Nokia and GFiber (Google Fiber) recently announced that the two companies collaborated on a live field trial of 50G PON technology. GFiber is already deploying Nokia 25G PON and says the 50G PON can overlay on that platform. Nokia now has 10G and 25G PON available to ISPs, the 50G PON in field trial, and 100G PON available as a lab demo.

In the GFiber test, the company was able to simultaneously operate both the 10G and 25G PON, and also the 25G and the 50G PON together. Nokia says there is now more than a dozen ISPs using the 25G PON worldwide. The company also says there are now five ONT vendors supporting 25G PON and more than sixty vendors on board in some aspect of the product, including chipset and optical suppliers. The next step for 50G PON would be to introduce it to industry vendors.

Nokia has chosen a unique technology path for the 50G PON. The upstream link for the technology can only transmit data for short, intensive bursts at preset time slots. This makes the electronics for 50G more complicated. This is also a variation from the industry standard that is being developed by the Chinese. This kind of disparity can cause issues with the supply chain if vendors support different versions of the solution. Nokia says their solution was needed since the technology is pushing the limits of physics.

Probably the most important question is if ISPs will be interested in 50G PON. It’s not unusual today for ISPS using PON for residential service to still use active Ethernet when connecting to large business customers that want speeds greater than 10 Gbps. Most PON vendors have electronics that will selectively support PON or ActiveE over specific fibers. However, an ISP operating a network with a lot of large broadband users, like a network supporting cell sites, might prefer the benefits of PON over activeE, with the primary being that one fiber could be used to support multiple cellular towers or other large customers from a single fiber.

The primary question is if 50G PON brings any benefits to ISPs serving residential and small business customers. Skeptics will say that we don’t need technology at these faster speeds. But in only twenty years, we’ve gone from broadband delivered by dial-up to bandwidth delivered by 10-gigabit technology on XGS-PON. None of these skeptics can envision the demands for data that can be unleashed over the next decade or two. If there is any lesson we’ve learned from the computer age, it’s that we always find a way to use faster technology within a short time after it’s developed. But it’s still a giant technology leap from 2.5 GB on GPON to 50G PON.

Most of the vendors that make or will be making 25G and 50G PON argue that the faster PON networks are cheaper on a per-customer basis. But I have to wonder if that is really true if ISPS don’t use the full capacity of the technology. The vast majority of ISPs using GPON limit the number of customers on a given PON neighborhood to no more than 32 customers. The upgrade to XGS-PON allows an ISP to easily put 128 customers into a neighborhood PON. The 25G and 50G PON platforms would allow a lot more customers on a single PON.

One of the inherent advantages of PON is that a card failure or fiber cut in a neighborhood doesn’t take many customers out of service. Most ISPs I work with will not want to risk putting hundreds of customers on the same PON if that increase risk of large scale outages. Over the past decade, cable companies have greatly reduced the size of their nodes to the range of 100 customers, and fiber providers should be careful to not give away one of their primary advantages over cable.