GB1584249A - Optical cables - Google Patents

Optical cables Download PDF

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Publication number
GB1584249A
GB1584249A GB2023077A GB2023077A GB1584249A GB 1584249 A GB1584249 A GB 1584249A GB 2023077 A GB2023077 A GB 2023077A GB 2023077 A GB2023077 A GB 2023077A GB 1584249 A GB1584249 A GB 1584249A
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GB
United Kingdom
Prior art keywords
elongate
optical cable
bore
optical
cable
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
GB2023077A
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 GB2023077A priority Critical patent/GB1584249A/en
Publication of GB1584249A publication Critical patent/GB1584249A/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
    • G02B6/4411—Matrix structure
    • 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
    • G02B6/4415—Cables for special applications
    • G02B6/4416—Heterogeneous cables
    • G02B6/4422—Heterogeneous cables of the overhead type
    • 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 exclusively, 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 crosssection but, in some circumstances, it may be of non-circular 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 towards the outer surface of the fibre and cables including one 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 reflection of light being transmitted along the fibre, confines at least a major proportion of the light within the core. A composite optical fibre is generally, but not necessarily, made up of two glasses of different refractives indices, the glass forming the core having a higher refractive index than 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. 1479427 there is described and claimed 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 and/or at least one separate optical fibre, an outer protective sheath surrounding the plurality of tubes and, embedded in or surrounded by the outer protective sheath, at least one elongate reinforcing member 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 member or members.
By the expression "optical bundle" as used in the specification and claims of the aforesaid patent 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 can take place when the cable is flexed. The tubes themselves may be loosely housed in the sheath thereby permitting limited relative movement 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 according to the present invention at least one, and preferably each, of the separately formed tubes of rubber or plastics material of the optical cable forming the subject of the main patent is an extruded elongate body that has at least one bore extending throughout its length, in which the optical bundle or bundles and/or the separate optical fibre or fibres is or are loosely housed, and that has a transverse crosssection of elongate shape whose width is substantially greater than its thickness, the transverse dimension of the or each bore measured in a direction normal to the width of the elongate body being substantially less than the thickness of the body. Preferably, said transverse dimension of the or each bore is less than a third of the thickness of the elongate body.
In each elongate body, the or each bore preferably extends substantially parallel to the longitudinal axis of the body and, where the body has two or more bores, preferably the bores are transversely spaced side by side. Preferably, also, the axis of the or each bore and the longitudinal axis and major transverse axis of the body lie in a substantially common plane. The or each bore may be of any transverse crosssectional shape which is not such that an optical fibre or bundle can become trapped in a corner; a bore of substantially circular cross-section is preferred.
The or each bore may be lined by at least one longitudinally extending tape of metal or metal alloy which has been transversely folded or otherwise arranged to form a tube lining the bore. Preferably the or each tape has a layer of rubber or plastics material on its outer surface which is bonded to the material of the elongate body.
In a preferred embodiment, each elongate body has a transverse cross-sectional shape whose longer sides are of rectilinear form and are substantially parallel to one another and are joined at each of their ends by end parts of curvilinear form, e.g. of semi-circular form.
Preferably, the elongate bodies are so assembled within the sheath that each follows a substantially helical path along the length of the cable.
Preferably, as described and claimed in the Complete Specification of our copending Patent Application No. 3145/77 (Serial No. 1582851), a plurality of elongate reinforcing members are embedded in the sheath at spaced positions around the sheath, each reinforcing member extending substantially lengthwise of the cable and 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 outer protective sheath may be lined by at least one longitudinally extending tape of metal or metal alloy which has been transversely folded or otherwise arranged to form a tube providing an internal lining of the sheath. Preferably, the or each tape has a layer of rubber or plastics material on its outer surface which is bonded to the material of the sheath.
The or each optical bundle and/or separate optical fibre loosely housed in the or a bore in an elongate body may be of a length substantially greater than that of the bore but preferably the or each optical bundle and/or separate optical fibre and the bore in which it is loosely housed are of equal or approximately equal lengths.
One or more than one insulated elongate electric conductor may be assembled with the elongate bodies.
The optical cable of the present invention may include any one or more of the features of the optical cables described and claimed in the Complete Specifications of the main patent and of our co-pending Patent Application Nos. 3145/77 (Serial No. 1582851) and 7572/77 (Serial No.
1572877).
The invention is further illustrated by a description, by the way of example, of one preferred optical cable with reference to the accompanying drawing which shows a transverse cross-sectional view of the cable, drawn on an enlarged scale.
Referring to the drawing, the optical cable comprises a plurality of optical cable elements 1 which are assembled together and loosely housed in an extruded outer protective sheath 11 of polyethylene. Each optical cable element 1 comprises an extruded elongate body 2 of polyethylene having a pair of bores 3 transversely spaced side by side and extending throughout the length of the body, the body having a transverse cross-section of elongate shape whose longer sides are of rectilinear form and are substantially parallel to one another and are joined at each of their ends by end parts of curvilinear form. The bores 3 in each body 2 each loosely houses a separate optical fibre 4, limited relative movement being permitted between the optical fibres 4 and the body 2 when the cable is flexed.
Lining the outer protective sheath 11 is a longitudinally extending transversely folded aluminium tape 12 whose longitudinal edges butt and which has on its outwardly facing surface a layer 13 of plastics material which is bonded to the material of the sheath.
Embedded at spaced positions around the sheath 11 are a plurality of elongate reinforcing members 14 each comprising a bunch of compacted yarns of glass fibre having, in the bunch, radially extending undulations that serve to improve the mechanical bonding of the bunch within the sheath 11 and the flexibility of the cable.
The optical cable can be used as a selfsupporting aerial cable because the strain that would otherwise be imparted to each optical fibre 4 when the optical cable is suspended is substantially eliminated by the embedded radially undulating reinforcing members 14.
In the Complete Specification of our copending Patent Application No. 20231177 (Serial No. 1584250) there is described and claimed an optical cable comprising an extruded elongate body of rubber or plastics material which has a transverse crosssection of elongate shape with a width substantially greater than its thickness and which has at least one bore extending throughout its length, the transverse dimension of the or each bore measured in a direction normal to the width of the elongate body being substantially less than the thickness of the body, and, loosely housed in the bore or in at least one of the bores, at least one separate optical fibre and/or at least one optical bundle.
WHAT WE CLAIM IS: 1. An optical cable comprising a plurality of separately formed extruded elongate bodies of rubber or plastics material each having at least one bore extending throughout its length and having a transverse cross-section of elongate shape whose width is substantially greater than its thickness, the transverse dimension of the or each bore measured in a direction normal to the width of the body being substantially less than the thickness of the body; at least one optical bundle and/or at least one separate optical fibre loosely housed in the bore or in at least one of the bores of each of some or all of the elongate bodies; an outer protective sheath surrounding the plurality of elongate bodies and, embedded in or surrounded by the outer protective sheath, at least one elongate reinforcing member of such a material and of such a cross-sectional area having regard to the material or materials and crosssectional 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 member or members.
2. An optical cable as claimed in Claim 1, wherein the or each bore in each elongate body extends substantially parallel to the longitudinal axis of the elongate body.
3. An optical cable as claimed in Claim 2, wherein at least one of the elongate bodies has two or more bores transversely spaced side by side within the body.
4. An optical cable as claimed in Claim 2 or 3, wherein, in each elongate body, the axis of the or each bore and the longitudinal axis and major transverse axis of the body lie in a substantially common plane.
5. An optical cable as claimed in any one of the preceding Claims, wherein, in each elongate body, said transverse dimension of the or each bore is less than a third of the thickness of the elongate body.
6. An optical cable as claimed in any one of the preceding Claims, wherein, in at least one of the elongate bodies, the or each bore is lined by at least one longitudinally extending tape of metal or metal alloy which has been transversely folded or otherwise arranged to form a tube lining the bore.
7. An optical cable as claimed in Claim 6, wherein the or each tape lining the or each bore has a layer of rubber or plastics material on its outer surface which is bonded to the material of the elongate body.
8. An optical cable as claimed in any one of the preceding Claims, wherein each elongate body has a transverse crosssectional shape whose longer sides are of rectilinear form and are substantially parallel to one another and are joined at each of their ends by end parts of curvilinear form.
9. An optical cable as claimed in Claim 1, wherein the elongate bodies are so assembled within the sheath that each follows a substantially helical path along the length of the cable.
10. An optical cable as claimed in any one of the preceding Claims, wherein a plurality of elongate reinforcing members are embedded in the sheath at spaced positions around the sheath, each reinforcing member extending substantially lengthwise of the cable and having, in the member, undulations that serve to improve the mechanical bonding of the member within the sheath and the flexibility of the cable.
11. An optical cable as claimed in Claim 10, wherein the undulations in each reinforcing member extend radially of the cable.
12. An optical cable as claimed in any one of the preceding Claims, wherein the outer protective sheath is lined by at least
