Producing optical fibre

Abstract: A take up apparatus 10 for drawn optical fibre comprises: a take-up stand 22 supporting a first, storage bobbin 12 about a first axis 20; a motor 32 for rotating this first bobbin about that axis; a supporting means 36 supporting a second, sampler bobbin 14 about a second, different axis 34; a second motor 38 for rotating this second bobbin about the second axis; and means for controlling the relative rates of rotation provided by the motors. In use drawn fibre is guided about the first bobbin to the second bobbin and the bobbins are rotated to wind the fibre about the first bobbin and onto the second bobbin during initial drawing of the fibre. Subsequently the fibre between the bobbins is cut and the drawn fibre is wound onto the first bobbin.

Description: This invention relates generally to producing optical fibre. A conventional method of producing optical fibre comprises the following steps: drawing the fibre from a heated end of a preform, cooling the fibre, applying one or more polymeric coatings to the fibre and winding the coated fibre onto a storage bobbin. Fibre and coating diameters and drawing tensions are controlled during such a method. During the start of the process contaminants may enter the coating system and this may not be detected until after the bobbin has been filled, leading to considerable waste. In order to avoid this problem in the present invention rather than wind the fibre directly onto the storage bobbin it is initially wound about the storage bobbin and onto another bobbin. When desired drawing conditions are reached, the fibre is cut between the bobbins and the drawn fibre is wound onto the storage bobbin. The fibre wound onto the other bobbin may then be tested whilst drawing continues. If the test results are unsatisfactory appropriate remedial action may be taken. In JP-A-01069537 in a method of drawing an optical fibre the fibre is initially wound about a storage bobbin and guided downstream of the storage bobbin where the optical fibre can be cut into samples. When the samples are of the desired quality, the leading end portion of the optical fibre is attached to the bobbin so that the optical fibre is wound onto the storage bobbin. The invention provides a method of drawing optical fibre including guiding the drawn fibre about a first bobbin to a second bobbin, rotating said bobbins to wind the fibre about the first bobbin and onto the second bobbin during initial drawing of the fibre, and when desired drawing conditions are reached subsequently cutting the fibre between the bobbins and winding the drawn fibre onto the first bobbin. The method may include testing fibre wound onto the second bobbin whilst winding fibre onto the first bobbin. The method may include controlling the tension of the fibre between the first and second bobbins during the step of winding the fibre about the first bobbin and onto the second bobbin by controlling the relative rates of rotation of said bobbins. The method preferably includes after the cutting step, adhering the upstream cut end of fibre to the surface of a hub of the first bobbin. In this regard the method may include providing a double-sided adhesive tape about the hub of the first bobbin and adhering the upstream cut end of the fibre to the tape. Alternatively, the method may include providing a tape which is adhesive on one side only, adhesive side out about the hub of the first bobbin and adhered to itself, and adhering the upstream cut end of the fibre to the tape. The invention also includes take-up apparatus for drawn optical fibre comprising: first supporting means for supporting a first bobbin about a first axis; first rotating means for rotating such a first bobbin, when supported by said first supporting means, about said first axis; second supporting means for supporting a second bobbin about a second, different axis; second rotating means for rotating such a second bobbin, when supported by said second supporting means, about said second axis; guide means for guiding a drawn optical fibre about a first bobbin when supported by said first supporting means and to a second bobbin when supported by said second supporting means; means for controlling the relative rates of rotation provided by the first and second rotating means; and means for causing drawn fibre attached, after cutting between said bobbins, at a leading end thereof to a first bobbin when supported by said first supporting means and rotated by said first rotating means to be wound onto such a bobbin in a plurality of layers. The invention also includes an optical fibre production line having apparatus as defined in the last preceding paragraph. The invention also includes apparatus as defined in the last but one preceding paragraph having a said first bobbin supported by said first supporting means and a said second bobbin supported by said second supporting means. Advantageously, the first bobbin is of greater capacity than said second bobbin. Preferably the first and second axes are substantially parallel. The first supporting means may be adapted to reciprocate a first bobbin, when supported thereby, along said first axis. In this case, typically the supporting means comprises a member slidably mounted for reciprocating movement along said first axis. The second supporting means may be adapted to reciprocate a second bobbin, when supported thereby, along said second axis. In this case preferably the second support means comprises a support fixedly mounted to said member for reciprocating movement therewith. Advantageously the support is located above said first supporting means. The invention also comprises an optical fibre production line having apparatus as specified above. In order