Optical waveguides – Accessories
Patent
1994-04-26
1995-12-05
Lee, John D.
Optical waveguides
Accessories
385 69, 385 86, 385100, G02B 644
Patent
active
054737230
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to optical fibre sheathing and particularly to protective sheathing for supporting and limiting the bend radius of optical fibre or optical fibre cable. The invention is applicable in situations where the fibre might have to follow a tight bend, for example adjacent to a connector board, in cable runs or in trunking.
The term "optical fibre" will be used in the rest of this specification to refer to both fibre alone and to optical fibre cable.
If an optical fibre is bent tightly, ie to a radius which is smaller than a critical radius, there is a significant increase in the transmission losses of the fibre. Below the critical radius the fibre no longer acts efficiently as a waveguide and so it is important to ensure that optical fibre as used in telecommunications and data communications is not bent below this critical radius. The problem is particularly apparent where it is necessary to have a large number of fibres connected through a single patch panel.
BACKGROUND ART
It is known to provide strain relief and/or bend limitation at the end of a fibre, where the fibre enters a fitting. Devices which provide such relief or bend limitation are known for example from EP 0,260,774, from DE 3,821,017 and from GB 2,142,788.
The present invention seeks to provide a structure which cannot be bent below a critical radius, or which can only be so bent by the application of extreme external force, and which provides mechanical protection to the fibre.
DISCLOSURE OF INVENTION
According to the invention, there is provided an optical fibre sheathing comprising a continuous length of tube, the tube being formed by extrusion and the outer surface of the tube wall being formed with circumferential grooves to permit bending of the tube until a predetermined radius of curvature has been reached, but to hinder bending of the tube beyond the predetermined radius of curvature.
The tube preferably has uniform properties over its whole length.
The tube may have a smooth internal bore. The internal bore is preferably dimensioned to accommodate a fibre as a loose fit within the bore.
The circumferential grooves in the surface have the effect of making any bending of the tube to a radius smaller than the predetermined radius very much more difficult than bending of the tube to the predetermined radius.
The circumferential grooves can be helical or annular. They may be formed by cutting, ie removing material from the outer tube surface, or (as is preferred) by local compression of the tube wall material around a helical or annular path.
In another embodiment, the tube wall can be shaped as a result of forming it from initially separate tube sections. The tube sections can comprise a first set having a first diameter and a second set having a second diameter, larger than the first diameter. The sections can then be joined to form a continuous tube length by positioning the first sections spaced apart and then bridging the gaps between the first sections by second sections which are joined to adjacent first sections.
Preferably, both sets of tube sections are formed from extruded tube lengths, with the first set having a relatively rigid inner wall and a relatively flexible outer wall and the second set having a relatively rigid outer wall and a relatively flexible inner wall. The inner and outer walls may be formed by a co-extrusion process, and the outer walls of the first set of sections can be joined to the inner walls of the second set of sections by adhesive or by a plastics welding process.
The tube may be internally sheathed with a smooth walled plastics material to provide a smooth inner wall and thereby to facilitate movement of the fibre within the tube.
The sheathing of the invention can be formed around an optical fibre during the production of the fibre's protective coatings, and may be an integral part of the fibre outer covering.
BRIEF DESCRIPTION OF DRAWINGS
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 s
REFERENCES:
patent: 2975785 (1961-03-01), Sheldon
patent: 3190286 (1965-06-01), Stokes
patent: 4801764 (1989-01-01), Ohlhaber
patent: 4826277 (1989-05-01), Weber et al.
patent: 5179617 (1993-01-01), Stockman
patent: 5202942 (1993-04-01), Collins et al.
Benton Simon C. T.
Stockman Anthony J.
Lee John D.
Stockman Anthony J.
LandOfFree
Optical fibre sheathing tube does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical fibre sheathing tube, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical fibre sheathing tube will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1380510