Coil body, optical fiber coil and method for producing a coil body

Abstract

The invention relates to a coil body (100) which is suitable for winding an optical fiber (200) thereon, having a cylindrical coil core (110) on which the optical fiber (200) is wound, said coil core (110) having a thread (120), in the depressions (121) of which the optical fiber (200) can be laid.

Description

[0001] Description

[0002] Coil former, fiber optic coil and method for producing a coil former

[0003] The present invention relates to a coil former for a fiber optic coil, a fiber optic coil, and methods for producing the coil former / fiber optic coil. The fiber optic coil is particularly suitable for use in fiber optic gyroscopes.

[0004] Fiber optic gyroscopes use fiber coils in which a glass fiber is wound around a coil body. Light is coupled into the fiber, and its phase shift can be measured as the fiber coil rotates. Based on the measured phase shift, the applied angular rate can be determined.

[0005] For this purpose, the fiber coils must be manufactured with as little tension, pressure, and torsion on the fiber as possible, as these can impair the propagation of light in the fiber and lead to measurement errors. On the other hand, the fiber coils should be designed as compactly as possible.

[0006] Accordingly, fiber coils are wound as shown in Figure 1 such that the individual fiber sections 21 of the glass fiber 20 are densely packed within the fiber windings. Typically, fiber layers are wound onto a cylindrical coil core such that, within the individual fiber layer n1, n2, n3, n4, ..., i.e., the layers of fiber sections 21 equidistant from the coil core, the adjacent fiber sections 21 touch each other. The subsequent fiber layer is then wound onto the previous fiber layer in the axial direction x, offset by half the fiber diameter d.

[0007] This type of winding has the disadvantage that the depressions that form between the fiber sections of a fiber layer are relatively small compared to the fiber diameter d, as shown by curve A. This makes it possible for the fiber to slip out of its intended position during winding. This disrupts the order / structure of the intended construction of the winding and can lead to tension, pressure, or torsion on the glass fiber 20. The object of the present invention is therefore to provide glass fiber spools whose winding enables fiber sections to be deposited on the previous fiber layers with as little error and as precise a position as possible. In particular, the object of the invention is to provide spool bodies that simplify such a winding and winding methods that enable such a winding.

[0008] These problems are solved by the subject matter of the independent claims.

[0009] A spool body suitable for winding a glass fiber thereon accordingly has a cylindrical spool core on which the glass fiber is wound, wherein the spool core has a structure with recesses, preferably a thread, in whose recesses the glass fiber can be deposited.

[0010] The structure or thread defines predetermined deposition positions for the first fiber / winding layer. In this way, the first fiber layer can be deposited in a well-defined manner. The recesses prevent the glass fiber from slipping sideways and thus allow the distance between the fiber sections of the various windings to be set arbitrarily, depending on the selected spacing of the recesses, in particular depending on the selected thread pitch. This makes it possible to define a gap between the fiber sections of the first fiber layer, into which fiber sections of the subsequent fiber layer can be deposited in a guided manner, secured against sideways slipping. Gaps are also created in this and the subsequent fiber layers, which serve to securely deposit the next fiber layer. This enables error-free, precisely positioned deposition of fiber sections on the previous fiber layer.This makes it possible to wind fiber coils on the coil body with great precision, such as those required for the operation of high-precision fiber optic gyroscopes.

[0011] The "thread" on the spool core does not have to be a complete thread with a continuous thread profile. It is sufficient if the number of thread crests is sufficient to secure the fiber optic cable against lateral slippage. In this sense, individual protrusions on the spool core are also considered threads if they fulfill the same function as a complete thread, namely to secure the first fiber layer on the spool core against lateral slippage. Equivalently, it is also possible to fix the first fiber layer to the spool core using adhesive. It is also possible to use circumferential grooves or ridges without a thread pitch as a structure with recesses instead of a thread, which are not continuous in the circumferential direction of the spool core. The axial offset of the fiber optic cable then occurs in the gaps between these grooves / ridges, i.e., in areas of the spool core where no grooves / ridges are formed.

