Method for machining a preform blank, preform and device

Abstract

The invention relates to a method for machining a preform blank, to a method for manufacturing a preform, to a preform, and to a device for machining a preform blank. In a method for machining a preform blank (7) for manufacturing a preform (1) for a multicore optical fiber, an eccentric hole (2) is manufactured in the preform blank (7) using a drill (20). The hole extends along the longitudinal extent of the preform blank (7). The position of the preform blank (7) and / or the drill (20) is chosen such that a drift (D) of the drill (20) occurring during drilling causes a change in the position of the hole (2) within the cross section (14) of the preform blank (7) which is greater in the azimuthal direction (17) than in the radial direction (18). In this way, a harmful radial drift component can be minimized and a particularly high-quality preform can be manufactured.

Description

Technical Field

[0001] The present invention relates to a method for processing a preform blank for manufacturing a preform for a multi-core optical fiber, a method for manufacturing a preform for a multi-core optical fiber, a preform for a multi-core optical fiber, and an apparatus for processing a preform blank for manufacturing a preform for a multi-core optical fiber. Background Technology

[0002] To manufacture optical fibers, a preform is first created, and then the fiber is manufactured from the preform. To create the preform, holes are drilled in the preform blank. A core rod is then inserted into these holes. In the case of multi-core fibers, multiple holes for the core rod are created in the preform blank. Drilling must be extremely precise to meet the optical performance requirements of the fiber to be manufactured.

[0003] During drilling, the drill bit drifts. On one hand, as the length increases, the drill bit is pulled downwards due to gravity, causing a generally downward drift. In addition, other effects also contribute to the drift, which can be directed in any direction. Drift can depend on, for example, the direction of the drill bit's rotation, the drill bit's rotational speed, and the direction of gravity. These effects can be superimposed, thus resulting in a drift that varies along the length of the hole. The goal is to produce the longest possible hole with the greatest possible accuracy.

[0004] DE102012006410B4 discloses a method for manufacturing hollow quartz glass cylinders, wherein an end hole extending coaxially with a central axis is created in a starting cylinder. The continuously changing position of the drill bit is determined by means of a measuring device, and the position is returned to the target position in case of deviation. This is achieved by rotating the starting cylinder about the central axis so that the drill bit position is again above the central axis.

[0005] EP0777544B1 discloses a method and apparatus for influencing the trajectory of deep hole drilling. Here, a pressure element, i.e., a separate body, is positioned between the drill rod and the inner wall of the already drilled hole. In this way, the drill rod bends, and the drill bit deflects in a specific direction.

[0006] JP5498086B2 describes a deep drilling method and associated machinery for horizontal drilling. The downward deflection of the drill bit due to gravity is measured. A control device corrects the position of the tip of the deep hole drill bit to compensate for the deflection.

[0007] US9272337B2 discloses a method for creating a hole through a workpiece with a drill bit by monitoring drill bit alignment and hole position and adjusting the drill path as needed. Adjusting the drill path includes selectively applying axial pulses to the drill bit when it is aligned at a specific azimuth angle. An acoustic transmitter and receiver are used to monitor the drill bit alignment and hole position, moving at the same speed as the drill bit's axial movement through the workpiece. Summary of the Invention

[0008] The purpose of this invention is to improve the manufacturing of preforms for multi-core optical fibers.

[0009] This objective is achieved by a method for processing preform blanks according to claim 1, and by a method for manufacturing preforms according to adjacent claims, a preform for multi-core optical fibers, and an apparatus for processing preform blanks. Advantageous embodiments are specified in the dependent claims.

[0010] To achieve this objective, a method for processing a preform blank is used. The preform blank is used to manufacture a preform for a multi-core optical fiber. An eccentric hole is created in the preform blank using a drill bit, the eccentric hole extending along the longitudinal direction of the preform blank. Specifically, the positions of the preform blank and / or the drill bit are selected such that drill bit drift occurring during drilling causes a change in the position of the hole within the cross-section of the preform blank, the change being greater in the azimuth direction than in the radial direction.

[0011] According to the invention, the objective is not to prevent drift that occurs during drilling, but to guide the drift in a direction that is less harmful to the multi-core optical fiber to be manufactured. It has been shown that a larger drift in the azimuth direction than in the radial direction has significantly less destructive effects than a drift in the radial direction. In this way, particularly high-quality preforms for multi-core optical fibers can be manufactured with very little effort, and thus, particularly high-quality multi-core optical fibers can be produced.

[0012] Holes are made using drill bits. Drill bits are especially rotary drill bits. Drill bits particularly include a drill head and / or a drill rod for driving the drill head. The drill rod is usually driven by a motor. Drilling can be performed by creating blind holes and, in particular (e.g., by sawing), separating the undrilled ends of a particular preform blank. In this way, through holes can be made. During the creation of blind holes, the drill bit moves relative to the preform blank from an initial drilling position to a final position. Drilling is performed, in particular, as thrust drilling, i.e., by advancing the free end of the drill bit, in particular the drill head, into the preform blank. However, jacking is not excluded. The drill bit enters the preform blank, particularly at a first end surface. Specifically, drilling continues until the drill bit reaches a position before reaching a second end surface located on the opposite side. Drilling is performed, in particular, in the preform blank, which is solid at least in the area where the hole to be made. However, enlarging existing holes, such as previously made holes, during drilling is not excluded.

