GB2205972A - Filled optical fibre cable manufacture - Google Patents

Filled optical fibre cable manufacture Download PDF

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Publication number
GB2205972A
GB2205972A GB08814400A GB8814400A GB2205972A GB 2205972 A GB2205972 A GB 2205972A GB 08814400 A GB08814400 A GB 08814400A GB 8814400 A GB8814400 A GB 8814400A GB 2205972 A GB2205972 A GB 2205972A
Authority
GB
United Kingdom
Prior art keywords
advancing
undulating
water
die
tape
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08814400A
Other versions
GB8814400D0 (en
GB2205972B (en
Inventor
Stephen Thomas Spedding
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Balfour Beatty PLC
Original Assignee
BICC PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BICC PLC filed Critical BICC PLC
Publication of GB8814400D0 publication Critical patent/GB8814400D0/en
Publication of GB2205972A publication Critical patent/GB2205972A/en
Application granted granted Critical
Publication of GB2205972B publication Critical patent/GB2205972B/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
    • G02B6/4479—Manufacturing methods of optical cables
    • G02B6/4483—Injection or filling devices
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
    • G02B6/4401—Optical cables
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
    • G02B6/4401—Optical cables
    • G02B6/4402—Optical cables with one single optical waveguide
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
    • G02B6/4479—Manufacturing methods of optical cables
    • G02B6/4484—Manufacturing methods of optical cables with desired surplus length between fibres and protection features

Abstract

In a sheathed optical cable having a bore 3 filled with a greasy water-impermeable medium 8 in which a resiliently set undulating optical fibre ribbon 1 is completely embedded, the optical fibre ribbon is caused to travel through an elongate die in which the amplitude of the undulations of the ribbon is reduced and the medium 8 is continuously fed around it. An advancing, optionally laminated, tape 4 is transversely folded around the advancing extrudate to form a closed tube 2 is filled throughout its length with the medium 8 in which the ribbon 1 is embedded, and a plastics sheath 7 is extruded around the tape-covered extrudate. Preferably, the medium 8 is introduced into the elongate die through an inlet port intermediate of the ends of the die and opening into a helical groove in the wall bounding the bore of the die. <IMAGE>

Description

OPTICAL CABLE MANUFACTURE This invention relates to plastics sheathed optical cables of the kind comprising an elongate body having a bore of substantially circular cross-section in which is housed at least one optical fibre element which has a transverse cross-sectional shape of elongate form and which follows a path of smoothly curved undulations whose axes of curvature lie substantially parallel to one another and to the major transverse axes of the element and substantially normal to the longitudinal axis of the element. An optical cable of this kind will hereinafter, for convenience, be referred to as "of the kind described".
The invention is especially, but not exclusively, concerned with a plastics sheathed optical cable of the kind described which is described and claimed in the specification of our U.K. Patent No: 2141558B and which comprises an elongate body having a bore of substantially circular cross-section in which is loosely housed at least one optical fibre element consisting of an optical fibre ribbon structure comprising a plurality of optical fibres and at least one flexible elongate reinforcing element of substantially resilient material arranged side by side and embedded in an elongate body of plastics material, the or each resilient reinforcing element being resiliently set in such a form that the ribbon structure follows a path of smoothly curved undulations whose axes of curvature lie substantially parallel to one another and to the major transverse axes of the ribbon structure and substantially normal to its longitudinal axis. The arrangement is such that, when the resiliently set undulating ribbon structure is subjected to a longitudinally applied tensile force, the ribbon structure will straighten in a lengthwise direction against the action of its resilient set thereby to reduce the tensile force applied to the or each optical fibre and, when the tensile force is removed, the ribbon structure will return under the action of its resilient set towards its original form.
In plastics sheathed optical cables comprising an elongate body of tubular form having a bore in which at least one optical fibre or optical fibre element is loosely housed, it is common practice to fill those parts of the bore not occupied by the optical fibre or fibres or optical fibre element or elements with a water-impermeable filling medium of a grease-like or semi-liquid nature which will permit relative movement between the or each optical fibre or optical fibre element and the elongate body and, where there is more than one optical fibre or optical fibre element present, between the optical fibres and/or optical fibre elements. Many methods of introducing such water-impermeable filling medium into the bore of an optical cable have been proposed and used.
We have found that in the case of a plastics sheathed optical cable of the kind described - in which the bore of circular cross-section will normally have a diameter lying in the range 8 to 20mm - it is difficult to extrude the overall sheath of plastics material and ensure those parts of the bore not occupied by the undulating optical fibre element or elements throughout the length of the cable are substantially filled with water-impermeable medium of a grease-like or semi-liquid nature without damaging an optical fibre of an optical fibre element, or distorting or reducing the undulations of or otherwise effecting damage to an optical fibre element, to an undesirable extent.
It is an object of the present invention to provide an improved method of manufacturing a plastics sheathed optical cable of the kind described in which those parts of the bore not occupied by the undulating optical fibre element or elements are substantially filled with water-impermeable medium in a grease-like or semi-liquid state.
According to the invention, the improved method comprises causing at least one optical fibre element, which has a transverse cross-sectional shape of elongate form and which is so resiliently set that the element follows a path of smoothly curved undulations whose axes of curvature lie substantially parallel to one another and to the major transverse axes of the element and substantially normal to its longitudinal axis, to travel in the direction of its length through an elongate die in which the amplitude of the undulations of the advancing resiliently set undulating element is reduced;; so continuously feeding wAter-impermeable medium in a grease-like or semi-liquid state into the die and around the reduced resiliently set undulating element that the undulating element is completely embedded in an extrudate of approximately circular cross-section of water-impermeable medium in a grease-like or semi-liquid state; causing at least one tape, e.g. of metal or metal alloy, to travel in the direction of its length and so transversely folding the advancing tape around the advancing extrudate of water-impermeable medium with the resiliently set undulating element embedded therein that the neighbouring longitudinal edges of the tape overlap or abut to form a closed tube substantially filled throughout its length with water-impermeable medium in a grease-like or semi-liquid state in which at least one resiliently set undulating element is completely embedded; and extruding an overall sheath of plastics material around the advancing tape-covered extrudate of water-impermeable medium with the resiliently set undulating element completely embedded therein.
By virtue of the fact that the amplitude of the undulations of the resiliently set undulating element is so reduced that the element is completely embedded in the extrudate of water-impermeable medium, there is negligible risk that damage to an optical fibre of the element, or to the element itself, will occur when the extruded plastics sheath cools and shrinks around the tape-covered extrudate of water-impermeable medium.
Preferably, water-impermeable medium in a grease-like or semi-liquid state is introduced into the elongate die through at least one inlet port downstream of the position at which the amplitude of the undulations of the advancing resiliently set undulating element is reduced, which inlet port opens into a helically extending groove in the surface of the wall bounding the bore of the die so that water-impermeable medium in a grease-like or semi-liquid state flows helically around the advancing element and transversely into the spaces between the smoothly curved undulations of the resiliently set element as the element travels through the die.
Preferably the tape transversely folded around the advancing extrudate is of laminated form and comprises a metal tape to the outer surface of which is bonded a coating of plastics material.
A plurality of bunches of flexible elongate reinforcing elements, e.g. compacted yarns of glass fibre, may be fed into the extrusion machine by which the overall sheath is formed so that these bunches are embedded in the overall sheath at uniformly circumferentially spaced positions.
Upstream of the extrusion machine by which the sheath of plastics material is extruded around the advancing tape-covered water-impermeable medium with the undulating element embedded therein, the overlapping or abutting longitudinal edges of the advancing transversely folded tape may be heated or otherwise treated to effect a longitudinally continuous seal.
Where two or more resiliently set undulating optical fibre elements are advancing in the direction of their lengths, preferably each of the elements travels alongside at least one other element with its undulations nesting in those of the or each adjacent element. Where n undulating optical fibre elements are advancing in the directions of their lengths and n is an even number greater than three, two stacks of undulating elements, each comprising n2 elements nested together, may be arranged to travel side by side.
The water-impermeable filling medium. may be any suitable filling medium of a grease-like or semi-liquid nature used or proposed for use in optical cables and capable of extrusion in the form of a substantially solid extrudate. One suitable filling medium is described and claimed in our co-pending U.K. Patent Application No: 8529090.
The invention further includes an optical cable manufactured by the improved method as hereinbefore described.
In this optical cable, the or each optical fibre element may take any known form. Three forms of optical fibre element that are preferred are illustrated in Figure 1 of the drawings of our British Patent No: 2141558B and in Figures 2 and 3 of the drawings of our British Patent No: 2156094B.
The improved method of the present invention has the important advantage that all operating steps of the method are of linear form, i.e. involve no stranding or reverse-lay stranding operations, thereby making the method efficient in labour, time and space, and offering scope for tandemisation.
The invention is further illustrated by a description, by way of example, of a preferred optical cable of the kind described and of the preferred method of manufacturing the preferred optical cable with reference to the accompanying drawing, in which: Figure 1 is a sectional side view of the preferred optical cable, and Figure 2 is a diagrammatic plan view of the apparatus employed in the preferred method of manufacture of the preferred optical cable.
Referring to Figure 1, the preferred optical cable comprises an elongate body 2 of composite form having a bore 3 of circular cross-section in which is housed an optical fibre ribbon 1 as claimed in our British Patent No: 2141558B. The optical fibre ribbon 1 is so resiliently set that the ribbon follows a path of smoothly curved undulations whose axes of curvature lie substantially parallel to one another and to the major transverse axes of the ribbon and normal to the longitudinal axis of the ribbon. The composite elongate body 2 comprises a longitudinally extending transversly folded laminated tape 4 consisting of an inner metal tape 5 to the outwardly facing surface of which is bonded a coating 6 of plastics material. An extruded sheath 7 of plastics material surrounds and is bonded to the plastics coating 6 of the transversely folded laminated tape 4.Throughout its length, those parts of the bore 3 of the composite elongate body 2 not occupied by the undulating optical fibre ribbon 1 are filled with a water-impermeable medium 8 of a grease- like nature which will permit relative movement between the optical fibre ribbon and the composite elongate body when the optical cable is flexed or stretched.
When the optical fibre ribbon 1 is subjected to a longitudinally applied tensile force, the ribbon will tend to straighten in a lengthwise direction against the action of its resilient set, relative to the composite elongate body 2 thereby to reduce the tensile force applied to each optical fibre of the ribbon and, when the tensile force is removed, the ribbon will return under the action of its resilient set towards its original form.
As will be seen on referring to Figure 2, the preferred optical cable shown in Figure 1 is manufactured by causing the resiliently set optical fibre ribbon 1 to travel in the direction of its length with the major transverse axes of its smoothly curved undulations lying horizontal into.an elongate die 10 through a sizing tube 12 at the upstream end of the die.
The sizing tube 12 is of such a transverse cross-sectional shape and size that, as the resiliently set optical fibre ribbon 1 advances through the tube, the amplitude of the undulations of the advancing element is reduced. Water-impermeable medium 8 in a grease-like or semi-liquid state is introduced into the elongate die 10 through an inlet port 11 downstream of the sizing tube 12. The inlet port 11 opens into a helically extending groove in the surface of the wall bounding the bore of the die 10 so that water-impermeable medium 8 in a grease-like or semi-liquid state flows helically around the advancing element and transversely into the spaces between the smoothly curved undulations of reduced amplitude so that the ribbon is completely embedded in water-impermeable medium 8.An extrudate 8 of approximately circular cross-section of water-impermeable medium in a grease-like or semi-liquid state in which the resiliently set optical fibre ribbon 1 is completely embedded emerges from the elongate die 10 and passes into a forming die 15 at which the composite tape 4 travelling in the direction of its length immediately under the advancing extrudate 8 with the major surfaces of the composite tape horizontal and with the metal tape 5 uppermost, is folded around the extrudate so that the neighbouring longitudinal edges of the tape overlap to form a closed tube filled throughout its length with water-impermeable medium 8 in a grease-like or semi-liquid state in which the resiliently set optical fibre ribbon 1 is completely embedded. Downstream of the outlet 16 of the forming die 15, the overlapping longitudinal edges of the transversely folded laminated tape 4 are heated at station 17 to effect a longitudinally continuous seal. After sealing the longitudinal edges of the transversely folded laminated tape 4, the tape-covered extrudate 8 passes into an extrusion machine 18 at which a sheath 7 of plastics material is extruded around, and bonds to the plastics coating 6 of, the transversely folded laminated tape 4.

Claims (10)

CLAIMS:
1. A method of manufacturing a plastics sheathed optical cable of the kind described in which those parts of the bore not occupied by the undulating optical fibre element or elements are substantially filled with water-impermeable medium in a grease-like or semi-liquid state, which method comprises causing at least one optical fibre element, which has a transverse cross-sectional shape of elongate form and which is so resiliently set that the element follows a path of smoothly curved undulations whose axes of curvature lie substantially parallel to one another and to the major transverse axes of the element and substantially normal to its longitudinal axis, to travel in the direction of its length through an elongate die in which the amplitude of the undulations of the advancing resiliently set undulating element is reduced; so continuously feeding water-impermeable medium in a grease-like or semi-liquid state into the die and around the reduced resiliently set undulating element that the undulating element is completely embedded in an extrudate of approximately circular cross-section of water-impermeable medium in a grease-like or semi-liquid state; causing at least one tape to travel in the direction of its length and so transversely folding the advancing tape around the advancing extrudate of water-impermeable medium with the resiliently set undulating element embedded therein that the neighbouring longitudinal edges of the tape overlap or abut to form a closed tube substantially filled throughout its length with water-impermeable medium in a grease-like or semi-liquid state in which at least one resiliently set undulating element is completely embedded; and extruding an overall sheath of plastics material around the advancing tape-covered extrudate of water-impermeable medium with the resiliently set undulating element completely embedded therein.
2. A method as claimed in Claim 1, wherein water-impermeable medium in a grease-like or semi-liquid state is introduced into the elongate die through at least one inlet port downstream of the position at which the amplitude of the undulations of the advancing resiliently set undulating element is reduced, which inlet port opens into a helically extending groove in the surface of the wall bounding the bore of the die so that water-impermeable medium in a grease-like or semiliquid state flows helically around the advancing element and transversely into the spaces between the smoothly curved undulations of the resiliently set element as the element travels through the die.
3. A method as claimed in Claim 1 or 2, wherein a sizing tube at the upstream end of the elongate die is of such a transverse cross-sectional shape and size that the amplitude of the undulations of the resiliently set undulating element is reduced as the element advances through said tube into the die.
4. A method as claimed in any one of the preceding Claims, wherein the tape is of laminated form and comprises a metal tape to the outer surface of which is bonded a coating of plastics material.
5. A method as claimed in Claim 4, wherein upstream of the extrusion machine by which the sheath of plastics material is extruded around the extrudate, the overlapping or abutting longitudinal edges of the advancing transversely folded tape are heated or otherwise treated to effect a longitudinally continuous seal.
6. A method as claimed in any one of the preceding Claims in which two or more undulating resiliently set optical fibre elements are advancing in the directions of their lengths, wherein each of the elements except one of the elements travels above and rests in the adjacent underlying element.
7. A method as claimed in any one of Claims 1 to 5 in which n resiliently set optical fibre elements are advancing in the directions of their lengths and n is an even number greater than 3, wherein two stacks of undulating elements, each comprising n2 elements nested together, are arranged to travel side by side.
8. A method as claimed in any one of the preceding Claims, wherein the water-impermeable filling medium is the medium described and claimed in our co-pending U.K.
Patent Application No: 8529090.
9. A method of introducing manufacturing a plastics sheathed optical cable of the kind described substantially as hereinbefore described with reference to the accompanying drawing.
10. An optical cable manufactured by the method as claimed in any one of the preceding Claims.
GB8814400A 1987-06-17 1988-06-17 Filled optical fibre cable manufacture Expired - Lifetime GB2205972B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB878714162A GB8714162D0 (en) 1987-06-17 1987-06-17 Optical cable manufacture

Publications (3)

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GB8814400D0 GB8814400D0 (en) 1988-07-20
GB2205972A true GB2205972A (en) 1988-12-21
GB2205972B GB2205972B (en) 1991-04-03

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GB878714162A Pending GB8714162D0 (en) 1987-06-17 1987-06-17 Optical cable manufacture
GB8814400A Expired - Lifetime GB2205972B (en) 1987-06-17 1988-06-17 Filled optical fibre cable manufacture

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GB878714162A Pending GB8714162D0 (en) 1987-06-17 1987-06-17 Optical cable manufacture

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2232501A (en) * 1989-02-06 1990-12-12 Telephone Cables Ltd Optical fibre cable core for submarine use
FR2655740A1 (en) * 1989-12-12 1991-06-14 Alcatel Nv PILOT LINE RESISTANT TO TRACTION FOR REMOTE CONTROL DEVICES.
EP0591867A1 (en) * 1992-10-07 1994-04-13 Siemens Aktiengesellschaft Method for tubing lightwaveguides and apparatus for performing this method
WO1997022028A1 (en) * 1995-12-11 1997-06-19 Siemens Aktiengesellschaft Filler compound for an optical transmission component and process for its production

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8709076D0 (en) * 1987-04-15 1987-05-20 Bicc Plc Optical cable manufacture

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2232501A (en) * 1989-02-06 1990-12-12 Telephone Cables Ltd Optical fibre cable core for submarine use
GB2232501B (en) * 1989-02-06 1993-09-29 Telephone Cables Ltd Optical fibre cable core for submarine use
FR2655740A1 (en) * 1989-12-12 1991-06-14 Alcatel Nv PILOT LINE RESISTANT TO TRACTION FOR REMOTE CONTROL DEVICES.
EP0591867A1 (en) * 1992-10-07 1994-04-13 Siemens Aktiengesellschaft Method for tubing lightwaveguides and apparatus for performing this method
WO1997022028A1 (en) * 1995-12-11 1997-06-19 Siemens Aktiengesellschaft Filler compound for an optical transmission component and process for its production

Also Published As

Publication number Publication date
GB8814400D0 (en) 1988-07-20
GB8714162D0 (en) 1987-07-22
GB2205972B (en) 1991-04-03

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19930617