Fiber optics and fiber optic products

Abstract

The present invention relates to an optical fiber (1) with at least one fiber core (10), with at least one fiber sheath (11) which at least substantially encloses the fiber core (10) in the circumferential direction (U) and along the longitudinal axis (X), and with at least one fiber coating (12) which substantially encloses the fiber sheath (11) in the circumferential direction (U) and along the longitudinal axis (X), wherein the optical fiber (1) has at least one first exposed section (13a) where the fiber sheath (11) is exposed from the fiber coating (12) for removing light (B) at least from the fiber sheath (11), wherein at least the fiber sheath (11) has a plurality of depressions (14) at least substantially in the radial direction (R) which are configured to at least partially remove the light (B) from the fiber sheath (11).wherein the depressions (14) are formed as longitudinal depressions (14) each at least section by exactly along the longitudinal axis (X). The glass fiber (1) is characterized in that at least some of the longitudinal depressions (14) have at least section by a plurality of elevations (15) at least on their bottom (14d).

Description

[0001] The present invention relates to a glass fiber according to the preamble of patent claim 1 and to a glass fiber product comprising such a glass fiber according to patent claim 22.

[0002] Glass fibers are used in many different technical fields today. Glass fibers are typically drawn as thin threads from molten glass, so that a glass fiber is a long, thin fiber made of glass. Glass fibers can be used, for example, in textile fabrics for thermal insulation and / or sound insulation. Short pieces of glass fiber are also commonly added to plastics to improve their mechanical properties; such components can be referred to as glass-fiber-reinforced plastics.

[0003] However, there are also numerous technical and, in particular, high-tech applications in which optical fibers are used for light transmission. For example, optical fibers are used for data transmission via light; in this case, the optical fibers can also be referred to as optical waveguides or passive optical fibers. Optical fibers are also used in medicine, for example, for lighting and for generating images in microscopes, inspection cameras, and endoscopes. Furthermore, optical fibers are used in sensors, which can then be referred to as fiber optic sensors.

[0004] Another application for fiber optics is laser technology. Here, the laser radiation can be guided from a laser source to a processing location using a fiber optic cable, for example, to perform cutting or welding in materials processing or medicine. The laser beam can also be guided to a sample in this way, for example, in metrology, microscopy, or spectroscopy. Fiber optics can be used to guide a laser beam in applications such as mechanical engineering, telecommunications, medical technology, and sensor technology.

[0005] Glass fibers can also be used to generate laser light and are referred to as active glass fibers. Fiber lasers or fiber amplifiers have a doped fiber core (see below), which forms the active medium of the laser. Common doping elements in the laser-active fiber core are neodymium, ytterbium, erbium, thulium, and holmium. Such fiber lasers are usually optically pumped by coupling radiation, for example from diode lasers or other radiation sources, as pump light parallel to the signal light in the fiber core into the fiber cladding or directly into the fiber core. If the pump light is radiated into the fiber optic cable in the direction of propagation of the signal to be amplified, this is typically referred to as "forward pumping." If the pump light is radiated against the direction of propagation of the signal to be amplified, this is typically referred to as "backward pumping."The laser radiation that is guided through the laser-active fiber experiences a very high amplification due to its great length.

[0006] Glass fibers used for light transmission or to generate laser radiation usually have a fiber core, which can be made of pure glass such as pure quartz glass or can also be doped. Depending on the size and numerical aperture of the fiber core, a distinction can be made between single-mode and multi-mode glass fibers. In addition, the fiber core can also have polarization-maintaining properties for the light. The fiber core is usually surrounded radially from the outside by at least one fiber cladding, which is usually closed in the circumferential direction and thus completely surrounds the fiber core, apart from the two open ends of the glass fiber.

[0007] Typically, the optical fiber is surrounded by a fiber coating, e.g., made of a polymer similar to the fiber cladding, which can then be added to the fiber. The fiber coating can serve to mechanically protect the glass interior of the fiber and also influence its optical properties. Typically, in optical fibers in which the light is guided exclusively in the fiber core (single-clad optical fibers), the fiber coating primarily serves to provide mechanical protection. Optical fibers that guide light in both the fiber core and the fiber cladding (double-clad optical fibers) are typically designed with a fiber coating to meet both mechanical and optical properties.

[0008] Two commonly used cross-sectional shapes for the fiber cladding are cylindrical and octagonal. The octagonal shape for the fiber cladding is used particularly for active glass fibers.

[0009] Such glass fibers can be produced in long lengths and are usually available in rolls. The diameter of the fiber cladding typically varies between approximately 80 µm and approximately 1 mm. Especially with larger fiber diameters, the term "rod-type fiber" is often used in practice.

[0010] In fiber-optic optical systems, particularly in laser systems, optical radiation can thus be generated, amplified, and transported. Furthermore, in various applications, it may be necessary, or at least advantageous, to safely and effectively dissipate optical radiation or optical power from the fiber optic cable in order to prevent damage to or destruction of the fiber-optic optical system and / or peripheral devices and / or, for example, workpieces, analysis samples, measurement objects, or persons. For example, in fiber lasers, the unabsorbed optical pump power and / or interfering optical signal power can typically be dissipated from the fiber cladding in a controlled manner using a suitable fiber component.

[0011] In fiber optic beam guidance from the laser to the workpiece, such as with diode, fiber, and solid-state lasers, such a fiber optic component can typically be used for the controlled removal of light located in the fiber cladding rather than in the fiber core. For example, in a laser diode module with an optical output power of approximately 2 kW, for example, when coupled into a glass fiber with a core diameter of approximately 100 µm, optical power losses of approximately 15% can occur due to the rectangular beam profile (slow / fast axis). This can require the corresponding optical fiber component to handle an optical power loss of approximately 300 W. For example, in ytterbium fiber laser systems with an optical output power of several kW that operate at a wavelength of around 1 µm, unabsorbed pump light of several hundred W usually has to be safely removed by a corresponding optical fiber component.The safe and targeted removal of optical radiation from the fiber cladding can also be used specifically for various applications, e.g. in medical or lighting technology.

