Cable Laying

The submarine cable segments of our network were laid by seven cable ships between July 1999 and January 2001. The oceanic laying of each segment of the network follows three main phases:


Cable Landings: The marine operation begins with the landing of the cable from a cable ship. The cable is generally floated ashore, suspended by buoys to avoid damage on the ocean floor. Once the cable is secured, the buoys are removed so that the cable can settle on the ocean floor. Alternatively, the cable is winched ashore through a conduit (typically around 1km in length) or bore-drilled from the shore.
 
This process is repeated at the other end of the segment, where the cable end is sealed and buoyed-off ready for pick-up by the cable ship following trans-oceanic laying.


Trans-Oceanic Laying: The cable ship follows a pre-determined route (the result of a detailed ocean-floor survey). The cable is either buried by plough-burial simultaneously with laying or surface-laid as required (the Southern Cross cable is buried in depths of less than 2000m wherever feasible). As cable ploughs cannot operate below about 1500m water depth, post-lay jet burial using ROVs was done from the end of cable ploughing down to water depths of 2000m. Adjustments to the cable slack and ship position are used to ensure that the cable rests on the ocean floor.
 


Final Splice: Upon arrival at the other end of the segment, the previously installed end is recovered aboard and the position of the cable ship taken. A final splice is then made and the cable lowered to the ocean floor.
 
For long network segments, cable laying may need to be carried out by multiple cable ships. The Auckland-Hawaii leg of the Southern Cross Cable Network, for instance, was laid using three ships during September and October 1999. The CS Innovator laid 1,371km northeast from Auckland and the CS Nexus 3,306km southwest from Hawaii. The CS Vercors spliced on to the cable end from the Innovator and completed the segment with a 3,318km lay to a final splice position established earlier by the cable laid from the Nexus.The maximum depth of the cable is 7,585m on the Kermadec Trench between New Zealand and Hawaii.
 
Cable Repairs


A cable fault is initially located to a specific repeater section or repeater through testing conducted from the landing stations. A repair vessel recovers the cable from the ocean floor using a grapnel device that can simultaneously seize and cut the cable. One end is raised and brought aboard the cable ship and tested to determine if the fault is present in the recovered section. If this end contains the fault, the cable is recovered back to the fault which is cut out and the cable sealed and buoyed-off. If not, the cable is simply sealed and buoyed-off.
 
The second cable end is then brought aboard the cable ship and any defective cable or repeater removed and replacement cable and repeater jointed in. The cable ship then re-lays cable back to the buoyed-off end, recovers this aboard and completes the circuit by splicing the ends together.

The submerged plant and cable of the segment under repair by a cable repair ship is tested for normal powering before the cable is lowered to the seabed. Once on the seabed, a series of electrical and transmission tests are made on the repaired segment to ensure it is working properly and to also obtain revised base data for use in any subsequent cable repair operation required. Control of the repaired segment is then returned to the Network Operating Centre, in Auckland New Zealand, for returning to traffic carrying mode.

 

 

Contact Us

For any Technical or Network queries about Southern Cross or its products, please contact:

David Clampett

NETWORK ADMINISTRATOR

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