that the invention may be well understood, an embodiment thereof which is given by way of example only, will now be described with reference to the accompanying drawings, in which: Figure 1 is a front elevation of a take-up apparatus for drawn optical fibre in use during a start-up procedure of the drawing process; and Figure 2 is a side elevation of the same apparatus. In the Figures, a take-up apparatus 10 for drawn optical fibre is shown with a first, or storage, bobbin, or spool, 12 and a second, or sampler, bobbin, or spool, 14 fitted thereto and an optical fibre 16 which has been provided with at least one polymeric coating upstream of the apparatus 10 guided over a roller 18, about bobbin 12 to bobbin 14. The storage bobbin 12 is supported for rotation about an axis 20 by a support means 22 which comprises a conventional take-up stand. The take-up stand includes side members 24 mounted for reciprocating moving along the axis 20 on a track 26. Spindles 28 and 30 extending towards each other from the side members 24 support the bobbin 12 for rotation about axis 20. A motor at location 32 rotates spindle 30 to cause the bobbin 12 to rotate. The sampler bobbin 14 is supported within a guard 33 for rotation about an axis 34, which is parallel to axis 20, on a spindle 35 by a supporting means. This supporting means includes a support 36 fixedly mounted by an upright 37 to the side member 24 from which the spindle 28 extends. A motor 38 mounted on support 36 is provided for rotating the spindle 35 and thus the bobbin 14. The relative rotation of the spindles 30 and 35 and thus the bobbins 12 and 14 is controlled by an electronic control circuit (not shown) so that the tension of the fibre between the bobbins 12 and 14 is maintained between predetermined limits. In this connection it has been established that if the fibre tension at this location is too low, problems may occur in the control of the draw rate of the fibre and if the fibre tension is too high, fibre breakage may occur. As illustrated the bobbin 14 is supported directly above the bobbin 12 thereby leading to no increase in the length or width of the optical fibre production line at the location of the take-up stand. In use, at start-up of a fibre drawing process, drawn fibre provided with a polymeric coating is thread over roller 18 between a pair of roller guides 40 and then about bobbin 12 for less than one complete turn and through a pair of roller guides 42 to bobbin 14 to which the end of the drawn fibre is secured. The bobbins are rotated to wind the drawn fibre onto bobbin 14. During this winding operation the side members 24 of the take-up stand are reciprocated together on track 26 over an axial distance substantially corresponding to the axial length of the belly, or hub, of the bobbin 14 which is simultaneously reciprocated over the same distance in view of the mounting of the support 36 to the side member 24. In this way fibre is wound onto the bobbin 14 in layers, whilst the path of the optical fibre is substantially maintained. The capacity of the sampler bobbin 14 is considerably less than the capacity of the storage bobbin 12 since it only needs to accommodate fibre drawn during the initial start-up procedure in a fibre drawing process. When the required drawing conditions are reached (typically after about 8km of fibre has been drawn) the fibre is cut between the bobbins 12 and 14 and the subsequently drawn fibre is wound onto the storage bobbin 12. In order to cause the fibre to wind onto the rotating storage bobbin 12, the upstream cut end, ie the leading end, of the fibre is fixed to the surface of a hub 44 of the bobbin 12. This is advantageously achieved by adhering this cut end to the surface of the hub. Specifically in the embodiment a length of double-sided adhesive tape 46 is provided about the hub 44. One side of the tape adheres the tape to the hub and the fibre cut end is adhered to the other, radially outwardly facing side. In the embodiment, the tape extends 360° about the hub and is about 2 inches (50.8 mm) wide. Just before the fibre is cut between the bobbins the positions of the same are such that the fibre may be cut over the tape so that the fibre wraps around the storage bobbin hub 44 and the cut end is not free to flail and damage the subsequent windings on the hub 44. Alternatively a tape with adhesive on one side only may be used adhesive side out and adhered to itself. In either case the fibre may be wound onto the bobbin over an axial extent of the hub which excludes the tape so that the cut end will not damage the fibre being wound onto the storage bobbin if it separates from the adhesive tape. During the winding of the fibre onto the storage bobbin, the side members 24 of the take-up stand are reciprocated on track 26 over an axial distance substantially corresponding to the axial length of the hub 44 of the storage bobbin 12 until a predetermined amount of fibre is wound onto the hub, as indicated by chain-dotted line 48 or until the drawing of fibre from the preform is complete. As will be understood, reciprocation of the take-up stand as described above causes the drawn fibre attached at a leading end thereof to the storage bobbin 12 supported by the take-up stand and rotated by the motor at location 32 to be wound onto the bobbin 12 in a plurality of layers. Whilst the fibre is being wound onto the storage bobbin 12 the fibre wound onto the sampler bobbin is tested. If the test results are unsatisfactory, appropriate remedial action may be taken. In particular, if an uncorrectable defect is detected the fibre drawing process can be halted. As will be readily understood, this is preferable to carrying out tests after winding onto the storage bobbin has been completed.

