GB1582851A - Optical cables - Google Patents

Optical cables Download PDF

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Publication number
GB1582851A
GB1582851A GB314577A GB314577A GB1582851A GB 1582851 A GB1582851 A GB 1582851A GB 314577 A GB314577 A GB 314577A GB 314577 A GB314577 A GB 314577A GB 1582851 A GB1582851 A GB 1582851A
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GB
United Kingdom
Prior art keywords
cable
optical
optical cable
reinforcing members
tubes
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.)
Expired
Application number
GB314577A
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
Priority to GB314577A priority Critical patent/GB1582851A/en
Priority to AU32727/78A priority patent/AU508215B2/en
Publication of GB1582851A publication Critical patent/GB1582851A/en
Expired 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
    • G02B6/4401—Optical cables
    • G02B6/441—Optical cables built up from sub-bundles
    • G02B6/4414—Optical cables built up from sub-bundles with internal serpentine waveguides
    • 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
    • G02B6/4429—Means specially adapted for strengthening or protecting the cables
    • G02B6/443—Protective covering
    • G02B6/4432—Protective covering with fibre reinforcements

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Communication Cables (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO OPTICAL CABLES (71) We, BICC LIMITED, a British Company of 21 Bloomsbury Street, London, WC1B 3QN, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to optical cables for the transmission of the ultraviolet, visible and infra-red regions of the electromagnetic spectrum, which regions, for convenience, will hereinafter all be included in the generic term "light", and especially, but not exelusively, to optical cables for use in the communication field adapted for transmission of light having a wavelength within the range 0.8 to 1.3 micrometres.
For the purpose of transmitting light in an optical transmission system it has been proposed to employ optical guides in the form of cables including one or more than one optical fibre. Each optical fibre is usually of substantially circular cross-section but, in some circumstances, it may be of noncircular cross-section.
Optical cables with which the invention is concerned include cables comprising one or more than one optical fibre of glass or other transparent material whose refractive index is arranged to decrease over at least a part of the radius of the fibre in a direction towards the outer surface of the fibre and cables including ont or more than one optical fibre of composite form comprising a core of transparent material clad throughout its length with another transparent material of lower refractive index which, by total internal refraction of light being transmitted along the fibre, confines at least a major propor tion of the light within the core. A composite optical fibre is generally, but not necessarily, made up of two glasses of different refractive indices, the glass forming the core having a higher refractive index then the glass forming the cladding; the refractive index of the glass of the core may gradually decrease in a direction towards the outer surface of the core over at least a part of the distance between the central axis of the core and its outer surface. In an alternative form of composite fibre the core may be made of a transparent liquid having a higher refractive index than that of the cladding.
In the Complete Specification of our Patent No. B1,479,427 one of several forms of optical cable that are described and claimed comprises a plurality of separately formed tubes of rubber -or plastics material in each of some or all of which is or are loosely housed at least one optical bundle and/or at least one separate optical fibre and, surrounding the plurality of tubes, an outer protective sheath in which elongate reinforcing members are embedded at spaced positions around the sheath, each elongate reinforcing member being of such a material and of such a cross-sectional area having regard to the material or materials and cross-sectional area of the bundle or bundles and/or of the separate optical fibre or fibres that the strain otherwise imparted to the or each optical fibre when the cable is stressed in such a way as to tend to subject the or any optical fibre to a tensile force is eliminated or reduced at least to a substantial extent by the reinforcing members.
By the expression "optical bundle" as used in the specification and claims of the aforesaid patent, and as used herein, is meant a group of optical fibres or a group of fibres including at least one optical fibre and at least one non-optical reinforcing fibre or other reinforcing elongate member.
Each optical fibre of the optical bundle may be used independently as a separate light guide, each with its own modulated light source and detector, or a plurality of optical fibres of a bundle may be used together as a single light guide, with a single light source.
By virtue of being housed loosely in a tube, limited relative movement between the or each optical bundle and/or between the or each separate optical fibre and the tube in which it is loosely housed can take place when the cable is flexed. The tubes themselves may be loosely housed in the sheath thereby permitting limited relative move ment between the tubes when the optical cable is flexed.
The present invention is an improvement in or modification of the invention forming the subject of the aforesaid patent, hereinafter referred to as the main patent, and provides an optical cable of such a form that it is especially, but not exclusively, suitable for use as a self-supporting aerial cable.
According to the present invention a plurality of elongate reinforcing members are embedded in and at spaced - positions around the sheath, which reinforcing members extend substantially lengthwise of the cable and each of some or all of which reinforcing members having, in the member, undulations, preferably radially extending undulations, that serve to improve the mechanical bonding of the member within the sheath and the flexibility of the cable.
The elongate reinforcing members having undulations therein may each comprise a single wire or a plurality of wires stranded together; the wire or group of stranded wires being crimped at spaced positions along its length to form undulations but, with a view to maintaining the weight of the cable as low as possible, preferably each of these elongate reinforcing members comprises a bunch of compacted yarns of glass fibre or other inorganic reinforcing material.
