Method for producing a semi-finished product for manufacturing a bend-optimized optical fiber

Abstract

Method for producing a semi-finished product for manufacturing a bend-optimized optical fiber with a structured refractive index profile consisting of trench structures, gradations or combinations of several trenches of different widths and intermediate refractive index-enhanced webs, characterized by a convergent production process consisting of partial production of individual components, in which the semi-finished product is first pre-manufactured in the form of individual components, whereby the individual components are machined and pre-assembled as desired and joined together in a final production step, whereby the semi-finished product is formed, whereby the individual partial productions take place independently of each other, where at least two individual components are joined together at the end of the convergent production process to form the semi-finished product, wherein each partial production of the respective individual component includes at least one of the following partial production steps (A to I) carried out on a sheath tube (1) with a lower sheath refractive index compared to the light-guiding core: - Performing a partial manufacturing step (A) comprising applying at least one protective, intermediate and / or barrier layer (3) to an inner and / or outer surface (2, 4) of the casing tube, - Performing a partial manufacturing step (B) comprising an external and / or internal deposition of preferably light-guiding layers (5, 6, 7) on the inner and / or outer surface of the casing tube, - Performing a partial manufacturing step (C) comprising at least partial collapse of the coated or uncoated casing tube into a capillary or rod, - Performing a partial manufacturing step (D), comprising circumferencing the individual component and / or a rotationally symmetric substrate with at least one sheathing tube with a desired refractive index, - Performing a partial manufacturing step (E), comprising removing a protective, intermediate and / or barrier layer (3) arranged on the inner surface of at least one individual component, - Performing a partial manufacturing step (F) comprising removing a protective, intermediate and / or barrier layer (3) arranged on the outer surface of at least one individual component, - Performing a partial manufacturing step (G), comprising a change in the inner diameter of the casing tube (1) or the individual component by means of an inflation, compression and / or stretching process, - Performing a partial manufacturing step (H) comprising a change in the outer diameter of a rotationally shaped rod and / or tube and / or the individual component by means of an upsetting or stretching operation, - Performing a partial manufacturing step (I) comprising heat and / or tempering treatment and / or plasma and / or fire polishing.

Description

[0001] The invention relates to a method for producing a semi-finished product for manufacturing a bend-optimized optical fiber according to the preamble of claim 1.

[0002] EP 1 388 525 A2 discloses a method for manufacturing an optical fiber preform, also a preform manufactured according to this process, and an optical fiber resulting from this process. The subject of the teaching disclosed therein is the manufacturing process for a fiber in which the fiber attenuation at certain wavelengths is to be minimized as much as possible. The document does not concern the production of bend-insensitive fibers. It discloses a manufacturing process for a preform with a core and a multilayer cladding, in which a core with an inner cladding layer is provided, onto which a tube is collapsed in a further manufacturing step. The teaching contained therein aims to create a preform in which damage during a subsequent fiber drawing process is to be prevented by certain adjustments to viscosity properties.

[0003] JP H03-16930A discloses the fabrication of an optical fiber with a complex refractive index distribution. The subject of the disclosed method is a so-called rod-in-tube process, in which an outer tube is collapsed onto an inner rod. According to the method shown therein, an inner rod is first subjected to a coating process and, in a second step, surrounded by the outer tube.

[0004] DE 10 2008 047 736 B3 discloses a bend-insensitive optical fiber, a quartz glass tube as a semi-finished product for its manufacture, and a method for manufacturing the fiber.

[0005] The subject of the teaching disclosed therein is the manufacture of so-called zone tubes. This involves a deposition process in which the fluorine-doped quartz glass intended for the ring zone of the optical fiber is applied to a substrate body by means of a plasma deposition process. This substrate body can be a tube or a rod made of quartz glass, which may be undoped or partially doped.

[0006] The subject of the teaching disclosed therein is the project to deposit the largest possible layer thicknesses for the annular zone layer onto a substrate tube using the POD external deposition methods described therein. According to the publication, the zone tube thus produced can either subsequently collapse into a core rod or be used as a capping tube to encase a core rod, thereby generating the preform of an optical fiber.

