NBN Co has signed up Arris to upgrade the Optus and Telstra hybrid fibre-coaxial (HFC) networks.

In a $400 million deal announced this week, Arris will install new cable modem termination systems (CMTS) and upgrade approximately 230 exchanges across Sydney, Brisbane, and Melbourne.

Arris beat out rival telecommunications giant Cisco to sign the three-year agreement.

NBN Co paid billions of dollars for ongoing access to the HFC networks last year, and now intends to start connecting customers in March next year. Some pilot services will be ready in the fourth quarter of 2015.

Reports say the networks will be DOCSIS3.0, and there are no plans to upgrade to 3.1.

NBN Co is aiming to offer download speeds up to 100Mbps.

There is plenty of work to do to NBN build lead-ins for about a third of the 3.27 million premises passed by the networks.

Despite this, Communications Minister Malcolm Turnbull is confident that the bulk of the HFC network upgrades will be completed by the time of the next election.

Arris Asia-Pacific CTO Joshua Eum has told tech media outlets that ‘multi-technology mix’ model of the NBN would give HFC "a new lease of life".

“The issue with the HFC network is that it has been a dead man walking for the better half of half a decade, where investments have not flowed into the network itself; rather, it has gone to DSL and fibre-to-the-node technologies,” he said.