Cable Landing Station: What’s inside?

The internet doesn’t seem physical, We type in a web address and within a second, it’s loaded, but in reality, it’s a very physical process that has to take place.

As your request whizzes down your broadband connection, onto your ISP’s network and onto an internet exchange or peering point. From there it will be routed via the fastest path to its destination before the data you’ve request gets sent back to your computer. All within a few seconds with the inital request typically taking milliseconds.

These networks use under-ground, over-ground and under-sea fibre optics and need to be switched inter-connecting with other network paths and the signal on each fibre path will need to be regenerated often. All of these processes needs physical hardware.

Going from land to sea is a major element as the signal will need to be regenerated at sea, so power will need to be supplied from the cable landing station.

What is a cable landing station?
These typically unmanned buildings are on either end of the under-sea cable, on the coast or within a few miles from the landing site. Each installation varies with each cable landing station due to their planned use, capacity, local area, etc.

Common designs match neighbouring homes or industrial units and are used to house equipment for power and switching. These also house fire suppression and advanced air conditioning.

Many cable landing stations built before the boom used re-purposed telephone exchanges or purpose-built ‘telephone exchange’ type buildings copying from BT’s/General Post Office designs. (See: Winterton-on-sea)

During the boom in the late ’90s, purpose-built warehouses were built to accommodate the ever growing need for under-sea connections. These were designed with fresh eyes and some even winning architecture awards. (See: Skewjack) These were built with growth in mind, so many have excess space, sometimes re-purposed and sold as server co-location.

With off-site prefabrication methods proving most cost-effective, the most recent cable landing stations are built to fit. (See: Brean). These are built to serve the designed cables with no space for growth.

What’s inside?
It’s industrialised, with rows of rack space, overhead cable trays, air conditioning, backup power and fire suppression. Much like a data centre, just on a smaller scale.

Each section will have its own room, with backup power batteries and switchgear in one room, rack space in another room and control equipment in another.

The cable will enter through one duct, which is terminated on a centralised block (CTB) within a rack and then patched to an optical distribution frame (ODF). This will then be patched to another centralised block (CTB) within another rack before leaving via a second duct.

This process means switching fibre routes is seamless, so in the event of a fibre-break, traffic can be re-routed. This also means swapping equipment can be made easier with patching to replacement equipment being done in seconds.

In our example, We look at the modern cable landing station in Brean. The Air Conditioning is powered by Liebert DSE and Liebert PDX thermal management units, with each room of the station. This keeps a constant temperature to ensure the best performance environment for equipment inside.

Fire suppression is most likely used via a gas suppressant system to protect the electrical equipment, which will stay operational in the event of a fire. The room will fill with an anti-oxidant, starving the fire of oxygen.

These sites are very secure and house very high voltage equipment. They are monitored with CCTV, infra-red and security patrol. Silent alarms will also notify the police of trespass. It’s important to stress, these are high profile sites and arrest will be likely.  

Due to the under-sea cable needing power for repeating every 73 km approximately (with a tolerance of approximately +/- 3.5 km) – under-sea regeneration will use land supplied power. In the event of a power outage, batteries will pick up the load while diesel generators will fire up and recharge the batteries.

The same CAT generator sets were installed at both sites, providing around 50kW of power, via a 5000 litre tank, providing around 2 weeks worth of power. There is a fail safe of a second generator installed alongside.

It’s also believed AquaComms (AEConnect) will use the same design/locations.

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