CA1144793A - Optical communication cable - Google Patents
Optical communication cableInfo
- Publication number
- CA1144793A CA1144793A CA000369253A CA369253A CA1144793A CA 1144793 A CA1144793 A CA 1144793A CA 000369253 A CA000369253 A CA 000369253A CA 369253 A CA369253 A CA 369253A CA 1144793 A CA1144793 A CA 1144793A
- Authority
- CA
- Canada
- Prior art keywords
- cable
- bore
- optical
- optical fibre
- tube
- 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
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Abstract
A B S T R A C T
In an optical communication cable for the transmission of light, the or each optical fibre is so housed that it is capable of limited movement relative to the cable when the cable is flexed, thereby reducing risk of fracture of the optical fibre. The optical fibre is loosely housed in, and has a diameter less than the diameter of, a bore in an extruded elongate body of insulating material, which body has a transverse cross-sectional shape of elongate form. The bore has a smooth continuous boundary wall and is of uniform transverse cross-section throughout its length. To provide reinforcement for the cable, two separate elongate reinforcing members are embedded in the extruded body throughout its length and are arranged on opposite sides of and parallel to the bore. Because limited movement of the optical fibre can take place within the cable, there is substantially no risk of fracture of or damage to the optical fibre during manufacture and installation of the cable and, as compared with optical communication cables hitherto proposed, the optical cable is simple and inexpensive because no unnecessary material is employed.
In an optical communication cable for the transmission of light, the or each optical fibre is so housed that it is capable of limited movement relative to the cable when the cable is flexed, thereby reducing risk of fracture of the optical fibre. The optical fibre is loosely housed in, and has a diameter less than the diameter of, a bore in an extruded elongate body of insulating material, which body has a transverse cross-sectional shape of elongate form. The bore has a smooth continuous boundary wall and is of uniform transverse cross-section throughout its length. To provide reinforcement for the cable, two separate elongate reinforcing members are embedded in the extruded body throughout its length and are arranged on opposite sides of and parallel to the bore. Because limited movement of the optical fibre can take place within the cable, there is substantially no risk of fracture of or damage to the optical fibre during manufacture and installation of the cable and, as compared with optical communication cables hitherto proposed, the optical cable is simple and inexpensive because no unnecessary material is employed.
Description
1~4~g3 This is a division of Canadian paten-t application Serial No. 291,828, filed 28 ~ovember, 1977.
This invention relates to optical guides for the transmission of the ultra-violet, 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 waveguides for use in the communications field adapted for transmission of light.
The present invention provides an optical communication cable that is relatively inexpensive and simple to manufacture.
~ ccording to the present invention the optical cornmunication cable comprises an extruded elongate body of insulating material having a transverse cross-sectional shape of elongate form and having extending throughout its length at least one bore which is defined by a substantially smooth continuous boundary wall and which is of substantially uniform transverse cross-section throughout the length of the bore; at least one optical fibre which is housed loosely in and throughout the length of the bore and which is of a diameter substantially less than the diameter of the bore so that at any transverse cross-section of the cable throughout the whole of its length, limited relative movement between the optical fibre and the extruded elongate body can take place when the cable is flexed; and, embedded in the extruded elongate body throughout the whole of the length of the body and arranged on opposite sides of and substantially parallel to the bore~ at least two separate elongate reinforcing members.
~. ~
~1~4~93 Instea~ of or in addition to the or each optical fibre housed loosely in the bore, at least one optical bundle may be housed loosely in the bore.
By the expression "optical bundle" is meant a group of optical fibres or a group of fibres including one or more optical fibres and one or more non-optical reinforcing fibres or other reinforcing elongate elements. Each optical fibre and/or non-optical fibre may be of circular or non-circular cross-section.
By virtue of being housed loosely in a bore extending lengthwise in the extruded elongate body, limited relative movement between the or each optical bundle and/or between the or each separate optical fibre and the extruded elongate body can take place when the cable is flexed.
Preferably the axes of the bore or bores and of the reinforcing members lie in a substantially common plane and, the or each bore preferably lies wholly in the space bounded by two planes located on opposite sides o two reinforcing members and touching both members so that the optical fibre or fibres is or are protected by the reinforcing members against crushing. Preferably, also, the reinforcing members are of substantially the same diameter.
The or each optical bundle and/or separate optical fibre may be of a length substantially greater than that of the bore in which it is loosely housed but preferably the or each bundle and/or separate optical fibre and the bore are of equal or approximately equal lengths.
