Stay up to date with all of ADTRAN's news, products and services with posts from the leaders in our industry.



Stay up to date with all of ADTRAN's news, products and services with posts from the leaders in our industry.


In prior blogs, we’ve explained what Combo PON is and discussed why deploying XGS-PON using Combo PON technology is better for a fiber network operator. Most fiber network operators now recognize its most basic benefit as a technology that empowers operators to enable both Gigabit Passive Optical Network (GPON) and Ten-Gigabit Symmetric Passive Optical Network (XGS-PON) on the same Optical Distribution Network (ODN) over a single, common OLT port. In this blog, I will focus on the power of PON coexistence using Combo PON and how it enables operators to extend the lifespan of their fiber infrastructure, specifically looking at when GPON can be expected to have fulfilled its useful life.

First, we have attempted to construct a predictive model to help determine when a GPON port will become a bottleneck for Gigabit broadband consumption. Federal Communications Commission (FCC) has defined three user types in its Household Broadband Guide. Similar to these guidelines, we have constructed the following model with four user types – Super Users, Heavy Users, Regular Users, and Low Users. The average measured Busy Hour Offered Load (BHOL) used in this model is 4.75Mbps with an expected CAGR of 30-50%. 4.75Mbps BHOL is based on measured industry wide data usage estimates.

Using a conservative growth rate in BHOL of 30%, we can predict the useable lifetime of a GPON port to the point that it becomes impossible to reliably deliver 1Gbps speed to a subscriber thus risking expensive contact center inquiries. Reminder that a GPON port supports an aggregate 2.5Gbps downstream and 1.25Gbps upstream. The charts below show that at a 1x32 split and a 1x64 split, GPON will have less than 1Gbps headroom by 2028 and 2026 respectively, making it impossible to deliver reliably 1Gbps in busy hour – which is when it is most needed! With such limited lifespan, greenfield deployments built using GPON will struggle to deliver normal payback of 8-10 years before needing to be upgraded to XGS-PON.

GPON Capacity

So, the big question – is how do you extend the lifespan of GPON? The answer – Combo PON! The solution lies in the power of coexistence and the underlying technology that builds coexistence into the transceiver.

Combo PON

Combo PON enables operators to deploy GPON and XGS-PON simultaneously off a single active port. The resulting architecture allows for interesting scenarios in segregating the heavy, moderate, and light users by appropriate PON technology. For instance, if we put all heavy and top half of the moderate users on XGS-PON and leave the remaining on GPON we notice that the lifespan of GPON technology in such a deployment increases by 2-3 years.

Low Usage Subs (GPON)High Usgae (XGS-PON)

Put in perspective, GPON technology, if deployed natively will become a bottleneck for Gigabit services in 5 years on a 1x64 split, but the same will survive 2-3 years longer if deployed over Combo PON technology through suitable allocation of PON resources based on broadband needs. This equates to an 40% increase in the lifespan of GPON.

Low Usage Subs (GPON)High Usgae (XGS-PON)

One might make the case that an integrated coexistence element isn’t necessary to see benefits of lifespan extensions. While true, the advantage of using a single active device or module that accepts a Combo PON transceiver is many folds as shown below. These benefits are relative to a disaggregated GPON and XGS-PON solution combined with an external coexistence module.

  • Price point of GPON – Capacity of XGSPON
    • Operators can begin deployment with GPON but have built-in capacity to migrate to XGS-PON anytime with little effort
  • 20% greater service coverage
    • An external coexistence element takes additional dBs hits that limits the distance at which subscribers can be supported
  • 66% less energy
    • A single-device solution uses half the power of a two-device solution
  • 75% less equipment space
    • A single device solution uses about 75% less space than two device solutions with an external coexistence module

In summary, coexistence with Combo PON provides tremendous flexibility in deployment scenarios that enables operators to start with a combination of GPON and XGS-PON and extend the life of their underlying infrastructure by suitably allocating resources to users based on broadband usage, thereby reducing the associated depreciation expenses and upgrade costs. Combined with the power, space, cost and service reach benefits afforded by the built-in multiplexing functionality in the PON transceiver, Combo PON makes for a fantastic choice for many small city and regional service providers looking to make the most of their fiber network investments.