[0013] The preform blank may be solid or at least partially hollow. When manufacturing the holes, one or more central holes and / or eccentric holes may already exist, wherein these holes extend particularly along the longitudinal direction. A central hole may exist along the central longitudinal axis. The preform blank may be made of, for example, quartz glass, particularly synthetic quartz glass.

[0014] An eccentric hole is positioned eccentrically relative to the cross-section of the preform blank. Therefore, the center of the hole is a certain distance from the center of the cross-section. An eccentric hole typically does not extend through the central longitudinal axis of the preform blank. In a circular cross-section, the center of the cross-section is the center of the circle. In a cross-section with a basic circular shape, the center of the basic shape can be used as the center. For a non-circular cross-section, the centroid can be used as the center. Specifically, multiple holes are manufactured such that, when viewed in cross-section, these holes lie on a circle called the pitch circle. Specifically, the holes are evenly distributed on the circle.

[0015] The hole extends along the longitudinal direction of the preform blank. Specifically, the hole extends from a first end surface or end face of the preform blank to a second end surface or end face. In principle, it is desirable for the hole to be manufactured to extend parallel to the central longitudinal axis of the preform blank at a certain distance from the central longitudinal axis. However, this is not entirely possible due to drift.

[0016] Multicore optical fiber is a fiber with multiple cores. The specific number of cores is independent of the method. For example, multicore optical fiber can have two, four, or more cores.

[0017] Specifically, the preform blank is elongated, such as cylindrical. Therefore, the cross-section of the preform blank is the same throughout its longitudinal direction. In one embodiment, the preform blank is cylindrical.

[0018] In one embodiment, the preform blank has a basic cylindrical shape. The term "basic cylindrical shape" implies that some deviation from a precise cylindrical shape is permissible. In one example, the preform blank may have a basic cylindrical shape, but may deviate from a precise cylindrical shape due to a flattened portion. The flattened portion may extend along the entire length of the preform blank and / or be aligned parallel to the longitudinal axis. For example, a flattened portion may be present for marking. In another example, the preform blank may have a basic cylindrical shape, but may have one or two inclined end surfaces.

[0019] Drill bit drift occurs within the preform blank and causes a change in the position of the hole within the cross-section of the preform blank. Therefore, the hole's position changes along the longitudinal direction of the preform blank. In other words, the hole "wanders." Drift causes a deviation between the actual position of the drill bit or hole and the target position, and a deviation between the drill bit and its starting position. This deviation is particularly radial and / or azimuth deviation. The positions of the preform blank and / or drill bit are chosen such that the drift of the drill bit during drilling causes a change in the hole's position within the cross-section of the preform blank, with this change being greater in the azimuth direction than in the radial direction. For example, the positions of the preform blank and / or drill bit can be chosen relative to the direction of gravity.

[0020] For example, if drilling begins at a midpoint between the center of the cross-section of the preform blank and the 12 o'clock position on the outer edge at the first end surface, the drill bit moves in a defined direction, such as upward and to the right, as the length of the hole increases. At the end of the hole at the second end surface, when viewed in the same direction, the drill bit is closer to the outer edge and positioned further to the right. In this case, the position of the hole in the cross-section changes in both the azimuth and radial directions. The radial direction refers to the direction outward from the center of the cross-section. The azimuth or circumferential direction refers to the angular position relative to the center or the central longitudinal axis.

[0021] Radial positional variations (also known as the radial component of drift) have disadvantages. To manufacture multi-core optical fibers, multiple eccentric holes are typically fabricated. These eccentric holes are arranged in the cross-section of the preform blank, particularly at uniform intervals on pitch circles concentric and / or coaxial with the central longitudinal axis. Radial drift causes the diameter of the circles to change along the length of the preform blank. Consequently, the position of the core rods in the fiber manufactured from it is no longer constant, but the core spacing changes, leading to optical loss and splicing loss in the fiber, and impairing its performance. Conversely, it has been shown that changing the position or azimuth component of the drift in the azimuth direction does not cause the described disadvantages. Because the position of the holes is larger in the azimuth direction than in the radial direction, the disadvantages can be minimized with reasonable effort. This enables the manufacture of high-quality multi-core optical fibers.

[0022] To ensure that the drift extends in a specific direction relative to the cross-section, the appropriate position of the preform blank and / or drill bit is selected. For example, the position where the drill bit contacts the preform blank, i.e., the relative position of the drill bit to the preform blank, can be adjusted. This position affects how the drift extends within the cross-section. For example, it may have been shown that under certain conditions the drift extends towards the upper right in the 2 o'clock direction. If the position where the drill bit contacts the preform blank is chosen to be upper left in the 10 o'clock direction relative to the center of the cross-section, the resulting drift extends essentially in the azimuth direction, or in other words, causes a circumferential positional change.

[0023] The position of contact between the drill bit and the preform blank can be adjusted, for example, by spatially aligning the preform blank and the drill bit together. Spatially co-aligning refers specifically to the spatial positioning of the drill bit and the preform, such that the drill bit is arranged relative to the first end surface such that a hole can be formed at the desired location by moving the drill bit and / or the preform blank along the longitudinal axis (especially the common longitudinal axis). The drill bit is typically aligned at least substantially parallel to, and especially parallel to, the preform blank. For example, the drill bit may be positioned in front of the first end surface.

[0024] A particular advantage is the ability to position and / or move the precast blank while keeping the drill bit stationary. This eliminates the need for components that move the drill bit, such as drill bushings, guide bushings, and / or drive units.