With a view to preventing mechanical damage to the surface of any optical fibre arising from abrasion with another optical fibre or other fibre when flexing of -the optical cable occurs, the interstices between the fibres of the or each bundle and between the or each bundle and the boundary wall oE the bore or of at least one of the bores and/or between the separate optical fibres in said bore and between said fibres and the boundary wall of said bore may be filled throughout the length of the cable wi-th a greasy filling medium which will permit relative sliding movement between fibres when the cable is flexed. If the filling medium is a water-impermeable medium customarily employed in fully-filled telecommunication cables it will also serve as a longitudinally continuous barrier to the ingress of moisture along interstices in the bore. Preferably the filling medium employed consists of, or comprises as a major constituent, petroleum jelly.
Where the interstices in said bore are filled with petroleum jelly or other water impermeable medium, to reduce the risk that the water-impermeable medium might permeate into the insulating (e.g. rubber or plastics (material of the extruded elongate body, the bore may be lined with a material that is impermeable to the water-impermeable medium. Where the medium is petroleum jelly, the lining may be formed of a metallic tape ha~ing on at least its surface contiguous with the extruded elongate body a coating of polyethylene or other plastics material that is preferably bonded to the material of the body.
As a precaution against mechanical damage arising from contact with other fibres housed in the bore, some or all of the optical fibres may have a continuous coating of a metallic material.
- ~44'793 Each reinforcing member is of such a material and of such a cross-sectional area having regard to -the material or materials and cross-sactional area of the bunclle 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.
I0 Each elonyate reinforcing member may be a single solid element or, with a view to making the optical cable as flexible as possible, each reinforcing member may comprise a plurality of elements stranded together. Each element is preferably of steel, carbon fibre or any other suitable material having the necessary Young's Modulus.
Where each reinforcing member is of stranded form, for instance a strand of steel wires, the strand is preferably die-formed; that is to say a strand that has been passed through a die which effects a reduction in the overall diameter of the strand. Such a compacted strand has the advantage over non-compacted strands of a higher apparent Young's Modulus at low strain.
The reinforcing members may be made of or may be coated with a metal or metal alloy of high electrical conductivity to provide a ci.rcuit or circuits, for instance for feeding electrical power to repeaters or regenerators.
Where each reinforcing member is of stranded form, at least one of the elements of each of at least two of the stranded reinforcing members may be of metal or metal alloy of high electrical conductivity. For exampla, in a stranded 4~33 reinforcing member consisting of six elements stranded around a central element, -the central element may be of steel and the surrounding six elements of copper or, in an alternative construction, a~l of the elements of the strand may be of hard drawn copper or cadmium copper.
Suitable materials of which the extruded elongate body may be made include polyethylene, or example high density polyethylene, a hard polyolefin such as polypropylene or a modified polypropylene, for example propylene ethylene copolymer. The extruded elongate body may have an oversheath of a material having a low friction coefficient, such as nylon.
An optical cable according to the invention can be manufac~ured using conventional extrusion techniques well known in the manufacture of electric cables. The or each optical fibre and the separate elongate reinforcing members are fed side by side into the upstream end of an extrusiGn machine which, by means of an appropriate hollow core point and an outer die at the extrusion orifice, extrudes insulating material about the advancing optical Eibre or fibres and reinforcing members in such a way as to form an extruded body which has a bore extending throughout its length, the or each optical fibre being loosely hoased in the bore and each reinforcing member being embedded in the extruded bcdy.
The invention is further illustrated by a description, by way of example, of two preferred forms of optical cable with reference to the accompanying drawings in which:
~ 6 --Figure 1 is a cross-sectional view of a first form of optical cable drawn on an enlarged scale; and Figure 2 is a cross-sectional view of a second form of optical cable drawn on an enlarged scale.
The optical cable shown in Figure 1 comprises an extruded elongate body 4 of polyethylene having a transverse cross-sectional shape of elongate form and having a bore 2 and, embedded in the extruded body on opposite sides of the bore, two steel wires 3 so arranged that their axes and the axis of the bore are substantially parallel and lie in a substantially common plane. I~o separate optical fibres 1 are housed loosely in the bore 2. The elongate body 4 has a major transverse dimension of ~ mm and a minor transverse dimension of 4 mm. Each wire 3 has a diameter of 1.2 mm and the bore 2 has a major transverse dimension of 2 mm and a minor transverse dimension of 1 mm.