[0012] WO 2011 067 908 A1 describes a method for processing a glass fiber such that the glass fiber has a section for removing the light from the fiber cladding. In this section of the glass fiber, the fiber coating is removed, leaving the fiber cladding exposed radially outward. Groove-like depressions extending in the circumferential direction are introduced into the radially outer surface of the fiber cladding. These groove-like depressions can be arranged at equal or different distances from one another along the longitudinal axis of the glass fiber, which is the elongated extension direction of the glass fiber. The groove-like depressions can be continuous or discontinuous in the circumferential direction.

[0013] Because the laser light propagates along the longitudinal axis of the optical fiber and the circumferential groove-like depressions are perpendicular to the longitudinal axis, the laser light striking the surfaces of the groove-like depressions can be specifically removed from the fiber cladding in this area. In this area, the exiting laser light can be specifically absorbed by a heat sink, and the heat generated by the dissipated, absorbed laser light outside the optical fiber can be dissipated without causing damage. Further along the optical fiber, after the section for removing the light from the fiber cladding, the laser light traveling within the fiber cladding can be reduced accordingly or even completely eliminated.

[0014] The disadvantage, however, is that the circumferential groove-like depressions on the radially outer surface of the fiber cladding can weaken the tensile strength of the glass fiber along its longitudinal axis. This can lead to breakage or tearing of the glass fiber. Particularly in fiber optic applications that require high reliability, i.e., high fracture resistance, such as deep-sea fiber optic cables or fiber optic applications for medical technology or aviation, such material weakening of the fiber cladding can pose a significant risk.

[0015] To minimize such a weakening of the tensile strength of the glass fiber despite the circumferential groove-like depressions, the circumferential groove-like depressions can be formed with the smallest possible radial depth. However, this reduces the aforementioned desired effect of the circumferential groove-like depressions, i.e., the targeted removal of the laser light from the fiber cladding. This leads to a conflict of objectives between the most efficient removal of the laser light from the fiber cladding and the maintenance of the tensile strength of the glass fiber in the region of the circumferential groove-like depressions on the radially outer surface of the fiber cladding.

[0016] Therefore, US 2020 / 0041719 A1 discloses a method for ablating an optical fiber, which involves generating a laser beam for a plurality of discrete time periods. The laser beam strikes the optical fiber and ablates it during each discrete time period. Each discrete impact of the laser beam during one of the plurality of discrete time periods is at a different location on a surface of the cladding. The ablation of the optical fiber during the plurality of discrete time periods forms a plurality of discrete craters or holes with a predetermined diameter and a predetermined depth, which have a semicircular or substantially cylindrical shape. The plurality of discrete craters are spaced from one another in an array that extends along a longitudinal axis of the optical fiber and around a circumference of the optical fiber.Between the discrete time periods, either the optical fiber or the laser beam source is moved and positioned for the next laser beam.

[0017] It is therefore advantageous that the point-like, discrete craters or holes can reduce material weakening compared to the circumferentially extending groove-like depressions of the radially outer surface of the fiber cladding of WO 2011 067 908 A1. For this reason, the point-like, discrete craters or holes of US 2020 / 0041719 A1 can also be formed radially relatively deep toward the fiber core without excessively reducing the tensile strength.

[0018] The disadvantage, however, is that even with a radially relatively deep formation of the point-like discrete craters or holes of US 2020 / 0041719 A1 towards the fiber core, the dissipative effect of the discrete craters or holes due to their semicircular or substantially cylindrical shape is nevertheless less than the dissipative effect of the groove-like depressions of the radially outer surface of the fiber cladding of WO 2011 067 908 A1 running in the circumferential direction, which form a significantly larger area perpendicular to the propagation direction of the laser light in the fiber cladding, which can lead to the laser light being dissipated out of the fiber cladding.

[0019] If necessary, a high number or density of craters or holes of US 2020 / 0041719 A1 and / or their radially very deep formation towards the fiber core can increase their overall effect and approximate the effect of the circumferentially extending groove-like depressions of the radially outer surface of the fiber cladding described in WO 2011 067 908 A1. However, this can lead to a significant mechanical weakening of the stability of the fiber cladding, particularly in the longitudinal direction of the glass fiber. In other words, the lower efficiency of the craters or holes of US 2020 / 0041719 A1 compared to the circumferentially extending groove-like depressions of WO 2011 067 908 A1 can be at least partially compensated for by a high spatial density of holes. However, this can significantly limit or reduce the mechanical stability of the glass fiber.

[0020] US 2010 / 0097822 A1 describes a light-scattering device for use in photodynamic therapy, which has a progressively distally increased exposed amount of core fibers defining a light-emitting section. This prevents excessive light emission at proximal locations and provides an increased amount of available light energy at distal locations, enabling uniform emission of light energy along the light-emitting section.

[0021] US 5 248 311 A describes a fiber optic probe for guiding laser beams during the removal of deposits from blood vessels, the deposits having a shape, the fiber optic probe comprising an optical fiber having a beam entrance end and a beam exit end, the beam exit end having specific boundaries corresponding to the shape of the deposits.

[0022] US 2015 / 0362684 A1 describes a pump beam stripper comprising an optical fiber including a core, a primary cladding configured to surround the core, and a secondary cladding configured to surround the primary cladding, the secondary cladding including an opening exposing a portion of the primary cladding; and an atypical glass substance irregularly deposited on a surface of the primary cladding exposed by the opening.

[0023] US 2020 / 0099190 A1 describes a multi-clad light stripper (CLS) for optical fibers having an inner cladding with one or more recessed surface regions to remove light propagating within the inner cladding. A CLS can have such recessed surface regions along two or more azimuthal angles around the fiber axis, for example, to improve the stripping effect. One or more dimensions or the spatial distribution of the recessed surface regions can be randomized, for example, to improve the uniformity of stripping for a variety of modes propagating in the cladding. Adjacent recessed surface regions can abut one another, for example, as segments of a recess that occupies most or even all of the length of a fiber surrounded by a heat sink.One or more dimensions or angular positions of individual of the abutting depressed surface areas may vary according to a regular or irregular pattern.

