How we laid fibre in Sydney Harbour

This complex logistical endeavour is made that much harder when you add about 500 gigalitres of water (that’s 500, 000, 000, 000 litres!). Here’s how we ran fibre under Sydney’s Middle Harbour in March 2024.

Why the harbour?

Despite the logistical difficulties, we were committed to extend our fibre network through Middle Harbour to shore up the resilience of our network in Sydney. Having multiple pathways is key to providing a smooth connection for customers – if one pathway goes down, we have backups to keep you connected.

The plan

Running regular fibre cables on land is hard enough. To make a new connection, you usually start at a fibre pit. Then you can either blow the cables all the way through a pipe (called a conduit) using a high-power air compressor, or pull it through with a winch or manually by hand. Once the cable has reached the end of the conduit, it’s spliced into the rest of the fibre network in the pit on the other side.

In Middle Harbour, there wasn’t an existing conduit for us to use. Instead, we needed to directly bury the cable under a 600-metre stretch of water. This would prevent it moving and, once finished, blend into the landscape of the seafloor.

Wading through bureaucra-sea

Planning this took months of talks with the local council and government to get approvals for the project – ensuring we could provide customers with a stronger network whilst minimising disruptions to residents or wildlife.

In discussions with local authorities, they wanted to make sure there was minimal impact to the marine habitat. The shores around Middle Harbour are also a National Park, so we knew we had to make protecting these environments our top priority.

One such concern was how the installation might impact seagrass in the area. These grasses provide necessary shelter and sustenance for dozens of underwater faunae.

We hired a team of specialised divers, who assessed the area and found a path that was far enough away from the seagrass (the one time we don’t recommend touching grass). The path was also where other utility cables had previously been buried, so we knew this was the safest option.

We were also prepared to replant any seagrass that was disrupted, but thankfully it wasn’t necessary as the cable was laid out of the way of this important habitat.

From grass to glass

Now that we had our path planned out, we needed to pick a launch site. Despite being in a harbour, options for where we could launch the barge to lay the cable from were scarce.

One option was to bring boats all the way from Sydney Harbour, but this would be a time-consuming trip to transport all the people and equipment. We only had one day to roll the cable out, and if we missed our window, it would take a few more months of planning and preparation before we got another chance. Who knew fibre could be so dramatic!

Thankfully, the Harbourmaster of Middle Harbour let us use a nearby boat ramp instead. It was a little cramped while we used a crane to load a 5640kg cable drum onto the barge. After loading that on, we managed to squeeze in a team of barge operators, a team of divers, coordinators, and a drone pilot. We couldn’t complain though, as it was still a faster option.

The next problem was a recent storm, which had made the gradient from the shore to the harbour floor very steep. This ruled out traditional drilling; it wasn’t safe for our team and it could bend the fibre too much.

Instead, we used an air compressor to blow away the top level of sand to reveal the existing utility cables, leaving them unharmed. The dive team carefully laid the heavily armoured cable from the barge along the 600-metre-long stretch of the harbour floor. While regular fibre cables have some shielding, this cable needed extra protection as it was going directly into the ground instead of a protected conduit. It also helped weigh the cable down.

Burying the lead

Once the cable was in the trench, the dive team started filling it back in while our landlubber fibre techs began splicing the cable into the rest of the fibre network through a pit on the surface. While laying the cable with the barge took one day, refilling the trench took 12 more days to complete as we did it manually to ensure minimal damage to the cables and the natural habitat.

It was a huge effort from everyone involved. From planning to execution, the process took almost a year of patience and dedication from our intrepid fibre team.

If you’d like to learn more about our fibre network and where it reaches, click here to see our Network map.