Preferably each undulating elongate reinforcing member extends substantially parallel to the axis of the cable but, in some instances, each member may extend helically around the axis of the cable, if desired the- direction of lay of the helically extending undulating reinforcing member being reverts sed at spaced positions along the length of the cable.
The elongate reinforcing members having undulations therein provide means for takingup the tensile load when. the cable is suspended. Moreover, since limited relative move ment between the or each optical bundles and/or between the or each separate optical. fibre and- the tube in which it is loosely housed can take place when the cable is flexed, the optical cable of- the present invention can be suspended with - negligible risk that fracture of optical fibres will occur when the cable is installed or whilst it is in services The. outer protective sheath. of the optical cable. is preferably an extruded tube of rubber or plastics material- and the undulating elongate reinforcing members embedded therein are preferably at uniformly spaced positions around the sheath.
Where the undulating elongate reinforcing members are bunches of compacted yarns ofglass fibre. or of other inorganic reinforcing. material, preferably these yarns are not pre-impregnated with an agent for binding to the material of the sheath and preferably, also, there is substantially no air in the interstices between the elementary fiaments of each bunch. Each bunch may consist of elements of glass fibre or of other inorganic material of the same kind and/or thickness or it may consist of a combination of elements of different kinds from one another, for example single or doubled yarns, and/or of different thicknesses from one another.
The mutual spacing between adjacent elongate reinforcing members with undulations therein is preferably at leas't twice the diameter of a reinforcing member and the radial distance of each member from the radially inner surface of the sheath is preferably, also, at least twice the diameter of a reinforcing member.
Where the elongate reinforcing members. with undulations therein are bunches of compacted yarns of glass fibre or of other inorganic reinforcing material, it is preferred to manufacture the outer protective sheath of the optical cable by the method described and claimed in U.K. Patent No. 1,413,674.
In this method, the amplitude of the undulation determines the maximum permissible diameter of the bunches in the cable for optimum results. The diameter of the bunches. may be greater,. the greater the amplitude of the undulations.
Suitable materials of which the outer protective sheath may be made include polyethylene, for example high densitypolyethylene, a modified polyethylène such as ethylene vinyl acetate, or hard polyolefin such as polypropylene or a modified polypropylene, for example propylene ethylene copolymer. The outer protective sheath may have an oversheath, for example a.n oversheath of a material having a low friction coefficient, such as nylon, and/or an undersheath may be provided around the. plurality of tubes and- under the outer protective. sheath. Where, an oversheath and/or undersheath is provided, the outer protective sheath and the oversheath and'/ our the outer protective sheath and. the undersheath may be- separated' by an armouring layer or by a. layer of metallic tape having on its- major surfaces coatings of plastics material that may be bonded to the materials of the outer protective sheath and of the oversheath or undersheath, as the case may be.
The plurality of separately formed; tubes of the optical- cable may have at least one tape of insulating materials helically or longitudinally applied; around the assembly of tubes before the outer protective sheath, or undersheath when to be provided, is applied The tape or tapes may be so - applied. that limited relative movement between the tubes and the surrounding tape or tapes can. take nlace when the cable is flexed: Where. the- plurality of- tubes do not have a tape or tapesapplied therearound, the outer 7 protective sheath, or when present the undersheath, is preferably so applied to the assembly of tubes that limited relative movement between the tubes and the outer protective sheath or undersheath can take place when the cable is flexed.
As described in the Complete Specification of the main patent, one or more than one of the tubes may have loosely housed in the tube at least one elongate electric conductor.
Alternatively or additionally at least one elongate bare or insulated electric conductor may be assembled with the plurality of tubes and, for example, may constitute an elongate central core around which the tubes are arranged.
The or each optical bundle and/or separ- ate optical fibre may be of a length substan- tially greater than that of the tube in which it is loosely housed but preferably the or each bundle and/or separate optical fibre and the tube are of equal or approximately equal lengths.
The optical cable of the present inventiOn may also include any one or more than one of the optional features of the Optical cable described and claimed in the Complete: Specification of the main patent.
The invention is further illustrated by a description, by way of example, of a preferred- optical cable with reference to the accompanying diagrammatic: drawing in which: - Figure 1 is a transverse cross-sectional view of the cable drawn on an enlarged scale, and Figure 2 is a fragmental sectional side view taken on the line II-II of the sheath of the optical cable shown in Figure 1 drawn on a larger scale.
The optical cable shown in: Figures 1 and 2 comprises seven tubes 2 of extruded: polyethylene in each of which are loosely housed two separate optical fibres 1. The tubes 2 are arranged with six: tubes: extent ding helically around a central tube constituting an elongate central core. The assembly of tubes is surrounded by an extruded. outer protective sheath 7 of polyethylene in which. are embedded' at spaced positions around- the. sheath elongate reinforcing members 3 Each reinforcing member 3 comprises a. bunch of compacted yarns of glass fibre having, in the bunch, radially extending undulations 4 that serve to improve the mechanical bonding of the bunch within the sheath 7 and the flexibility Of:' the- cable.
Limited relative movement between the optical fibres 1 and the tube 2 in which they are loosely housed can take place when the cable is flexed.
The optical cable shown in Figures 1 and 2 can be used as a self-supporting aerial cable because the strain that would otherwise be imparted to each optical fibre 1 when the optical cable is suspended is substantially eliminated by the embedded radially undulating reinforoing members 3.

Claims (22)

WHAT WE CLAIM IS:
1. An optical cable comprising a plurality of separately formed tubes of rubber or plastics material in each of some or all of which is or are loosely housed at least one optical bundle as hereinbefore defined and/or at least one separate optical fibre, an outer protective sheath surrounding the plurality of tubes and, embedded in and at spaced positions around the sheath, a plurality of elongate reinforcing members which extend substantially lengthwise of the cable, each of the reinforcing members being of such a material and of such a cross-sectional area having regard to the material or materials and cross-sectional area of the bundle or bundles and/or of the separate optical fibre or fibres that the strain otherwise imparted to the or each optical fibre when the cable is stressed in such a way as to- tend to subject the or any optical fibre to a tensile force is eliminated or reduced at least to a substantial extent by the reinforcing members and each of some or all of the reinforcing members having, in the member, undulations that serve to improve the mechanical bonding of the member within the sheath and the flexed bility of the cable.
2. An optical cable as claimed in Claim 1, wherein the undulations in each undulating reinforcing member extend radially of the cable.
3. An optical cable as claimed in Claim 1 or 2, wherein at least one of the undulating reinforcing members is a single wire or a plurality of wires stranded together, the wire or group of stranded wires being crimped at spaced positions along its length to form said undulations.
4. An optical cable as claimed in Claim 1 or 2,- wherein at least one of the undulating reinforcing members comprises a bunch of compacted yarns of glass fibre or other inorganic reinforcing material.
5. An optical cable comprising a plurality of separately formed tubes- or rubber or plastics material in each of some or all of which is or are loosely housed at least one optical bundle as hereinbefore defined and/or at least one separate optical fibre, an outer protective sheath surrounding the plurality of tubes and, embedded in and at spaced positions around the sheath, a plurality of elongate reinforcing members which extend substantially lengthwise of the cable, each of the reinforcing members comprising a bunch of compacted yarns of glass fibre or other inorganic reinforcing material and of such a cross-sectional area having regard to the material or materials and cross-sectional area of the bundle or bundles and/or of the sep arate optical fibre or fibres that the strain otherwise imparted to the or each optical fibre when the cable is stressed in such a way as to tend to subject the or any optical fibre to a tensile force is eliminated or reduced at least to a substantial extent by the reinforcing members and each of the reinforcing members having, in the member, radially extending undulations that serve to improve the mechanical bonding of the member within the sheath and the flexibility of the cable.
6. An optical cable as claimed in Claim 4 or 5, wherein the compacted yarns of each bunch of glass fibre or of other inorganic reinforcing material are not pre-impregnated with an agent for binding to the material of the sheath.
7. An optical cable as claimed in Claim 4, 5 or 6, wherein in each bunch of compacted yarns of glass fibre or of other inorganic reinforcing material, there is substantially no air in the interstices between the elementary filaments of the bunch.
8. An optical cable as claimed in any one of the preceding Claims. wherein each undulating reinforcing member extends substantially parallel to the axis of the cable.
9. An optical cable as claimed in any one of Claims 1 to 7, wherein each undulating reinforcing member extends helically around the axis of the cable.
10. An optical cable as claimed in Claim 9, wherein the direction of lay of the helically extending undulating reinforcing members is reversed at spaced positions along the length of the cable.
11. An optical cable as claimed in any one of the preceding Claims, wherein the undulating reinforcing members are embedded at uniformly spaced positions around the sheath.
12. An optical cable as claimed in any one of the preceding Claims, wherein the mutual spacing between adjacent undulating reinforcing members is at least twice the diameter of a reinforcing member.
13. An optical cable as claimed in any one of the preceding Claims, wherein the outer protective sheath is an extruded tube of rubber or plastics material.
14. An optical cable as claimed in any one of the preceding Claims, wherein the outer protective sheath is surrounded by an oversheath of a material having a low friction coefficient.
15. An optical cable as --claimed in any one of the preceding Claims, wherein an undersheath is provided around the plurality of tubes and under the outer protective sheath.
16. An optical cable as claimed in Claim 14 or 15, wherein the outer protective sheath and the oversheath and/or the outer protective sheath and the undersheath are separated by an armouring layer or by a layer of metallic tape having on its major surfaces coatings of plastics material that are bonded to the materials of the outer protective sheath and of the oversheath or undersheath, as the case may be.
17. An optical cable as claimed in any one of the preceding Claims, wherein the plurality of separately formed tubes have at least one tape of insulating material helically or longitudinally applied around the assembly of tubes, which layer of tape underlies the outer protective sheath, or undersheath when present.
18. An optical cable as claimed in any one of the preceding Claims, wherein at least one of the tubes has loosely housed in the - tube at least one elongate electric conductor.
19. An optical cable as claimed in any one of the preceding Claims, wherein at least one elongate electric conductor is assembled with the plurality of tubes.
20. An optical cable as claimed in any one of the preceding Claims, wherein the or each optical bundle and/or separate optical fibre and the tube in which it is loosely housed are of equal or substantially equal lengths.
21. An optical cable as claimed in any one of the preceding Claims, wherein the cable incorporates the feature claimed in any one or more than one of Claims 3 to 26 of Patent No. B1,479,427.
22. An optical cable substantially as hereinbefore described with reference to and as shown in the accompanying drawing.
GB314577A 1977-01-26 1977-01-26 Optical cables Expired GB1582851A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB314577A GB1582851A (en) 1977-01-26 1977-01-26 Optical cables
AU32727/78A AU508215B2 (en) 1977-01-26 1978-01-25 Optical cables