[0012] The structure with depressions, preferably the thread, can be designed in such a way that between fiber sections of a first layer that are laid in the depressions, such gaps or depressions are created that fiber sections of a next, second layer that are laid in the resulting gaps / depressions have a distance of d / 2 from the fiber sections of the first layer in the radial direction of the spool core, where d is the diameter of the glass fiber to be wound. This means that the gaps between the fiber sections allow the fiber sections of the next fiber layer to sink between the fiber sections of the previous layer by half the fiber diameter d. Viewed in the axial direction of the spool core, each fiber layer is covered half - and thus completely - by the two adjacent fiber layers. In this way, the densest packing of the fiber sections can be achieved.

[0013] Likewise, the structure with recesses, preferably the thread, can be designed such that the recesses of the thread can accommodate half the diameter of the fiber optic cable to be wound. Then, the first fiber layer is half covered by the recesses / thread. The fiber optic cable then lies tightly packed on the spool core.

[0014] The thread can have a pitch P of P = 2d • cos 30°, where d is the diameter of the glass fiber to be wound up. With a thread pitch P of this type, the gap between axially adjacent fiber sections of a fiber layer is exactly large enough that the fiber sections of the next fiber layer that lie within it are packed as closely as possible. Since the width of the gap caused by the thread pitch P in each fiber layer means that the gaps between the fiber sections allow the fiber sections of the next fiber layer to sink by half the fiber diameter d between the fiber sections of the previous layer, the spool body with the thread pitch P = 2d • cos 30° enables a glass fiber with a diameter d to be wound up as closely packed and with precise positioning. This enables the production of high-precision glass fiber spools. The thread can have a flank angle of 60°.Such flank angles are technically common and facilitate the production of the coil body.

[0015] The thread can have a thread depth h = 5P / (16 • cos 30°), where P is the thread pitch, a flat thread root of width b1 = P / 4, and flattened thread crests of width b2 = P / 3. Such a thread is easy to manufacture and allows for the densest packing of the wound fiber.

[0016] The coil former can further comprise a first flange at a first end of the coil core and a second flange at a second end of the coil core, with the thread extending up to the flanges. Thus, the thread covers the entire coil core. The fiber optic cable can be wound from flange to flange. This prevents the fiber optic cable from extending laterally beyond the winding, or, in a winding pattern that does not require a lateral extension, saves space and prevents fiber from slipping into a gap between the thread / winding and the flanges. This allows for the production of compact fiber optic cable coils.

[0017] A fiber optic spool can have a spool body as described above and a fiber optic cable wound around the spool body. The thread on the spool core allows the fiber optic cable to be deposited accurately and precisely, as described above. This allows the fiber optic spool to be easily manufactured with little or no tension, pressure, and / or torsion on the fiber optic cable. The fiber optic spool can thus be used in high-precision fiber optic gyroscopes.

[0018] At least along a cross-section through the fiber winding, the fiber sections of different layers can lie on top of each other in the radial direction of the fiber optic coil without any axial offset. This means that, starting from the cylindrical coil core, the fiber sections ideally lie on top of each other perpendicular to the center line / axis of the cylinder, i.e., in the radial direction, without being offset from each other in the axial direction. Ideally, this applies to as many cross-sections through the fiber optic coil as possible, i.e., the fiber crosses itself as little as possible within the fiber optic coil, i.e., there are as few places in the fiber optic coil as possible where overlapping fiber sections lie perpendicular to each other.

[0019] The fiber sections can be packed as tightly as possible within the cross-section. The winding pattern of the winding then corresponds to the winding pattern of a conventional, tightly packed winding, rotated by 90°, in which the fiber sections of a fiber layer are laid in an axial direction without radial offset and directly adjacent to one another.

[0020] A method for producing a spool body comprises: turning a metric ISO thread with a thread pitch P and a thread depth of 3 / 4 (P • cos 30°) on a cylinder with a thread chisel whose tip is blunt and meets the cylinder with a width of P / 4 and removing the thread crests of the thread produced in this way by P / (4 • cos 30°). In this way, a spool body as described above can be produced in a simple manner, in particular a spool body with a thread with a flank angle of 60°, a thread depth h of 5P / (16 • cos 30°), a thread pitch P; a flat thread root of width b1 = P / 4 and flattened thread crests of width b2 = P / 3.

