Making optical networking feel like cycling downhill

BT’s chief architect, Neil McRae, is a fervent believer in the internet, a technology built on the continual progress of optical networking. He discussed both topics during his invited talk at the recent OFC 2021 virtual conference and exhibition.

Neil McRae’s advocacy of the internet as an educational tool for individuals from disadvantaged backgrounds stems from his childhood experiences.

Neil McRae

“When I was a kid, I lived in a deprived area and the only thing that I could do was go to the library,” says McRae, chief architect and managing director for architecture and technology strategy at BT.

His first thought on discovering the internet was just how much there was to read.

“If I’m honest, everything I’ve learnt in technology has been pretty much self-taught,” says McRae.

This is why he so values the internet. It has given him a career where he has travelled widely and worked with talented and creative people.

“Anyone who is out there in the world can do the same thing,” he says. “I strongly believe that the internet brings opportunities to people who are willing to spend the time to learn.”

Optical networking

McRae surveyed the last 20 years of optical networking in his OFC talk. He chose the period since it was only at the end of the last century that the internet started to have a global impact.

“The investment in networking [during this period] has been orders of magnitude bigger than prior years,” says McRae. “There has also been a lot of deregulation across the world, more telecoms companies, more vendors and ultimately more people getting connected.”

In 2000, networks used the SONET/SDH protocol and fixed wavelengths. “We have brought in many new technologies - coherent, coloured optics, programable lasers and silicon photonics - and they have been responsible for pretty significant changes.”

McRae likens optical network to gears on a bike. “It powers the rest of what we do in the network and without those advances, we wouldn’t be the digitally connected society we are today,” says McRae. “If I think about the pandemic of the last year, can you imagine what the pandemic would have been like if it had happened in the year 2000?”

McRae says he spends a fifth of his time on optical networking. This is more than previously due to the relentless growth in network bandwidth.

“Ultimately, if you get optical wrong, it feels like you are in the wrong gear cycling uphill,” says McRae. “If you get it right, you are in the right gear, you are going as fast as you can go and it feels like a downhill ride.”

And it’s not just bandwidth but also from a cost, capability and customer experience perspective. “We recognise the value that it brings to all the other layers right up to the application,” he says.

Research 

BT Labs has an optical networking programme that is run by Professor Andrew Lord. The programme’s remit is to help BT address existing and future issues.

“There is a longer-term research aspect to what Andrew and his team do, but there are some here-and-now issues that they support me on like the hollow-core fibre work and some of the 400-gigabit [coherent] platforms we have been reviewing recently,” he says.

He cites as examples the work the programme did for BT’s next-generation optical platform that was designed for growth and which indeed has grown massively in the last decade. “We have launched optical services as a product because of the platform,” says McRae.

The programme has also helped Openreach, BT Group’s copper and fibre plant subsidiary, with its fibre-to-the-premise (FTTP) deployments that use such technologies as GPON and XGS-PON.

Reliable, dynamic, secure networks

McRae admits he is always nervous about predicting the future. But he is confident 400 gigabits will be a significant optical development over the next decade.

This includes inside the data centre, driven by servers, and in the network including long haul.

“The challenge will be around getting the volume and interoperability as quickly as we possibly can,” says McRae.

The other big opportunity is the increased integration of IP and optical using a control plane aligned to both.

“The biggest networking technology out there is IP,” says McRae. "And that will not change in the coming decade."

The Layer-3 capabilities include working around issues but it is bad at managing bandwidth. Optical is the opposite: great at managing bandwidth but less dynamic for working around problems. Merging the two promises significant benefits.

This idea, advocated as IP-over-DWDM, has long been spoken of but has not been deployed widely. The advent of 400-gigabit coherent implemented using client-side modules means that the line-side interface density can equal that of the host. And other developments such as software-defined networking and artificial intelligence also help.

Software-defined networking will make a big difference because it will enable the move to automation and that will enable new technologies such as artificial networking (AI) and machine-learning to be introduced.

McRae talks of a control plane capable of deciding which interface to send packets down and also determine what paths to create across the optical infrastructure.

“We have seen some of that but we have not seen enough,” says McRae. AI and machine-learning technologies will provide networks with almost autonomous control over which paths to use and enable for the various traffic types the network sees.

McRae stresses that it is getting harder to get the maximum out of the network: “If we maintain human intervention, the network will never see its full potential because of complexity, demands and scale.” 

He predicts that once the human component is taken out of the network, some of the silos between the different layers will be removed. Indeed, he believes networks built by AI and aided by automation will look very different to today’s networks.

Another technology McRae highlights is hollow-core fibre which BT Labs has been researching.

“Increasingly, we are starting to reach some limits although many folks have said that before, but hollow-core fibre gives us some interesting and exciting opportunities around latency and the total use of a fibre,” says McRae.

There are still challenges to be overcome such as manufacturing the fibre at scale but he sees a path in many parts of the network where hollow-core fibre could be valuable to BT.

Quantum key distribution (QKD) and the importance of network security is another area starting to gain momentum.

“We have gone from a world where people were scared to send an email rather than a fax to one where the network is controlling mission-critical use cases,” says McRae. “The more secure and reliable we make those networks, the more it will help us in our everyday lives.”

McRae believes this is the decade where the underlying optical network capability coupled with QKD security will take effect.

Making a difference

McRae has run several events involving children with autism although during the pandemic this has not happened. He uses gaming as a way to demonstrate how electronics works - switching things on and off - and then he introduces the concept of computer programming.

“I find that kids with autism get it really quickly” he says. BT runs such events two or three times a year.

McRae also works with children who are learning to program but find it difficult. “Again, it is something self-taught for me,” he says although he quips that the challenge he has is that he teaches them bad programming habits.

“I’m keen to find the next generation of fantastic engineers; covid has shown us that we need them more than ever,” he says.