[0024] An object of the present invention is to provide a glass fiber of the type described above so that the possibilities for removing light from the fiber cladding can be improved and / or expanded. In particular, the tensile strength of the glass fiber along its longitudinal extension direction should be maintained as much as possible. At the very least, an alternative to known glass fibers of this type should be created.

[0025] The object is achieved according to the invention by a glass fiber having the features of patent claim 1 and by a glass fiber product having the features of patent claim 22. Advantageous further developments are described in the subclaims.

[0026] The present invention therefore relates to a glass fiber with at least one fiber core, with at least one fiber cladding which at least substantially encloses the fiber core in the circumferential direction and along the longitudinal axis, and with at least one fiber coating which substantially encloses the fiber cladding in the circumferential direction and along the longitudinal axis, wherein the glass fiber has at least a first exposed section, where the fiber cladding is exposed from the fiber coating, for removing light at least from the fiber cladding, wherein at least the fiber cladding has a plurality of depressions at least substantially in the radial direction, which are designed to at least partially conduct the light at least from the fiber cladding.

[0027] The glass fiber according to the invention is characterized in that the depressions are formed as longitudinal depressions, at least in sections, exactly along the longitudinal axis.

[0028] In other words, the recesses of the glass fiber according to the invention are formed, at least in sections, to run exclusively along the longitudinal axis of the glass fiber, i.e., its elongated extension direction. This can be achieved by a relative movement between the glass fiber and the tool for forming the recesses, which movement occurs exclusively along the longitudinal axis of the glass fiber.

[0029] The present invention is based on the finding that, in this way, the area of ​​the longitudinal recesses, by means of which light can be conducted outward at least from the fiber cladding of the glass fiber, can be increased compared to the cylindrical craters or holes of US 2020 / 0041719 A1, without reducing the material of at least the fiber cladding in the circumferential direction, i.e., perpendicular to the longitudinal axis. In this way, a further weakening of the mechanical stability of the glass fiber along the longitudinal axis can be avoided, while the conduction of light outward at least from the fiber cladding of the glass fiber can be increased.

[0030] The removal of light at least from the fiber cladding of the glass fiber can, in a manner comparable to the cylindrical craters or holes in US 2020 / 0041719 A1, take place at the front side of the longitudinal depressions, which faces the direction of propagation of the light at least in the fiber cladding along the longitudinal axis. In addition, at least the base or floor of the longitudinal depressions, which extends along the longitudinal axis and faces radially towards the fiber core, can be used to remove light at least from the fiber cladding of the glass fiber. This can, in particular compared to the cylindrical craters or holes in US 2020 / 0041719 A1, increase the area which can be effective for removing light at least from the fiber cladding of the glass fiber. At the same time, the longitudinal depressions can have an extension in the circumferential direction which is comparable to the cylindrical craters or holes in US 2020 / 0041719 A1.holes of US 2020 / 0041719 A1, so that the longitudinal depressions can cause a comparable and, in particular, no greater weakening of the mechanical stability of the glass fiber in the circumferential direction than the cylindrical craters or holes of US 2020 / 0041719 A1.

[0031] Thus, a glass fiber according to the invention can be created which has at least comparable mechanical properties to the cylindrical craters or holes of US 2020 / 0041719 A1, but due to the elongated extension of the longitudinal depressions along the longitudinal axis can offer a larger effective area between the material of at least the fiber cladding and the environment, which can serve to dissipate light at least from the fiber cladding.

[0032] For this purpose, the longitudinal depressions can be introduced at least into the fiber cladding precisely in the radial direction and obliquely to the radial direction. The longitudinal depressions can also run obliquely or rectilinearly in the circumferential direction in sections of their elongated extension. In any case, however, the longitudinal depressions run at least partially precisely along the longitudinal axis of the glass fiber and preferably directly radially. The longitudinal depressions can also be implemented in combination with other depressions, such as the known circumferentially extending grooves of WO 2011 067 908 A1 and / or the point-like craters or holes of US 2020 / 0041719 A1. This can increase the design options. To utilize the previously described advantages of longitudinal depressions according to the invention, it can, however, be advantageous to design the depressions at least of the fiber cladding exclusively as longitudinal depressions.

[0033] According to one aspect of the invention, the longitudinal recesses are each formed completely precisely along the longitudinal axis and / or completely precisely in the radial direction. This can maximize the implementation and utilization of the previously described properties and advantages of longitudinal recesses according to the invention. It can also simplify the introduction of the longitudinal recesses according to the invention, at least into the fiber cladding, since this can be achieved with a relative movement between the fiber and the tool exclusively along the longitudinal axis of the fiber and / or precisely radially aligned to the fiber.

[0034] According to a further aspect of the invention, the longitudinal recesses each have a width in the circumferential direction that corresponds to the width of a tool with which the longitudinal recesses were introduced at least into the fiber cladding. Such a tool can be a laser beam, a milling tool, or the like. This makes it easy to form the longitudinal recesses so that they extend completely along the longitudinal axis, at least in sections.

[0035] According to a further aspect of the invention, at least some of the longitudinal recesses are spaced differently from one another in the circumferential direction and / or along the longitudinal axis. This can increase the design options for the effect of the longitudinal recesses to guide light outward, at least from the fiber cladding.

[0036] According to a further aspect of the invention, the longitudinal depressions are increasingly spaced from one another along the longitudinal axis in the direction of light propagation. This can increase the design options for the effect of the longitudinal depressions to conduct light at least from the fiber cladding to the outside. In particular, this makes it possible to take into account that light from at least the fiber cladding to the environment can already be conducted from the first longitudinal depressions, which the light can strike at least in the fiber cladding along the longitudinal axis, and thus the light can be reduced at least in the fiber cladding. The longitudinal depressions following at least in the fiber cladding along the longitudinal axis in the direction of light propagation can thus be spaced further apart, since increasingly less light can be conducted at least from the fiber cladding as the glass fiber progresses.At the same time, this can minimize the effort required to create the longitudinal recesses in the fiber optic cable.