[0021] The invention is further described below with reference to the figures. The following description is to be understood as purely exemplary. It does not limit the invention, which is defined solely by the claims. It shows:

[0022] Fig. 1 shows schematically a fiber winding as it is known from the state of

[0023] technology is known;

[0024] Fig. 2 is a schematic representation of a fiber optic coil formed from a fiber optic coil wound around a coil body;

[0025] Figs. 3A and 3B are schematic representations of further glass fiber wound around a bobbin;

[0026] Fig. 4: Geometric dimensions of densely packed fiber sections of a glass fiber wound around a spool; Fig. 5: Geometric dimensions of a thread produced from a metric ISO thread on a spool;

[0027] Fig. 6 is a flow chart of a method for producing a coil body with a thread;

[0028] Fig. 7 is a flowchart of a method for manufacturing a fiber optic coil;

[0029] Fig. 8 shows another flowchart of the method for producing a fiber optic coil;

[0030] Fig. 9 is a schematic partial view of a fiber optic coil;

[0031] Fig. 10 shows another flow chart of the method for producing a fiber optic coil; and

[0032] Fig. 11A to 11D are schematic partial views of a fiber optic coil during different times of the winding process.

[0033] Fig. 2 shows a schematic cross-sectional view of a coil former 100. The coil former 100 is suitable for winding a glass fiber 200 thereon to form a glass fiber coil 300, which can be used, for example, in fiber optic gyroscopes.

[0034] The coil body 100 has a cylindrical coil core 110 onto which the glass fiber 200 can be wound. The coil core 110 is provided with a thread 120, in the recesses 121 of which the glass fiber 200 can be deposited. The coil core 110 is made of a material suitable for supporting glass fibers 200, e.g., a metal such as aluminum, or a plastic. The thread 120 can be cut into the coil core 110 by a machining process, i.e., the recesses 121 are created by removing material from the coil core 110. However, the thread 120 can also be applied to the coil core 110. In particular, the thread 120 can also consist of only a sequence of projections and / or recesses on the coil core 110, which are suitable for guiding the optical fiber 200 over the coil core 110. The thread 120 can also be produced by 3D printing.

[0035] As shown in Fig. 2, the glass fiber 200 can be inserted into the recesses 121 of the thread 120 in a first fiber layer 211. This secures the fiber sections 201 of this first fiber layer 211 against lateral slippage, i.e., against slippage in the axial direction x of the cylindrical coil core 110. The (axial) position of the first fiber layer 211 is thus defined accurately and without error by the thread 120.

[0036] In addition, gaps / recesses are created between the fiber sections 201 of the first fiber layer 211, which can (partially) accommodate the fiber sections 201 of the next, second fiber layer 212, i.e. into which the fiber sections 201 of the next, second fiber layer 212 can be deposited. These gaps have a width defined by the pitch of the thread, which can be adjusted by selecting a suitable pitch such that glass fiber sections 201 lying in the gaps are also secured against axial slipping. This can be compared in particular with the situation in Fig. 1. By comparing curves A and B in Figs. 1 and 2, it is easy to see that the surface of the first fiber layer 211 is significantly more heavily structured due to the provision of the thread and the resulting distance between fiber sections 201 of the first fiber layer 211.As a result, the fiber sections 201 of the second fiber layer 212 find a much better hold and can thus be placed in a precisely positioned manner on the first fiber layer 211.

[0037] In the same way, the third fiber layer 213 and subsequent fiber layers (not shown) can be deposited into the gaps / recesses of the preceding fiber layers. The coil core 110 of the coil former 100, provided with the thread 120, thus enables error-free and precisely positioned winding of a fiber optic coil 300.