[0007] German patent DE 10 2005 034 594 A1 discloses a method for producing glass fiber preforms with a large core diameter. The document specifically discloses the so-called rod-in-tube technique, in which a tubular outer casing is collapsed onto an internally inserted rod.

[0008] US patent 2002 / 0189296A1 discloses a method for manufacturing a multi-segmented optical fiber and a preform. The patent also discloses the rod-in-tube process involving the joining and joining of a rod and a surrounding tube. However, it does not cover semi-finished products for bend-insensitive fibers.

[0009] US Patent 2009 / 0290841A1 discloses reduced bending sensitivity and catastrophic bending loss in single-mode fibers and a method for generating such properties in fibers. The patent discloses a number of exemplary refractive index profiles consisting of steps, trenches, and constant refractive index regions with which such properties can be achieved, but it does not specify a method for easily producing such refractive index profiles with the required variability.

[0010] Bending-optimized optical fibers exhibit bending behavior tailored to their specific application, particularly a bending sensitivity adapted to their optical conductivity. This applies on the one hand to optical fibers that require a particularly high bending sensitivity, such as sensor fibers in optical bending sensor arrangements, and on the other hand to optical fibers that require as little bending sensitivity as possible, such as those needed for transmitting high-bandwidth data.

[0011] Such optical fibers have a cross-section with a structured refractive index profile. This applies particularly to trench structures, graduated profiles, or even complex combinations of multiple trenches of varying widths and intermediate struts with increased refractive index. Manufacturing such fibers using conventional methods, i.e., known chemical and / or physical deposition processes, is very complex. While the refractive index profile of a single fiber can be precisely controlled, switching to a different refractive index profile often requires significant changes to the production process because the deposition parameters sometimes need to be fundamentally altered.

[0012] The task is therefore to specify an economical and effective method for producing a semi-finished product for manufacturing the bend-optimized fiber, whereby the required refractive index profile can be planned precisely and manufactured with a minimized expenditure of time.

[0013] The problem is solved by a method for manufacturing a semi-finished product for producing a bend-optimized optical fiber with the characterizing features of claim 1. The dependent claims contain advantageous embodiments and configurations of the method.

[0014] The method for producing a semi-finished product for manufacturing a bend-optimized optical fiber with a structured refractive index profile consisting of trench structures, gradations or combinations of several trenches of different widths and intermediate refractive index-enhanced webs is characterized according to the invention by the following features: A convergent production process is employed, consisting of partial manufacturing of individual components. The semi-finished product is initially prefabricated in the form of individual components, which are then machined and pre-assembled as desired before being joined together in a final manufacturing step. This final step results in the formation of the finished semi-finished product. According to the invention, the individual partial manufacturing processes are independent of one another.

[0015] At least two individual components are joined together at the end of the convergent production process to form the semi-finished product.

[0016] Each partial production of the respective individual component contains at least one of the following partial production steps, which are carried out on a sheath tube with a lower refractive index compared to the light-guiding core: Performing a partial manufacturing step includes applying at least one protective, intermediate and / or barrier layer to an inner and / or outer surface of the casing pipe.

[0017] Performing another partial manufacturing step includes the external and / or internal deposition of preferably light-guiding layers on the inner and / or outer surface of the casing tube.

[0018] Performing a further partial manufacturing step involves at least a partial collapse of the coated or uncoated casing tube into a capillary or rod.

[0019] In a partial manufacturing step, the individual component and / or a rotationally symmetrical substrate is enclosed with at least one sheathing tube with a desired refractive index. A further partial manufacturing step involves removing a protective, intermediate and / or barrier layer arranged on the inner surface of at least one individual building block.

[0020] Performing a further partial manufacturing step involves removing a protective, intermediate and / or barrier layer arranged on the outer surface of at least one individual component.

[0021] Performing a partial manufacturing step involves changing the inner diameter of the casing tube or the individual component through an inflation, compression and / or stretching process.

[0022] In a further partial manufacturing step, a change in the outer diameter of a rotationally shaped rod and / or tube and / or the individual component is carried out by a compression or stretching process.

