for positioning the anti-resonant element preform (300) at the target position.

14. The method according to claim 1 or 2, characterized in that, The inner hole of the cladding tube is produced by machining.

15. The method according to claim 1 or 2, characterized in that, The inner bore of the cladding tube is produced by means of drilling, milling, grinding, honing and / or polishing.

16. The method according to claim 1 or 2, characterized in that, The cladding tube (200) has an outer diameter in the range of 65 nm to 300 mm and a length of at least 1 m.

17. The method according to claim 1 or 2, characterized in that, The cladding tube (200) has an outer diameter in the range of 90 nm to 250 mm and a length of at least 1 m.

18. The method according to claim 1 or 2, characterized in that, The method comprises the following steps: • A cladding tube closure (240) is generated by at least partial closure of the front end of the cladding tube bore (220).

19. A method for manufacturing a secondary preform from a preform (100), capable of drawing hollow optical fibers from the secondary preform, wherein the preform (100) is manufactured by the method according to any one of claims 1 to 12, the method for manufacturing the secondary preform comprising the following steps: • The preform (100) is further processed into the secondary preform, wherein the further processing includes one or more of the following thermoforming processes performed once or repeatedly: i.) Lengthen (2300), ii.) Collapse (2100), iii.) Collapse (2100) and simultaneously elongate (2300), iv.) Add (2200) additional cladding material, v.) Add (2200) additional cladding material and then stretch (2300), vi.) Add (2200) additional cladding material and stretch (2300) at the same time.

20. A method for manufacturing an anti-resonant hollow optical fiber (2400) from a preform (100), wherein the preform (100) is manufactured by the method according to any one of claims 1 to 12, the method for manufacturing the anti-resonant hollow optical fiber (2400) comprising the following steps: The preform (100) is further processed into the anti-resonant hollow fiber (2400). The further processing described herein includes one or more of the following thermoforming processes, performed once or repeatedly: i.) Lengthen (2300), ii.) Collapse (2100), iii.) Collapse (2100) and simultaneously elongate (2300), iv.) Add (2200) additional cladding material, v.) Add (2200) additional cladding material and then stretch (2300), vi.) Add (2200) additional cladding material and stretch (2300) at the same time.

21. The method according to any one of claims 19 or 20, characterized in that, The relative internal pressure is set in the range of 0.05 mbar to 20 mbar during the elongation (2300) in the core region.

Images