Fiber network topology—the arrangement of connectivity components between the optical line terminal (OLT) and the customer’s optical network terminal (ONT)—is a critical factor in broadband deployment. In an interview with Fierce Network’s Linda Hardesty, Paul Hubbard, senior solutions architect for North America broadband at CommScope, explained that topology choices affect network flexibility, scalability, and long-term performance. Each OLT port typically serves 32 to 64 customers, and splitting signals efficiently is key to sustaining network quality while preparing for future growth.
Hubbard highlighted that most U.S. fiber networks, including early Fios deployments, use centralized architectures suited to urban and suburban environments. But as providers expand into rural and low-density areas, other topologies may be more appropriate. Selecting the right network design involves balancing cost, revenue potential, and physical layout, while ensuring the network can adapt to future changes, such as new premises or added services. Proper planning also considers competitive landscape and user expectations, with an emphasis on flexibility to deliver multiple service types efficiently. By carefully evaluating these factors, operators can maximize efficiency and ensure a positive return on investment for decades to come.
Linda Hardesty:
Hi everyone, I'm Linda Hardesty, chief analyst for Communications Technologies at Fierce Network, and I'm here today with Paul Hubbard, he's senior director of Solutions Architecture for North America Broadband at CommScope. Welcome, Paul.
Paul Hubbard:
Thank you. Thank you for having me today.
Linda Hardesty:
I wanted to ask a few questions and follow up to the recent Fierce Network research report that you and I worked on together, about fiber network topologies. And my first question is, can you explain to the audience what a fiber network topology is?
Paul Hubbard:
Yeah, sure. So, really a fiber topology is looking or concerned with the arrangement of the network connectivity items, which make up the outside plant environment. So, it's really between the connection between the OLT and the ONT located at the customer's premise. Each of the OLTs can service between 32 and 64 customers per port. So, we split that signal out in the network, and really where that splitting happens is what defines what a network topology is. And that splitting could happen either very close to the end customer or in more of a centralized location, and that really defines what those different architectures look like.
So, there's four different main architectures that we consider, these are PON architectures, both from a centralized, a distributed, a cascaded, and an optical tap network, they're just really concerned with where that splitting happens. Now, in general, the closer to the end customer that splitting happens, the lower the amount of fiber that's being utilized within that network. But it can have some negative impacts on network flexibility and scalability in the future as well.
Linda Hardesty:
Okay, that's a good summation of the basic network topologies. What is the most typical network topology?
Paul Hubbard:
Yeah, so fiber networks have been deployed in the US, particularly for over 20 years now, I think the original Fios network that Verizon performed back in 2004 was certainly based on a centralized architecture. And a lot of telcos have really followed that same model, and centralized architectures really have been the norm to date. But I would stress that networks that have been built in the US have predominantly been focused on urban and suburban environments, which really lends itself towards that centralized architecture. As we reach these new frontiers of deploying in more rural and lower density environments, that selection may change slightly, and that's really what the research paper goes into in detail.
Linda Hardesty:
Yeah, that's certainly a hot topic happening in the US right now, is closing the digital divide. And finally, what are the key considerations when selecting a topology?
Paul Hubbard:
Great question. Thank you, Linda. So, there's several considerations that need to be taken into account when selecting a topology. First of all, these networks are designed to last for multiple decades into the future, and as we all know, the environment will change. There'll be [inaudible 00:03:40], moves, and additional premises being built, so having a network which is able to scale and last for the longevity of that network is super critical. The other thing is really the combination of cost versus revenue, it's the business case. You need to really consider what does the existing landscape look like? What are the competitive threats? What are the offerings out there at the moment? So, canvassing the subscribers or the users that are intended to use this network can be critical. That can also lead to highlighting service level requirements, so there may be a lot of business type services required within that area.
So, the network topology should be selected to offer that flexibility to be able to deliver these different services to different types of users. And then, finally, the physical layout of the network as well. If we consider more of a suburban environment, which has lots of cul-de-sacs, that may drive to a certain network topology selection versus somewhere in a rural environment with a very longitudinal type layout, then there may be different selections there. So, really the architecture is a tool for you to be able to use and drive that efficiency within the network, and make sure the return on investment is positive.
Linda Hardesty:
Well, thank you so much, Paul, it's been awesome chatting with you and working with you on the report. And to our listeners, if this topic is of interest, I would encourage you to read the full report, which you can find under research reports at the top of the Fierce Network website. Thank you so much.