High mechanical and heat performance optical cable

Details High mechanical and heat performance optical cable High mechanical and heat performance optical cable

1999-05-03

2001-05-01

Palmer, Phan T. H. (Department: 2874)

Optical waveguides

Optical transmission cable

Loose tube type

C385S101000, C385S104000, C385S106000, C385S112000

Reexamination Certificate

active

06226430

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
The present invention refers to an optical cable, preferably for aerial applications. However it can also be used underground and has high mechanical and heat performance properties because of its construction.
Optical cables in aerial networks are installed in electrical power distribution networks of medium and low tension or in its own pole line, in urban and rural areas. In rural areas, accidents frequently occur with optical cables, due to fire caused by natural or forced burning of local vegetation and also caused by hunter's shots.
Other important aspects of aerial optical cables are the installation conditions, i.e., maximum distance between poles and sag, climatic conditions, etc., which must be seriously taken into account.
Therefore, an object in the design of aerial optical cables is to meet the above mentioned installation conditions, as well as, when necessary, to withstand heat conditions caused by the above-mentioned fires or the mechanical damage caused by hunter's guns, without damaging the fibers or altering their optical characteristics.
In the market there are different types of totally dielectric aerial optical cables, which have several advantages over the traditional solutions of metallically sheathed cables, which use corrugated or smooth aluminium or steel tapes. However, principally from the resistance point of view against fires and gun shots, the dielectric solutions exhibit a low performance and complexity in the production process.
Furthermore, the construction of totally dielectric aerial optical cables, to be installed with large spans, requires a great number of textile pull elements so as to resist the mechanical stress in the climatic and more critical installation conditions (e.g. maximum wind force, minimum temperature, etc.). This excessive number of textile elements, in addition to presenting difficulties in the cable's manufacturing cycle, increases the unit weight as well as the cable's outside diameter, making its dimensions more critical.
An alternative, having high efficiency and proven through various practical applications, is the use of lightning conductors optical cables (OPGW). These OPGW cables have exceptional optical and mechanical characteristics, since they have around their dielectric nucleus, where the optical fibers are housed, an aluminium tube and surrounding it one or more layers of metallic wires.
These cables are preferably indicated for new aerial installations in power transmission lines or replacing conventional lightning conductor cable, offering one of the highest security coefficients against accidents caused by different factors, including fire and gun shot.
These cables also have been used in distribution networks or their own pole lines, to take advantages of their exceptional optical and mechanical features. However, for these installations, this alternative is not always the best solution from the economical point of view.
SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the invention, a high mechanical and heat performance optical cable for aerial or underground applications comprises optical fibers housed with a dimensional clearance inside protective polymeric tubes, a filling, a peripheral pulling element, an external flame resistant sheath and helically applied metallic elements forming an external ring, the protection tubes being assembled around a central element of dielectric material, on a helicoid structure, via fastenings of polymeric wires and binding with helicoid shaped polymeric tapes.
The optical cable also preferably provides the use of water superabsorbent elements in the interstitial areas forming a dry nucleus.
Moreover, the optical cable preferably provides the use of heat resistant material in the binding such as polyaramide or fiber glass tapes.
As a result, the present invention provides an alternative, which is technically and economically viable, of an aerial optical cable project, so as to assure that the above-mentioned optical cable works according to the project's conditions and, therefore, guarantee the mechanical and optical integrity of the optical fibers, against anticipated mechanical stress and temperature limits. It also shows better performance regarding heat requirements resulting from fires, as well as impacts caused by gun shots.
To better understand the present invention, it will now be explained based on the following detailed description and accompanying drawing disclosing an embodiment of the above-mentioned optical cable.


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patent: 5229851 (1993-07-01), Rahman
patent: 5305411 (1994-04-01), Arrovo
patent: 5455881 (1995-10-01), Bosisio et al.
patent: 5751880 (1998-05-01), Gaillard
patent: 0 528 653 B1 (1993-02-01), None
patent: 0 613 033 B1 (1994-08-01), None
patent: 0 632 301 B1 (1995-01-01), None

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