PON Technology: What Lies Ahead and How Will It Evolve?

Last year, Broadband Forum hosted the “Future of PON Technology Update” vBASe webinar, focused on the emerging technologies set to revolutionize the passive optical network (PON) market as well as the evolution and changing trends ahead for the worldwide deployment of gigabit technology. This feature highlights key research results, a history of PON, use cases, and a preview of the emerging technologies as discussed in that webinar.

As ongoing demand for full fiber access and connectivity inside the home continues to heighten, a seamless customer experience becomes more critical than ever. A key piece of the puzzle is how networks can continue to evolve, grow, and develop to keep up with demand and at pace.

Over the past two years, there has been a significant shift in broadband traffic. For the first time, the traffic growth rate for fixed networks has exceeded that for mobile. Fixed network traffic has grown by 42% worldwide throughout 2020, including emerging countries – a substantially higher growth than forecast before the pandemic.

While many mobile operators may argue that the introduction of 5G nationwide rollouts will buck this trend, what is most relevant is that whether you are using a mobile device or WiFi-enabled device when in the home or the office, most developed countries depend on the fixed broadband network to transport this traffic. The transport of 5G and fixed traffic will depend on the fiber access network. Progressively this will become a PON.

The history of PON

Since the insertion of PON into the telecom world in 1993, it has developed, changed, and morphed to keep up with demand and expectation, and this pattern is very likely to continue. In the early 1990s PONs provided a maximum shared bandwidth of 54 Mbps, which was sufficient at the time to support Plain Old Telephone Service (POTS) and Integrated Services Digital Network (ISDN) interfaces. We have come a long way since then and so has PON – regularly adapting to meet the ever-increasing demand for bandwidth. This evolution has resulted in the industry introducing several generations of PON over the years. The next generation of PON is likely to look very different as the call for fiber technology is growing, faster than ever, and we will likely see a critical change in its overall usage.

The driver of these substantial changes is the demand for superfast fiber networks; government broadband targets, requirements for 5G backhaul, and increased use of the fixed network as a result of the Covid pandemic are all factors. PON is playing a significant role in this expansion due to rapidly growing PON deployments.

Latest PON developments

The next phase for PON will be to facilitate a new wave of innovative applications. Gigabit Passive Optical Network (GPON) is considered a legacy technology that is now being replaced by 10 Gigabit Symmetrical PON (XGS-PON) deployments in some areas. XGS-PON will play an even greater role as network capacity requirements grow exponentially. Therefore, the industry will start to see a strong emphasis on supporting the global shift from GPON to XGS-PON; this focus is supported by the fact that XGS-PON is seeing increased telco investment.

The speed of XGS-PON deployment was initially seen in new fiber rollouts where it made business sense to deploy PON technologies that will meet consumer broadband demands for the next 5 to 10 years. In addition, XGS-PON is increasingly being deployed in existing “brownfield” deployments to coexist with any existing GPON services. This is especially true in high-density urban areas as well as meeting the increasing demand for gigabit-plus business services across the shared fiber infrastructure. Service providers such as CityFibre (UK), AT&T (USA), and Chorus (New Zealand) have demonstrated the business and use case for such investments in XGS-PON.   

In the years ahead

As with all technology, it is very unlikely to stop at XGS-PON. In the years ahead, there will be a predicted shift towards even higher capacity PON technology, with 25G/50G EPON set to make its debut this year. As it stands, 10G-PON will still be the standard for residential fiber-to-the-home connectivity for the next decade, with 25G or 50G PON becoming widely used for enterprises with higher bandwidth requirements.

The need for future specification coexistence is an emerging debate in the industry, and it is to become an important feature for the future evolution of PON technology, helping to facilitate the development of emerging industry standards. Essentially operators need to design the most expensive part of any fiber broadband service, the physical optical distribution network, to ensure a single fiber build, whatever technologies you currently or plan to deploy.  

Handling increased traffic

PON coexistence is seen as the most beneficial method for turning away from outdated technologies when they’re no longer viable solutions. However, the truth of this is dependent on the operator’s use case, as the solution wouldn’t be applicable to residential and smaller capacity connectivity.

The growth rates for fixed and mobile will ultimately converge, with fixed access growth overtaking that of mobile by 2025 according to Analysys Mason. The market research firm predicts that there might be slower fixed traffic growth in the short term as the effects of lockdowns continue to diminish. As in years past, access networks and the operators who run them are tasked with coping with this enormous growth in traffic. As the requirement for continuous fiber-based connectivity continues to grow, so too does the need for cost-effective and speed-efficient PON technology.

The future 'multi-service' PON network and technology choices

Speaking with many network operators, large and small, the future goal of the fiber access network and hence, PON investment is to build one converged network that becomes truly multi-service. One that supports residential, smart cities, IoT, business, and mobile xHaul requirements.

This means that speed and network capacity become just one criterion when choosing an investment roadmap in future technologies. Security, latency, delay, resilience, and virtualization of network functions will all have an impact on technology investment decisions.

There will be many different network and target customer requirements across any particular multi-service fiber access network. These different requirements will drive a variety of PON network deployments. Variables include the choice of technology and the timeframes and possible multi-staged investment decisions, from GPON and XGS-PON to 25G/50G/100G enabled networks.

Next steps

PON standardization efforts have focused largely on defining highly cost-effective systems for the mass market and thus promoting high-volume deployment of fiber broadband infrastructure. Now that this goal has been achieved in many areas, the task for standards makers now becomes how to broaden the applications of PON to increase its use and value. Organizations such as ITU-T, ETSI, and Broadband Forum are all working towards this goal.

Because of such efforts, we can look forward to a time where technology advances enable fiber to go beyond the residential segment to connect enterprises, 5G cells, and smart cities and support Industry 4.0. Expect the industry to come together through these organizations to drive efforts to enhance PON interoperability, management architectures, home connectivity, and other areas relevant for getting more value from PON networks.

Frank Effenberger is rapporteur of ITU-T Q2/15 and Ana Pesovic is Marketing Director at Nokia.