In the optical cable shown in Figure 2, an extruded elongate body 14 of polyethylene has a transverse cross-sectional shape of elongate form and has two bores 12 spaced on opposite sides of, and sxtending substantially parallel to, the axis of the body. Two steel wires 13 are embedded in the body 14 on opposite sides of the two bores 12 with their axes substantially parallel to, and lying in substantially the same plane as, the axes of the bores.
~oused loosely in each bore 12 is an optical bundle 11 comprising three optical fibres assembled together. The elongate body 14 has a major transverse dimension of 11 mm and a minor transverse dimension of 4 mm. Each wire 13 has a diameter of 1. 02 mm and each bore 12 has a major transverse ~4793 dimension of 1.5 mm and a minor transverse dimension o~
1 mm.
~ .
,
This invention relates to optical guides for the transmission of the ultra-violet, 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 waveguides for use in the communications field adapted for transmission of light.
The present invention provides an optical communication cable that is relatively inexpensive and simple to manufacture.
~ ccording to the present invention the optical cornmunication cable comprises an extruded elongate body of insulating material having a transverse cross-sectional shape of elongate form and having extending throughout its length at least one bore which is defined by a substantially smooth continuous boundary wall and which is of substantially uniform transverse cross-section throughout the length of the bore; at least one optical fibre which is housed loosely in and throughout the length of the bore and which is of a diameter substantially less than the diameter of the bore so that at any transverse cross-section of the cable throughout the whole of its length, limited relative movement between the optical fibre and the extruded elongate body can take place when the cable is flexed; and, embedded in the extruded elongate body throughout the whole of the length of the body and arranged on opposite sides of and substantially parallel to the bore~ at least two separate elongate reinforcing members.
~. ~
~1~4~93 Instea~ of or in addition to the or each optical fibre housed loosely in the bore, at least one optical bundle may be housed loosely in the bore.
By the expression "optical bundle" is meant a group of optical fibres or a group of fibres including one or more optical fibres and one or more non-optical reinforcing fibres or other reinforcing elongate elements. Each optical fibre and/or non-optical fibre may be of circular or non-circular cross-section.
By virtue of being housed loosely in a bore extending lengthwise in the extruded elongate body, limited relative movement between the or each optical bundle and/or between the or each separate optical fibre and the extruded elongate body can take place when the cable is flexed.
Preferably the axes of the bore or bores and of the reinforcing members lie in a substantially common plane and, the or each bore preferably lies wholly in the space bounded by two planes located on opposite sides o two reinforcing members and touching both members so that the optical fibre or fibres is or are protected by the reinforcing members against crushing. Preferably, also, the reinforcing members are of substantially the same diameter.
The or each optical bundle and/or separate optical fibre may be of a length substantially greater than that of the bore in which it is loosely housed but preferably the or each bundle and/or separate optical fibre and the bore are of equal or approximately equal lengths.
With a view to preventing mechanical damage to the surface of any optical fibre arising from abrasion with another optical fibre or other fibre when flexing of -the optical cable occurs, the interstices between the fibres of the or each bundle and between the or each bundle and the boundary wall oE the bore or of at least one of the bores and/or between the separate optical fibres in said bore and between said fibres and the boundary wall of said bore may be filled throughout the length of the cable wi-th a greasy filling medium which will permit relative sliding movement between fibres when the cable is flexed. If the filling medium is a water-impermeable medium customarily employed in fully-filled telecommunication cables it will also serve as a longitudinally continuous barrier to the ingress of moisture along interstices in the bore. Preferably the filling medium employed consists of, or comprises as a major constituent, petroleum jelly.
Where the interstices in said bore are filled with petroleum jelly or other water impermeable medium, to reduce the risk that the water-impermeable medium might permeate into the insulating (e.g. rubber or plastics (material of the extruded elongate body, the bore may be lined with a material that is impermeable to the water-impermeable medium. Where the medium is petroleum jelly, the lining may be formed of a metallic tape ha~ing on at least its surface contiguous with the extruded elongate body a coating of polyethylene or other plastics material that is preferably bonded to the material of the body.
As a precaution against mechanical damage arising from contact with other fibres housed in the bore, some or all of the optical fibres may have a continuous coating of a metallic material.
- ~44'793 Each reinforcing member is of such a material and of such a cross-sectional area having regard to -the material or materials and cross-sactional area of the bunclle 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.
I0 Each elonyate reinforcing member may be a single solid element or, with a view to making the optical cable as flexible as possible, each reinforcing member may comprise a plurality of elements stranded together. Each element is preferably of steel, carbon fibre or any other suitable material having the necessary Young's Modulus.