[0023] Another partial manufacturing step includes heat and / or tempering treatment and / or plasma and / or fire polishing.

[0024] The manufacturing of the semi-finished product is designed as a convergent production process. This means that the semi-finished product, in the form of individual components, building blocks, or a series of sheathing tubes, is initially prefabricated as individual components. These individual components can be machined and pre-assembled in virtually any way desired. This allows for the very precise production of individual sections of the later desired refractive index profile. The individual building blocks are then assembled; in other words, the individual production steps converge into a final manufacturing step, and the semi-finished product for the optical fiber is thus formed. The individual production steps are therefore carried out independently of one another and only culminate in a final step at the end.

[0025] The following partial production steps are carried out during an initial, appropriate partial production phase: First, a partial manufacturing step is carried out in which the protective, intermediate and / or barrier layer in the form of a quartz glass layer is applied to the outer surface of the casing tube.

[0026] Then a partial manufacturing step is carried out in which an internal deposition of quartz glass doped with germanium and / or phosphorus is performed on the inner surface of the jacket tube.

[0027] In a further manufacturing step, the core then collapses into a solid rod. This is followed by plasma polishing of the solid core rod. The resulting individual component is then combined with a quartz glass casing tube to form the finished semi-finished product.

[0028] Following the aforementioned plasma polishing step, the outer protective layer can be removed by appropriately modifying the manufacturing steps. The resulting individual component is then combined with a quartz glass casing tube to form the finished semi-finished product.

[0029] Following the aforementioned plasma polishing step, with appropriate modification of the partial manufacturing steps, at least one further external coating with doped and / or undoped quartz glass can subsequently be applied using a plasma coating.

[0030] The aforementioned partial production processes can easily be carried out in parallel to each other, with the individual components produced in the process ultimately being combined.

[0031] In a first embodiment, the outer casing is provided in the form of a fluorine-doped quartz glass tube. This results in a reduction of the refractive index in the material of the outer casing.

[0032] In a preferred embodiment, a fluorine-doped layer of desired thickness and refractive index is deposited onto an undoped quartz glass tube, which in turn is coated with undoped quartz glass as a protective layer.

[0033] In another advantageous embodiment, the light-guiding layers are built up using a CVD and / or plasma process and / or flame pyrolysis.

[0034] The protective, intermediate, and / or barrier layer is preferably made of quartz glass with a higher melting point compared to the melting point of the outer casing material. This results in increased stability of the subsequent semi-finished product and reduces ovality and eccentricity in the structure.

[0035] The protective, intermediate, and / or barrier layer advantageously possesses a diffusion-preventing blocking function against volatile glass components, especially dopants that alter the refractive index and / or fluorine. This stabilizes the refractive index profile and allows it to be modified at a later stage of production, if necessary.

[0036] At the same time, the protective, intermediate, and / or barrier layer can fulfill a further function. With a suitable design, the protective, intermediate, and / or barrier layer has a chemical composition that, when the semi-finished product is applied to a further substrate, minimizes the thermal, physical, and / or chemical differences between the semi-finished product and the further substrate, in particular the differences in the coefficients of thermal expansion and / or the different chemical compositions. This minimizes the stresses in the resulting overall system or reduces them to a suitable level.

[0037] After the formation of the light-guiding layers, at least one further inner and / or outer protective, intermediate, and / or barrier layer can be deposited. This prepares the modified outer casing tube accordingly, either internally or externally, or on both sides.

[0038] With a suitable design, the outer casing pipe allows for the targeted adjustment of ambient pressure and / or internal pipe pressure using at least one pressure control system.

[0039] Subsequently, if the design is continued appropriately, it collapses into a solid rod or a capillary.

[0040] In a related process, after the light-guiding layers have been built up, the outer casing collapses onto another substrate. This additional substrate can be either a solid rod or another outer casing.

[0041] In a suitable embodiment of the method, after the formation of the light-guiding layers, a partial or complete collapse process takes place to form a capillary or a solid rod. Following this partial or complete collapse process, mechanical processing to create a polygonal rod can then be performed.