[0038] During the winding process, the glass fiber sections 201 can be additionally glued to one another to provide additional fixation. In principle, it is also possible, in an equivalent manner, to glue the first fiber layer 211 to a spool core 110 without a thread 120. However, this requires precise positioning of the adhesive and glass fiber 200 on the spool core 110 within the diameter range of the glass fiber (5 to 50 μm), which is technically much more complex to implement than a corresponding thread.

[0039] Fig. 2 shows flanges 130, 135 which support the fiber winding laterally, i.e. in the axial direction. These flanges 130, 135 can be an integral part of the coil core 110, i.e. they are inseparably connected to the coil core 110 and also form part of the finished fiber optic coil 300. However, they can also serve as a supporting wall only during the winding process and be removed after the winding process, since the fiber sections 201 remain in position even without the flanges 130, 135, e.g. due to the tensile force applied during winding or by gluing / potting. In this case, the flanges 130, 135 can also be regarded as part of the winding device and not as part of the coil former 100.

[0040] Fig. 2 shows a distance between the thread 120 and the flanges 130, 135. The glass fiber 200 thus protrudes beyond the thread 120 or also runs in a gap between the thread 120 and the flanges 130, 135. This gap can also be designed such that the glass fiber 200 can be guided laterally past the winding and away from the coil core 110. This can be useful to prevent the glass fiber 200 from overlapping within the winding. On the other hand, with such a gap, there is a risk that fiber sections 201 located at the edge of the winding could slip into the gap, thereby disrupting or destroying the winding.

[0041] Therefore, the thread 120 is preferably extended to the flanges 130, 135. This ensures that the winding always begins and ends at the flanges 130, 135. This reliably prevents the winding from slipping sideways in the axial direction.

[0042] In the example of Fig. 2, due to the pitch of the thread, the distance between the fiber sections 201 of a fiber layer in the axial direction R is such that channels 202 running in the circumferential direction of the winding are formed between the fiber sections 201. As shown in Figs. 3A and 3B, the thread 120 can also be designed such that between the fiber sections 201 of the first fiber layer 211, which are deposited in the depressions 121 of the thread 120, such intermediate spaces / depressions are created that fiber sections 201 of a next, second fiber layer 212, which are deposited in the resulting intermediate spaces / depressions, have a distance of d / 2 from the fiber sections 201 of the first layer 211 in the radial direction R of the coil core 110.This means that a straight line parallel to the axial direction x through the centers of fiber sections 201 deposited in the second fiber layer 212 has a distance of d / 2 in the radial direction from a straight line also parallel to the axial direction x through the centers of the fiber sections 201 of the adjacent first fiber layer 211, where d is the fiber diameter (cf. the distance indication in Fig. 3A).

[0043] In Fig. 3A, the depth of the thread 120 is such that the glass fiber 200 has no contact with the coil core 110, while in Fig. 3B the thread 120 is designed such that the recesses 121 of the thread 120 can also accommodate half the diameter of the glass fiber 200 to be wound.

[0044] In this way, by appropriately selecting the pitch of the thread 120, a flawless and precisely positioned deposition of the glass fiber 200 can be achieved, resulting in the glass fiber 200 being densely packed in the finished glass fiber coil 300. This reduces the space required for the winding in the radial direction R.

[0045] In particular, the fiber sections 201 of different layers lie on top of one another in the radial direction R of the fiber optic coil 300 at least along a cross-section through the fiber winding without any axial offset. In this cross-section, the densest packing achieved in this way can be understood as a 90° rotation of the usual winding shown in Fig. 1. Viewed along the circumferential direction, the winding is carried out in such a way that the densest packing of fiber optic sections is achieved along as many or even all cross-sections through the winding as possible. This reduces intersections of the fiber optic 200 within the winding. The densest packing of the fiber optic 200 can be achieved in particular if the thread 120 has a pitch P of the size P = 2d • cos 30°, ie if the thread 120 is matched to the diameter d of the fiber optic 200 to be wound.