[0037] According to a further aspect of the invention, at least some of the longitudinal recesses are equally spaced from one another in the circumferential direction and / or along the longitudinal axis. This can increase the design options for the effect of the longitudinal recesses to conduct light outward, at least from the fiber cladding. In particular, this can ensure the most uniform possible conduction of light, at least from the fiber cladding, in the circumferential direction and / or along the longitudinal axis.

[0038] According to a further aspect of the invention, at least one first longitudinal recess has a first length along the longitudinal axis, and at least one second longitudinal recess has a second length along the longitudinal axis, wherein the first length and the second length are different. This can increase the design options for the effect of the longitudinal recesses to guide light outward at least from the fiber cladding.

[0039] According to a further aspect of the invention, at least one first longitudinal recess has a first width in the circumferential direction, and at least one second longitudinal recess has a second width in the circumferential direction, wherein the first width and the second width are different. This can increase the design options for the effect of the longitudinal recesses to guide light outward at least from the fiber cladding.

[0040] According to a further aspect of the invention, at least one first longitudinal recess has a first depth in the radial direction, and at least one second longitudinal recess has a second depth in the radial direction, wherein the first depth and the second depth are different. This can increase the design options for the effect of the longitudinal recesses to guide light outward at least from the fiber cladding.

[0041] According to a further aspect of the invention, the first exposed section is surrounded by a heat sink at least in sections, preferably completely, in contact with it or at a distance, wherein the heat sink, facing the exposed section, is designed to absorb and / or reflect the light at least from the fiber cladding at least in sections. Such a heat sink can be formed by at least one arbitrary body that is capable of absorbing and / or reflecting the light emitted at least from the fiber cladding and thus keeping it away from the glass fiber and the environment. The heat sink can in particular be a body made of metal or plastic, which can absorb the light emitted at least from the fiber cladding and store it as heat and / or, for example, with cooling fins or the like directed outwards away from the glass fiber, dissipate it to the environment away from the glass fiber.For this purpose, the body can, in particular, have a black, matte coating facing the first exposed section of the fiber optic cable, which can promote the absorption of light. This can also be done by contact or at a distance from the body.

[0042] According to a further aspect of the invention, the optical fiber has at least a second exposed section, where the fiber cladding is exposed from the fiber coating, for conducting light at least from the fiber cladding, wherein the first exposed section and the second exposed section are arranged at least partially, preferably completely, at an angle to one another, preferably parallel to one another. In this way, the previously described properties and advantages can be implemented in two sections spaced apart from one another along the longitudinal axis of the optical fiber. As a result, each of the two exposed sections can be made shorter along the longitudinal axis without limiting the effect as a whole.

[0043] In particular, the glass fiber can extend at an angle along its elongated extension along the longitudinal axis between the two exposed sections, allowing a comparatively compact arrangement of the two exposed sections of the glass fiber. For this purpose, the two exposed sections can be bent, in particular, at right angles to one another and, in particular, arranged in a U-shape and parallel to one another, which can particularly reduce the installation space of the glass fiber in this region of their elongated extension. As a result, the glass fiber with the two exposed sections, particularly in a parallel arrangement, can form a comparatively compact glass fiber component, by means of which the properties and advantages described above can be realized.

[0044] According to a further aspect of the invention, the glass fiber has an optical element which is arranged at an open end of the fiber core and forms an open end of the glass fiber along the longitudinal axis. Such an optical element can also be referred to as an optical window and, for example, be designed as an optical lens. By means of such an optical element, the light traveling in the fiber core can be coupled out of the glass fiber in a predetermined manner and thus emitted to the outside at the end of the glass fiber. The optical element can serve to guide the light from the fiber core and / or to mechanically connect the glass fiber to a component that transmits the light further.In particular, the laser beam diameter can be widened as light from the fiber core by means of the optical element in the form of an optical window, or the laser beam can be collimated as light from the fiber core by means of the optical element in the form of an optical lens.

[0045] According to a further aspect of the invention, at least some of the longitudinal recesses extend radially into the fiber core. In this way, light can also be additionally guided outward from the fiber core, which may be necessary or useful for specific applications. This can further increase the design flexibility of the optical fiber according to the invention.

[0046] According to the invention, at least some of the longitudinal recesses, preferably all of the longitudinal recesses, have a plurality of elevations at least partially, preferably completely, at their base. These elevations are also designed to conduct light outward, at least from the fiber cladding. For this purpose, the elevations can be integrally bonded to the material of the fiber cladding.

[0047] The present invention is based on the finding that by enlarging the surface area of ​​at least the fiber cladding outwardly through elevations, the area can be increased or an additional area can be created through which light can be dissipated outwardly, at least from the fiber cladding. This can promote the dissipation of light outwardly, at least from the fiber cladding. Arranging the elevations within the longitudinal recesses at their base or on their bottom can, in particular, promote the dissipation of light at least from the fiber cladding there.

[0048] According to a further aspect of the invention, the outer surface of the fiber cladding has a plurality of elevations at least directly adjacent to at least some of the longitudinal depressions, preferably adjacent to all of the longitudinal depressions, at least in sections, preferably completely. This can enable the previously described elevations to be used on the outer surface of the fiber cladding as well, in order to additionally conduct light there too, at least from the fiber cladding to the environment. Depending on the material, thickness, shape, distribution, refractive index and other properties, the elevations can significantly contribute to the conduction of unwanted laser radiation as light at least from the fiber cladding of the glass fiber, without reducing the tensile strength of the glass fiber. Thus, the efficient light conduction can be significantly increased if necessary by the elevations and thus if necessary.the longitudinal depressions are minimized, which can contribute to a further increase in the tensile strength of the glass fiber.

[0049] According to a further aspect of the invention, the elevations of the same longitudinal depression and / or multiple longitudinal depressions are at least partially, preferably completely, identical or different in terms of material, thickness, refractive index, shape, distribution, and / or density. This can increase the design flexibility for the formation of the previously described elevations.