[0042] The collapse processes can also occur successively. In one embodiment, at least one further doped and / or undoped casing tube or semi-finished product subsequently collapses. In this case, the chemical composition of at least one dopant of each individual substrate can have a constant, linear, and / or gradual profile radially within a collapsed doped casing tube or semi-finished product. By such a procedure, different refractive index profiles, in particular grooves, gradations, or constant sections, are added radially outwards and combined with one another.

[0043] This manufacturing process can be combined with at least one additional outer coating.

[0044] It is advantageous to combine glasses of the same or similar chemical composition during the collating processes. This increases the yield of the process step.

[0045] In a final manufacturing step, at least one of the protective, intermediate, and / or barrier layers can be at least partially removed. This allows diffusion processes to be induced within the internal structure, enabling further modifications to the refractive index profile.

[0046] The aforementioned manufacturing steps can be combined with surface treatments. In an intermediate and / or a final manufacturing step, a surface treatment, preferably plasma and / or fire polishing, is therefore expediently carried out.

[0047] The process will now be explained in more detail using exemplary embodiments. The following serve to illustrate this: Fig. 1 and Fig. 2. The same reference symbols are used for identical or equivalent parts.

[0048] It shows: Fig. 1. A series of exemplary processing steps on a casing pipe, Fig. 2. The joining of several sheathing tubes and a solid rod to form a semi-finished product for fiber optic manufacturing, Fig. 3 an advantageous embodiment of a casing tube, Fig. 4 another advantageous embodiment of a casing tube.

[0049] Fig. Figure 1 shows a series of exemplary processing and manufacturing steps for a casing tube 1. The casing tube forms the starting point for an individual component or the partial manufacturing steps carried out on this individual component. These can be modified for other individual components manufactured in parallel.

[0050] In this example, the outer casing consists of a quartz glass tube of a specific thickness. The quartz glass is coated with one or more dopants that alter the refractive index. These dopants can include, in particular, fluorine, fluorine compounds, germanium, phosphorus, aluminum, boron, or other halogens and their compounds, as well as other substances. The refractive index of the outer casing is adjusted so that it is lower than the refractive index of the core of the subsequent optical fiber.

[0051] The outer casing serves as a carrier for the coatings and surface modifications of the individual component carried out in the following steps. In a first step, at least one protective, intermediate, and barrier layer 3 is applied to the inner and / or outer surface 2, 4 of the outer casing. This layer is essentially impermeable to the dopants present inside the outer casing and, after the coating process, uniformly covers the inner surface of the outer casing. It prevents the refractive index-changing dopants from diffusing out of the quartz glass matrix of the outer casing during the subsequent manufacturing steps.

[0052] The coating process can be carried out using established methods. This applies particularly to wet chemical immersion processes, but especially to vapor and gas phase deposition processes known as Chemical Vapor Deposition (CVD). In wet chemical coating processes, the casing pipe is either completely immersed in a bath or the coating solution is flushed through its interior. For CVD coating, the casing pipe is heated locally from the outside and a gas stream flows through its interior. This gas stream contains the components intended for the coating in finely dispersed form. These components are deposited thermophoretically at the locally heated area of ​​the casing pipe.To coat the entire inner surface of the casing pipe, the point of local heating is shifted longitudinally along the casing pipe, resulting in a uniform inner coating with the protective, intermediate, and barrier layer 3. The protective, intermediate, and barrier layer preferably consists of quartz glass with a melting point higher than that of the casing pipe. This allows the barrier layer to exert an additional stabilizing function.

[0053] Furthermore, the protective, intermediate and barrier layer 3, arranged both inside and outside, serves as an adhesion promoter and / or as a compensating intermediate layer, which minimizes the differences between the coefficients of expansion of the material of the casing pipe on the one hand and the layers following the protective, intermediate and barrier layer 3.

[0054] The jacket tube, modified with the protective layer, is now available for further coating processes to be carried out on its inner or outer surface. In the present example, the jacket tube is coated on its inner surface with a light-guiding coating 6. The light-guiding coating can be doped with germanium. This serves as the starting structure for the light-guiding structure within the subsequent optical fiber. In principle, the same coating processes used for the inner coating of the jacket tube can be used for both the inner and outer coatings.

