Q&A: How an all-fibre diet could kill phone exchanges

BT

First fibre-only exchange goes live, and could change UK's network

BT has started trials for infrastructure changes that would mean some areas would be switched entirely to fibre - ending residents' reliance on copper.

If the company can move more towns - such as the pilot testbed of Deddington in Oxfordshire - to an all-fibre diet it could mark the end of the line for hundreds of exchanges built for a copper-based phone system.

According to BT, the trial should highlight the potential problems associated with enabling ISPs and other providers to offer their consumer services over fibre, with voice calls one potential challenge.

The benefit for BT, however, would be a fleet of exchange buildings that could be sold off, potentially paying for the network modernisation.

We spoke to BT project director Phil Allington to find out what the network changes mean to users, and to BT itself.

Q. What are the big changes in Deddington and how will they affect consumers?

A. The main advantages will be faster broadband speeds for customers, and we would expect the voice products to be of a higher quality as well, because fibre can carry a better signal. We can carry truer signals over a much long distance using fibre than with copper.

Q. Why Deddington - how does it fit into the plans?

A. We wanted a pilot where we could learn how this could work in the long term. The location was suitable because we wanted a small rural exchange so we didn't have huge numbers of customers involved, but also to give a good mix and use of services. Customers at Deddington aren't all BT customers, there are other providers with a mix of products. We've re-engineered the telephone network in the area for fibre, for a settled set of buildings.

Q. So the copper's been replaced?

A. We've started off by overlaying it, so we've used a lot of the existing ducts, and it has a good network with space to get the fibre through, which kept overheads down. The copper cables are still in place and services are still provided, but we're beginning to offer the new fibre services and what we want to learn is how customers use and migrate to those services.

Q. So is this an upgrade to equipment in the exchange as well?

A. Today, we have DSLAMS, MSLAMS or a multiplexer in the local exchange that performs the role of converting or communicating between a digital IP signal and the analogue signal that goes to the customer over the copper network. And that's currently in the local exchange. In Deddington, what we've done is go straight to the green street-side cabinets (the primary connection points in the network) that route the connection out to the community and provide the link to the exchange... we've fibred those cabinets and linked them back to a serving exchange further away from Deddington.

Q. Cutting the exchange out of the loop, then?

A. We now go back to a handover point on our core network at Banbury exchange, completely bypassing what would have been the MSLAM or DSLAM. The IP traffic is now carried right the way through to the customer. It's not converted at the local exchange so the role for broadband at the local exchange is completely removed. Deddington is served directly from Banbury and we built a spine that links to the cabinets in Deddington – it's about 14km. Current class C optics would allow that length to be anything up to 29km.

Q. It'd presumably be very expensive to run that sort of connection to every town or village in the UK?

A. That's one of the things we're hoping to learn – what the economics look like, as well as what services people want and how they would use them. Rather than try and do that in an office, it's better to do it practically, but yes it's expensive.

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