[0046] The equation P = 2d • cos 30° can be explained with reference to Fig. 4. As shown in Fig. 4, the thread 120 has a pitch P, i.e. after one revolution of the thread / thread turn by 360°, the axial position has shifted by the amount P. The centers of the cross sections through the fiber sections 201 deposited in the recesses 121 are therefore also located apart in the axial direction by the amount P. Furthermore, the centers of the cross sections through three adjacent fiber sections 201 are connected by an isosceles triangle with edge length d, i.e. by a triangle whose three interior angles are each 60°. The right-angled triangle shown in Fig. 4 with the hypotenuse of length d therefore has interior angles of 90°, 60° and 30°. For cos 30°, cos 30° = (P / 2) / d then applies. This gives P = 2d • cos 30° = ^3 • d.

[0047] If the fiber diameter d is known, it is easy to determine the thread pitch P that the thread 120 of the coil body must have in order to achieve a winding with the most densely packed glass fiber 200.

[0048] Figures 2 to 4 show various shapes for the thread 120, in particular rectangular and semicircular thread profiles. This demonstrates that the thread profile can essentially be any desired shape, as long as the glass fiber 200 can be deposited in the recesses of the thread 120 without errors and with precise positioning.

[0049] Preferably, the thread 120 can have a flank angle of 60°. This corresponds to the flank angle of common, industrially manufactured threads, such as the metric ISO thread. This simplifies the production of the thread 120 on the coil core 120.

[0050] A particularly preferred embodiment of the thread 120, based on the metric ISO thread, is shown as a schematic cross-section in Fig. 5. The thread 120 is indicated here by solid lines. The thread 120 has a thread depth h = 5P / (16 • cos 30°) = 5d / 8, a flat thread root of width b1 = P / 4, and flattened thread crests of width b2 = P / 3. These dimensions guarantee that the fiber sections 201 deposited on the thread are packed as tightly as possible. In particular, each subsequent fiber layer sinks into the previously deposited fiber layer by d / 2.

[0051] In Fig. 5, the shapes of a metric ISO thread are shown next to the thread 120 with long dashed lines (short dashed lines are auxiliary lines). This metric ISO thread is constructed from imaginary isosceles triangles of height H and edge length P, which are rounded at their tips to form the ISO thread. Compared to the ISO thread, the thread 120 of the coil core does not have a rounded thread root, but rather a thread root flattened to P / 4. Furthermore, the thread crests are shortened and flattened by d / 2 instead of H / 8 to enable the fiber sections 201 of the second fiber layer to be fully deposited on the fiber sections 201 of the first fiber layer.

[0052] A flowchart of a method for manufacturing a coil former 100, as shown in Fig. 5, is shown in Fig. 6. At S100, a metric ISO thread with a thread pitch P and a thread depth of 3 / 4 (P • cos 30°) is turned on a cylinder. The thread cutter used here has a blunt tip and impacts the cylinder with a width of P / 4.

[0053] First, a thread is turned that differs from a metric ISO thread in that it has a flattened thread root with a width of P / 4. The thread depth of 3 / 4 (P • cos 30°) is the depth 3H / 4 shown in Fig. 5. Then, at S110, the thread crests of the thread thus created are removed by P / (4 • cos 30°), i.e., by d / 2. This creates the flattened thread crests with a width of P / 3. Furthermore, the thread depth is reduced to 5d / 8 = 5P / (16 • cos 30°).

[0054] The coil body 100 produced in this way then has a thread 120 onto which a glass fiber 200 can be wound in the densest possible packing.

[0055] A fiber optic coil 300 can be manufactured on such a coil former 100 using a method according to the flowchart in Fig. 7. However, the method in Fig. 7 can be applied not only to coil formers 100 with a thread 110, but generally to coil formers with flanges 130, 135 at the ends of the coil core 110. It is also possible to remove the flanges 130, 135 after winding. Without the use of a thread 120, the fiber sections 201 of the first fiber layer 211 must be held in place in another way, e.g., by gluing the fiber optic 200 to the coil core 110.

[0056] The method for manufacturing a fiber optic coil 300 comprises: at S200, providing the coil body 100 having a cylindrical coil core 110 and a first flange 130 at a first end of the coil core 110 and a second flange 135 at a second end of the coil core 110.