[0055] Parallel to the first individual building block described above, further individual building blocks, in particular a second and a third individual building block, as well as a germanium-doped core are manufactured.

[0056] The individual components differ from the first component in their coating sequence. The second component consists of a fluorine-doped jacket tube, which is coated on its outside with a protective, intermediate, and barrier layer and on its inside with a germanium-doped coating.

[0057] The third individual component consists of a fluorine-doped jacket tube, which contains a protective, intermediate and barrier layer exclusively on its inner surface.

[0058] For applying an outer coating, the use of a plasma deposition process proves particularly advantageous. For this purpose, the outer casing is placed within the flame zone of a plasma torch located underneath it and movable along the longitudinal axis of the tube, and rotated about its longitudinal axis. Within the plasma torch's flame stream, the substances intended for the outer light-guiding coating are added. These are then deposited on the outside of the outer casing.

[0059] Both the inner and outer surfaces of the casing tube can now undergo further coating processes. The number of coating processes is, in principle, unlimited. In particular, complex layer structures can be created within the casing tube using thermophoretic methods.

[0060] Depending on the intended structure of the semi-finished product or the optical fiber to be manufactured from it, further modifications to the overall structure can be made as needed. In particular, this includes applying an additional protective, intermediate, or barrier layer to the outside of the coated tube, or modifying the outer contour of the tube. This includes, in particular, incorporating flattened areas, converting the round outer tube contour into a polygonal shape, especially a uniform hexagonal, octagonal, or square shape, or introducing local indentations or longitudinal grooves along the outer tube. Such modifications can be carried out, for example, by local etching, laser treatments, or sputtering processes.

[0061] The subsequent manufacturing processes performed on the casing tube depend on where the casing tube is to be inserted into the semi-finished product. If the casing tube is used in the core area of ​​the later semi-finished product, a collapse process can be carried out on the casing tube, whereby the casing tube collapses into a solid core rod. This collapse process can be controlled. A pressure gradient is created between the inside and outside of the casing tube, causing it to collapse at a controllable speed and / or to a controllable radius. The pressure gradient can be created either by generating a negative pressure inside the tube or by applying positive pressure from the outside.

[0062] The semi-finished product is ultimately manufactured from several such individual components and / or a rod or capillary in a convergent production process. This means that several outer tubes and the rod with different sizes and coatings are manufactured in parallel and combined in a final manufacturing process, whereby the initially independent production steps of the individual outer tubes ultimately merge into the final step, i.e., converge.

[0063] Fig. Figure 2 shows the final converging manufacturing process for producing the semi-finished product. In this case, a core rod 8, a middle sheath tube 9, and an outer sheath tube 10 are provided. Each of the sheath tubes can have the previously described internal and / or external coatings in different designs and modifications. It is also possible that at least one of the sheath tubes has a cross-section that deviates from a circular shape.

[0064] The joining of the casing tubes is carried out as a series of collapses. The core rod 8 serves as the starting substrate. This consists of a previously collapsed casing tube, but it can also be a solid rod.

[0065] The core rod 8 and the middle sheath tube 9 are pushed together. The middle sheath tube is then collapsed onto the core rod. This collapse process can occur either spontaneously or under controlled conditions with a set pressure gradient. The protective, intermediate, and barrier layers located either on the inside of the middle sheath tube or on the outside of the core rod are crucial here. These layers reduce or equalize stress during the collapse process.

[0066] The same collapse process now takes place between the middle sheath tube 9 and the outer sheath tube 10. The middle sheath tube, which has collapsed together with the core rod, now serves as a substrate for the collapse of the outer sheath tube. The result is a concentric layered structure formed by the base material of the sheath tubes on the one hand and their inner and outer coatings on the other. This structure consists of different refractive index ranges, which transition either gradually or abruptly into one another. Particularly in the coating areas of the sheath tubes, trench or step structures are formed. After the optical fiber is pulled, these trench structures result in refractive index profiles that are tailored to the required bending sensitivity of the optical fiber.

[0067] The resulting assembly can be subjected as a whole to plasma and / or fire polishing and / or temperature treatment in order to achieve a stress-free semi-finished product with a flawless surface.

[0068] Further examples of how to manufacture the individual components and the semi-finished product are explained below.

[0069] Fig. Figure 3 describes an advantageous embodiment of a casing tube comprising an inner protective layer 15, a refractive index-reduced region 16, an undoped or doped intermediate layer 17, a further refractive index-reduced region 18 and an outer protective layer 19.

[0070] Fig.Figure 4 describes an advantageous embodiment of a casing tube comprising an inner protective layer 15, a refractive index-reduced region 18 and an outer protective layer 19. The outer diameters of the embodiments are 30 to 40 mm and the inner diameters are 25 to 35 mm.

[0071] In the first step of tube manufacturing, an auxiliary material is provided. This is preferably a graphite or SiC rod, although any other heat- and temperature-resistant material can also be used. In the example given, a graphite rod is used.

[0072] The graphite rod is then coated with an inner protective layer 15 with a wall thickness of 1-2 mm, preferably 1.5 mm. This layer can either be collapsed onto the graphite rod in the form of a substrate tube or formed by direct coating. This inner protective layer preferably consists of undoped quartz glass, although it may also contain at least one dopant, depending on the application. Subsequently, a fluorine-doped trench 18 with a wall thickness of 1.5-2.5 mm, preferably 2 mm, and a refractive index reduction of Δn between -0.006 and -0.012, preferably -0.009, is formed by deposition processes, preferably using the POVD or MCVD process or a smoker.

[0073] The outer protective layer of 0.2-3mm, preferably 1mm, is then applied, either by collapsing a tube with the desired glass composition or by direct coating using the aforementioned methods.

[0074] After removing the auxiliary material - in this example the graphite rod - the inner surface is processed and / or cleaned and / or heat treated.

[0075] This procedure is followed by a stretching step, resulting in an outer diameter of the new tube that is between 24 and 36 mm, preferably 32 mm. Light-guiding layers are deposited in this tube using either CVD or PIVD processes, with the refractive index increasing continuously after a certain number of layers. Finally, the resulting tube is collapsed into a capillary or a solid rod.

[0076] The resulting product, after its outer surface has been prepared, is either encased in at least one tube of the desired refractive index and wall thickness, or coated with further layers of the desired refractive index and wall thickness using direct coating. This ensures the correct core-to-cladding ratio in the final optical fiber.

[0077] The first step involves providing an auxiliary material for tube manufacturing, preferably a graphite or SiC rod, although any other heat- and temperature-resistant material can also be used. In the example given, a graphite rod with an outer diameter of 43 mm is used.

[0078] The graphite rod is then coated with a layer of carbon black of the desired refractive index. This is followed by the deposition of the inner protective layer 15, preferably consisting of undoped quartz glass with a thickness between 0.2 and 1.2 mm, preferably 0.7 mm. Subsequently, a first doped trench 16 with a wall thickness of 0.2 to 1.3 mm, preferably 0.7 mm, and a refractive index change of Δn between 0.001 and -0.005, preferably 0.0025, is formed by deposition processes, preferably using the POVD or MCVD process or a smoker.

[0079] A further intermediate layer of quartz glass with a wall thickness between 0.01 mm and 2.5 mm, preferably 0.7 mm, is applied using the aforementioned methods, wherein it is either undoped quartz glass or doped quartz glass, wherein in the latter case the following preferably applies to its refractive index difference Δn2: Δn2=Δn+ / −0.001

[0080] Following this intermediate layer 17, a fluorine-doped trench 18 is formed with a wall thickness of 0.3–2.5 mm, preferably 1.0 mm, and a refractive index reduction of Δn between -0.006 and -0.012, preferably -0.009. The remaining steps are the same as those of embodiment 1.

[0081] In another embodiment, the first step involves providing an auxiliary material for tube production, preferably a graphite or SiC rod, although any other heat- and temperature-resistant material can also be used. In the example given, a graphite rod with an outer diameter of 43 mm is used.

