Optical waveguides – Accessories – Plug/termination device
Patent
1991-07-23
1993-08-31
Lee, John D.
Optical waveguides
Accessories
Plug/termination device
385 81, G02B 636
Patent
active
052416186
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a joint for optical telecommunications cables and, more specifically, to a ferrule for terminating a cable so as to facilitate jointing.
BACKGROUND OF THE INVENTION
The jointing of optical cables gives rise to many problems. The joints are complicated because each joint must connect all the systems in the cables, e.g. the optical fibres, the tensile elements, and the electrical conductors. This is particularly true of submarine cables which are designed to survive the stringent conditions imposed by a life of 25 years submerged in the sea or ocean.
It is desirable to test joints not only in commercial operations such as manufacturing cables, laying cables and repairing damaged cables but also in research. One test comprises measuring the attenuation of fibres in the joint before and after the joint is stressed with a simulated working load. Faulty jointing technique is shown by increased attenuation t the joint; in extreme instances communication is broken at the joint. In less extreme manifestations the attenuation is acceptable when the joint is first made but the lift of the joint is substantially less than the requirement. The problems of jointing are more severe when it is necessary to joint two cables with different structures.
SUMMARY OF THE INVENTION
This invention relates to a ferrule for terminating an optical cable wherein the ferrule secures all the structural elements of the cable against relative displacement. Joints are made by connecting terminated cables. Preferably the elements of the cable are terminated in sequence. In the cable the sequence is from the outside to the centre, e.g. the king wire. On the ferrule the sequence is linear but in the same order. Most suitably all cable elements, except the outer plastics sheath, are terminated to the ferrule. The invention includes:
These are more fully defined in the claims.
We have found that good quality joints are conveniently made from cables terminated to a ferrule as described above. The loss of performance, observed after stressing, is less severe than in prior art joints.
Optical cables are designed to minimise the stresses and strains imparted to the glass fibres. Also, to reduce ingress of water in case of accidental breakage, the cables are packed with oily materials. It appears that these various circumstances create a potential for displacement of various cable elements. In a continuous run of cable there is little or no chance that the potential could become actual but there is a discontinuity at a joint. It is possible the observed loss in performance is due to movements within the joint and these movements either reduce the lift of fibres, cause higher attentuation or, at worst, break the fibres. The termination of the invention holds the fibre elements in their relative configuration, and hence degradation caused by relative movement is reduced. Furthermore it is possible to terminate different cable structures onto a standard termination so that the differences in cable structure do not affect the joints.
BRIEF DESCRIPTION OF THE DRAWINGS
Cable terminations and joints in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 shows a plan view of a ferrule insert according to the invention. A clamp member is also shown;
FIGS. 2 and 3 show two different cables configurations.
FIG. 4 shows the cable of FIG. 2 secured to a ferrule which includes the insert of FIG. 1;
FIG. 5-8 are cross sections through FIG. 4;
FIG. 9 corresponds to FIG. 5 but it shows the termination of a cable with the configuration shown in FIG. 3;
FIG. 10 shows a connection comprising two terminations (as shown in FIGS. 4-8 and/or 4 and 9) connected by means of a tubular strength member;
FIG. 11 shows the connection of FIG. 10 with a jointing bobbin for the fibre joints, and
FIG. 12 shows an alternative configuration for FIG. 7.
DETAILED DESCRIPTION OF THE DRAWINGS
The ferrule insert shown in FIG. 1 is formed out of a singl
REFERENCES:
patent: 4441786 (1984-04-01), Hulin et al.
patent: 4447121 (1984-05-01), Cooper et al.
patent: 4516830 (1985-05-01), Guazzo
patent: 4738505 (1988-04-01), Jones
patent: 4961624 (1990-10-01), Savitsky et al.
"Low Cost Fiber-Optic Connector with Integral Staking" IBM Technical Disclosure Bulletin, vol. 24, No. 3, Aug. 1981 by Balliet and S. B. Greenspan--pp. 1624-1626.
"Anchor Device for Optical Submarine Cable" 56-106205--Nov. 13, 1981, vol. 5, No. 177 (P-89) (849).
British Telecommunications public limited company
Lee John D.
Ngo John
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