[0050] According to a further aspect of the invention, at least some of the elevations, preferably all of the elevations, are formed by fiber cladding material, which is produced by at least one tool during the introduction of the longitudinal recesses, at least into the fiber cladding. For this purpose, the process parameters for introducing the longitudinal recesses can be specifically coordinated to remove fiber cladding material at all or to remove a sufficient amount and simultaneously apply it as elevations to the bottom of the longitudinal recess and / or to the outside of the fiber cladding. A laser beam, in particular, can be used as a tool for this purpose.In this case, a targeted adjustment of the process parameters for the introduction of the longitudinal depressions may be necessary in order to be able to process and use the fiber cladding material in this way, since usually when the longitudinal depressions are introduced, at least into the material of the fiber cladding, the removed fiber cladding material evaporates or evaporates and no fiber cladding material at all or only to an insufficiently small extent can form the elevations described above.

[0051] This aspect of the invention is based on the finding that the introduction of longitudinal depressions at least into the fiber cladding of the glass fiber, for example by means of a tool in the form of a laser beam, with an appropriate and deliberate choice of the process parameters, can lead to the removal of fiber cladding material. The processing parameters can be specifically selected in such a way that fiber cladding material is released, which can settle on the base or bottom of the longitudinal depressions and / or on the outer surface of the fiber cladding, at least immediately adjacent to the longitudinal depressions, and adhere there. Due to the heating of the fiber cladding material by the laser processing, the fiber cladding material can have a sufficiently high temperature or viscosity, particularly at this moment, to form a film on the heated fiber cladding material of the base or bottom of the longitudinal depressions and / or on the outer surface of the fiber cladding.or to adhere firmly to the outer surface of the fiber sheath at least immediately adjacent to the longitudinal depressions and to harden there.

[0052] This allows the previously described elevations to be formed on the base or floor of the longitudinal recesses and / or on the outer surface of the fiber cladding by directly inserting the longitudinal recesses into the glass fiber, thus avoiding an additional processing step. At the same time, the elevations can be formed from the same material as the fiber cladding. This can promote a stable bond between the elevations and the fiber cladding material. This can similarly apply to the base or floor of longitudinal recesses if the longitudinal recesses extend radially into the fiber core.

[0053] According to a further aspect of the invention, at least one longitudinal recess, preferably several longitudinal recesses, particularly preferably all longitudinal recesses, have at least one material filling, preferably several different material fillings, at least in sections, preferably completely, wherein the material of the material filling differs from the material of the fiber core and / or from the material of the fiber cladding. A material or a material filling is understood to mean a material and in particular not a gas such as air.

[0054] This aspect of the invention is based on the idea that the removal of light from at least the fiber cladding of the optical fiber can be facilitated by filling the longitudinal recess, which can be filled with gas, such as air, at least partially and preferably completely, with at least one material that differs from the material of the fiber core or the fiber cladding of the optical fiber. This allows the removal or dissipation of at least the cladding light to the outside to be additionally influenced and, in particular, improved.

[0055] In this case, the longitudinal recess can be filled in sections or partially along the elongated extent in the direction of the longitudinal axis and / or perpendicular thereto in width and / or height with at least one material. This can be done the same or different for several or all longitudinal recesses. Different materials can also be combined with one another as material fillings for each longitudinal recess. Furthermore, the section-by-section or partial filling in the direction of the longitudinal axis and / or perpendicular thereto in width and / or height can be designed as desired for the different materials and in particular the same or different for several or all longitudinal recesses.

[0056] According to a further aspect of the invention, the material of the material filling has a refractive index that favors the removal of light at least from the fiber cladding. This can promote the implementation of the previously described properties and advantages of the material filling.

[0057] According to a further aspect of the invention, at least two longitudinal recesses, preferably all longitudinal recesses, are filled with the material filling of different lengths, widths, and / or heights. This can increase the design possibilities of the material filling.

[0058] According to a further aspect of the invention, at least two longitudinal recesses, preferably all longitudinal recesses, have different materials for the material filling. This can increase the design possibilities for the material filling.

[0059] The present invention also relates to a fiber optic product comprising at least one fiber optic as described above. A fiber optic product can be any product or device in which a fiber optic according to the invention can be used as intended. In particular, these can be products or devices in laser technology, measurement technology, medical technology, and the like, as described above. Such a fiber optic product can be an end product for use by a user and / or an intermediate product or a component of such an end product. In this way, the properties and advantages of a fiber optic according to the invention can be implemented and utilized.

[0060] Several embodiments and further advantages of the invention are illustrated schematically below and explained in more detail in conjunction with the following figures. Fig. 1 shows a longitudinal section through a glass fiber according to the invention according to a first embodiment; Fig. 2 a side view of the fiber optic cable of the Fig. 1; Fig. 3 a cross-section of the glass fiber of the Fig. 1; Fig. 4 a perspective view of the fiber optic cable of the Fig. 1 with only one exemplary longitudinal recess; Fig. 5 shows a longitudinal section through a glass fiber according to the invention according to a second embodiment; Fig. 6 a side view of the fiber optic cable of the Fig. 5; Fig. 7 shows a longitudinal section through a glass fiber according to the invention according to a third embodiment; Fig. 8 a side view of the fiber optic cable of the Fig. 7; Fig. 9 shows a longitudinal section through a glass fiber according to the invention according to a fourth embodiment; Fig. 10 a side view of the fiber optic cable of the Fig. 9; Fig. 11 a first cross-section of the glass fiber of the Fig. 9; Fig. 12 a second cross-section of the glass fiber of the Fig. 9; Fig. 13 a longitudinal section through a glass fiber according to the invention according to a fifth embodiment; Fig. 14 a side view of the fiber optic cable of the Fig. 13; Fig. 15 a cross-section of the glass fiber of the Fig. 13; Fig. 16 shows a longitudinal section through a glass fiber according to the invention according to a sixth embodiment; Fig. 17 a side view of the fiber optic cable of the Fig. 16; Fig. 18 a cross-section of the glass fiber of the Fig. 16; Fig. 19 shows a longitudinal section through a glass fiber according to the invention according to a seventh embodiment; Fig. 20 shows a longitudinal section through a glass fiber according to the invention according to an eighth embodiment; Fig. 21 shows a longitudinal section through a glass fiber according to the invention according to a ninth embodiment; Fig. 22 a cross-section of the glass fiber of the Fig. 21.

