Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
  • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
  • C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
  • C03B37/02781—Hollow fibres, e.g. holey fibres
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/012—Manufacture of preforms for drawing fibres or filaments
  • C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
  • C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
  • C03B37/0122—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube for making preforms of photonic crystal, microstructured or holey optical fibres
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/012—Manufacture of preforms for drawing fibres or filaments
  • C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
  • C03B37/01225—Means for changing or stabilising the shape, e.g. diameter, of tubes or rods in general, e.g. collapsing
  • C03B37/0124—Means for reducing the diameter of rods or tubes by drawing, e.g. for preform draw-down
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/02—Optical fibres with cladding with or without a coating
  • G02B6/02295—Microstructured optical fibre
  • G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
  • G02B6/02319—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by core or core-cladding interface features
  • G02B6/02323—Core having lower refractive index than cladding, e.g. photonic band gap guiding
  • G02B6/02328—Hollow or gas filled core
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/02—Optical fibres with cladding with or without a coating
  • G02B6/02395—Glass optical fibre with a protective coating, e.g. two layer polymer coating deposited directly on a silica cladding surface during fibre manufacture
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2203/00—Fibre product details, e.g. structure, shape
  • C03B2203/10—Internal structure or shape details
  • C03B2203/14—Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2203/00—Fibre product details, e.g. structure, shape
  • C03B2203/10—Internal structure or shape details
  • C03B2203/14—Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface
  • C03B2203/16—Hollow core
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2203/00—Fibre product details, e.g. structure, shape
  • C03B2203/42—Photonic crystal fibres, e.g. fibres using the photonic bandgap PBG effect, microstructured or holey optical fibres

Definitions

• the invention relates to a method for producing an anti-resonant hollow core fiber which has a hollow core extending along a longitudinal axis of the fiber and a cladding area surrounding the hollow core which comprises several anti-resonant elements, with the process steps:
• the invention also relates to a method for producing a preform for an anti-resonant hollow core fiber or for producing a semi-finished product from which the anti-resonant hollow core fiber is obtained by elongation, which has a hollow core extending along a longitudinal axis of the fiber and the inner cladding area surrounding the hollow core includes several anti-resonance elements, with the process steps:
• hollow core fibers in which the core comprises an evacuated, gas or liquid-filled cavity.
• the interaction of the light with the glass is less than in solid core fibers.
• the refractive index of the core is smaller than that of the cladding, so that light transmission through total reflection is not possible and the light would normally escape from the core into the cladding.
• hollow core fibers are divided into “photonic bandgap fibers” and “anti-resonance reflection fibers”.
• the hollow core area is surrounded by a cladding in which small hollow channels are periodically arranged.
• the periodic structure of the hollow channels in the cladding causes the effect known as the “photonic band gap” based on semiconductor technology, according to which light from certain wavelength ranges scattered on the cladding structures interferes constructively in the central cavity due to Bragg reflection and cannot propagate transversely in the cladding.
• the hollow core area is surrounded by an inner cladding area in which so-called “antiresonant elements” (or “antiresonant elements”; in short: “ AREs ”) are arranged.
• the walls of the anti-resonance elements evenly distributed around the hollow core can act as anti-resonance-operated Fabry-Perot cavities that reflect the incident light and guide it through the fiber core.
• This fiber technology promises low optical attenuation, a very broad transmission spectrum (also in the UV or IR wavelength range) and low latency in data transmission. '
• hollow core fibers are in the field of data transmission, high-performance beam guidance, for example for material processing processing, modal filtering, non-linear optics, especially for supercontinuity generation, from the ultraviolet to the infrared wavelength range.
• a disadvantage of antiresonant hollow core fibers is that higher order modes are not necessarily suppressed, so that they are often not purely single-mode over long transmission lengths and the quality of the output beam deteriorates.
• the effective mode suppression depends on the center wavelength of the transmitted light and on structural parameters of the fiber design, such as the radius of the hollow core and the difference in diameter between nested ring structures in the anti-resonance elements.
