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.


This is the first in a two-part series of articles exploring XGS-PON vs. Active Ethernet. In this article, we will explore why operators must seriously consider ceasing the use of Active Ethernet in their new fiber deployments. The second article will discuss innovative solutions that will enable operators to leverage XGS-PON with any existing Active Ethernet network deployments, thus providing substantial power, space, and equipment cost savings.


We live in a world where most people are accustomed to the joys of broadband internet, whether it be talking to their TVs, doing group calls with people across the globe, or cultivating virtual lives in cloud-hosted video games where the shackles of reality are left behind. It is absurd to think that less than three decades ago, the World Wide Web was born! The transformational impact on culture, commerce, and technology born from the internet was nothing short of revolutionary! Gigabit speeds are rapidly becoming the norm today. While many contend that users don’t need Gigabit, everyone agrees that this next speed tier is what operators are leveraging to attract customers onto their new fiber networks - Gigabit speeds today with multi-gigabit speeds just around the corner!

While most internet early adopters leveraged ‘twisted copper pairs’ used for analog telephony as dial-up internet access mechanisms, the internet truly began its journey toward democratization with the emergence of “always-on” Digital Subscriber Lines (DSL). DSL became the de facto telco technology to bring internet to homes and businesses. While cable TV companies also began bringing internet access, telephony services, along with digital TV signals, over coaxial cable systems to their end-users.

A technology that began to emerge in the early 1980s was fiber optics. Fiber-optic communication benefited from low signal loss and very-high capacity, which translated to the possibility of transporting comparatively much larger amounts of information more reliably and with better quality over much greater distances. Unfortunately, the early expense of laying down fiber optics was prohibitive for most operators. As a result, many of the early builds were closely aligned with newly built premises, where the cost of laying fiber in the ground was largely eradicated. When the first scale Fiber-to-the-Home (FTTH) deployments began to emerge in the early 90s, Ethernet was modified to facilitate transmission over longer distance fiber optic cables, with the first deployments capable of delivering up to 100Mbps, at a time when those accessing the internet over copper lines or coax cables were receiving one-hundredth of that capacity. As technology progressed and the cost of fiber optic equipment plummeted, greater adoption of this approach continued. During the original Ethernet-over-Fiber approach became standardized as Active Ethernet. At the same time, innovative thinkers in British telecom proposed an approach that they believed could leverage the sharing of fiber cables across a larger number of users to help lower the deployment cost and accelerate deployment. This approach leveraged a concept called Passive Optical Networks (PON).


A PON is a fiber-optic network with a point-to-multipoint architecture. At its most basic level, a PON solution is comprised of a single strand of fiber optic cable, which the operator connects into its data equipment, often in a telecom exchange building. This equipment is referred to as an Optical Line Terminal (OLT). This cable then travels out towards the end-users, where it is then passed through a series of passive optical splitters. These splitters are pieces of glass that take the light signals coming in on the fiber cable coming from the OLT and spread that light across multiple other cables that travel onward to the end-user. Each of the cables that connect to the end-user, often referred to as the drop cable receives the same light signal data from the OLT. To ensure that users only receive the data signals meant for them, encryption scrambles the data so that only the equipment deployed at the end user’s premises can decipher the data meant for that user. Often referred to as the Optical Network Terminal (ONT) or the Optical Network Unit (ONU), several of these Optical Network Units (ONU) terminate the fiber from the splitters and constitute the user endpoints. The use of passive optical splitters that consume no power means that operators can utilize these components reliably out in the field to adapt the fiber network architecture to connect new locations that the fiber network can reach. With no active electronics deployed in the field, the robustness of these networks is significantly improved.


This solution enables the delivery of data from the single transmission point (the OLT) to multiple user endpoints, enabling service providers to save significantly on the amount of raw fiber needed to serve end subscribers, the space within the aggregation location or exchange building needed to manage all of the cables that connect to the end-users, and drastically reduce the size of the active equipment that transmits the data over the fiber network, along with the power and cooling demands of that equipment.


These PON fiber network architectures yielded other substantial cost and time to market-saving benefits in the field. With the PON network architecture, the number of fiber splices needed to build out a fiber network is significantly reduced, accelerating build time, and lowering costs. The added cost of a splitter is insignificant compared to the savings in raw fiber consumption and reduced fiber splicing, allowing for more efficient fiber deployment.


The power savings yielded from PON deployments vs. Active Ethernet point-to-point fiber deployments are extremely important for operators. With an ever-increasing focus from actors across society on climate change and the urgent need for both individuals and corporations to reduce their impact on the environment, operators can no longer choose to deploy a technological approach just because they have always done it that way. Operators must take control of the environmental impact of their business. They must stand accountable in their society, amongst their customers and peers. They must demonstrate proactive measures to reduce power consumption and get to a carbon neutral status to maintain parity with the larger operators in their market. They must also commit to strategies that will see them achieve a Net-Zero carbon status where they are on a path to reverse the environmental damage their company has caused historically. With an expected lifespan of at least 10 years for any active equipment placed in an operator’s network, it is vital that the architectural and technological selection choices mirror the 10-year environmental strategies of the business.


Active Ethernet is a fiber access technology built on a point-to-point fiber architecture, in which there is a direct connection between each OLT port and an ONU on the end of that fiber strand. In such a solution, an operator can deliver Gigabit speeds to every subscriber without being concerned with the use of a shared resource, as is the case with PON solutions.


A point-to-point architecture dictates that there needs to be an active port on the OLT allocated solely to that subscriber for every end subscriber. While this is great from a bandwidth allocation standpoint, providing certainty regarding the capacity from that port to the end-user can be challenging. This certainty of capacity is often cited as justification for continuing with point-to-point fiber deployments; however, this is a fallacy, as the Active Ethernet OLT equipment shares in a similar fashion to a passive PON splitter a finite amount of uplink capacity amongst all the users. It is not economical to provide dedicated uplink capacity from the OLT that matches the access capacity sold across all the end-users. Hence even in an Active Ethernet network, the capacities are shared.

From a fiber management perspective, point-to-point Active Ethernet can be a nightmare. Frequently consuming between 10 and 20 times the amount of cable handling space in central exchange buildings, cable ducts, and cable distribution cabinets in the field, point-to-point architectures drive real and substantial costs for operators.


A close look at the number of splice points needed will also point to inefficiencies of about 100% relative to the same needed for a PON solution – 128 splice points versus 66 splice points needed in a PON based solution. The greater the number of splice points, the greater are the number of points of failure.



PON arrived much later after few operators had already got their point-to-point deployments underway. Moving to a PON architecture proved very expensive at that time, especially given that in the early days of APON and BPON, PON as an approach versus a point-to-point solution was inferior. Even when Gigabit PON (GPON) first emerged with 2.5 Gbps downstream capacity and 1.25 Gbps upstream capacity, the choice was anything but clear for many operators. This was primarily attributed to the asymmetry associated with GPON and the issue of bandwidth sharing, which implied that guaranteeing gigabit service to a subscriber over a PON solution was difficult because the active port on an OLT was a shared resource between several subscribers.

In 2010, ITU-T introduced XGS-PON (G.9807.1) with 4x downstream (10 Gbps) and 8x upstream capacity (10Gbps) of GPON. ADTRAN was a major proponent of XGS-PON and had a strong influence on its standardization by ITU. Being a PON solution, XGS-PON benefited from the efficiencies of a point-to-multipoint architecture but enabled operators to assure Gigabit and multi-Gigabit speeds to end subscribers. Falling transceiver costs and the availability of multiple ONU chipset providers are making XGS-PON the technology of choice for many operators, as is indicated in the following forecast report presented by Omdia.


Advances in transceiver optical technology that enables simultaneous operation of GPON and XGS-PON on the same active port on an OLT also referred to as Combo PON, brings amazing flexibility in deployment scenarios for operators to further improve efficiencies in fiber optic deployment.


XGS-PON benefits from sufficient volumes that the associated transceiver cost has come down the cost curve far enough, enabling XGS-PON to be a credible and viable alternative to Active Ethernet electronics.


Comparatively, the options for an analogous a 10-Gigabit capable Active Ethernet solution isn’t very attractive, as 10-gigabit ONU suppliers are fewer in number, which renders the cost of ONUs to be exponentially higher, and expenses in electricity associated with having to support a larger number of active ports on the OLT are an order of magnitude higher.

The backdrop of the current and future costs of power and space are helping bring focus to the discussion. The rising need for marketers to have a multi-gig service offering to demonstrate the technical caliber of their networks is forcing the operators to do something new. Operators must either upgrade their Active Ethernet network to support 10GE or take the opportunity to move to a PON architecture and use symmetric XGS-PON.


Operators who want to avoid a rip-and-replace of old networks on Active Ethernet but want to jump over to PON can do so by using a coexistence element (CEx) module. The CEx module multiplexes the two signals as each operates on a different wavelength. The ability to multiplex light on a single fiber strand enables operators to make the most of their investment in fiber and leverage the highest returns through the versatility and capacity of XGS-PON.


We will learn more about this unique architecture in the next post. Stay tuned!

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.

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.