[0061] The above figures are viewed in cylindrical coordinates. A longitudinal axis X extends. A radial direction R extends perpendicular to the longitudinal axis X, away from the longitudinal axis X. A circumferential direction U extends perpendicular to the radial direction R and around the longitudinal axis X.

[0062] Fig. 1 shows a longitudinal section through a glass fiber 1 according to the invention according to a first embodiment. Fig. 2 shows a side view of the optical fiber 1 of the Fig. 1. Fig. 3 shows a cross section of the glass fiber 1 of the Fig. 1. Fig. 4 shows a perspective view of the optical fiber 1 of the Fig. 1 with only one exemplary longitudinal recess 14.

[0063] A glass fiber 1 extends along the longitudinal axis X and has a cylindrical shape. The glass fiber 1 has a fiber core 10, which is arranged centrally. The fiber core 10 is made of quartz glass. The fiber core 10 is completely enclosed in the radial direction R by a fiber cladding 11. The fiber cladding 11 extends cylindrically around the fiber core 10 along the longitudinal axis X. The fiber cladding 11 is radially enclosed from the outside by a fiber coating 12. The fiber coating 12 is made of a polymeric material. In the fiber core 10, light A can propagate as core light A along the longitudinal axis X. In the illustration of the Fig. 1, the core light A propagates from left to right. Similarly, light B propagates in the fiber cladding 11 as cladding light B.

[0064] The glass fiber 1 has a first exposed section 13a, in which the fiber coating 12 is removed from the fiber cladding 11 in the circumferential direction U and along the longitudinal axis X. In this first exposed section 13a, several depressions 14 in the form of longitudinal depressions 14 are introduced into the fiber cladding 11 from the radial outside along the longitudinal axis X. According to the first embodiment of the Fig. 1 to 4, the longitudinal recesses 14 are identically formed. The longitudinal recesses 14 each have a first length L1, a first width M1, and a first depth N1. The longitudinal recesses 14 are evenly distributed in the circumferential direction U and spaced apart from one another. Along the longitudinal axis X, the longitudinal recesses 14 are also equally spaced from one another.

[0065] The longitudinal recesses 14 each have a base 14d at their radially deepest point, which can also be referred to as the floor 14d of the longitudinal recesses 14. The two side surfaces 14e extend radially outward from the base 14d of each longitudinal recess 14. A front side 14f extends radially from the base 14d or from the floor 14d to the outer surface of the longitudinal recesses 14, see, for example, Fig. 4.

[0066] On the base 14d of each longitudinal recess 14 is a plurality of elevations 15, which are formed by glass dust 15 as fiber cladding material 15 and point at least substantially radially outward. Likewise, the edges of each longitudinal recess 14 along the longitudinal axis X are covered by elevations 15 in the form of glass dust 15 as fiber cladding material 15. The elevations 15 extend laterally on both sides in the circumferential direction U of each longitudinal recess 14 along the longitudinal axis X in the propagation direction of the core light A and away from the propagation direction of the cladding light B.

[0067] The longitudinal depressions 14 can be created in the fiber cladding 11 directly from the radial outside using a laser beam as a processing tool. A laser beam of a specific width can be used in the circumferential direction U and moved along the longitudinal axis X on the fiber cladding 11. Additionally or alternatively, the fiber cladding 11 can also be moved along the longitudinal axis X relative to the laser as a processing tool. The intensity of the laser beam and the speed of the movement along the longitudinal axis X can be used to create the width M1, M2 of the longitudinal depressions 14 in the circumferential direction U as well as their depth N1, N2 in the radial direction R and their length L1, L2, L3 along the longitudinal axis X. To create further longitudinal depressions 14, the laser beam as a processing tool must be repositioned relative to the fiber cladding 11.As a result, the longitudinal recesses 14 can be designed identically and arranged evenly distributed as described above, as in the first embodiment of the . Fig. 1 to 4. However, the longitudinal recesses 14 can also be arranged and / or formed differently in this way, as will be described with reference to the following exemplary embodiments.

[0068] According to the invention, the cladding light B can thus strike the front surface 14e of the longitudinal depressions 14 and there be conducted outward from the fiber cladding 11. In this way, a discharge of cladding light B from the fiber cladding 11 can be achieved. At the same time, the stability of the fiber cladding 11 can be reduced comparatively slightly. This can be achieved by the depressions 14 extending as longitudinal depressions 14 exactly along the longitudinal axis X. Thus, a weakening of the material of the fiber cladding 11 in the circumferential direction U can be avoided as far as possible. The elongated extension of the longitudinal depressions 14 along the longitudinal axis X can achieve a comparatively greater effect compared to known point holes or craters as depressions 14.

[0069] Likewise, the cladding light B can strike the elevations 15 and be discharged from the fiber cladding 11 at these points. This allows additional discharge of cladding light B as distant cladding light C from the fiber cladding 11 to be achieved.

[0070] Fig. 5 shows a longitudinal section through a glass fiber 1 according to the invention according to a second embodiment. Fig. 6 shows a side view of the optical fiber 1 of the Fig. 5.

[0071] According to the second embodiment, the optical fiber 1 or its first exposed section 13a is surrounded by a heat sink 16 in the form of a housing 16. The housing 16 encloses the first exposed section 13a as well as the adjacent regions of the fiber coating 12. In particular, the longitudinal recesses 14 are filled with the material of the housing 16. In this way, the distant cladding light C can be absorbed by the housing 16. As a result, the heat that can be generated by the distant cladding light C can be absorbed by the housing 16, whereby the corresponding heat can be kept away from the environment.

[0072] Fig. 7 shows a longitudinal section through a glass fiber 1 according to the invention according to a third embodiment. Fig. 8 shows a side view of the optical fiber 1 of the Fig. 7.

[0073] According to the third exemplary embodiment, the longitudinal recesses 14 are formed in different lengths L1, L2, L3 along the longitudinal axis X. Viewed from the direction of the core light A and the cladding light B, the longitudinal recesses 14 are initially formed as first longitudinal recesses 14a with the longest, first length L1. The length of the longitudinal recesses 14 shortens further along the longitudinal axis X to a middle, second length L2 of the second longitudinal recesses 14b and finally to a third, shortest length L3 of the third longitudinal recesses 14c. In this way, the discharge of cladding light B as removed cladding light C can be varied over the course of the first exposed section 13a. All longitudinal recesses 14 have the same first width M1 and the same first depth N1.