Where each reinforcing member is of stranded form, for instance a strand of steel wires, the strand is preferably die-formed; that is to say a strand that has been passed through a die which effects a reduction in the overall diameter of the strand. Such a compacted strand has the advantage over non-compacted strands of a higher apparent Young's Modulus at low strain.
The reinforcing members may be made of or may be coated with a metal or metal alloy of high electrical conductivity to provide a ci.rcuit or circuits, for instance for feeding electrical power to repeaters or regenerators.
Where each reinforcing member is of stranded form, at least one of the elements of each of at least two of the stranded reinforcing members may be of metal or metal alloy of high electrical conductivity. For exampla, in a stranded 4~33 reinforcing member consisting of six elements stranded around a central element, -the central element may be of steel and the surrounding six elements of copper or, in an alternative construction, a~l of the elements of the strand may be of hard drawn copper or cadmium copper.
Suitable materials of which the extruded elongate body may be made include polyethylene, or example high density polyethylene, a hard polyolefin such as polypropylene or a modified polypropylene, for example propylene ethylene copolymer. The extruded elongate body may have an oversheath of a material having a low friction coefficient, such as nylon.
An optical cable according to the invention can be manufac~ured using conventional extrusion techniques well known in the manufacture of electric cables. The or each optical fibre and the separate elongate reinforcing members are fed side by side into the upstream end of an extrusiGn machine which, by means of an appropriate hollow core point and an outer die at the extrusion orifice, extrudes insulating material about the advancing optical Eibre or fibres and reinforcing members in such a way as to form an extruded body which has a bore extending throughout its length, the or each optical fibre being loosely hoased in the bore and each reinforcing member being embedded in the extruded bcdy.
The invention is further illustrated by a description, by way of example, of two preferred forms of optical cable with reference to the accompanying drawings in which:
~ 6 --Figure 1 is a cross-sectional view of a first form of optical cable drawn on an enlarged scale; and Figure 2 is a cross-sectional view of a second form of optical cable drawn on an enlarged scale.
The optical cable shown in Figure 1 comprises an extruded elongate body 4 of polyethylene having a transverse cross-sectional shape of elongate form and having a bore 2 and, embedded in the extruded body on opposite sides of the bore, two steel wires 3 so arranged that their axes and the axis of the bore are substantially parallel and lie in a substantially common plane. I~o separate optical fibres 1 are housed loosely in the bore 2. The elongate body 4 has a major transverse dimension of ~ mm and a minor transverse dimension of 4 mm. Each wire 3 has a diameter of 1.2 mm and the bore 2 has a major transverse dimension of 2 mm and a minor transverse dimension of 1 mm.
In the optical cable shown in Figure 2, an extruded elongate body 14 of polyethylene has a transverse cross-sectional shape of elongate form and has two bores 12 spaced on opposite sides of, and sxtending substantially parallel to, the axis of the body. Two steel wires 13 are embedded in the body 14 on opposite sides of the two bores 12 with their axes substantially parallel to, and lying in substantially the same plane as, the axes of the bores.
~oused loosely in each bore 12 is an optical bundle 11 comprising three optical fibres assembled together. The elongate body 14 has a major transverse dimension of 11 mm and a minor transverse dimension of 4 mm. Each wire 13 has a diameter of 1. 02 mm and each bore 12 has a major transverse ~4793 dimension of 1.5 mm and a minor transverse dimension o~
1 mm.
~ .
,
Claims (24)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An optical communication cable for transmission of light, which cable comprises an extruded elongate body of insulating material having a transverse cross-sectional shape of elongate form and having extending throughout its length at least one bore which is defined by a substantially smooth continuous boundary wall and which is of substantially uniform transverse cross-section throughout the length of the bore; at least one optical fibre which is housed loosely in and throughout the length of the bore and which is of a diameter substantially less than the diameter of the bore so that at any transverse cross-section of the cable throughout the whole of its length, limited relative movement between the optical fibre and the extruded elongate body can take place when the cable is flexed; and, embedded in the extruded elongate body throughout the whole of the length of the body and arranged on opposite sides of and substantially parallel to the bore, at least two separate elongate reinforcing members.
2. An optical communication cable as claimed in claim 1, wherein the axes of the bore and the reinforcing members lie in a substantially common plane.
3. An optical communication cable as claimed in claim 1, wherein the or each bore lies wholly in the space bounded by planes located on opposite sides of the two reinforcing members and touching both members.
- Page 1 of Claims -
- Page 1 of Claims -
4. An optical communication cable as claimed in claim 1, wherein the reinforcing members are of substantially the same diameter.
