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Optical fibre cannot survive in the world on its own. It must be packaged in a manner suitable for its environment. Tensile strength, ruggedness, durability, flexibility, size, and resistance to the environment are important considerations when choosing a fibre optic cable.
General Cable offers 3 methods of construction to protect the fibres:
Distribution Type (D Type)
Breakout Type (B Type)
Loose Tube
Distribution Type
In a Distribution type cable each individual fibre is has an extruded PVC material placed over it. Some specifications will refer to this as a 900μm tight-buffered fibre. These individual tight-buffered fibres are colour coded for easy identification. The buffer provides each individual fibre with protection from the environment as well as physical support. The individual fibres are cabled together and aramid yarn is applied as the primary strength member. An overall sheath is then applied.
These cables are excellent for indoor use. They do not provide the best moisture and environmental protection and therefore are not recommended for outdoor applications.
These cables are designed for horizontal intrabuilding communications and computer backbones, they are also suitable for short (100m) vertical riser applications.
Breakout Type
In a Breakout type cable each tight buffered fibre is individually strengthened with aramid yarn, then PVC sheathed. This allows for easy separation, breakout and direct termination into connectors. The individually strengthened units are then stranded and overall sheathed.
These cables are designed for intrabuilding and computer backbone applications offering rugged individual fibre protection. They are suitable for both horizontal and vertical (up to 500m) installations.
Loose Tube
A loose tube is a hollow, plastic tube, which contains 1 to 12 optical fibres. The tube is large enough so that the fibres are free to move around. The tube is filled with a gel to prevent water penetration. The rigidity of the loose tube, combined with the gel filling provides the best level of protection for the fibres.
A loose tube cable consists of a number of loose tubes stranded around a central strength member. The cable is then covered with a protective sheath.
A loose tube cable provides a strain free environment for the fibres. This means the cable can be subject to worst case situations involving tension, temperature and crushing, without the fibres suffering any stress. This ensures the attenuation and bandwidth will remain stable and the fibres lifetime will not be shortened.
These cables are designed for long haul communication circuits where direct burial or installation in ducts is required.
Copyright 2000
GeneralCable New Zealand Limited, Last Modified August,
2004
Building & Construction Cables