[0074] Fig. 9 shows a longitudinal section through a glass fiber 1 according to the invention according to a fourth embodiment. Fig. 10 shows a side view of the optical fiber 1 of the Fig. 9. Fig. 11 shows a first cross section of the glass fiber 1 of the Fig. 9. Fig. 13 shows a second cross section of the glass fiber 1 of the Fig. 9.

[0075] According to the fourth embodiment, the longitudinal recesses 14 vary between a first, longer length L1 of the first, longer longitudinal recesses 14a and a second, shorter length L2 of the second, shorter longitudinal recesses 14b. The second, shorter longitudinal recesses 14b are further formed in the radial direction R with a second, smaller depth N2, see Fig. 12, as the first, greater depth N1 of the first, longer longitudinal depressions 14a, see Fig. 11.

[0076] As a result, a closer or denser arrangement of the second, shorter longitudinal recesses 14b can be achieved in the circumferential direction U, see for example also Fig. 10. This can result in the elevations 15 being formed adjacent to one another in the circumferential direction U, thereby completely enclosing the radially outer surface of the fiber cladding 11 in the circumferential direction U between the second, shorter longitudinal recesses 14b. This can increase the light-dissipating effect of the elevations 15.

[0077] Fig. 13 shows a longitudinal section through a glass fiber 1 according to the invention according to a fifth embodiment. Fig. 14 shows a side view of the optical fiber 1 of the Fig. 13. Fig. 15 shows a cross section of the glass fiber 1 of the Fig. 13.

[0078] According to the fifth embodiment, the first longitudinal recesses 14a and the second longitudinal recesses 14b differ from the previously described fourth embodiment by a different width M1, M2. This can also further increase the design flexibility in the formation of the longitudinal recesses 14.

[0079] Fig. 16 shows a longitudinal section through a glass fiber 1 according to the invention according to a sixth embodiment. Fig. 17 shows a side view of the optical fiber 1 of the Fig. 16. Fig. 18 shows a cross section of the glass fiber 1 of the Fig. 16.

[0080] According to the sixth exemplary embodiment, the longitudinal recesses 14 extend in the radial direction R into the fiber core 10, which in this case is comparatively thick. In other words, the longitudinal recesses 14 penetrate the fiber cladding 11 in the radial direction R and protrude into the fiber core 10. In this way, the fiber cladding 11 can be completely penetrated by the longitudinal recesses 14 in the radial direction R, and a corresponding amount of cladding light B can be discharged from the fiber cladding 11 as removed cladding light C. In addition, at least some core light A can be discharged outward from the fiber core 10 as removed core light D.

[0081] Fig. 19 shows a longitudinal section through a glass fiber 1 according to the invention according to a seventh embodiment.

[0082] The glass fiber 1 according to the seventh embodiment corresponds with regard to its first exposed section 13a of the longitudinal recesses 14 introduced therein to the first embodiment of the Fig. 1 to 4. In contrast, the fiber core 10 and the fiber cladding 11 terminate along the longitudinal axis X on the right side, however, together with an open end, at which an optical element 17 is arranged as an optical window 17 in the form of a glass body. The optical window 17 can also be designed as an optical lens 17. In this way, the core light A can be guided outward at this point with a wider radial distribution.

[0083] Fig. 20 shows a longitudinal section through a glass fiber 1 according to the invention according to an eighth embodiment.

[0084] In this case, the glass fiber 1 according to the invention has, in addition to the previously discussed first exposed section 13a, a further second exposed section 13b. Both exposed sections 13a, 13b have several of the previously described longitudinal recesses 14 according to the invention, which can be of identical or different configurations and / or can be spaced identically or differently from one another.

[0085] Between the two exposed sections 13a, 13b, the glass fiber 1 is bent into a U-shape, so that the two exposed sections 13a, 13b are arranged and aligned parallel to each other. In this way, the two exposed sections 13a, 13b can be arranged in a space-saving manner, allowing a compact arrangement to be created in this area of ​​the glass fiber 1. Due to the bend, the diameter or cross-section of the fiber core 10 in the bent area between the two exposed sections 13a, 13b can be slightly smaller than in the two exposed straight sections 13a, 13b.

[0086] Fig. 21 shows a longitudinal section through a glass fiber 1 according to the invention according to a ninth embodiment. Fig. 22 shows a cross section of the glass fiber 1 of the Fig. 21.

[0087] The optical fiber 1 according to the ninth embodiment corresponds to the optical fiber 1 according to the first embodiment, with the difference that all longitudinal recesses 14 are approximately half-filled in height or in the radial direction R with a material filling 18 of the same material. The material of the material filling 18 differs from the material of the fiber cladding 11. The material of the material filling 18 and its complete contact with the respective base 14d of the longitudinal recesses 14 and approximately half with the respective front side 14e of the longitudinal recesses 14 can promote the removal of the cladding light B from the fiber cladding 11. LIST OF REFERENCE SYMBOLS (part of the description) A Core light; light in the fiber core 10 B Sheath light; light in the fiber cladding 11 C distant cladding light D distant nuclear light L1 first length of the longitudinal recesses 14 L2 second length of the longitudinal recesses 14 L3 third length of the longitudinal recesses 14 M1 first width of the longitudinal recesses 14 M2 second width of the longitudinal recesses 14 N1 first depth of the longitudinal recesses 14 N2 second depth of the longitudinal recesses 14 R radial direction to the longitudinal axis X U circumferential direction to the longitudinal axis X X Longitudinal axis of the glass fiber 1 1 fiber optic 10 fiber core 11 Fiber sheath 12 Fiber coating 13a first exposed section 13b second exposed section 14 recesses; longitudinal recesses; longitudinal slots 14a first longitudinal depressions 14b second longitudinal recesses 14c third longitudinal depressions 14d Base or floor of the longitudinal recesses 14 14e Front of the longitudinal recesses 14 14f Side walls of the longitudinal recesses 14 15 elevations; fiber cladding material; glass dust 16 Heat sink; housing 17 optical element; optical window; optical lens 18 Material filling

