Communications ducting system and method of laying same
View Patent ↗A communications ducting system, and method of laying a communications duct assembly below a surface, usually in a carriageway or footpath, using an open slot which is subsequently backfilled. The width of the slot is preferably not substantially greater than the narrowest outer cross sectional width of the duct assembly. In at least one direction, the duct assembly has a dimension of less than 20 mm and thus the slot need be no more than 20 mm wide. The duct assembly can be laid along the bottom of the slot, preferably on a layer of sand or other bedding material. Access chambers may provide fiber blowing points along the slot for installing optical fiber in the duct assembly after the assembly is in place, either for the original installation of the fibers or for repair purposes. The access chambers can also be used to accommodate changes in direction of the slot and for repairs in the duct assembly.
1. A method of burying an optical communications duct assembly below a surface, a cross section of the duct assembly having two outer dimensions in orthogonal directions, at least one of said two dimensions being no more than 20 mm, which method comprises the steps of:
cutting a slot extending through a surface of a bound layer of material, the slot having a width in a range from more than 12 mm up to and including 30 mm, said slot width being greater than a smaller one of said two dimensions and being less than a larger one of said two dimensions, wherein the surface is a bearing surface and a depth of the slot is greater than a thickness of the bound layer of material and a bottom of the slot being provided entirely in an unbound material;
laying the duct assembly in the slot into the unbound material such that the duct assembly is supported by a bottom of the slot;
backfilling the slot; and
installing at least one optical fibre in said duct assembly after the step of backfilling the slot;
wherein the step of laying the duct assembly in the slot comprises laying the duct assembly into or onto a supporting material at the bottom of the slot, the duct assembly being thus supported at least partially via the supporting material.
2. A method according to claim 1 , wherein the slot has a width in the range from 13 mm to 20 mm.
3. A method according to claim 1 , wherein the width of the slot is at least 4 mm greater than a smaller one of said two dimensions.
4. A method according to claim 1 , wherein the slot has a depth below the surface in the range from 150 mm to 400 mm.
5. A method according to claim 1 , wherein the duct assembly is airtight at ambient pressures.
6. A method according to claim 1 , wherein the supporting material comprises a granular material.
7. A method according to claim 1 , further comprising:
forming a binder layer around the duct assembly with the supporting material, wherein said binder layer protrudes into said unbound material, and
wherein the supporting material is selected from one or more of: sand, Grano dust, foams, polymeric and plastics materials, and an elasticated foam rod.
8. A method according to claim 1 , further comprising:
positioning the duct assembly fully beneath an underside of said bound layer of material.
9. A method according to claim 1 , wherein the duct assembly has a brightly coloured sheath.
10. A buried optical communications duct assembly having two outer dimensions in orthogonal directions, at least one of the two outer dimensions being no more than 20 mm, said buried optical communications duct assembly comprises:
a slot that is cut into and extending through a surface of a bound layer of material, the slot having a width ranging from more than 12 mm up to and including 30 mm, said slot width being significantly greater than a smaller one of said two dimensions and being less than a larger one of said two dimensions, wherein the surface is a bearing surface and a depth of the slot is greater than a thickness of the bound layer of material and a bottom of the slot being provided entirely in an unbound material;
a duct assembly laid in the slot into the unbound material such that the duct assembly is supported by a bottom of the slot, wherein the duct assembly has at least one duct for the installation of optical fibres subsequent to burial of the assembly below the surface; and
a backfilling of the slot;
wherein the duct assembly is laid in the slot into or onto a supporting material at the bottom of the slot, the duct assembly being thus supported at least partially via the supporting material.
11. A buried optical communications duct assembly according to claim 10 , further comprising two or more ducts for carrying optical fibres.
12. A buried optical communications duct assembly according to claim 10 , further comprising at least three ducts for carrying optical fibres.
13. A buried optical communications duct assembly according to claim 12 , wherein a cross section of the duct assembly is elongate.
14. A buried optical communications duct assembly according to claim 13 , wherein the cross section of the duct assembly has two dimensions in mutually orthogonal directions, neither one of the two dimensions measuring more than 20 mm.
15. A buried optical communications duct assembly according to claim 13 , wherein the at least three ducts are arranged linearly in the plane of the cross section, one duct being positioned between at least two other ducts.
16. A buried optical communications duct assembly according to claim 13 , wherein the at least three ducts are arranged in a triangular formation in the plane of the cross section.
17. A buried optical communications duct assembly according to claim 11 , comprising more than one duct wherein at least two ducts do not have the same diameter.
18. A buried optical communications duct assembly according to claim 17 , comprising at least three ducts, wherein a larger duct is arranged with two smaller ducts in a triangular formation in the plane of the cross section.
19. A buried optical communications duct assembly according to claim 10 , further comprising at least one access chamber to give access to a buried length of duct assembly.
20. A buried optical communications duct assembly according to claim 19 , wherein a section of the duct assembly extends across the access chamber in a curved formation to accommodate a change in direction between a first section of the slot and a second section of the slot.
21. A buried optical communications duct assembly according to claim 20 , wherein the duct assembly is continuous between said first and second sections.
22. A buried optical communications duct assembly according to claim 10 , wherein the duct assembly comprises a repaired section of the duct, said repaired section being directly buried so as to continue the slot.
23. A buried optical communications duct assembly according to claim 10 , further comprising a duct having a wall whose performance in a transverse direction across the duct is less than pressurised watertight.
24. A buried optical communications duct assembly according to claim 10 , wherein said duct assembly is positioned completely beneath an underside of said bound layer of material.
25. A method of repairing a buried optical communications duct assembly, a cross section of the duct assembly having two outer dimensions in orthogonal directions, at least one of said dimensions being no more than 20 mm, said optical communications duct assembly being buried in a method comprising the steps of:
cutting a slot into and extending through a surface of a bound layer of material, the slot having a width ranging from more than 12 mm up to and including 30 mm, said slot width being significantly greater than a smaller one of said two dimensions and being less than a larger one of said two dimensions, wherein the surface is a bearing surface and a depth of the slot is greater than a thickness of the bound layer of material, and a bottom of the slot being provided entirely in an unbound material;
laying the duct assembly in the slot into the unbound material such that the duct assembly is supported by a bottom of the slot;
backfilling the slot; and
installing at least one optical fibre in said duct assembly after the step of backfilling the slot;
wherein the method of repairing the buried optical communications duct assembly comprises:
installing at least one access chamber at a damaged section of the duct assembly;
removing said damaged section; and
installing at least one optical fibre in said duct assembly from the access chamber;
wherein the step of laying the duct assembly in the slot comprises laying the duct assembly into or onto a supporting material at the bottom of the slot, the duct assembly being thus supported at least partially via the supporting material.
26. A method of repairing a buried optical communications duct assembly according to claim 25 , further comprising installing said at least one optical fibre in said duct assembly from a fibre blowing point positioned along the slot.
27. A method of repairing a buried optical communications duct assembly according to claim 25 , further comprising:
cutting a hole into the surface at a site of damage to the duct assembly;
repairing the duct assembly; and
backfilling the hole so as to rebury the repaired duct assembly and continue the slot.
28. A method of repairing a buried optical communications duct assembly according to claim 25 , further comprising:
positioning the duct assembly fully beneath an underside of said bound layer of material.