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. is bonded to the material of the sheath. Embedded at spaced positions around the sheath 11 are a plurality of elongate reinforcing members 14 each comprising a bunch of compacted yarns of glass fibre having, in the bunch, radially extending undulations that serve to improve the mechanical bonding of the bunch within the sheath 11 and the flexibility of the cable. The optical cable can be used as a selfsupporting aerial cable because the strain that would otherwise be imparted to each optical fibre 4 when the optical cable is suspended is substantially eliminated by the embedded radially undulating reinforcing members 14. In the Complete Specification of our copending Patent Application No. 20231177 (Serial No. 1584250) there is described and claimed an optical cable comprising an extruded elongate body of rubber or plastics material which has a transverse crosssection of elongate shape with a width substantially greater than its thickness and which has at least one bore extending throughout its length, the transverse dimension of the or each bore measured in a direction normal to the width of the elongate body being substantially less than the thickness of the body, and, loosely housed in the bore or in at least one of the bores, at least one separate optical fibre and/or at least one optical bundle. WHAT WE CLAIM IS:
1. An optical cable comprising a plurality of separately formed extruded elongate bodies of rubber or plastics material each having at least one bore extending throughout its length and having a transverse cross-section of elongate shape whose width is substantially greater than its thickness, the transverse dimension of the or each bore measured in a direction normal to the width of the body being substantially less than the thickness of the body; at least one optical bundle and/or at least one separate optical fibre loosely housed in the bore or in at least one of the bores of each of some or all of the elongate bodies; an outer protective sheath surrounding the plurality of elongate bodies and, embedded in or surrounded by the outer protective sheath, at least one elongate reinforcing member of such a material and of such a cross-sectional area having regard to the material or materials and crosssectional 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 member or members.
2. An optical cable as claimed in Claim 1, wherein the or each bore in each elongate body extends substantially parallel to the longitudinal axis of the elongate body.
3. An optical cable as claimed in Claim 2, wherein at least one of the elongate bodies has two or more bores transversely spaced side by side within the body.
4. An optical cable as claimed in Claim 2 or 3, wherein, in each elongate body, the axis of the or each bore and the longitudinal axis and major transverse axis of the body lie in a substantially common plane.
5. An optical cable as claimed in any one of the preceding Claims, wherein, in each elongate body, said transverse dimension of the or each bore is less than a third of the thickness of the elongate body.
6. An optical cable as claimed in any one of the preceding Claims, wherein, in at least one of the elongate bodies, the or each bore is lined by at least one longitudinally extending tape of metal or metal alloy which has been transversely folded or otherwise arranged to form a tube lining the bore.
7. An optical cable as claimed in Claim 6, wherein the or each tape lining the or each bore has a layer of rubber or plastics material on its outer surface which is bonded to the material of the elongate body.
8. An optical cable as claimed in any one of the preceding Claims, wherein each elongate body has a transverse crosssectional shape whose longer sides are of rectilinear form and are substantially parallel to one another and are joined at each of their ends by end parts of curvilinear form.
9. An optical cable as claimed in Claim 1, wherein the elongate bodies are so assembled within the sheath that each follows a substantially helical path along the length of the cable.
10. An optical cable as claimed in any one of the preceding Claims, wherein a plurality of elongate reinforcing members are embedded in the sheath at spaced positions around the sheath, each reinforcing member extending substantially lengthwise of the cable and having, in the member, undulations that serve to improve the mechanical bonding of the member within the sheath and the flexibility of the cable.
11. An optical cable as claimed in Claim 10, wherein the undulations in each reinforcing member extend radially of the cable.
12. An optical cable as claimed in any one of the preceding Claims, wherein the outer protective sheath is lined by at least
one longitudinally extending tape of metal or metal alloy which has been transversely folded or otherwise arranged to form a tube providing an internal lining of the sheath.
13. An optical cable as claimed in Claim 12, wherein the or each tape lining the sheath has a layer of rubber or plastics material on its outer surface which is bonded to the material of the sheath.
14. An optical cable as claimed in any one of the preceding Claims, wherein the or each optical bundle and! our separate optical fibre and the bore in which it is loosely housed are of equal or approximately equal lengths.
15. An optical cable as claimed in any one of the preceding Claims, wherein one or more than one insulated elongate electric conductor is assembled with the elongate bodies.
16. An optical cable substantially as hereinbefore described with reference to and as shown in the accompanying drawing.
GB2023077A 1978-05-12 1978-05-12 Optical cables Expired GB1584249A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB2023077A GB1584249A (en) 1978-05-12 1978-05-12 Optical cables

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Application Number Priority Date Filing Date Title
GB2023077A GB1584249A (en) 1978-05-12 1978-05-12 Optical cables

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GB1584249A true GB1584249A (en) 1981-02-11

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Cited By (3)

* 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
GB2156094A (en) * 1984-03-14 1985-10-02 Bicc Plc Optical fibre element comprising resiliently set flexible tube
GB2244568A (en) * 1990-04-28 1991-12-04 Kabelmetal Electro Gmbh Optical cabling element and its production

Cited By (5)

* 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
GB2156094A (en) * 1984-03-14 1985-10-02 Bicc Plc Optical fibre element comprising resiliently set flexible tube
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
GB2244568A (en) * 1990-04-28 1991-12-04 Kabelmetal Electro Gmbh Optical cabling element and its production
GB2244568B (en) * 1990-04-28 1994-11-02 Kabelmetal Electro Gmbh Optical cabling element and its production

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

Effective date: 19960203