[0082] The graphite rod is then coated with a layer of carbon black of the desired refractive index. This layer is at least partially fused into a glass layer by subsequent coating processes. A fluorine-doped trench 18 with a wall thickness of 0.4–2.5 mm, preferably 1.5 mm, and a refractive index reduction of Δn between -0.006 and -0.012, preferably -0.009, is then formed by deposition processes, preferably using the POVD or MCVD process or a so-called smoker. This tube is provided with an outer protective layer 19, which preferably consists of undoped quartz glass and has a wall thickness between 0.1 and 3 mm, preferably 0.5 mm.

[0083] After the removal of the auxiliary material – in this example, the graphite rod – the inner surface is machined and / or cleaned and / or heat-treated. One or more stretching processes may follow.

[0084] The desired refractive index sequence is then produced using internal deposition processes such as MCVD or PIVD (Plasma Inside Vapor Deposition). After completion of the internal coatings, heat treatment and / or stretching processes can be carried out. Following surface preparation, the resulting product is encased with at least one tube of the desired refractive index and wall thickness, or, in the case of direct coating, coated with further layers of the desired refractive index and wall thickness. This ensures the correct core-to-cladding ratio in the final optical fiber.

[0085] It goes without saying that the exemplary embodiments presented here, in terms of the sequence of individual steps and coating parameters such as refractive index, wall thickness, diameter specifications, number of layers and sequence, must be adapted by a person skilled in the art according to the task to be solved.

[0086] The method has been described using exemplary embodiments. Further embodiments are described in the dependent claims and within the scope of professional practice. Reference symbol list 1 casing pipe 2 Inside 3 Protective, intermediate and barrier layer 4 Outside 5 light-guiding coating 6 inner light-guiding coating 7 outer light-guiding coating 8 core rod 9 middle jacket tube 10 outer casing pipe 15 inner protective layer 16 first endowed trench 17 Intermediate shift 18 fluoro-doped trenches 19 outer protective layer