Since ADTRAN pioneered XGS-PON, there has been an ongoing industry debate regarding when and where a FTTH network operator should employ fiber broadband services using GPON versus XGS-PON standards. The availability of Combo PON capabilities built into second-generation XGS-PON solutions concludes the debate, as an operator can now leverage both FTTH standards without sacrificing in terms of cost or capability.

OK. You aren’t quite sure about the choice between Gigabit Passive Optical Network (GPON) and Ten Gigabit Symmetric Passive Optical Network (XGS-PON) to power your optical distribution network (ODN).

Let’s face it. The difference in the cost for a GPON based Optical Networking Unit (ONU) and an XGS-PON based ONU can be large enough, especially that when scaled to 100,000 subscribers or more, to tilt you to favor deploying your access network with GPON.

Many operators, though, look beyond the 20-30% increased cost of XGS-PON electronics over GPON and compare the overall cost to connect a FTTH subscriber. With the ONU making up a small portion of the overall connection cost, the cost adder for using XGS-PON over GPON ranges most of the time between 2 and 3%. So, is the extra cost delta justifiable?

In case you missed it, NBN Co announced that it has become the first Australian commercial network operator to join the Silicon Valley-based Open Networking Foundation (ONF). Why does this matter? According to NBN, this important investment “puts its vendors on notice that it is keen to explore the cost savings of open source network technologies.” As more operators around the world adopt this philosophical and business mindset, open ecosystems are sure to be the future of global networking.

As a valued strategic partner of NBN Co, ADTRAN welcomes the decision to join us in the ONF, which is focused on delivering open, disaggregated architectures and disrupting the status quo in the access network. This open architecture approach enables service providers to have the freedom to choose a variety of elements and control the introduction and rollout of new customer applications and broadband technologies, which helps eliminate costs and improve efficiencies.

FTTH subscriber connection costs and capabilities have evolved considerably in the last 15 years. Fiber installation techniques such as micro trenching and public-private partnerships leveraging existing right of ways and improved regulatory policies have all helped to reduce FTTH construction costs. Innovations in fiber optics and improvements in fiber connection and distribution methods have reduced the cost to connect an FTTH subscriber from several thousands of dollars per home to as low as a few hundred dollars today. PON technology innovation, Moore’s Law, and economies of scale have greatly increased capabilities while at the same time reducing the cost of an FTTH connection. The days of $500 ONTs and optics connected to expensive two-port OLTs have given way to $50 ONTs and high-density 16-port OLTs. Fiber access nodes have evolved from supporting dozens of 30Mbps residential services to supporting thousands of 100Mbps and Gigabit residential and business services – all on a single access node. It should be noted that this decade worth of increased FTTH service differentiation or utility has all occurred using Gigabit PON (GPON) and Ethernet PON (EPON) technology paired with innovations in the cost and scale of Ethernet switching, electronics packaging, and pluggable or integrated fiber optics. So how much further can we improve the business case for fiber and how will that occur? Will additional small steps in ONT cost improvement or higher density OLTs be enough to persuade broadband service providers operating within broadband underserved areas to deploy more FTTH or will a bigger step in innovation be required to spur further investment?

With that fascinating question, Jeremy Harris, ADTRAN Director of Subscriber Solutions and Experience, kicked off an insightful Light Reading radio show on "Virtualizing the Subscriber Experience."


In the battle for the broadband customer, service providers are beginning to recognize that marketing "speed" alone will not help them win customers. As outlined in part 1 of this blog, service providers need to understand innovation dimensions and double-down on efforts to impact the "subscriber experience" to effectively compete for subscribers' wallet-share. So where do you start?


Historic $2 Billion CAF II Auction Will Provide Broadband Expansion Funding

The FCC is in the middle of planning a historic broadband funding opportunity. This initiative will provide as much as $2 billion in funding for broadband carriers who elect to bring broadband services to unserved and underserved areas of the country. Hailing myself from rural Kentucky, I am especially eager to see the benefits realized from these communities being broadband-enabled, just like those hailing from other densely populated communities. "Closing the digital divide is my number one priority, and through this innovative Connect America Fund auction, we are poised to take the next big step in reaching that goal," said FCC Chairman Ajit Pai in a press release announcing the auction. "In rural America, broadband opens the doors of opportunity by connecting remote communities to global markets, jobs, education, health care and information."

Operators selected from these auctions will be required to deliver 10/1 Mbps broadband to thousands of census blocks across the country. These are high-cost areas, and winning broadband providers agree to build broadband facilities at the lowest cost, among all the bidders. Winning bidders must also offer at least one voice and one broadband service. Service fees must be reasonably comparable to similar offerings in urban areas.

History has shown how potential becomes artificially restricted with the presence of imbalance. The world we live in is forever evolving, with the old being replaced by the new.

Production and distribution models are being flipped on their heads, while the marriage of creation and consumption is being blown apart. The access networks that underpin much of this change will themselves be permanently altered by it. The good news is next generation platforms have the potential to capitalize on this new reality and shift the balance back in favor of their owners.

Symmetry: The Dominant Design in Evolution

Before we detail how symmetry can disrupt the telco industry, let’s take a closer look at its beginnings and how it’s disrupting other industries.

As availability of Gigabit services increases across cities and communities nationwide, over 50 million (18%) Americans now have access to Gigabit services. With cable MSOs and telcos expanding coverage, it’s becoming common to see multiple Gigabit providers and, as a result, broadband speeds are becoming less of a competitive differentiator. So how can service providers innovate to win in this highly competitive broadband battle?

In a recent USTelecom webinar, Jeremy Harris, ADTRAN Director of Subscriber Experience Solutions, pointed to a powerful analogy about innovation in the Audio Industry taken from The Harvard Business Review’s article on Technology Innovation. While the Audio industry was focused on delivering higher audio quality (Super Audio CD vs. DVD Audio), MP3s revolutionized the music industry by focusing on music portability and file sharing, at a lower audio quality.

by: Dieter Kortmann, Director, Partner Management Europe and Harald Bock, VP, Network & Technology Strategy

Broadband fixed and mobile network operators can’t compromise. They must be able to scale quickly to meet capacity demands for new services and applications. They must escalate operations to run mobile, residential, and enterprise on the same infrastructure to address the evolving requirements of IoT and cloud computing. But how do they meet these demands while reducing space, power, and footprint? Coriant and ADTRAN are committed to delivering best-of-breed open, programmable, and scalable solutions. Merging highly scalable CORD-based physical layer agnostic SD-Access architectures with high performance, low power 100G+ aggregation and transport affords our customers cost-effective rapid service innovation while providing the highest QoE and optimal service choices for subscribers.

Earlier this month, the SDN use case for broadband access progressed further within the open networking consortiums. AT&T submitted the first version of Virtual Optical Line Termination Hardware Abstraction (VOLTHA) software-defined access (SD-Access) specification into the Open Networking Foundation (ONF). VOLTHA provides a framework to support broadband access in the cloud, pairing nicely with the Central Office Rearchitected as a Datacenter (CORD) initiative. Regarding CORD, it was AT&T, again, and other forward thinking service providers that partnered with ON.Labs several years ago to develop the architecture. The goal of CORD is to provide a reference architecture for SD-Access evaluation platforms for field trial on commercial operator networks. It should be noted that ON.Labs was folded into ONF around a year ago, so CORD, VOLTHA and (Open Networking Operating System) ONOS all fall under the purview of the ONF.