Claims: A method of drawing optical fibre (16) including guiding the drawn fibre about a first bobbin (12) to a second bobbin (14), rotating said bobbins to wind the fibre about the first bobbin and onto the second bobbin during initial drawing of the fibre, and when desired drawing conditions are reacted subsequently cutting the fibre between the bobbins and winding the drawn fibre onto the first bobbin. A method as claimed in claim 1 including testing fibre (16) wound onto the second bobbin (14) whilst winding fibre onto the first bobbin (12). A method as claimed in claim 1 or 2 including controlling the tension of the fibre (16) between the first (12) and second (14) bobbins during the step of winding the fibre about the first bobbin and onto the second body by controlling the relative rates of rotation of said bobbins. A method as claimed in claim 1, 2 or 3 including after the cutting step, adhering the upstream cut end of fibre (16) to the surface of a hub (44) of the first bobbin (12). A method as claimed in claim 4 including providing a double-sided adhesive tape (46) about the hub (44) of the first bobbin (12) and adhering the upstream cut end of the fibre (16) to the tape. A method as claimed in claim 4 including providing a tape which is adhesive on one side only, adhesive side out about the hub (44) of the first bobbin (12) and adhered to itself, and adhering the upstream cut end of the fibre (16) to the tape. Take up apparatus (10) for drawn optical fibre (16) comprising: first supporting means (22) for supporting a first bobbin (12) about a first axis (20); first rotating means (32) for rotating such a first bobbin, when supported by said first supporting means, about said first axis; second supporting means (36) for supporting a second bobbin (14) about a second, different axis (34); second rotating means (38) for rotating such a second bobbin, when supported by said second supporting means, about said second axis; guide means (18, 40, 42) for guiding a drawn optical fibre (16) about a first bobbin when supported by said first supporting means and to a second bobbin when supported by said second supporting means; means for controlling the relative rates of rotation provided by the first and second rotating means; and means for causing drawn fibre attached, after cutting between said bobbins, at a . leading end thereof to a first bobbin when supported by said first supporting means and rotated by said first rotating means to be wound onto such a first bobbin in a plurality of layers. Apparatus as claimed in claim 7, wherein said first (20) and second (34) axes are substantially parallel. Apparatus as claimed in claim 7 or 8, wherein said first supporting means (22) is adapted to reciprocate a first bobbin (12), when supported thereby, along said first axis (20). Apparatus as claimed in claim 9, where said first supporting means (22) comprises a member (24) slidably mounted for reciprocating movement along said first axis (20). Apparatus as claimed in claim 10, wherein said second supporting means (36) is adapted to reciprocate a second bobbin (14), when supported thereby, along said second axis (34). Apparatus as claimed in claim 11, wherein said second supporting means comprises a support (36) fixedly mounted to said member (24) for reciprocating movement therewith. Apparatus as claimed in any one of claims 7 to 12, wherein said second supporting means (36) is located above said first supporting means (22). Apparatus as claimed in any one of claims 7 to 13 having a said first bobbin (12) supported by said first supporting means (22) and a said second bobbin (14) supported by said second supporting means (36). Apparatus as claimed in claim 14, wherein said first bobbin (12) is of greater capacity than said second bobbin (14). An optical fibre production line having apparatus as claimed in any one of claims 7 to 15. An optical fibre production line as claimed in claim 16, having a first bobbin (12) supported by said first supporting means (22), said first bobbin being provided with an adhesive tape (46) for fixing a leading end of a drawn optical fibre to said first bobbin.

Inventors: DAVIES PAUL ALEXANDER, HADLEY JOHN ALFRED, ROGERSON JOHN WILLIAM, DAVIES, PAUL ALEXANDER, HADLEY, JOHN ALFRED, ROGERSON, JOHN WILLIAM
Applicants: PIRELLI GENERAL PLC
Application year: 1999
Main classification: C03B37
IPC codes: D01D5, C03B37, B65H54, G02B6, B65H65