Claims

[1] Method for producing a semi-finished product for manufacturing a bend-optimized optical fiber with a structured refractive index profile consisting of trench structures, gradations or combinations of several trenches of different widths and intermediate refractive index-enhanced webs, characterized by a convergent production process consisting of partial production of individual components, in which the semi-finished product is first pre-manufactured in the form of individual components, whereby the individual components are machined and pre-assembled as desired and joined together in a final production step, whereby the semi-finished product is formed, whereby the individual partial productions take place independently of each other, where at least two individual components are joined together at the end of the convergent production process to form the semi-finished product, wherein each partial production of the respective individual component includes at least one of the following partial production steps (A to I) carried out on a sheath tube (1) with a lower sheath refractive index compared to the light-guiding core: - Performing a partial manufacturing step (A) comprising applying at least one protective, intermediate and / or barrier layer (3) to an inner and / or outer surface (2, 4) of the casing tube, - Performing a partial manufacturing step (B) comprising an external and / or internal deposition of preferably light-guiding layers (5, 6, 7) on the inner and / or outer surface of the casing tube, - Performing a partial manufacturing step (C) comprising at least partial collapse of the coated or uncoated casing tube into a capillary or rod, - Performing a partial manufacturing step (D), comprising circumferencing the individual component and / or a rotationally symmetric substrate with at least one sheathing tube with a desired refractive index, - Performing a partial manufacturing step (E), comprising removing a protective, intermediate and / or barrier layer (3) arranged on the inner surface of at least one individual component, - Performing a partial manufacturing step (F) comprising removing a protective, intermediate and / or barrier layer (3) arranged on the outer surface of at least one individual component, - Performing a partial manufacturing step (G), comprising a change in the inner diameter of the casing tube (1) or the individual component by means of an inflation, compression and / or stretching process, - Performing a partial manufacturing step (H) comprising a change in the outer diameter of a rotationally shaped rod and / or tube and / or the individual component by means of an upsetting or stretching operation, - Performing a partial manufacturing step (I) comprising heat and / or tempering treatment and / or plasma and / or fire polishing. [2] Method according to claim 1, characterized by a partial production consisting of the partial production steps (A), (B), (C), (I), wherein - during the execution of the partial manufacturing step (A), the protective, intermediate and / or barrier layer (3) in the form of a quartz glass layer is applied to the outer surface of the casing tube, - during the execution of the partial manufacturing step (B), an internal deposition of germanium and / or phosphorus-doped quartz glass is carried out on the inner surface of the casing tube, - during the execution of the partial manufacturing step (C), a collapse into a solid core rod occurs, - during the execution of the partial manufacturing step (I), plasma polishing is carried out on the solid core rod, and subsequently the individual component thus created is combined with a cladding tube made of quartz glass to form the finished semi-finished product. [3] Method according to claims 1 and 2, characterized by a partial production process consisting of the partial production steps (A), (B), (C), (F), wherein after the execution of the partial production steps (A), (B) and (C) - during the execution of the partial manufacturing step (F) the outer protective layer is removed, and subsequently the individual component thus created is combined with a casing tube made of quartz glass to form the finished semi-finished product. [4] Method according to any one of the preceding claims, characterized bya partial production process consisting of the partial production steps (A), (B), (C), (I) and (B), wherein after the execution of the partial production steps (A), (B) and (C) - a plasma polish is performed during the execution of the partial manufacturing step (I), - in a sub-production step (B) following sub-production step (I) and carried out for the second time, at least one further outer coating with doped and / or undoped quartz glass is applied using a plasma coating. [5] Method according to any one of the preceding claims, characterized by , that the jacket tube (1) is provided in the form of a fluorine-doped quartz glass tube. [6] Method according to any one of the preceding claims, characterized by , that the formation of light-guiding layers (5, 6, 7) is carried out using a CVD and / or plasma process and / or flame pyrolysis. [7] Method according to any one of the preceding claims, characterized by , that the protective, intermediate and / or barrier layer (3) is preferably made of quartz glass with a higher melting point compared to the melting point of the material of the casing tube. [8] Method according to any one of the preceding claims, characterized by , that the protective, intermediate and / or barrier layer (3) has a diffusion-preventing blocking function against glass components, in particular refractive index-reducing dopants and / or in particular fluorine. [9] Method according to any one of the preceding claims, characterized by , that the protective, intermediate and / or barrier layer (3) has a chemical composition which, when the semi-finished product is applied to a further substrate, minimizes the thermal, physical and / or chemical differences between the semi-finished product and the further substrate, in particular the differences in the coefficients of thermal expansion and / or the different chemical compositions. [10] Method according to any one of the preceding claims, characterized by , that after the formation of the light-guiding layers (5, 6, 7) a deposition of at least one further inner protective, intermediate and / or barrier layer (3) is carried out. [11] Method according to any one of the preceding claims, characterized by , that with the help of at least one pressure control system, a targeted adjustment of an ambient pressure and / or an internal pipe pressure is carried out. [12] Method according to any one of the preceding claims, characterized by , that after the formation of the light-guiding layers (5, 6, 7) the outer casing collapses onto another substrate. [13] Method according to any one of the preceding claims, characterized by , that after the formation of the light-guiding layers (5, 6, 7) a partial or complete collapse process is carried out to form a capillary or a solid rod. [14] Method according to any one of the preceding claims, characterized by , that after the partial or complete collapsing process, mechanical processing to form a polygonal bar takes place. [15] Method according to any one of the preceding claims, characterized by , that a subsequent collapse of at least one further doped and / or undoped jacket tube or semi-finished product occurs, wherein in a collapsed doped jacket tube or semi-finished product the chemical composition of at least one dopant of each individual substrate assumes a constant, linear and / or gradual course radially. [16] Method according to any one of the preceding claims, characterized by that at least one further outer coating is applied. [17] Method according to any one of the preceding claims, characterized by , that in a final manufacturing step at least one of the protective, intermediate and / or barrier layers (3) is removed again. [18] Method according to any one of the preceding claims, characterized by that in an intermediate step and / or a final manufacturing step a surface treatment, preferably a plasma and / or fire polishing, is carried out. [19] Method according to any one of the preceding claims, characterized by that when glasses collapse, those of the same or similar chemical composition are combined.

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