The term “last mile” typically evokes images of exhausted marathon runners somehow finding their second wind to stumble across the finish line. It’s the last expulsion of energy required to finish the race, and while the elite can do it, others slow to a walk or crawl — if they don’t completely stop altogether.
When we talk the last mile in an internet sense, we’re referring to the final rollout of infrastructure from the point-of-presence to the end user. But instead of exhaustion, network providers face great cost when extending fiber to its final destination. So, it’s often existing copper cables that are used to complete the journey. Other network providers may finish the job with a mobile network or even satellite technologies, which cater to many users at once wirelessly, but can suffer speed and capacity degradation when many users connect at once or have propagation interference.
Last mile fiber access was once considered a luxury, not a necessity. However, the move to work from home, remote learning, telehealth and streaming entertainment marked a swift and sudden shift in networking requirements far beyond the capabilities that copper and mobile networks could deliver consistently. Latency-sensitive content was being created at the edge, which was now everywhere and required across residential and mobile networks more than ever. Suddenly, fiber access at the end of the last mile became critical, yet the conundrum remained: for many network providers, fiber to all simply didn’t make economic sense.
But what if we could take the capacity inherent in fiber optics and make it a one-to-many proposition? The last mile doesn’t seem so arduous now; it’s almost as if a shortcut has been found.
It’s why network providers are looking at passive optical networking (PON) as the shot of adrenaline they need to burst through the finish line.
Desperately needing PON
PON isn’t new; in short, it’s an architecture in which a single optical wavelength can be split using passive fiber-optic splitters to serve multiple end users in a cost-effective manner. In plain terms, the technology makes it possible for a single fiber-optic cable to provide very-high-speed broadband access to multiple users.
Due to surges in IP television (IPTV) and high-speed internet access, PON has become increasingly more popular as a last-mile option, particularly with 15-year-old Ethernet PON (EPON) and gigabit PON (GPON) technologies running out of steam.
So why hasn’t it been used to solve the last mile conundrum before? Well, over short distances it’s been effective at enabling high-speed access to many. It has a completely passive outside plant (OSP) that eliminates active electronics, which are often fault-generating points, thereby simplifying network operation.
However, over long feeders, the OSP/optical distribution network (ODN) cost for the traditional PON architecture increases rapidly. Also, limitations in system reach/distance due to optical splitting power loss creates a major disadvantage for the traditional PON architecture.
Therefore, the key to making PON more mainstream is evolving the traditional PON architecture and reducing the cost — do that, and fiber for all could become more commonplace and enable something akin to a jog than a slog through the last mile.
Addressing the PON pain points
Network providers need to do more with less; that is the cost of sharing a fiber cable across the maximum amount of subscribers. One of the main limitations has traditionally been simply a matter of hardware.
Traditionally, PON applications have been supported by large optical line terminal (OLT) chassis deployments. Evolution in hardware design has led to the development of pluggable micro-OLTs which fit neatly into 10G optical transceiver routing and switching ports, making life much simpler and cost-effective for network providers by saving on both space and power.
In addition, network providers are increasingly looking to extend optical technology into the access network to support a growing range of high-bandwidth applications, including small and medium-size business (SMB) and small office/home office (SOHO). But PON applications are typically symmetrically limited to 1Gb/s for up to 32 customers. This needs to be expanded, as we’re moving well beyond 1Gb/s as a baseline need. Therefore, adding 10G PON-capable IP and Ethernet platforms will allow providers to deliver 10 times more bandwidth and enable higher-bandwidth applications across up to 64, and even 128, end customers.
There’s a reason PON hasn’t been rolled out en masse and solved the last mile issue previously, but with the evolution of various technologies that reasoning is slowly fading away. Networking technology is evolving with the expansion of the network toward the edge, and as it does we’ll begin to see last-mile fiber access as the norm, because it has to be.
As more applications move to the edge and increasingly crave more and more bandwidth, network providers are looking to solve the last mile conundrum as an imperative, with PON the most likely answer to the age (of the internet)-old riddle.
