You will have to excuse the quality of these photos — they were all taken with my Nokia camera phone and stitched together afterwards. The quality is shocking, but at least you get the idea.

Laying cables?

A cable laying ship’s primary job is laying fibre cables in the ocean. When you type ‘google.com.au’ most likely, (if you’re not in the US), your traffic is passed along these cables via fibre. Voice calls are also carried over it. A whole tonne of traffic is carried over these little fibres.

Ile de Sein

This ship is big, but not massive. It’s gross tonnage is 13,978, and has the capacity to store 5000 tonnes of cable.

ile de sein

Docked in Sydney

Docked in Sydney

Cable bins

Cables are stored in massive cable bins. The Lle de Sein has two bins, as pictured below. These two bins had deep water cable and shallow water cable.

Deep water cable bin

Shallow water cable bin

The difference between the two types of cable is that the shallow cable needs to be armoured and strengthened to avoid ships scraping the cable, whereas the deep sea cable just needs to protect the fibre cables.

The ship lays the deep water cable at around 10km/h. The cable will finally rest on the ocean floor some 20km behind the ship. Shallow water cable is layed at 500m/h. The reason for the slow speed is that at shallow depths they have to bury the cable to at least a metre below the ocean floor. To do this they use the.…

Trencher

Which is just a massive plough that they drag behind the ship and it lays the cable in the trench as it goes. The trencher depth can be controlled from the bridge.

Trenching tool — side on

The leading edge, which is on the left hand side of this photo has replaceable titanium blades. Apparently after a long haul the blades come up smooth and shiny and as sharp as a razor blade.

Trenching tool — closeup

Trenching tool — from it’s rear.

Roller feeders

Whether it’s deep water or shallow water cable that’s being layed; the laying speed has to be controlled accurately. To do this the cable is brought out of the bins .…

Cable run — from the cable bins

.… and fed through a series of rollers. In the background of the following picture you can see the series of rollers that feed the cable out. The foreground is the roller drum which is used during cable repair.

Cable feeders — laying feeders

Cable feeders — repair feeder

Cable feeders — repair feeder

When cable has to be repaired, the ship will sever the cable on the ocean floor, pick up the cable and move back 6km. The reason is that the cable doesn’t have enough slack to pull it all the way up from the ocean floor, (5000km down). Cable to be repaired will be wrapped several times around the big drum and hauled from the ocean floor. A join will then be made on the cable.

Repeaters

Repeaters have the job of amplifying the signal every so often. There is usually a repeater every 75km.

Repeater A/C unit

Unfortunately I didn’t get a chance to take a photo of one of them. But I took a photo of the A/C unit. The repeaters have to be kept cool and at a constant temperature. The reason is that temperature changes can affect them — and when you’re about to literally sink $100k for each repeater you want to look after it. The seabed is roughly 2C.

Each repeater also has to be powered which by a 5kV DC source. When the ship is laying cable they actually power up the cable and run the repeaters. This is so they can check the quality of the layed cable and ensure there are no issues.

The Bridge

The Bridge is where all the action is.

The Bridge

Cable control room

These days cable laying ships are fully automated. They have high accuracy GPS that can enable them to lay cables pretty exactly. The ship is kept at a constant speed to ensure the cable doesn’t over-stretch or sag. There are two bridges one facing forwards for general operations, (coming and going into port), and one facing backwards for cable laying.

You can download all these images by clicking on the download image below:

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