May 10, 2022
There’s no question XGS-PON has center stage for now, but a debate is raging in the telecom industry about what’s next for PON beyond 10-gig technology. Most are of the opinion that either 25-gig or 50-gig will win out, but Adtran has a different idea: wavelength overlays.
Ryan McCowan is Adtran’s CTO for the Americas. He told Fierce the question of what to do next is driven by three primary use cases, including residential, enterprise and mobile backhaul. As far as residential service is concerned, McCowan said he believes XGS-PON offers plenty of headroom to grow throughout the current decade, even in a world where 1-gig service becomes the norm rather than a premium tier. And even for most enterprise users he said XGS-PON likely has enough capacity to meet rising demand for 1-gig and 2-gig services. It’s when you look at enterprises that want a true 10-gig service and mobile backhaul that there’s an issue. That’s what’s driving the need to move forward.
It’s true 25-gig could help alleviate the pressure, he said. But moving to 25-gig to serve, for instance, two 10-gig mobile sectors would leave less room than before for other users like residential customers. “I don’t think it really solves that problem in a meaningful way because you can’t put enough small cells on a PON, particularly if you’re doing fronthaul, to make it worth your while, at least at 25 gigs,” he stated.
While 50-gig could be a solution in the longer term, McCowan argued most mobile operators and 10-gig-hungry enterprises will likely want some kind of dedicated connection anyway, like the wavelength services and dark fiber they get from long-haul transport providers. So, rather than trying to squeeze these users on a shared optical network, McCowan said operators could use wavelength overlays to get more from their existing infrastructure.
“In any case it’s using wavelengths that aren’t already being used by the PON,” he explained, adding these are generally in the high 1500 nm range. “There’s a lot of wavelength capacity on fiber and PON uses very little of it. One way that this has been standardized is there’s actually part of the NG-PON2 standard that talks about point-to-point wavelengths and it sets aside a wavelength band for those point-to-point services over the PON and treats that as a part of the standard.”
McCowan continued: “It seems like a better way to handle those really exceptional use cases versus trying to sort of put in an in-between PON standard in between 10-gig and 50-gig. If you look at some of the PON standards we’ve done over the last ten years, we’ve made that mistake before. XG-PON1 is kind of the poster child for that. It was more than residential needed, but it wasn’t symmetric so you really couldn’t use it for business or mobile backhaul.”
For the record, Adtran doesn’t offer wavelength overlay capabilities – at least not yet. McCowan said the company is working on developing the technology, though, and views it as a fairly near-term solution that will be accessible in the next 12 months or so. The CTO added it would allow operators to reuse much of the equipment they already have and would not require new optical network terminals or optical line terminals.
McCowan acknowledged he could be wrong about where things are headed, but concluded that based on the patterns in the network and what operators say they want to buy he just doesn’t “see 25-gig being the next mass market technology.”
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