5. An optical communication cable as claimed in claim 1, wherein the or each optical fibre and the bore are of substantially equal lengths.
6. An optical communication cable as claimed in claim 1, wherein the interstices between the optical fibres and the boundary wall of the bore in which they are loosely housed are substantially filled throughout the length of the cable with a greasy filling medium.
7. An optical communication cable as claimed in claim 6, wherein the filling medium consists of, or comprises as a major constituent, petroleum jelly.
8. An optical communication cable as claimed in claim 6, wherein the boundary wall of the bore is lined with a material that is impermeable to the filling medium.
9. An optical communication cable as claimed in claim 6, wherein the boundary wall of the bore is lined with a metallic tape having on at least its surface contiguous with the extruded elongate body a coating of plastics material that is bonded to the material of the extruded elongate body.
- Page 2 of Claims -
- Page 2 of Claims -
10. An optical communication cable as claimed in claim 1, wherein the optical fibre or each of at least some of the optical fibres in the bore has a continuous coating of a metallic material.
11. An optical communication cable as claimed in claim 1, wherein each elongate reinforcing member comprises a plurality of elongate elements stranded together.
12. An optical communication cable as claimed in claim 1, wherein each elongate reinforcing member comprises a plurality of elongate elements stranded together and die-formed.
13. An optical communication cable as claimed in claim 1, wherein each of at least two said elongate reinforcing members is made of or coated with a metal or metal alloy of high electrical conductivity.
14. An optical communication cable as claimed in claim 1, wherein the extruded elongate body has an oversheath of a material having a low friction coefficient.
15. An optical fibre cable comprising at least one optical fibre, a buffer tube surrounding such fibre, and a reinforcement for the buffer tube to accommodate axial loads applied to the cable, the reinforcement comprising a plurality of separate substantially inextensible elongate elements having a modulus of elasticity at least equal to that of the optical fibre, extending solely in the axial - Page 3 of Claims -direction of the tube and being taut in the axial direction of the tube and in a normal condition of the cable.
16. A cable according to Claim 15, wherein the substantially inextensible elongate elements are embedded within the buffer tube.
17. A cable according to Claim 16, wherein the substantially inextensible elongate elements are glass fibres.
18. A cable according to Claim 17, wherein the glass fibres are in the form of monofilaments.
19. An optical fibre cable comprising at least one optical fibre, a buffer tube surrounding such fibre and of substantially greater internal diameter than the diameter of such fibre, and a reinforcement for the buffer tube to accommodate axial loads applied to the cable, the reinforcement comprising a plurality of separate substantially inextensible elongate elements having a modulus of elasticity at least equal to that of the optical fibre, extending solely in the axial direction of the tube and being taut in the axial direction of the tube and in a normal condition of the cable.
20. A cable according to Claim 19, wherein the substantially inextensible elongate elements are embedded within the buffer tube.
- Page 4 of Claims -
- Page 4 of Claims -
21. A cable according to Claim 20, wherein the substantially inextensible elongate elements are glass fibres.
22. A cable according to Claim 21, wherein the glass fibres are in the form of monofilaments.
23. A method of making an optical fibre cable comprising locating at least one optical fibre within an extruded buffer tube and, during extrusion of the tube, passing substantially inextensible elongate elements through an extrusion orifice to embed the substantially inextensible elongate elements within the tube in such a way that they extend solely in the axial direction of the tube and are taut in the axial direction of the tube to accommodate axial loads upon the cable.
24. A method of making an optical fibre cable comprising locating at least one optical fibre within an extruded buffer tube having a substantially greater internal diameter than the diameter of such fibre and, during extrusion of the tube, passing a plurality of separate substantially inextensible elongate elements through an extrusion orifice to embed the substantially inextensible elongate elements within the tube in such a way that they extend solely in the axial direction of the tube and are taut in the axial direction of the tube to accommodate axial loads upon the cable.
- Page 5 of Claims -
- Page 5 of Claims -
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000369253A CA1144793A (en) | 1977-11-28 | 1981-01-23 | Optical communication cable |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000291828A CA1118252A (en) | 1977-11-28 | 1977-11-28 | Optical communication cable |
| CA000369253A CA1144793A (en) | 1977-11-28 | 1981-01-23 | Optical communication cable |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1144793A true CA1144793A (en) | 1983-04-19 |
Family
ID=25668601
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000369253A Expired CA1144793A (en) | 1977-11-28 | 1981-01-23 | Optical communication cable |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1144793A (en) |
-
1981
- 1981-01-23 CA CA000369253A patent/CA1144793A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |