The beauty of fiber broadband is in its potential to support huge bandwidth. Every new generation of fiber technology unlocks more of that potential. With the recent advances to 25G PON and 50G PON, there has been debate about which provides the best path beyond 10G. But that discussion is moot: it is not 25G or 50G, but 25G and 50G.
 
There have always been various flavors of PON technology, and all of them have been deployed successfully: EPON, GPON, XGS-PON, TWDM... Operators make a choice of technology for various reasons: cost, service focus, competition, business priorities, timing or usually a combination. No two markets are the same, no two operators are the same, and hence there is no one-size-fits-all fiber technology. 

The same holds true for 25G and 50G. Wavelength plans chosen by the standardization bodies enable them to co-exist on the same fiber, meaning there’s no technology lock-in. It is all about individual choices steered by economics and strategy. 

When choosing the right technology, operators are looking at three defining factors. Namely, there must be a business need, the technology should be timely, and the PON approach should come at the right cost.

Business need

Fiber broadband is extending its use beyond the residential segment, bringing new revenue streams over fiber networks. The new applications for IND 4.0 rely on high-speed connectivity to aid real-time processing of big data in the cloud, better decision making, automation, etc. For enterprises, 10 Gb/s is the gold standard and 25G and 50G PON can deliver that capacity and more, enabling a much more cost-effective and greener solution than dedicated point-to-point connectivity. 

Another near-term need to go beyond 10 Gb/s is 5G mobile transport. As 5G moves to the faster mmWave deployments, it will need new cell sites and additional transport capabilities for these sites. 5G densification will first happen in urban areas where FTTH networks already exist. Operators can leverage these fiber networks for efficient mobile transport, gaining cost and operational benefits. But the density of 5G cells in these areas, the higher number of connected devices, and the higher throughput per cell, will also demand more than XGS-PON can deliver, making the case for 25G and 50G PON.

Consumers, too, will eventually need more capacity as applications increase their bandwidth requirements. Sure, XGS-PON will serve us well for many years, so the timing of a move to a new technology will, to a large extent, depend first on the competitive position to which an operator aspires. Being at the front end of the bandwidth claim would favor 25G deployment; being later to the game allows operators to wait for 50G solutions.

Technology timing

The fundamental difference between 25G and 50G PON is timing. 25G PON is already mature and available, making it the only PON technology that can deliver >10 Gb/s broadband. It can also be added alongside GPON and XGS-PON on the same fiber assets. China’s Academy of Information and Communications Technology (CAICT) doesn’t expect to see significant deployments of 50G PON before 2029. This will drive the solution maturity from prototype to volumes that are needed to bring down costs. 

Technology cost

Cost is crucial in order to deploy broadband on a massive scale, and 25G PON has a head start as it leverages optical technologies and components from the world of data centers. The data center business is booming, of course, and 25G PON has benefited from the mature eco-system and huge volumes that achieve cost-efficiency. In addition, 25G is very easy to introduce on the hardware deployed for GPON and XGS-PON today, and can be managed the same way. 

50G has some work to do to catch up. 50G is the first generation of PON technology to need optical amplification and digital signal processing (DSP), which adds to the cost. To bring the cost down, DSP will be implemented on SOC (system on chip), and these will only reach cost-efficiency with volumes by the end of the decade. 

Every operator should evaluate if they can afford to wait for 50G PON or make the jump into 25G PON to address immediate opportunities. It is important to have different PON technologies because they help operators compete through unique commercial, business, technical, and operational imperatives. In a $10b market with hundreds of different broadband providers, there is a need for multiple evolution paths. 

That’s why 25G and 50G PON will both succeed. The difference is: 25G is now, 50G is the future.

You can learn more about both technologies in our white paper, The Future of PON.