HIGH FIBRE DIET A high count fibre submarine cable family with extension of unrepeatered transmission span lengths
During the recent years there has been an increased demand for high fibre count in both terrestrial and submarine cables, especially in coastal applications as part of a terrestrial network. This requires high fibre count in submarine cables, together with a demand for G655 fibre types to cover future bit rate upgrades. The submarine cable development has been accompanied by the development of designated cable joints and equipment for remote amplification.
by Vegard Briggar Larsen A branching unit (BU) and cable joint boxes have been developed and qualified for 2000m sea depth. The BU, which splits the fibre count between single and double legs is for example used in transmission links between oil platforms in order to pull in and hang off one submarine cable instead of two.
The single tube configuration can also accommodate up to 96 fibres, in a 5.6 mm OD steel tube. Furthermore, the single tube configuration can be fitted with a smaller tube (j 2.3 mm) for deep sea installations. Optical testing during manufacturing and qualification have clearly shown that the stainless steel tube provides a stable and reliable environment for the fibres over the whole optical bandwith. This has been demonstrated for standard single mode fibres (G.652), G.654 as
CABLE DESIGN DESIGN OBJECTIVES The main design objective for the high fibre count sub sea cables has been to provide a family (URC-1 family) of reliable and cost effective cable designs suitable for both present and future fibre types. Hence, the cables developed provide excellent physical protection of the fibres with very low stresses and environmental impacts on the fibre during all service conditions (/1/-/6/).
Optical Package The optical package presented in Figure 1 is based on the steel tube technology in which the fibres are protected inside a jelly filled, laser welded stainless steel tube. The cable core consists of up to eight SZ stranded, 3.7 mm OD, steel tubes, each with a capacity of 48 fibres. Thus, up to 384 fibres can be accommodated. The fibres in each tube are uniquely colour coded.
SINGLE TUBE FIBRES
JELLY
MULTI TUBE (I)
STEEL TUBE
Figure 1. Optical package.
MULTI TUBE (II)
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