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB314577A GB1582851A (en) 1977-01-26 1977-01-26 Optical cables

Publications (1)

Publication Number Publication Date
GB1582851A true GB1582851A (en) 1981-01-14

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GB314577A Expired GB1582851A (en) 1977-01-26 1977-01-26 Optical cables

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AU (1) AU508215B2 (en)
GB (1) GB1582851A (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0067724A1 (en) * 1981-06-17 1982-12-22 BICC Public Limited Company An improved optical cable
GB2159291A (en) * 1984-05-23 1985-11-27 Telephone Cables Ltd Optical fibre cables
US4652323A (en) * 1984-01-09 1987-03-24 Olin Corporation Plasma deposition applications for communication cables
US4690499A (en) * 1984-03-14 1987-09-01 Bicc Public Limited Company Optical fibre element housed in a tube resiliently set in a form such that its longitudinal axis follows a path greater than the rectilinear distance between points to be connected
US4699461A (en) * 1984-03-14 1987-10-13 Bicc Public Limited Company Overhead flexible electric conductor
EP0677759A1 (en) * 1994-04-13 1995-10-18 Alcatel Kabel AG & Co. Optical cable with stain and compression resistant bundels
WO2006025812A1 (en) * 2004-07-16 2006-03-09 Charles Glew Hollow support separators for communications cable
GB2470284A (en) * 2009-05-14 2010-11-17 Draka Comteq Bv Aerial signal conductor holder having strength member(s) with weakening section(s)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0067724A1 (en) * 1981-06-17 1982-12-22 BICC Public Limited Company An improved optical cable
US4798443A (en) * 1981-06-17 1989-01-17 Bicc Public Limited Company Optical cable
US4652323A (en) * 1984-01-09 1987-03-24 Olin Corporation Plasma deposition applications for communication cables
US4690499A (en) * 1984-03-14 1987-09-01 Bicc Public Limited Company Optical fibre element housed in a tube resiliently set in a form such that its longitudinal axis follows a path greater than the rectilinear distance between points to be connected
US4699461A (en) * 1984-03-14 1987-10-13 Bicc Public Limited Company Overhead flexible electric conductor
GB2159291A (en) * 1984-05-23 1985-11-27 Telephone Cables Ltd Optical fibre cables
EP0677759A1 (en) * 1994-04-13 1995-10-18 Alcatel Kabel AG & Co. Optical cable with stain and compression resistant bundels
WO2006025812A1 (en) * 2004-07-16 2006-03-09 Charles Glew Hollow support separators for communications cable
GB2470284A (en) * 2009-05-14 2010-11-17 Draka Comteq Bv Aerial signal conductor holder having strength member(s) with weakening section(s)
GB2470284B (en) * 2009-05-14 2014-05-14 Draka Comteq Bv Aerial signal conductor holder

Also Published As

Publication number Publication date
AU3272778A (en) 1979-09-06
AU508215B2 (en) 1980-03-13

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Date Code Title Description
PS Patent sealed
PE20 Patent expired after termination of 20 years

Effective date: 19960203