[0057] At S210, winding a first fiber layer 211 by depositing fiber sections 201 of glass fiber 200 at a distance of P = 2d • cos 30°, where d is the diameter of the glass fiber 200. As shown above, the fiber sections 201 of the first fiber layer 211 at this distance enable the fiber sections 201 of the second fiber layer 212 deposited thereon to overlap by d / 2 with the fiber sections 201 of the first fiber layer 211 in the radial direction R of the coil body 100 or the glass fiber coil 300 and that the glass fiber 200 can be wound around the coil core 110 in the densest packing.

[0058] At S220, further fiber layers 212, 213, 214 are wound by depositing fiber sections 201 in recesses between fiber sections 201 in the preceding, first fiber layer 211, wherein the fiber layers 211, 212, 213, 214 are wound by alternately winding the first end / first half of the glass fiber 200 clockwise around the spool core 110 and the second end / second half of the glass fiber 200 counterclockwise around the spool core 110 and at the ends of the spool core 110 directly adjacent to the flanges 130, 135.

[0059] The result of such a winding process is a winding pattern, as shown, for example, in Figs. 3A and 3B, with the fiber ends located on the outside of the winding. In particular, a quadrupole winding can be realized in this way. As can be seen in Figs. 3A and 3B, the glass fiber 300 is laid down in such a way that, at least along a cross-section through the fiber winding, fiber sections 201 of different fiber layers 211, 213; 212, 214 lie on top of one another in the radial direction R of the glass fiber spool 300 without any axial offset. This corresponds to a 90° rotation of the usual winding pattern shown in Fig. 1.

[0060] A fiber optic coil 300 wound in this way is particularly suitable for use in fiber optic gyroscopes. Due to the deeper recesses between axially adjacent fiber sections 201 compared to the conventional winding pattern shown in Fig. 1, the fiber optic coil 300 manufactured in this way is characterized by low positioning errors. Furthermore, it eliminates any clearance between the fiber optic 200 and the flanges 130, 135, which further increases the positioning accuracy of the fiber optic 200 wound therein.

[0061] The method of Fig. 7 can be modified or expanded according to the flowchart shown in Fig. 8. In particular, the glass fiber 200 can be deposited such that at least along a cross section through the fiber winding:

[0062] - the winding of the first or second end of the glass fiber 200 is terminated when a corresponding fiber section 201 rests against one of the flanges 130, 135 (S300),

[0063] - the subsequent winding of the other end of the glass fiber 200 leaves a space for a fiber section 201 on the respective flange 130, 135 (S310) and is terminated after the laying of a fiber section 201 on the other flange 135, 130 (S320) and

[0064] - the subsequent winding begins with the deposition of a fiber section 201 in the space left free (S330).

[0065] Based on the commonly used quadrupole winding, the winding of the first layer with one fiber half of the glass fiber 200 is terminated when a flange is reached (S300). The subsequent winding of the two following layers with the other fiber half of the glass fiber 200 leaves a space free at the reversal point for a fiber section 201 on the respective flange 130, 135 (S310) and is terminated after a fiber section 201 has been deposited on the other flange 135, 130 (S320). Winding then continues with the deposit of a fiber section 201 in the vacated space.

[0066] The winding is therefore always carried out up to one of the flanges 130, 135. In the subsequent winding step, which takes place in the opposite direction, a position on this flange is left free and the winding is completed on the other flange. If the winding is resumed in the first direction, the winding is resumed at the left-free position. The glass fiber 200 can then be easily deposited precisely at this position.

[0067] This is shown by way of example in Fig. 9 for a partial cross-section through a fiber optic spool 300. In Fig. 9, the patterning of fiber optic sections 201 indicates that one end / half of the fiber optic 200 was wound around the spool core 110 in one circumferential direction, e.g., clockwise or into the plane of the drawing. For the fiber optic sections 201 shown in white, the other end / half of the fiber optic 200 was wound in the opposite direction, e.g., counterclockwise or out of the plane of the drawing.

[0068] The winding shown in Fig. 9 begins with the glass fiber 200 being placed at position 1 on the coil core 110, e.g. by gluing or by placing it in the recess of a thread 120. The glass fiber 200 is wound at its one (first) end in the axial direction x onto the flange 135 and reaches it at position 2.

[0069] The winding of the first end is completed, and the other, second end is wound in the opposite direction toward the other flange 130, reaching it after two turns (positions 3 and 4). Then, the winding of the second end is completed, and the winding of the first end is resumed.

[0070] This is first wound on flange 130 (position 5) and then along the coil body 110 (positions 6 and 7). However, a space is left at flange 130 where the winding of the second end was completed, and the winding returns to the output flange 135 (positions 8 to 10), where the winding is completed.

[0071] The second end is placed in the released position (position 11), then wound along the coil core 110, initially away from the output flange 130 (positions 12 to 14) and then back toward it, while a position is kept free on the opposite flange 130 (positions 15 to 17). The process then continues in the same way with the winding of the first end (position 18) until the fiber optic coil 300 is completely wound. This modification of the quadrupole pattern allows a flawless and precisely wound fiber optic coil 300 to be realized without the need to maintain gaps between the winding and the flanges 130, 135. Before winding at the first position in a layer, the fiber is already in place and does not have to be fetched from the penultimate layer by passing the gap between the winding and the flange.Without a gap between the winding and the flange, slipping of the fiber in its position at the edge of the winding is prevented.

[0072] This process can be further specified according to the flowchart in Fig. 10. This process is shown schematically in Figs. 11A to 11D using a partial section of a fiber optic spool 300. Here, too, the patterning / lack of patterning indicates the two fiber halves or different winding directions along the circumference of the spool body 110.

[0073] Here, at S400, a central fiber section 201 is deposited at a location on the coil core 110 adjacent to the first flange 130, and at S410, a first end of the glass fiber 200 is wound up to the second flange 135. These are positions 1 to 3 in the schematic representation of Fig. 11A. At the second flange 135, the winding of the first end of the glass fiber 200 is terminated.

[0074] At S420, the second end of the glass fiber 200 is first wound in the direction of the second flange 135 and - before the second flange 135 is reached - the second end is wound in the direction of the first flange 130. This is shown in Fig. 11A by the fiber sections at positions 4 to 7. The glass fiber 200 is first laid between positions 1 and 2 (position 4) and then wound towards the second flange 135 (position 5). Before this is reached, the (axial) winding direction is reversed, and winding takes place in the next fiber layer back to the first flange 130 (position 6). The winding of the second end ends when the first flange 130 is reached. In this method, too, a position marked by the black circle on the second flange 135 is kept free, i.e., on the flange at which the winding step did not begin.At S430, the first end of the optical fiber 200 is first wound along the second flange 135, i.e., the optical fiber 200 is deposited in the previously released position. This is illustrated in Fig. 11 B by the arrow pointing from position 3 to position 8. Since this released position creates a significant recess in the winding, the fiber can be deposited accurately and without errors.

[0075] The first end is then initially wound toward the first flange 130. This is illustrated by the glass fiber being deposited in positions 9 and 10 of Fig. 11 B. However, the (axial) winding direction is reversed and wound again toward the second flange 135 before reaching the first flange 130, as illustrated by the glass fiber 200 in positions 11 and 12 of Fig. 11 B. Here, too, a position marked by the black circle is kept free at the flange where the winding step did not begin, i.e., at the first flange 130.

[0076] At S440, the ends of the glass fiber 200 are alternately wound such that they are first wound along the adjacent flange 130, 135, then in the direction of the opposite flange 135, 130, and then back to the adjacent flange 130, 135 before reaching the opposite flange 135, 130. This is shown schematically in Figs. 11C and 11D for two further winding steps. Fig. 11C shows the ascending winding of the second end of the glass fiber on the first flange 130 from position 7 to position 13 and the subsequent winding away from the first flange 130 (positions 14 and 15) and towards the first flange 130 (positions 16 and 17), leaving free the position on the opposite, second flange 135. Fig. 11D then shows again, in a manner analogous to Fig. 11B, the next winding step using the first end of the glass fiber 200.

[0077] The process can be iterated in this way as desired until the fiber optic coil 300 is completed. In this way, fiber optic coils 300 with an error-free and precisely positioned fiber optic cable 200 can be achieved.

[0078] It goes without saying that the number of turns in the axial direction of the fiber optic coil 300, the number of fiber layers in the radial direction of the fiber optic coil 300, and the dimensions shown in Figs. 11A to 11D, as well as in the other figures, are purely exemplary and were chosen only for clarity. Fiber optic coils 300 typically have 50 to 300 turns in the axial direction and 20 to 200 fiber layers. It is also possible to apply the winding processes discussed above to fibers other than glass fibers.

[0079] In the above description, a bobbin 110 with a thread 120 was used as an example. Alternatively, a bobbin 110 can be used on which a series of parallel circumferential grooves are arranged, which circumferentially surround the bobbin without a pitch, ie, at a fixed position along the axial direction x. The dimensions and arrangement of these circumferential grooves allow the glass fiber to be deposited in the circumferential grooves at a distance of P = 2d • cos 30°.

[0080] To enable the transition from one circumferential groove to an adjacent circumferential groove, the coil former 110 has at least one region extending in the axial direction x, in which the circumferential grooves are interrupted in the circumferential direction, i.e., in which no circumferential grooves are formed. In this at least one transition region, the glass fiber 200 can be moved axially over the coil former 110. Furthermore, fiber sections can preferably be crossed by overlying fiber sections in the transition region.

Claims

Claims 1 . A coil former (100) suitable for winding a glass fiber (200) thereon, the coil former (100) comprising: a cylindrical coil core (110) onto which the glass fiber (200) is wound; wherein the coil core (110) has a structure with recesses, preferably a thread (120), in whose recesses (121) the glass fiber (200) can be deposited.

2. Coil former (100) according to claim 1, wherein the structure with depressions, preferably the thread (120), is designed such that between fiber sections (201) of a first fiber layer (211) which are laid down in the depressions (121), such intermediate spaces are created that fiber sections (201) of a next, second layer (212) which are laid down in the intermediate spaces have a distance of d / 2 to the fiber sections (201) of the first layer (211) in the radial direction (R) of the coil core (110), where d is the diameter of the glass fiber (200) to be wound up.

3. Coil body (100) according to one of the preceding claims, wherein the structure with recesses, preferably the thread (120), is designed such that the recesses (121) can accommodate exactly half the diameter of the glass fiber (200) to be wound up.

4. Coil body (100) according to one of the preceding claims, wherein the thread (120) has a pitch P of the size P = 2d • cos 30°, with d being the diameter of the glass fiber (200) to be wound up.

5. Coil former (100) according to one of the preceding claims, wherein the thread (120) has a flank angle of 60°.

6. Coil former (100) according to claim 5, wherein the thread (120) has a thread depth h = 5P / (16 • cos 30°), with P being the pitch of the thread; the thread (120) has a flat thread root of width b1 = P / 4; and the thread (120) has flattened thread crests of width b2 = P / 3.

7. The coil former (100) according to any one of the preceding claims, further comprising a first flange (130) at a first end of the coil core (110) and a second flange (135) at a second end of the coil core (110); wherein the thread (120) extends to the flanges (130, 135).

8. A fiber optic coil (300) comprising a coil body (100) according to any one of the preceding claims; and a fiber optic coil (200) wound around the coil body (100).

9. Glass fiber coil (300) according to claim 8, wherein at least along a cross section through the fiber winding, fiber sections (201) of different layers lie on one another in the radial direction (R) of the glass fiber coil (300) without axial offset.

10. A fiber optic coil (300) according to claim 9, wherein the fiber sections (201) are densely packed within the cross section.

11. A method for producing a coil former (100), the method comprising: Turning a metric ISO thread with a thread pitch P and a thread depth of 3 / 4 (P • cos 30°) on a cylinder with a thread cutter whose tip is blunt and hits the cylinder with a width of P / 4; and Removing the thread crests of the thread thus created by P / (4 • cos 30°).

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