• An anti-resonant hollow core fiber is known from EP 3 136 143 A1 (referred to there as “hollow core fiber without band gap”), in which the core can conduct other modes in addition to the fundamental mode. For this purpose, it is surrounded by an inner jacket with “non-resonant elements”, which provide phase matching of anti-resonant modes with the higher modes.
• the hollow core fiber is manufactured using a so-called “stack-and-draw technique”, in which the starting elements are arranged in an axially parallel ensemble and fixed in a preform, and the preform is then elongated.
• a cladding tube with a hexagonal internal cross-section is used and in the Six so-called “ARE preforms” (anti-resonance element preforms) are fixed to the inner edges of the cladding tube.
• This preform is drawn into a hollow core fiber in two stages.
• a method for producing a preform for anti-resonant hollow core fibers is known in which a first cladding area comprises a large number of rods and a second cladding area comprises a plurality of tubes which are surrounded by a cladding tube. Rods, tubes and cladding are put together using the “stack and draw” technique to form a preform. Before the preform is elongated, the preform end is sealed, which is done by applying a sealing compound. A UV adhesive, for example, is used as the sealing compound.
• Antiresonant hollow core fibers and especially those with nested structural elements have complex internal geometries, which makes their exact and reproducible manufacture difficult. This is all the more true because, in order to maintain the resonance or anti-resonance conditions, even small dimensional deviations in the order of magnitude of the working wavelength of the light to be conducted cannot be tolerated. Deviations from the target geometry can be caused by the configuration of the fiber preform, and they can also occur as a result of undesired, out-of-scale deformations during the fiber drawing process.
• Antiresonance element preforms each consisting of an antiresonance element outer tube (short: ARE outer tube) and an antiresonant element inner tube (short: ARE inner tube) welded on one side of the inner surface of the ARE outer tube, can be attached to the inside of a cladding tube.
• the aim of the invention is to specify a method for the cost-effective production of an anti-resonant hollow core fiber which avoids the limitations of conventional production methods.
• the aim of the invention is to provide a method for producing an anti-resonant hollow core fiber and a preform for anti-resonant hollow core fibers with which high precision of the structural elements and exact positioning of the anti-resonant elements in the fiber can be achieved in a sufficiently stable and reproducible manner can.
• this object is achieved according to the invention, based on a method of the type mentioned at the beginning, in that the provision and / or the arrangement of the anti-resonant element preforms and / or the implementation of a process according to method step (d) involves fixing -Measure and / or a sealing measure using a sealing or bonding compound containing amorphous SiC particles.
• the starting point for the manufacture of the anti-resonant hollow core fiber is a preform, which is also referred to here as a “primary preform”. It comprises a cladding tube in which or on which precursors or preforms for forming anti-resonant elements in the hollow core fibers (referred to here as “anti-resonant elements” for short) are contained.
• the primary preform can be elongated into the hollow core fiber; As a rule, however, the primary preform is further processed in order to produce a preform, referred to here as a “secondary preform”. If necessary, the hollow core fiber is made by elongating the secondary preform generated.
• the primary preform or the secondary preform are surrounded by components with an overlay cylinder or with a plurality of overlay cylinders, forming a coaxial ensemble, and the coaxial ensemble is elongated directly to form the hollow core fiber.
• the general term “preform” is understood here to denote that component or that coaxial ensemble of components from which the hollow core fiber is ultimately drawn.
• the sealing or bonding compound used in the method according to the invention for sealing or fixing contains amorphous SiC particles which are absorbed in a dispersion liquid, for example. This mass is placed between the surfaces to be connected or sealed and is usually liquid or pasty when used. When drying at a low temperature, the dispersion liquid is partially or completely removed and the mass is solidified.
• the sealing or bonding compound, and in particular the solidified SiC -containing sealing compound or bonding compound obtained after drying meets the requirements for fixing and sealing.
