Telecom operators are eager to update their vast under-tapped pool of fiber connectivity resources to help power – and profit from – long-haul data center connectivity needs, but real-world challenges remain a significant hurdle toward driving high-tech updates into those sprawling systems.

That challenge was central to a carrier-led panel discussion at the recent OFC event, where network leaders were basically pleading for answers to bolster those networks to meet surging AI-fueled connectivity demands.

Jeff Mundt, senior director for optical transport planning at Verizon, highlighted three significant challenges and questions that the carrier – and the industry more broadly – are looking for help with.

The first is the ability to “squeeze” the most out of current fiber deployments. Mundt explained that Verizon’s extensive fiber footprint has been built on decades of consolidation that has resulted in an accumulation of assets dating back more than 40 years, much of which was deployed at a time when no one had any inkling of what would be needed decades down the road.

“That was direct-buried fiber. It was like we’ll never need more than 24 pair fiber … it's along railroad track and there is no extra conduit there. There is no micro ducts. There is no way for me to add extra fiber. I'm stuck with the fiber that I've got. I either have to lease it, or I've got to go build something new,” Mundt explained. “So my challenge is, how do I squeeze the most out of that fiber?”

Some work is happening in terms of adding new frequency bands to those installed fiber assets, but that comes with added complexity in dealing with the intricacies of those specific bands.

Mundt also noted growing interest in hollow-core fiber (HCF), which is where only a minor portion of the optical power propagates in the solid fiber material (or very little light travels through the solid part of the fiber).

Tests have shown a significant performance gain from such technology but durability concerns cloud real-world use.

“Between our labs, we've got some hollow-core fiber that we play with, but it's got great advantages: low latency, low loss, low dispersion, non-linearities aren't as big an issue, you can launch at a higher power, so a lot of positives with hollow-core fiber,” Mundt said. “So I'm really looking forward to when we can live in that world, but it's like 350-times as expensive. I can't afford to turn up hollow-core fiber. It doesn't package as dense. It is fragile. I literally have a one-kilometer link, and one of our hollow-core fibers is cracked already. … It seems to be fragile. There's issues with splicing it. So we need to overcome those negatives.”

Is multirail the answer?

That density issue was also core to Mundt’s third challenge around the use of multirail inline amplifiers. These platforms have started to gain steam from vendors, with the pitch being that such platform allow for denser packing of inline fiber amplifiers that are typically placed along the running length of a fiber deployment.

Cisco, Nokia, and Fujitsu’s 1Finity were among vendors that have recently unveiled multirail systems and support, each touting the density benefits of such systems.

Mundt explained that many current inline amplifiers are placed in those previously discussed “little eight-by-24 hut by the side of the railroad tracks” tying together fiber deployments that began decades ago. Mundt noted that while Verizon is indeed interested in multirail technology, the carrier has real-world “asks” of the vendor community tied to the size of such platforms.

“There are some practical questions here of how many lines or rails per rack can I put in, and what's the power and cooling that that's going to be required?” Mundt asked. “And a practical question that we're facing is, if I'm looking at a new fiber build right now, how much land do I buy at all of these ILA (inline amplifier) sites? Am I building and or buying an acre? My real estate team needs to go acquire an acre, because I can plan on putting two shelters and two generators there, or am I going to have to have 10 shelters there for all of these ILAs?”

This density potential has become a central talking point from vendors, with Nokia claiming its multirail platform has a density advantage over rivals.

“This will be the most dense solution in industry,” Rob Shore, head of optical network solutions marketing at Nokia, said during an OFC presentation. “You've probably heard some of our competitors out there talking about their version of this solution. They're getting 128 ILAs (inline amplifiers) per rack. We're getting 160 ILAs per rack. … When this comes out at the end of the year, this will be the highest density solution, about 25% more dense than any other solution that will exist in that time frame.”

For Mundt, the backing of those claims is a significant financial and logistical question.

“It's a very simple math: how many rails can I get into a rack? How many racks can fit into one of these shelters? Can I power it? Can I cool that? How many shelters do I need to set on ground for that?” Mundt said. “Am I buying one acre? Am I buying five acres? Am I buying 10 acres? And how much power do I need to go get the power company to deliver to the middle of a cornfield in the middle of nowhere, which is where ILAs typically land. So that's a big question for us.”