- Google Fiber wants to stay ahead of the evolution of PON technologies
- In China, operators skipped 25G PON and are already working with 50G PON
- But 50G PON has some issues that make it difficult to offer symmetrical speeds
Google Fiber (GFiber) Labs trialed 50 Gbps PON over its live network in Kansas City, using Nokia’s Lightspan fiber access platform.
Liz Hsu, senior director of Products & Billing with GFiber, told Fierce Network via email, “The 50 Gig test was done in a central office (or hut), but used our actual outside plant (traffic left the hut, came back into the hut).”
Asked what GFiber’s roadmap is for 50G PON, Hsu said this test is just the first step to start getting familiar with 50G and how it will coexist with other PON on its network. “This technology doesn’t just support faster in-home internet speeds, it will also allow ISPs to densify their networks, supporting more traffic across the entire network and allowing for more seamless response to spikes in demand or stress on the network. In the future, we may consider building new markets with 50G PON technology,” Hsu said.
The 50G PON trial follows on GFiber’s announcement in October 2023 that it was rolling out 25G to select residential and business customers.
In this week’s announcement, Nokia said, “Some operators currently deploying 25G PON include Google Fiber, EPB, Vodafone Qatar and OGI.”
For its part, Nokia is touting the latest 50G PON trial as a future upgrade path for its fiber broadband operator customers who are already using its 25G PON products.
But according to Jeff Heynen, VP of Broadband Access and Home Networking at Dell’Oro, not all operators in the world are following the same fiber upgrade paths. He said 50G in China already “has a head of steam because that’s what the Chinese vendors are pushing.” He said operators in China skipped 25G and moved directly from 10G to 50G.
In fact, Huawei made a splash at Mobile World Congress in February 2023 when it launched a 50G prototype targeted to enterprise customers who want to build Wi-Fi 7 campus networks.
50G non-symmetric
Unfortunately, the 50G trial between GFiber and Nokia did not provide symmetrical speeds.
Heynen said symmetrical gets tough at the 50G level because wavelengths sit closer to each other on the spectrum band, and there’s a need for digital signal processors (DSPs) to keep the uplink separate from the downlink. “That’s new and still going through tests, and some of the architectures are still being ratified,” said Heynen.
Stefaan Vanhastel, vice president of Marketing & Innovation at Nokia Fixed Networks, said, “The transmitters/receivers for 50G upstream are more complicated than for 50G downstream and not available yet.”
He said that transmitters and receivers for 50G upstream are only allowed to transmit each in turn in specific micro time slots. The transmitters need to be able to transmit at very high speeds, but also be able to start and stop transmitting quickly at the beginning and ending of their time slot.
“These ‘burst mode’ transmitters/receivers are non-trivial for 50G and still being developed,” said Vanhastel. “In the downstream direction, you are transmitting continuously, rather than in bursts – so the challenge was easier.”
Non-symmetric is not ideal, for sure. “Certainly, operators’ preference is to have a symmetric connection,” said Heynen. “It’s almost going to be a prerequisite, whether customers need it or not.”
Vanhastel said there are different views on how to implement 50G symmetrical in the International Telecommunication Union (ITU) standard, which has resulted in two different options. “This might fragment the market, and delay economies of scale (and lower cost points),” he said. “Keep in mind that 50G is more complex than previous generations of PON technology, simply because we are pushing the boundaries of physics with each new generation. As an industry, we need to work through these challenges.”
Asked how the Chinese vendors are dealing with this problem, Heynen said, “They’ve been developing DSP and shown proof of concepts. I guess you could say they have a bit of a head start.”
Do people need 50G?
Although 50G is the ITU’s next step function for PON technology, Heynen said it likely won’t see major uptake until 2029 or 2030 and into the following decade.
Nokia is more optimistic. Vanhastel said, “We expect limited early adoption in 2025, and more widespread adoption starting 2026-27.”
GFiber’s Hsu said, “This type of technology will allow for new uses we haven’t even imagined yet. As we continue to see growth in AI and quantum computing, the next generation of internet needs to be ready to keep up with whatever customers are ready for next.”
Of course, that explanation sounds a lot like the “build it, and they will come” arguments for 5G wireless. And we’ve all seen how that’s turned out.
Heynen said, “There’s a question as to whether end customers really need that bandwidth.” He said perhaps it will be important for certain use cases such as high-volume stock trading where milliseconds are critical. He thinks it will definitely be adopted first by businesses before it gets deployed widely for residential broadband. Even in China, 50G is being targeted for business services.
In fact, Huawei launched its 50G prototype for Wi-Fi 7 campus networks, and that use case could propel 50G in other countries as well.
Wi-Fi 7 theoretically supports throughput of 40 Gbps. And even though a single device might not need that amount of throughput, Wi-Fi 7 – in conjunction with 50G PON – could support a large number of devices in a campus or business setting.
Nokia has a Beacon 24 Wi-Fi router that supports Wi-Fi 7, which has a total wireless throughput of 24Gbps. “Keep in mind that all PON technologies use a point-to-multipoint network, so that 50G is shared between multiple subscribers,” said Vanhastel. “Wi-Fi 7 should provide enough capacity for 25G or 50G deployments.”