• the temperature required for drying is below 300 ° C, which favors compliance with the dimensional accuracy of the preform and avoids thermal impairments.
• the sealing or connecting compound can thus be completely compressed by heating and vitrified by heating during the hot molding process.
• the sealing compound or compound behaves like quartz glass; it becomes viscous and malleable.
• the sealing or connecting compound can thus be densified by heating and is preferably vitrified by heating when a process is carried out according to method step (d).
• the sealing or bonding compound does not decompose and it releases little impurities. It is thus characterized by thermal stability and purity during the elongation process and it avoids deformations that can otherwise occur as a result of different thermal expansion coefficients between a sealing or bonding compound made of a material that does not contain SiC particles.
• the thermal expansion coefficient of the SiC -containing sealing or bonding compound ideally corresponds to that of the surfaces to be bonded and / or sealed. It can be changed and adapted by adding one or more dopants. Al 2 O 3 , T1O2, Y2O3, AlN, S13N4, Zr02, BN, HfCte or Yb2Ü3 come into consideration as dopants.
• anti-resonant hollow core fibers and preforms for them can be produced precisely and reproducibly.
• the antiresonance element preforms are fixed on the inside of the cladding tube using the sealing or bonding compound.
• the fixation takes place selectively at one or more points or it extends over a greater length or over the entire length of the anti-resonance element preform.
• the anti-resonance element preforms are generally cylindrical and have two opposite end regions, the fixing using the sealing or connecting compound preferably being carried out exclusively on one of the end regions or exclusively on both end regions.
• Impairment of the light conduction by the sealing or connec tion compound is thus reduced and it is prevented if the volume areas of the preform covered with sealing or connection compound are subsequently removed or not used to pull the hollow core fibers.
• the sealing or bonding compound is applied, for example, to the target positions of the antiresonance element preforms in dots or strips on the inside of the cladding tube, and the antiresonance element preforms are pressed onto this and thus at least temporarily fixed.
• the application area is preferably as small as possible in order to minimize impairment of the light guide.
• the application area is preferably so small that it is in one Projection from the preform central axis onto the anti-resonance element preform is not visible, that is to say it is completely covered by the anti-resonance element preform.
• a procedure has also proven itself in which a cladding tube with a circular inner cross section is provided, with a longitudinal structure, preferably a longitudinal groove, being produced on the inside of the cladding tube wall, which has a recess on or in which the Antiresonance element preforms are fixed.
• the sealing or connecting compound is introduced into the recess of the longitudinal structure, so that the anti-resonance element preforms contact the sealing or connecting compound when arranged at the respective target position according to method step (c).
• the anti-resonance element preforms can touch the longitudinal edges of the recess at the same time.
• the recess serves not only to accommodate the sealing or connecting compound, but also as a positioning aid for the anti-resonance element preform by making it easier for the anti-resonance element preforms to assume predetermined, defined positions on the inside of the cladding tube.
• the accuracy of the positioning of the preforms is improved by the fact that the cladding tube is structured in advance by machining.
• the longitudinal structure on the inside of the cladding tube is therefore preferably produced by drilling, sawing, milling, cutting or grinding.
• these processing techniques provide more precise and filigree structures using heat and pressure and they avoid contamination of the surfaces by molding tools such as nozzles, presses or melt molding.
• arranging the antiresonance element preforms on the inside of the cladding tube includes fixing by means of a positioning template to be inserted into the inside bore of the cladding tube, the several radially outwardly facing holding elements for positioning the antiresonance element preforms at the target positions having.
• the structurally predetermined star-shaped arrangement of the holding elements facilitates the exact positioning of the anti-resonance element preforms at the respective target positions and their fixation by means of the sealing or connection compound.
• the positioning template is preferably used exclusively in the area of the cladding tube end faces, preferably in the area of both cladding tube end faces.
• the nested structural elements are fixed to one another using the sealing or connecting compound.