[0025] A specific position is selected for the preform blank and / or the drill bit. Specifically, the position of the preform blank and / or the drill bit is also adjusted. In one exemplary embodiment, the preform blank is moved relative to the drill bit to adjust the position. In one exemplary embodiment, the drill bit is moved relative to the preform blank to adjust the position. In one exemplary embodiment, both the preform blank and the drill bit are moved to adjust the position. The movement of the drill bit refers to a movement different from the rotation about the longitudinal axis during drilling, i.e., particularly additional movement.

[0026] In the first variation, as described above, relative movement can be made between the preform blank and the drill bit. However, this is not necessary. In the second variation, the preform blank and the drill bit can be moved in the same way, during which the relative positions between the preform blank and the drill bit do not change. For example, the drill bit can be positioned directly in front of the end surface of the preform blank, above the location where the hole is to be made. For example, joint positioning relative to the central longitudinal axis of the preform blank can be performed, for example, by rotating about a central longitudinal axis, in order to adjust the common position in space or relative to the direction of gravity.

[0027] The specific location of the preform blank and / or drill bit cannot be uniformly defined for all holes because it depends on drift, which typically depends on specific frame conditions. For example, drift may depend on the drill bit's rotation direction, drill bit speed, hole depth, and / or direction of gravity.

[0028] This method is used to process a preform blank by drilling. The processed preform blank is then manufactured. Once all the holes have been made in the preform blank and further steps, such as inserting a core rod, have been optionally performed, a preform of a multi-core fiber exists. The multi-core fiber can then be manufactured from the preform.

[0029] Specifically, the method is implemented such that, given a preform blank with an outer diameter of 200 mm, the position of the hole in the radial direction varies by at most ±0.3 mm. More specifically, the method is implemented such that the position of the hole in the radial direction varies by at most ±0.15% of the outer diameter.

[0030] This method may include fabricating a multi-core optical fiber from a preform. Specifically, the method is performed such that the positional variation of the aperture in the radial direction of the fabricated multi-core optical fiber is less than 200 nm.

[0031] In one embodiment, during drilling, i.e., during hole fabrication, the preform blank and drill bit are substantially horizontally aligned. Horizontal drilling requires significantly lower space and is therefore generally easier to implement. Although drift is increased during horizontal drilling, the position selection according to the invention allows for maximum accuracy.

[0032] In one embodiment, the method further includes adjusting the desired rotational position of the preform blank and the drill bit about the longitudinal axis of the preform blank, particularly the central longitudinal axis. Specifically, the rotational position of the preform blank and / or the drill bit is changed relative to the longitudinal axis to guide the drift in a desired direction. The rotational position refers to the position of the preform blank or drill bit arranged at a specific angle relative to the corresponding axis. The change in rotational position can be achieved by rotating about the longitudinal axis or about an axis parallel to the longitudinal axis.

[0033] In one embodiment, the drill bit and / or preform blank are moved to adjust the rotational position. In another embodiment, the drill bit and / or preform blank are rotated about a longitudinal axis. This allows the position of the drill bit and preform blank to be adjusted relative to the direction of gravity. Therefore, gravity-induced drift can be guided in the desired direction.

[0034] In one embodiment, the preform blank and the drill bit are positioned such that the drill bit, relative to the direction of gravity, is located in a position other than exactly above the central longitudinal axis of the preform blank. In other words, the drill bit is not exactly above the central longitudinal axis of the preform blank. Preferably, the angle between the vertical direction and the position of the drill bit, starting from the central longitudinal axis, is at least 10°, and especially at least 20°. For example, the relative position of the drill bit and / or the preform blank relative to the direction of gravity is between 9 o'clock and 12 o'clock, for example, between 9:30 and 11:30, preferably between 10 o'clock and 11 o'clock.

[0035] It has been shown that drift typically acts not only vertically downwards, but also, or even primarily, in the opposite direction. Therefore, the eccentric position of the drill bit is particularly effective in guiding the resulting drift in the appropriate direction.

[0036] In one implementation, the location of the preform blank and / or drill bit to be selected is determined based on at least one previously determined direction of the drift.

[0037] For example, drift can be pre-determined based on experience and / or estimation based on measurements. For instance, experience gained under similar conditions can be used, such as using the same drill bit, the same material, the same drilling location, the same rotational speed, and / or the same feed rate. In other words, the expected drilling path is pre-determined and used as input to select the desired location of the preform blank and / or the drill bit. Drift can also be determined by creating test holes.

[0038] In one embodiment, test holes are fabricated in the test preform blank prior to the fabrication of the holes, and at least one direction of drift in the test holes is determined.

[0039] Then, the determined orientation is used to select a specific position. For example, if a drift occurs from the starting center of the borehole toward the upper right in the 2 o'clock direction, the position of the preform blank and / or drill bit can be selected such that the preform blank and drill bit are rotated 60° counterclockwise from the position at the test hole, for example, around the central longitudinal axis of the preform blank. In this way, the resulting drift causes a positional change along the circumferential direction or on the pitch circle. The positional change in the radial direction becomes minimal. This adjustment can be made by moving the preform blank and / or drill bit (e.g., by displacement and / or rotation). For example, the preform blank and drill bit can be rotated together about the central longitudinal axis, an axis parallel to the central longitudinal axis, and / or a horizontal axis.

