Optical waveguides – Optical transmission cable – Ribbon cable
Patent
1993-01-11
1994-06-07
Bovernick, Rodney B.
Optical waveguides
Optical transmission cable
Ribbon cable
385109, 385110, G02B 644
Patent
active
053197305
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a cable, comprising (i) at least one package of fibre ribbons, which package consists of at least one fibre ribbon comprising several parallel optical fibres and a covering joining them together, and (ii) at least one reinforcing member extending in the longitudinal direction of the cable.
BACKGROUND AND PRIOR ART
It is known to use in a cable optical fibre ribbons, comprising typically 4 to 12 parallel optical fibres and a covering manufactured of plastic material joining them together.
In a known cable construction, fibre ribbons are normally packaged tightly inside a plastic tube and the plastic tube is surrounded by a protective structure comprising reinforcing members extending in the longitudinal direction of the cable, which members are placed at regular intervals in the peripheral direction of the cable.
Another known cable construction is a so-called V-groove cable, in which fibre ribbons are placed in spirally or oscillatingly winding grooves positioned in a common centre element.
A drawback of these known cable constructions is that, due to the complicated structures thereof, the production costs are high. In the abovementioned constructions, it is, furthermore, not possible to provide in a simple manner a proper play for the fibres against changing dimensions caused by mechanical forces directed to protective sheath or by thermal effects.
SUMMARY OF THE INVENTION
The object of the present invention is thus to avoid the drawbacks described above. This is achieved by means of a cable construction according to the invention, which is characterized by a combination in which (i) at least one package of fibre ribbons is arranged in a cavity with an elongated cross-section in such a way that the natural bending plane of the fibre ribbon package is substantially perpendicular with respect to the longitudinal plane of the cavity, and (ii) at least one reinforcing member is arranged in the cable construction in such a way that the bending plane of the whole cable defined thereby also is substantially perpendicular with respect to the longitudinal plane of the cavity.
The basic idea according to the invention is to arrange the fibre ribbons and the reinforcing members with respect to the elongated cavity formed in the cable in such a way that the fibre ribbons are allowed to move inside the cavity, while extending, compressing or bending the cable, in such a manner that they bend with respect to their natural bending plane.
Thanks to the construction of the invention, the fibres can in an easy way be provided with a large play. Due to its simple structure, the cable of the invention also keeps the production costs low, and thereby, a cable network can be constructed more economically than before. The solution according to the invention improves the profitability especially at the lowest level of an optical cable network, i.e. within the area of a local network, where the number of fibres is highest and where the need to achieve cheaper solutions than the present ones is greatest.
In the construction of the invention, the cavity, the fibre ribbons and the reinforcing members are mutually arranged in such a way that a manufacture by means of a stationary (not turning) tool is made possible and the fibres can be provided with the extra length they need with respect to the protective sheath simply by allowing them to bend with respect to their natural bending plane. Moreover, the cable geometry of the invention allows a minimization of the cross-section of the cable, and consequently, an increase in the packing density of the cable.
According to one preferred embodiment of the invention, the reinforcing members consist of a pair of metallic conductors, whereby they can be used also for data transmission or e.g. supply of power.
According to a second preferred embodiment of the invention, the reinforcing members confine the cavity space within themselves and protect it. Thanks to such a construction, it is easy to branch the cable without damaging the fibr
REFERENCES:
patent: 4846566 (1989-07-01), Barnett et al.
patent: 4859025 (1989-08-01), Houghton
patent: 4979794 (1990-12-01), Evans
patent: 4997257 (1991-03-01), Spedding
patent: 5067830 (1991-11-01), McAlpine et al.
patent: 5163116 (1992-11-01), Oestreich et al.
patent: 5224191 (1993-06-01), Zeidler
Rasanen Timo
Ravela Jussi
Bovernick Rodney B.
Nokia Kaapeli Oy
Sanghavi Hemang
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