• the individual nested structural elements are fixed to one another either selectively at one or more points, or they extend over a greater length or over the entire length of the structural elements, for example over a longitudinal strip on the cylindrical surface of cylindrical structural elements.
• the fixing of cylindrical structural elements using the sealing or connecting compound is preferably carried out only at one end or only at both ends of the structural elements.
• the preform is connected to a holder in order to carry out a process according to method step (d), where the bond between the preform and the holder is produced by means of the sealing or connecting compound.
• the holder is used to hold the preform with horizontally or vertically oriented preform longitudinal axis in a device for performing a hot forming process, for example on the feed device of an elongation or fiber drawing device. It can attack form on one end face or on both end faces and it is preferably made of glass.
• a fusion connection of these components is avoided, and thus also thermal deformations associated with the fusion connection.
• the preform is connected to a gas connection for carrying out a process according to method step (d), the connection between the preform and the gas connection being produced by means of the sealing or connecting compound.
• the gas connection is preferably made of glass and it is used for introducing a compressed gas or for evacuation.
• the route specified in the prior art is a connection sealed by a plastic compound. Although this is very flexible, it is not temperature stable. Leakages at high temperatures can lead to temperature fluctuations, especially during the fiber drawing process.
• the gas connection can rest on the preform as a whole, the connection being made with the cylinder jacket surface or with the end face of the outermost tube or the outermost material layer, and / or the gas connection can be made with individual components or parts of the preform, for example with nested structural elements of the Antiresonance element preforms.
• the use of ceramic adhesives can lead to tensions that can destroy the components.
• doping the SiC -containing sealing or connecting compound is advantageous in order to adapt the thermal expansion coefficient to that of the component or preform component to be connected.
• Al2O3, T1O2, Y2O3, AlN, S13N4, Zr02, BN, HfCte or Yb 2 0 3 come into consideration as dopants.
• open ends of the anti-resonance element preforms and / or individual nested structural elements of the anti-resonance element preforms and / or any annular gap between pipe elements are closed by means of the sealing or connecting compound to carry out a process according to process step (d).
• the anti-resonance element preforms consist of a single, non-nested structural element (for example a glass tube) or of several, smaller structural elements nested with one another, in which the glass tube encloses at least one tubular or planar component (nested elements).
• the sealing or connecting compound is used here for the fluidic sealing of individual or all structural elements of the preform. Sealing takes place by closing the openings on the end face of the structural elements concerned with the sealing compound or compound. In the case of structural elements that are open on both sides, it may be sufficient if one of the end openings is closed with the sealing or connecting compound. By closing structural elements, these are removed from the effects of pressurization or evacuation, which would otherwise act on the preform or on the non-closed structural elements. For example, in the case of structural elements that are nested with one another, the application of pressure or evacuation of one of the several smaller structural elements can be prevented in this way. This measure enables precise, defined pressure control, especially in the case of the fiber drawing process.
• the anti-resonance elements are arranged around the hollow core with an uneven symmetry.
• the accuracy of the positioning of the preforms in the cladding tube is further improved by providing tubular structural elements, at least some of which have a wall thickness in the range of 0.2 and 2 mm, preferably a wall thickness in the range of 0.25 and 1 mm, and wherein a cladding tube with an external diameter in the range of 90 and 250 mm and preferably with an external diameter in the range of 120 to 200 mm is provided.
• These components each have a length of at least 1 m and are relatively large-volume structural elements for the formation of anti-resonance elements. This simplifies handling.
• the gravitational force supports the parallelism and vertical alignment of the structural element longitudinal axes when the structural elements are each on their upper front end are positioned and fixed at the target position; for example and preferably using the sealing or connecting compound explained in more detail above and additionally or alternatively by means of the positioning template explained in more detail above.
• the technical problem given above is achieved according to the invention based on a method of the type mentioned at the beginning in that the provision and / or the arrangement of the anti-resonance element preforms and / or the implementation of a process according to Method step (d) comprises a fixing measure and / or a sealing measure using a sealing or bonding compound containing amorphous SiC particles.
• the preform is the starting point for the manufacture of the anti-resonant hollow core fibers.
• the primary preform By elongating the primary preform, either the anti-resonant hollow core fiber is drawn directly or another semi-finished product is first produced by further processing the primary preform, which is also referred to here as a “secondary preform” and from which the anti-resonant hollow core fiber can be drawn.
• the production of the preform includes the installation and connection of anti-resonance element preforms with a cladding tube.
• providing and / or arranging the Antiresonan zelement preforms includes a fixation measure using an amorphous SiO 2 particles containing and preferably glass-forming sealing compound or bonding compound when heated. Measures for producing the preform are explained above in connection with the production of the hollow core fiber and these explanations are hereby incorporated.
• the anti-resonance elements can be simple or nested structural elements of the hollow core fiber. They have at least two walls that, when viewed from the direction of the hollow core, have a negative curvature (convex) or have no curvature (flat, straight). They usually consist of a material that is transparent to the work light, for example glass, in particular doped or undoped S1O 2 , a plastic, in particular a polymer, a composite material or a crystalline material.
• anti-resonance element preforms Components or parts of the preform are referred to as anti-resonance element preforms, which essentially become anti-resonance elements in the hollow core fiber by simply elongating during the fiber drawing process.
• Antiresonance element precursors are components or parts of the preform that are only transformed into antiresonance element preforms or directly into antiresonance elements through reshaping.
• the anti-resonance element preforms can be simple or nested components on which positioning aids can also be fixed. They are originally in the primary preform.
• Nested antiresonance element preforms form nested antiresonance elements in the hollow core fiber. They are composed of an outer tube and at least one further structural element which is arranged in the inner bore of the outer tube.
• the further structural element can be a further tube which rests against the inner circumferential surface of the outer tube.
• the outer tube is referred to as the "anti-resonance element outer tube” or “ARE outer tube” for short, and the other tube as the “anti-resonance element inner tube” or “ARE inner tube” for short or as a “nested ARE inner tube”.
• At least one further structural element can be arranged in the inner bore of the nested ARE inner tube, for example a third tube resting on the inner surface of the nested ARE inner tube.
• a distinction is made between “outer nested ARE inner tube” and “inner nested ARE inner tube”.
• cross-section in connection with cylindrical anti-resonance element preforms and their cylindrical structural elements always refers to the cross section perpendicular to the respective cylinder longitudinal axis, namely - unless otherwise stated - the cross section of the outer contour (not: the cross section of the inner contour) for tubular components.
• intermediate products can arise in which the original anti-resonance element preforms are present in a shape that is different from the original shape.
• the changed shape is also referred to here as an antiresonance element preform or as an antiresonance element precursor.
• Preform / primary preform / secondary preform / core preform (cane)
• the preform is the component from which the anti-resonant hollow core fiber is drawn. It is a primary preform or a secondary preform produced by further processing the primary preform.
• the primary preform can be present as an enmul of at least one cladding tube and preforms or precursors for anti-resonance elements loosely received or firmly fixed therein.
• the further processing of the primary preform into a secondary preform from which the hollow core fiber is drawn can include performing one or more of the following hot forming processes once or repeatedly:
• a core preform is a preform obtained by collapsing and / or elongating a primary preform. Typically, it is covered with additional sheath material before or when the hollow core fiber is drawn.
• the primary preform When elongating, the primary preform is elongated.
• the elongation can take place without collapsing at the same time.
• the elongation can take place to scale so that, for example, the shape and arrangement of components or parts of the primary preform are reflected in the elongated end product.
• the primary preform can also be drawn out of scale and its geometry changed.
• the ensemble of at least one cladding tube and loosely received or firmly fixed preforms or precursors for anti-resonance elements is also referred to here as the “primary preform”.
• the primary preform includes the hollow core and a cladding area.
• This cladding area is also referred to as the “inner cladding area” if there is also an “outer cladding area” that has been created, for example, by collapsing onto the ensemble, and if a distinction is to be made between these cladding areas.
• the terms "inner jacket area” and "outer jacket area” are also used for the corresponding areas in the hollow core fiber or in intermediate products obtained by further processing the primary preform.
• pipe inside is also used as a synonym for “pipe inner jacket surface” and the term “pipe outside” is also used as a synonym for “pipe outer jacket surface”.
• inner bore in connection with a pipe does not mean that the inner bore was created by a drilling process.
• This processing creates a longitudinal structure which extends in the direction of the longitudinal axis of the filler tube and which serves as a positioning aid for the anti-resonance element preforms.
• the longitudinal structure is accessible from the inside of the cladding tube; it can also extend to the outside through the entire cladding tube wall.
• Particle size and particle size distribution of the SiC particles are characterized on the basis of the Dso values. These values are taken from particle size distribution curves which show the cumulative volume of the SiC particles as a function of the particle size.
• the particle size distributions are often characterized on the basis of the respective D10, D50 and D90 values.
• the Dio value characterizes the particle size that is not achieved by 10% of the cumulative volume of the Si0 2 particles, and accordingly the Dso value and the D90 value those particle sizes that are 50% and 90% of the cumulative Volume of the SiC particles is not reached.
• the particle size distribution is determined by scattered light and laser diffraction spectroscopy according to ISO 13320.
• FIG. 1 shows a first embodiment of a primary preform with antiresonance element preforms positioned therein and fixed using a SiO 2 -containing sealing or bonding compound for producing a preform for a hollow core fiber
• FIG. 2 shows a second embodiment of a primary preform with antiresonance element preforms positioned therein and fixed using a SiO 2 -containing sealing or bonding compound for producing a preform for a hollow core fiber
• FIG. 3 shows an enlarged view of an anti-resonance element preform, which is composed of several nested structural elements which are connected to one another using a SiO 2 -containing sealing or bonding compound,
• FIG. 4 shows a primary preform with anti-resonance element preforms positioned and fixed therein, some of which are closed using a sealing or bonding compound containing S1O2,
• FIG. 5 shows a primary preform with Antiresonan zelement preforms positioned and fixed therein, which are sealed gelungs- or bonding compound using a SiO 2 -containing sealing compound, and
• FIG. 6 shows a primary preform with a hollow core closed using a sealing or bonding compound containing SiO 2 and open anti-resonance element preforms positioned and fixed around the hollow core.
• the preform is used for fixing components or for sealing Hollow channels in the preform a S1O2-based sealing or connecting compound used.
• Amorphous SiC particles are obtained by wet grinding of grains made of high-purity quartz glass.
• An aqueous base slip is produced which contains the amorphous Si0 2 particles with a particle size distribution that is characterized by a D 50 value of about 5 pm and a D90 value of about 23 pm.
• the base slip is mixed with more amorphous Si0 2 grains with an average grain size of about 5 ⁇ m.
• the slip used as the bonding compound has a solids content of around 90%, of which at least 99.9% by weight consists of S1O2. To adapt the thermal expansion coefficient, small amounts of dopants can be present.
• the slip mass is applied to one or both of the contact surfaces to be connected. It is also possible to form a slip mass between the previously fixed contact surfaces. This is then solidified by drying and heating.
• the amorphous Si0 2 particles used for the formation of the slip consist of synthetically produced S1O2 or they are made on the basis of purified naturally occurring raw material.
• FIG. 1 shows schematically a primary preform 1 with a cladding tube 2 with a wall 2a, on the inside of which antiresonance element preforms 4 are fixed at previously defined azimuthal positions at a uniform distance; In the exemplary embodiment, there are six preforms 4.
• the cladding tube 2 is made of quartz glass and has a length of 500 mm, an outer diameter of 30 mm and an inner diameter of 24 mm.
• the anti-resonance element preforms 4 are present as an ensemble of interleaved structural elements (4a; 4b) made up of an ARE outer tube 4a and an ARE inner tube 4b.
• the ARE outer pipe 4a has an outer diameter of 7.4 mm and the ARE inner pipe 4b has an outer diameter of 3.0 mm.
• the wall thickness of both structural elements (4a; 4b) is the same and is 0.35 mm.
• the lengths of ARE outer tube 4a and ARE inner tube 4b correspond to the length of the cladding tube 1.
• the antiresonance element preforms 4 are fixed on the inner wall of the cladding tube 2 by means of the connecting compound 5 based on S1O2.
• the connecting compound 5 is applied in strips to the inside of the cladding tube wall and the antiresonance element preforms 4 are placed thereon using a positioning template with a structurally specified star-shaped arrangement of holding elements for the individual antiresonance element preforms 4.
• This method creates a precise and reproducible connection between the cladding tube 2 and the anti-resonance element preforms 4.
• longitudinal grooves 3 are produced in advance by milling on the inside of the wall 2a of the cladding tube 2 at the desired positions of the anti-resonance element preforms 4.
• the longitudinal grooves 3 are divided evenly around the inner circumference of the cladding tube 2 in six-fold symmetry.
• the connecting compound 5 is introduced into the longitudinal axis grooves 3 and the anti-resonance element preforms 4 are pressed against it so that they have two axially parallel lines of contact with the longitudinal edges of the longitudinal grooves 3.
• an exact alignment of the anti-resonance element preforms 4 is guaranteed.
• the anti-resonance element preforms 4 are therefore preferably pressed against the longitudinal grooves 3 by means of the above-mentioned positioning template during the gluing process.
• FIG. 3 schematically shows an embodiment of the anti-resonance element preform 4 in the form of an ensemble of interleaved structural elements (4a; 4b) made of an ARE outer tube 4a and an ARE inner tube 4b.
• the the two structural elements (4a; 4b) are connected to one another by means of the connection compound 5 based on S1O2.
• the primary preform 1 (that is the ensemble of cladding tube 2 and the structural elements (4a; 4b) used therein) is then processed into a larger, secondary preform for the hollow core fiber.
• a covering cylinder made of quartz glass and the coaxial ensemble of primary preform and covering cylinder is elongated at the same time to form the secondary preform.
• the upper ends of the primary preform and the overlay cylinder are connected to a holder made of quartz glass, the bond between the preform and holder being created using the bonding compound described .
• the secondary preform obtained after the collapsing and elongation process is also referred to as a “cane” in the English specialist literature. It is drawn to the hollow core fibers.
• the preform is additionally connected to a gas connection made of quartz glass, the connection between the preform and the gas connection also being produced by means of the connecting compound.
• their open ends are closed in advance by means of the SiO 2 -based sealing and connecting compound 5, as FIG. 4 shows schematically.
• the sealing and connecting compound 5 can be seen as a gray shaded area.
• sealing and connecting compound 5 closes a short length of the inner bore of the ARE inner tube 4b, preferably at that end which corresponds to the upper end when performing a hot forming process with a vertically oriented longitudinal axis of the preform.
• FIG. 5 shows an embodiment of the preform 1 in which both structural elements (4a; 4b) of the anti-resonance element preforms 4 are closed with the sealing and bonding compound.
• FIG. 6 shows an embodiment in which both structural elements (4a; 4b) of the antiresonance element preforms 4 are open, but the remaining cross section of the cladding tube inner bore is closed with the sealing and connecting compound 5. .

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• 2019
  • 2019-07-17 EP EP19186741.5A patent/EP3766843B1/de active Active
• 2020
  • 2020-07-15 CN CN202080035465.4A patent/CN113891864B/zh active Active
  • 2020-07-15 US US17/617,487 patent/US12240778B2/en active Active
  • 2020-07-15 JP JP2021570392A patent/JP7582976B2/ja active Active
  • 2020-07-15 WO PCT/EP2020/069977 patent/WO2021009211A1/de not_active Ceased

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