[0040] Specifically, the same drill bit is used to create the test holes. Specifically, the test preform blank is made of at least substantially the same material as the preform blank. Specifically, other parameters, such as drilling location, rotational speed, and / or feed rate, are similarly selected.

[0041] After determining the direction of drift in the test hole, multiple holes can be fabricated using the preform blank and / or the determined position of the drill bit.

[0042] In one embodiment, the position of the preform blank and / or drill bit changes between the fabrication of the first portion of the hole and the fabrication of the second portion of the hole. In another embodiment, the relative positions of the preform blank and the drill bit remain the same. This positional change can be performed by rotating the preform blank and the drill bit, for example, about an axis parallel to the central longitudinal axis (e.g., about the central longitudinal axis itself). The movement of the preform blank and the drill bit can, in principle, be at least intermittent, simultaneous, for example, jointly, or continuously. The advantage of joint movement is that the drilling process does not need to be interrupted, or only minimally interrupted. It is not necessary to remove the drill bit from the completed portion of the hole.

[0043] The portions of the hole are axially positioned one after the other. The portions of the hole are made continuously. Positional changes occur between the two portions of the hole. The position can be changed when the drill bit is not in operation. The position can be changed while the drill bit is drilling. In one exemplary embodiment, the hole is made into three or more portions, such as four, five, six, eight, or ten portions, in each case, the position changes between these portions.

[0044] Temporary changes in position can compensate for temporary changes in drift direction. This allows for particularly effective minimization of the radial drift component. For example, the downward drift component caused by gravity is only effective at longer borehole lengths. This component can be compensated for in a targeted manner, enabling the fabrication of longer holes with high accuracy.

[0045] In another embodiment, the common position of the preform blank and the drill bit in space is changed at least periodically while the hole is being created. Therefore, during drilling, the positions of the preform blank and the drill bit in space change simultaneously. Specifically, the preform blank and the drill bit rotate about an axis parallel to the longitudinal axis of the preform blank and / or the drill bit, or about a horizontal axis.

[0046] A continuous process is provided in which drift is influenced in a manner that minimizes the harmful radial component at any given time. This allows the aforementioned objective to be achieved more effectively.

[0047] In one embodiment, after holes have been made, the preform blank is rotated relative to the drill bit about its longitudinal axis, particularly its central longitudinal axis. Specifically, additional holes are then made. Specifically, the preform blank is rotated. In this way, multiple eccentric holes can be made consecutively. This allows for particularly efficient manufacturing of preforms. The positions of the preform blank and / or drill bit used to influence drift can remain the same or change between and / or during individual drilling operations.

[0048] In one embodiment, the position of the preform blank and / or drill bit in space is selected such that the change in the position of the hole is at least twice as large, especially at least four times, in the radial direction in the azimuth direction.

[0049] This factor is particularly at least 3 times, preferably at least 5 times. In one embodiment, the factor is at least 7 times, at least 10 times, and in one example at least 15 times. This allows for adjustment of particularly low radial drift. To calculate the factor, specifically, the same units are used for variations in the azimuth and radial directions, e.g., millimeters.

[0050] In one embodiment, the ratio of the preform blank's length to the hole's diameter is greater than 10, particularly greater than 20. This ratio can be greater than 30, for example, greater than 35. This ratio can be greater than 40 or 50. As the ratio of the preform's length to the hole's diameter increases, drift also increases, which offsets the required accuracy. The solution according to the invention allows such a ratio to have high accuracy. Such a ratio ensures short processing times and minimal setup times.

[0051] In one embodiment, multiple holes are fabricated. In another embodiment, the multiple holes drift in the azimuth direction with at least substantially the same magnitude. Specifically, the multiple holes drift in the azimuth direction have the same direction in the sense of having the same sign, i.e., they do not point in opposite directions. Therefore, in the multiple holes, or in all the holes, the drift is clockwise or counterclockwise relative to the center of the cross-section of the preform blank. In this way, the distance between the holes remains constant over the length of the preform. This minimizes optical loss and bonding loss.

[0052] Another aspect of the invention is a method for manufacturing a preform for a multi-core optical fiber, the method comprising the method according to the invention. Specifically, a plurality of eccentric holes are manufactured. The method may include inserting a core rod into the holes. All the advantages, features, and embodiments of the above method can be similarly applied to this method, and vice versa.

[0053] Another aspect of the invention is a preform for a multi-core optical fiber, which can be manufactured or produced using the method according to the invention. The preform includes eccentric holes extending along a longitudinal range of the preform. The position of the holes within the cross-section of the preform varies along its longitudinal range. The cross-section of the preform corresponds to the cross-section of the preform blank. Viewed in the cross-section of the preform, the positional variation is greater in the azimuth direction than in the radial direction. This allows the distance between multiple eccentric holes to be substantially constant. The preform may include a core rod inserted into the hole. All the advantages, features, and embodiments of the above method can be similarly applied to this preform, and vice versa.

[0054] Specifically, both the start and end points of the hole lie on pitch circles of the same diameter in their corresponding cross-sections. Specifically, each point between the start and end points of the hole lies on a corresponding circle of the same diameter. In this ideal embodiment, drift occurs only in the azimuth direction, and the radial drift is zero. The positional change of the hole is measured in the cross-section, i.e., transverse to the longitudinal range. The positional change of the hole is, in particular, continuous, i.e., not abrupt.