Claims

[1] Fiber optic (1) with at least one fiber core (10), with at least one fiber cladding (11) which at least substantially encloses the fiber core (10) in the circumferential direction (U) and along the longitudinal axis (X), and with at least one fiber coating (12) which substantially encloses the fiber sheath (11) in the circumferential direction (U) and along the longitudinal axis (X), wherein the glass fiber (1) has at least a first exposed portion (13a) where the fiber cladding (11) is exposed from the fiber coating (12) for removing light (B) at least from the fiber cladding (11), wherein at least the fiber cladding (11) has a plurality of recesses (14) at least substantially in the radial direction (R), which are designed to at least partially discharge the light (B) from the fiber cladding (11), wherein the recesses (14) are formed as longitudinal recesses (14) each at least in sections exactly along the longitudinal axis (X), characterized by , that at least some of the longitudinal recesses (14) have, at least on their base (14d), at least in sections, a plurality of elevations (15). [2] Glass fiber (1) according to claim 1, characterized by that the longitudinal recesses (14) are each formed completely exactly along the longitudinal axis (X) and / or completely exactly in the radial direction (R). [3] Glass fiber (1) according to claim 1 or 2, characterized by that the longitudinal recesses (14) each have a width (M1, M2) in the circumferential direction (U) which corresponds to the width of a tool with which the longitudinal recesses (14) were introduced at least into the fiber sheath (11). [4] Glass fiber (1) according to one of the preceding claims, characterized bythat at least some of the longitudinal recesses (14) are spaced differently from one another in the circumferential direction (U) and / or along the longitudinal axis (X). [5] Glass fiber (1) according to one of the preceding claims, characterized by that the longitudinal recesses (14) are increasingly spaced apart from one another along the longitudinal axis (X) in the propagation direction of the light (B). [6] Glass fiber (1) according to one of claims 1 to 3, characterized by that at least some of the longitudinal recesses (14) are equally spaced from one another in the circumferential direction (U) and / or along the longitudinal axis (X). [7] Glass fiber (1) according to one of the preceding claims, characterized by , that at least one first longitudinal recess (14a) has a first length (L1) along the longitudinal axis (X) and at least one second longitudinal recess (14b) has a second length (L2) along the longitudinal axis (X), where the first length (L1) and the second length (L2) are different. [8] Glass fiber (1) according to one of the preceding claims, characterized by , that at least one first longitudinal recess (14a) has a first width (M1) in the circumferential direction (U) and at least one second longitudinal recess (14b) has a second width (M2) in the circumferential direction (U), where the first width (M1) and the second width (M2) are different. [9] Glass fiber (1) according to one of the preceding claims, characterized by , that at least one first longitudinal recess (14a) has a first depth (N1) in the radial direction (R) and at least one second longitudinal recess (14b) has a second depth (N2) in the radial direction (R), where the first depth (N1) and the second depth (N2) are different. [10] Glass fiber (1) according to one of the preceding claims, characterized by , that the first exposed section (13a) is surrounded by a heat sink (16) at least in sections, preferably completely, in contact or at a distance, wherein the heat sink (16) facing the exposed section (13a) is designed to absorb and / or reflect the light (B) at least from the fiber cladding (11) at least in sections. [11] Glass fiber (1) according to one of the preceding claims, characterized by at least one second exposed portion (13b) where the fiber cladding (11) is exposed from the fiber coating (12) for removing light (B) at least from the fiber cladding (11), wherein the first exposed portion (13a) and the second exposed portion (13b) are arranged at least partially, preferably completely, at an angle to one another, preferably parallel to one another. [12] Glass fiber (1) according to one of the preceding claims, characterized byan optical element (17) which is arranged at an open end of the fiber core (10) and forms an open end of the glass fiber (1) along the longitudinal axis (X). [13] Glass fiber (1) according to one of the preceding claims, characterized by that at least some of the longitudinal recesses (14) extend in the radial direction (R) into the fiber core (10). [14] Glass fiber (1) according to one of the preceding claims, characterized by that all longitudinal recesses (14) have at least on their base (14d) at least in sections, preferably completely, a plurality of elevations (15). [15] Glass fiber (1) according to one of the preceding claims, characterized by that the outer surface of the fiber cladding (11) has a plurality of elevations (15) at least directly adjacent to at least some of the longitudinal depressions (14), preferably adjacent to all longitudinal depressions (14), at least in sections, preferably completely. [16] Glass fiber (1) according to claim 14 or 15, characterized by that the elevations (15) of the same longitudinal depression (14) and / or several longitudinal depressions (14) are at least partially, preferably completely, identical or different in terms of material, thickness, refractive index, shape, distribution and / or density. [17] Glass fiber (1) according to one of claims 14 to 16, characterized by that at least some of the elevations (15), preferably all elevations (15), are formed by fiber sheath material (15) which is produced by at least one tool when the longitudinal recesses (14) are made at least in the fiber sheath (11). [18] Glass fiber (1) according to one of the preceding claims, characterized by , that at least one longitudinal recess (14), preferably a plurality of longitudinal recesses (14), particularly preferably all longitudinal recesses (14), at least in sections, preferably completely, has at least one material filling (18), preferably a plurality of different material fillings (18), wherein the material of the material filling (18) differs from the material of the fiber core (10) and / or from the material of the fiber cladding (11). [19] Glass fiber (1) according to claim 18, characterized by that the material of the material filling (18) has a refractive index which promotes the removal of light (B) at least from the fiber cladding (11). [20] Glass fiber (1) according to claim 18 or 19, characterized by that at least two longitudinal recesses (14), preferably all longitudinal recesses (14), are filled with the material filling (18) of different lengths, widths and / or heights. [21] Glass fiber (1) according to one of claims 18 to 20, characterized by that at least two longitudinal recesses (14), preferably all longitudinal recesses (14), have different materials of the material filling (18). [22] Glass fiber product comprising at least one glass fiber (1) according to one of the preceding claims.

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