[0055] In one embodiment, the length of the prefabricated component is greater than 1.5m, and particularly at least 2.0m. The length can be at least 2.5m. This length can be manufactured with the required accuracy using the method according to the invention.

[0056] In one embodiment, the preform includes at least two eccentric holes extending along a longitudinal direction of the preform, and the positions of these holes within a cross-section vary along the longitudinal direction of the preform. Specifically, the distance between the holes, measured in the cross-section, is substantially constant along the longitudinal direction. The holes may be slightly twisted relative to each other, which has proven harmless to the optical fiber.

[0057] In one embodiment, the distance between the central longitudinal axis of the preform and the center of the hole is substantially the same at both the first end surface of the preform and the second end surface of the preform opposite to the first end surface. In other words, the positional variation of the hole is approximately zero in the radial direction. A deviation of up to 1%, particularly up to 0.5% or up to 0.2%, in the diameter of the preform blank is permissible.

[0058] Preferably, the change in the radial direction is at least twice as small as, and especially at least four times as small as, the change in the azimuth direction.

[0059] In another embodiment, the preform includes at least two eccentric holes extending along a longitudinal extent of the preform. The positions of the holes within the cross-section of the preform vary in the same direction along a curve about the central longitudinal axis of the preform along the longitudinal extent of the preform. Ideally, the curve can be a circular path. Specifically, the distance between two adjacent holes is substantially constant along the length of the preform. A deviation of up to 5%, particularly up to 2% or up to 1%, in the diameter of the preform blank is permissible.

[0060] Another aspect of the invention is an apparatus for processing preform blanks. The preform blanks are used to manufacture preforms for multi-core optical fibers. The apparatus includes: a holding device for holding the preform blank; a drill bit for creating an eccentric hole in the preform blank; and a positioning device designed to move the holding device and / or the drill bit to adjust the position of the preform blank and / or the drill bit such that drift of the drill bit during drilling causes a change in the position of the hole within the cross-section of the preform blank, the change being greater in the azimuth direction than in the radial direction. All the advantages, features, and embodiments of the above-described method and preform can be similarly applied to the apparatus, and vice versa.

[0061] The apparatus is specifically designed to perform the method according to the invention and / or to manufacture preforms according to the invention. The holding device is specifically designed to hold the preform blank in at least a substantially horizontal alignment. The drill bit is specifically aligned at least substantially horizontally.

[0062] The positioning device can be designed to move the drill bit and the holder together. The movement of the drill bit and / or the holder can be rotational. Rotation can occur about a central longitudinal axis of the preform blank held in the holder or about an axis parallel to it. The positioning device may include an actuator to move the drill bit and / or the holder.

[0063] In one embodiment, the positioning device is designed to rotate the preform blank about its central longitudinal axis. In this way, the relative rotational position of the preform blank and the drill bit relative to the central longitudinal axis can be adjusted particularly easily.

[0064] Alternatively or additionally, the positioning device can be designed to move the preform blank or drill bit in space. This can be achieved, for example, by two mutually perpendicular translational movements within the cross-section of the preform blank. Typically, the drill bit is stationary except for rotation about its longitudinal axis and the feed required to create the hole, and the preform blank is positioned and / or moved relative to the drill bit. By properly arranging the longitudinal axis of the drill bit and the longitudinal axis of the preform blank, the direction of drift can be adjusted as needed. The positioning device is particularly useful for adjusting different relative positions of the preform blank to the drill bit after holes have been created, in order to create additional holes in which the drift is also guided in a desired manner. This allows for the continuous creation of all holes in the preform.

[0065] The hole trajectory can be determined using ultrasonic, CT analysis, and / or, if necessary, optical measurement methods. The holding device may include a V-block for holding the preform blank. The device may also include a cutting oil supply device. The drill bit may be a drill bit used for the BTA drilling method. In this case, cooling lubricant is supplied externally, and generated chips are removed internally. The device includes a cutting oil supply device (BOZA) for supplying both coolant and lubricant. Preferably, a seal is implemented on the workpiece. Attached Figure Description

[0066] Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying drawings. Unless otherwise indicated, features of the exemplary embodiments can be combined individually or in combination with the claimed subject matter. The scope of protection claimed is not limited to the exemplary embodiments.

[0067] The attached diagram shows:

[0068] Figure 1 and Figure 2 Cross-sectional view of the precast component.

[0069] Figure 3 A schematic diagram of the drilling process.

[0070] Figure 4 A diagram showing the process before drilling begins.

[0071] Figure 5 and Figure 6 : Schematic diagram of the device,

[0072] Figures 7 to 9 : A schematic diagram of the process steps for processing precast blanks.

[0073] Figure 10 and Figure 11 A schematic diagram of drift during the drilling process, and

[0074] Figure 12 and Figure 13 : A diagram illustrating the method and steps. Detailed Implementation

[0075] Figure 1 and Figure 2 Cross sections 14 of different preforms 1 are shown as examples. Each preform has a circular cross section 14. Preform 1 may optionally include a central hole 2 extending along the central longitudinal axis of the corresponding preform 1.

[0076] Figure 2As an example, five eccentric holes 2 are shown in addition to the optional center hole 2. For example, these eccentric holes are regularly distributed on a pitch circle (not individually labeled), which may be arranged concentrically with the outer contour of the preform 1 and / or coaxially with the central longitudinal axis of the preform 1.

[0077] Figure 3 The drilling process for creating a hole 2 in a preform blank 7 is schematically illustrated. The drill bit 20 moves along a direction 23 parallel to the longitudinal axis 15 of the preform blank 7 and, in the process, rotates particularly about its longitudinal axis. The drill bit 20 typically includes a drill head 21, which is driven by a drill rod 22. These components are shown purely schematically here; typically, the diameter of the drill rod 22 is smaller than the diameter of the drill head 21. The drill rod 22 is driven, for example, by a drive unit not shown.

[0078] As can be seen, drill bit 20 has penetrated the preform blank 7 on the first end surface 11 and created hole 2 from there. Hole 2 is eccentric, i.e., off-center. The longitudinal axis of drill bit 20 is aligned parallel to the central longitudinal axis 15 of preform blank 7. Here, only as an example, the position where drill bit 20 contacts the first end surface 11 or enters the cross-section of preform blank 7 is shown at 6 o'clock in the viewing direction along direction 23.

[0079] Figure 4 The diagram shows the situation before eccentric drilling begins. The preform blank 7 may optionally already contain a center hole. The drill bit 20 is positioned in front of the first end surface 11 such that it can perform drilling by translating along its longitudinal axis or the central longitudinal axis 15. The drilling position 3 of the hole to be drilled is marked with a dashed line on the first end surface 11.

[0080] Figure 5 and Figure 6 A schematic diagram of some components of the device 30 is shown. The preform blank 8 is held by elements of the holding device 32. The holding device 32 can be used to rotate the preform blank 7 about its central longitudinal axis. For example, according to the invention, the position of the preform blank 7 can be adjusted, possibly together with the position of the drill bit 20. The holding device may accordingly be part of the positioning device 34.

[0081] The holding device 32 can also be used to adjust the position of the preform blank 7 relative to the drill bit 20, for example, so that a second eccentric hole can be manufactured after the first eccentric hole is manufactured, as follows: Figures 7 to 9 As shown in the diagram. Alternatively or additionally, the holding device 32 may be designed to move the preform blank 7 in a plane perpendicular to its longitudinal direction. For example, the holding device 32 includes two translation devices 38 perpendicular to each other, such as... Figure 6As shown schematically. The holding device 32 can interact with the positioning device 34 to move the holding device 32. Alternatively or additionally, the holding device 32 holds the preform blank 7 in a fixed position.

[0082] The drill bit 20 is held by an optional drill bit holder 39, which can be used to move the drill bit 20 in a plane perpendicular to its longitudinal direction. For example, the drill bit holder 39 includes two translation devices 38 perpendicular to each other, such as... Figure 6 The diagram is schematically shown. Therefore, a translation device 38 for the preform blank 7 and / or a translation device 38 for the drill bit 20 may be present. A drill bit holder 39 can be used to move the drill bit 20 relative to the preform blank 7 to adjust its position according to the invention. The drill bit holder 39 may be part of a positioning device 34 to move the holding device 32 and / or the drill bit 20. The positioning device 34 may include or consist of the drill bit holder 39. The drill bit holder 39 can be used to advance the drill bit 20 along its longitudinal axis during drilling.

[0083] Using the cross section 14 of precast blank 7 Figures 7 to 9 The method steps for manufacturing the preform are shown. For example, based on previously made test holes or experience based on a comparable system, it is known that the drill bit will be expected to drift to the upper right in a 1 o'clock direction. This can be determined at any drill bit position. To guide the drift relative to the cross section 14 of the preform blank 7 in the desired direction (see below for details)... Figure 10 and Figure 11 The position of the preform blank 7 and / or the drill bit position 4 marked with a crosshair are selected such that drilling in the cross section 14 is not performed vertically above the center of the cross section, which corresponds to the central longitudinal axis of the preform blank 7. Instead, the drill bit position is shifted slightly to the lower left to approximately 11 o'clock to minimize the radial component of the shift. Specifically, all holes 2 are formed in this position.

[0084] Before drilling the first hole, the desired position can be adjusted by positioning or moving the preform blank 7 and / or the drill bit. The preform blank 7 can be translated, i.e., displaced, for example, in the plane of its cross-section 14, and / or rotated about a rotation axis, for example, aligned parallel to the central longitudinal axis. Alternatively or additionally, the drill bit can be translated, i.e., displaced, for example, in the plane of its cross-section 14, and / or rotated about a rotation axis, for example, aligned parallel to the central longitudinal axis.

[0085] Figure 7 The diagram illustrates the situation before or during the first eccentric drilling operation. Optionally, a center hole can be pre-formed. The drill bit is positioned at drill bit position 4, marked with a cross, so that the hole can be made by translating the drill bit along the central longitudinal axis. Additionally, drill position 3, where the hole is also to be made, is marked with a dashed line.

[0086] After the holes are made, a movement is performed that corresponds to a clockwise rotation of 25° around the central longitudinal axis of the preform blank 7 at a defined angle. This is in Figure 8 As shown in the diagram. With the drill holes arranged at uniform intervals, the angle is calculated as 360° / n, where n is the number of holes to be drilled. Here, five holes are produced as an example only; therefore, the angle is 72°. After rotation, the completed hole 2 is positioned at approximately two o'clock in the upper right, and the drill bit position 4 is positioned in front of the next hole to be drilled, at approximately 11 o'clock.

[0087] To change the angle, as shown in the figure, it is simple and practical to rotate the preform blank 7 about its central longitudinal axis. The drill bit can then remain stationary. However, alternative or additional movements of the preform blank, rotation about different axes, and / or movements and / or rotations of the drill bit are not excluded. The positions of the drill bit and the preform blank in space can remain the same or vary. The key is simply to adjust the same relative position of the preform blank 7 with respect to the direction of gravity, i.e., at approximately 11 o'clock here, so that drift can be guided again as needed.

[0088] like Figure 9 As shown, repeat the above steps to create the next hole 2. After two further repetitions (not shown), all holes 2 are completed.

[0089] Figure 10 and Figure 11 A cut in cross-section 14 of the preform is shown to illustrate the conventional method ( Figure 10 ) and the method according to the invention ( Figure 11 The drift in the section is described. As an example, four holes evenly spaced on a pitch circle are to be produced in cross-section 14. This pitch circle is shown as the inner target pitch circle 43, indicated by a dashed line. The drill bit position 3, marked with a solid line, is positioned such that the center of each hole is located on the target pitch circle 43. The figure shows a top view of the first end surface where the drilling begins. Here, the drill bit position is located above the center of the cross-section. Ideally, the holes should terminate at the same point on the same pitch circle on the opposite second end surface.

[0090] However, drift occurs, causing the hole's position to deviate at the point where the drill bit is located at the end or after the hole has been drilled. These positions are shown using the final position 5 of the drill bit, marked with a dashed line. It can be seen that the drill bit moves to the upper right during the drilling process, i.e., according to the angle α relative to the horizontal line H perpendicular to the direction of gravity. The resulting drift D, radial component Dr, and azimuth component Da are shown. The radial component Dr extends in the radial direction 18, and the azimuth component Da extends in the azimuth direction 17. Furthermore, a coordinate system 40 is shown, with its origin at the center of the cross-section. From there, the target radius 45 and actual radius 46 of a specific pitch circle are shown. The target radius 45 of the target pitch circle 42 is the radius present at the first end surface 11. The actual radius 46 of the actual pitch circle 43 is the radius present at the second end surface and displaced due to the drift. The radial component Dr corresponds to the effective change in radius.

[0091] Figure 11 This illustrates the same situation when adjusting the position of the preform blank 7 and / or the drill bit causes drift, resulting in a change in the position of the hole within the cross-section 14, with the change being greater in the azimuth direction 17 than in the radial direction 18. (Name and...) Figure 11 Since they are the same as those in the original text, we will only discuss the differences.

[0092] The angle α is the same. However, due to the chosen relative positions of the drill bit and the preform blank 7 with respect to the direction of gravity, it corresponds here, for example, to the drilling position 3 between 10 o'clock and 11 o'clock. It can be seen that the drift D has the same... Figure 10 The situation shown has the same amplitude and direction. However, due to the changed position, the radial component Dr is significantly smaller, and the azimuth component Da is significantly larger. The ratio of Da to Dr is approximately 3.8. The deviation between the actual pitch circle 43 and the target pitch circle 42 is significantly smaller. In this way, the quality of the preform can be significantly improved, thereby improving the quality of the optical fiber manufactured from it. It can also be seen that a further counterclockwise rotation of the relative positions of the drill bit and the preform blank, i.e., a change in the azimuth position of the drill bit relative to the direction of gravity, will allow the radial component Dr to be further reduced. Then, the drift will extend tangentially to the target pitch circle 42 and have only the minimum radial component.

[0093] Figure 12 and Figure 13 Similarly, the cut in cross-section 14 is shown. The arrows indicate the drift from the drill position to the final position 5 in each case. For illustrative purposes, the figures are rotated around the center of cross-section 14 and deviate from actual conditions. Figure 12 Basically corresponds to Figure 11 The situation in the middle or the relative position for further optimization, where the desired position is adjusted once before drilling, and there is tangential drift, so there is still a radial component of the drift.

[0094] However, in Figure 13 In this process, continuous or quasi-continuous positional changes have occurred. For example, after the first portion of the hole is manufactured, the drill bit and preform blank rotate together and / or simultaneously, and then another portion of the hole is manufactured. This corresponds to a quasi-continuous process and can be repeated any number of times. Alternatively or additionally, the drill bit and preform blank may rotate together and simultaneously in space and / or relative to the direction of gravity during drilling. This corresponds to a continuous process. This results in continuously adapted drift, which ultimately occurs only in the azimuth angle, as indicated by simplified straight arrows.

[0095] Essentially, a distinction can be made between predictable and unpredictable drift. The total drift that occurs can be understood as a superposition of predictable and unpredictable drift. For example, information about predictable drift, such as its direction, can be determined before drilling. This can be made, for example, by creating a test hole under the same or similar conditions. Furthermore, unpredictable drift may occur.

[0096] In one embodiment, the position of the drill bit and / or the resulting drift is determined. This can be done during and / or continuously during drilling. Measurements, which may be referred to as online measurements, can be performed during drilling. For example, information regarding the position of a portion of the drill bit can be determined. Measuring devices can be used to determine such a position. For example, the position of at least a portion of the drill bit, preferably relative to or within the cross-section of the preform blank, can be measured. This determination can be performed as described in German patent application 102012006410.

[0097] When selecting the location of the preform blank and / or drill bit, measured position and / or drift can be taken into account. The location of the preform blank and / or drill bit can be changed based on measured position or drift. This can be done during drilling and / or between the fabrication of two parts of the hole. In this way, the hole trajectory may be affected. Therefore, unpredictable drift can be addressed.

[0098] Especially during drilling, it can be determined when a change of position is needed to reach a specific target. If a change is needed, the position can be changed. For example, a change can be made if a threshold is exceeded. For example, the target could be a larger drift in the azimuth direction than in the radial direction, which could be a factor as described, or a drift greater than the maximum absolute drift in the radial direction.

[0099] Basically, "horizontal" means that some deviation from horizontal alignment is allowed. The deviation from horizontal alignment is usually no more than 15°, and preferably no more than 10°.

[0100] List of reference numerals in the attached figures

[0101] Precast component 1

[0102] Hole 2

[0103] Drilling position 3

[0104] Drill bit position 4

[0105] Final position 5

[0106] Precast blank 7

[0107] First end surface 11

[0108] Second end surface 12

[0109] Cross section 14

[0110] Central longitudinal axis 15

[0111] Azimuth direction 17

[0112] Radial direction 18

[0113] Drill bit 20

[0114] Drill head 21

[0115] Drill pipe 22

[0116] Direction 23

[0117] Rotate 25

[0118] Device 30

[0119] Holding device 32

[0120] Positioning device 34

[0121] Translation device 38

[0122] Drill bit holder 39

[0123] Coordinate system 40

[0124] Target section circle 42

[0125] Actual pitch circle 43

[0126] Target radius 45

[0127] Actual radius 46

[0128] Drift D

[0129] Radial component Dr

[0130] Azimuth component Da

[0131] Horizontal H

[0132] Angle α.

Claims

1. A method for processing a preform blank (7) for manufacturing a preform (1) of a multi-core optical fiber, wherein an eccentric hole (2) is made in the preform blank (7) using a drill bit (20), the hole extending along a longitudinal range of the preform blank (7), wherein the position of the preform blank (7) and / or the drill bit (20) is selected such that a drift (D) of the drill bit (20) occurring during drilling causes a change in the position of the hole (2) within a cross section (14) of the preform blank (7), the change being greater in the azimuth direction (17) than in the radial direction (18).

2. The method according to the preceding claims, wherein the preform blank (7) and the drill bit (20) are substantially horizontally aligned.

3. The method according to any one of the preceding claims, further comprising: Adjust the desired rotational position of the preform blank (7) and the drill bit (20) around the central longitudinal axis (15) of the preform blank (7).

4. The method according to any one of the preceding claims, wherein the positions of the preform blank (7) and the drill bit (20) are such that the drill bit (20) is located relative to the direction of gravity at a position other than exactly above the central longitudinal axis (15) of the preform blank (7).

5. The method according to any one of the preceding claims, wherein the position of the preform blank (7) and / or the drill bit (20) to be selected is determined based on at least one previously determined direction of the drift (D).

6. The method according to the preceding claim, wherein, Before manufacturing the hole (2), a test hole is manufactured in the test preform blank, and at least one direction of the drift (D) in the test hole is determined.

7. The method according to any one of the preceding claims, wherein the position of the preform blank (7) and / or the drill bit (20) is changed between a first portion of making the hole (2) and a second portion of making the hole (2).

8. The method according to any one of the preceding claims, wherein while the hole (2) is being made, the common position of the preform blank (7) and the drill bit (20) in space is changed at least at intervals.

9. The method according to any one of the preceding claims, wherein after the hole (2) is made, the preform blank (7) is rotated about its central longitudinal axis (15) relative to the drill bit (20), and an additional hole (2) is subsequently made.

10. The method according to any one of the preceding claims, wherein the position of the preform blank (7) and / or the drill bit (20) is selected such that the change in the position of the hole (2) in the azimuth direction (17) is at least twice as large, especially at least four times as large, in the radial direction (18).

11. A method for manufacturing a preform (1) for a multi-core optical fiber, the method comprising the method according to any one of the preceding claims.

12. A preform (1) for a multi-core optical fiber, the preform being manufactureable by any one of claims 1 to 10, wherein the preform (1) includes an eccentric hole (2) extending along a longitudinal range of the preform (1), wherein the position of the hole (2) within a cross section (14) of the preform (1) varies over the longitudinal range of the preform (1), wherein the positional variation observed in the cross section (14) of the preform (1) is greater in the azimuth direction (17) than in the radial direction (18).

13. The preform (1) according to the preceding claim, wherein the preform (1) comprises at least two eccentric holes (2) extending along the longitudinal range of the preform (1), and the positions of the at least two eccentric holes within the cross section (14) of the preform (1) change in the same direction along a curve about the central longitudinal axis (15) of the preform (1) in the longitudinal range of the preform (1).

14. An apparatus (30) for processing preform blanks (7) to manufacture preforms (1) of multi-core optical fibers, the apparatus comprising: A holding device (32) for holding a preform blank (7); a drill bit (20) for making an eccentric hole (2) in the preform blank (7); and a positioning device (34) designed to move the holding device (32) and / or the drill bit (20) to adjust the position of the preform blank (7) and / or the drill bit (20) such that a drift (D) of the drill bit (20) occurring during drilling causes a change in the position of the hole (2) within the cross section (14) of the preform blank (7), the change being greater in the azimuth direction (17) than in the radial direction (18).

15. The apparatus according to the preceding claims, wherein the positioning device (34) is designed to rotate the preform blank (7) about the central longitudinal axis (15) of the preform blank (7).

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