A key goal of vendors and carriers is to upgrade the capacity of the networks upon which they rely while spending as little money doing it as possible. A prime example of this is the ongoing research and development on 5G. It is also driving carriers and their ecosystems toward increasing the capacity of passive optical network (PON) infrastructure while making as little physical change to it as possible.
Two of the tools to achieve this next wave are XPS PON and NG-PON2. Both are updates to Gigabit PON technology that has dominated access networks for the past decade or so. The two standards are headed to the same place, but have different development arcs. They both got first-stage approval from the International Telecommunication Union (ITU) last spring.
Lightwave suggested that which of the options a carrier takes likely depends on how immediate their needs are:
XGS-PON likely will be used as an intermediate step between GPON and NG-PON2, enabling operators to support symmetrical 10-Gbps applications that may not require the multi-wavelength future-proofing of NG-PON2 or where immediate competitive situations demand a lower-cost, more immediate approach. The lower expected cost versus the use of a single-wavelength NG-PON2 implementation is due to the use of fixed-wavelength optical transceivers, rather than the tunable optics the NG-PON2 specifications will codify.
XGS PON is just about here, according to insiders. A “plug fest,” in which equipment from different vendors is tested for interoperability, is a sure sign that the products are almost ready for sale to carriers. The first such event for XGS PON was held at LAN’s Digital Application Laboratory in Tauxigny, France. The year ahead is certain to feature a lot of news about sales of XGS PON equipment.
There’s also no shortage of use cases. Teresa McGaughey, the director of Solutions Marketing for Calix, says that XGS PON can be used for homes and businesses. The bandwidth, she wrote in response to emailed questions from IT Business Edge, theoretically can be divided between 256 subscribers, though in practice the limit is half that because real conditions are not as pristine as those in laboratories.
McGaughey echoes the point that XGS PON is an interim step. “The main advantage of XGS PON technology over, say, NG-PON2, which is also capable of 10G (and 40G) symmetrical, is that it may at least initially support optics at a lower cost and availability,” she wrote.
The great increase in applications and services during the past decade has created a need to deliver data far faster than ever. This has pushed the technology.
“The most basic use case is to create service offerings that simply cannot be achieved with GPON,” wrote Kurt Raaflaub, the head of Strategic Solutions Marketing for ADTRAN. “With symmetric 10G speeds, providers can create any number of lucrative multi-Gigabit business service offerings they see demand for among their customers.”
XGS PON is useful in furthering a basic tenet of data distribution: driving data as deep into the network as possible before subdividing it into smaller streams that go to other interim stops still deeper in the network or to end users’ premises. A greater capacity at the outset enables more bandwidth to traverse each step.
“Another compelling use case is scaling Gigabit Broadband, especially in areas where providers have dense GPON (1Gbps) FTTH deployments, XGS-PON is a cost-effective way to deliver more Gigabit streams deeper in their network, effectively extending the lifespan of that PON, considering the predicted annual load growth estimates,” Raaflaub wrote.
However, the new approach has limitations. The problem is that physics sometimes gets in the way of a good business case.
“[T]he disadvantages of XGS-PON are that it does not lend itself well to having residential and business traffic on the same fiber/wavelength and designating that fiber as operator ‘safe windows’ when the systems being upgraded are different,” according to Vincent O’Byrne, Verizon’s director of technology. “As a result, most operations groups will want to keep that traffic on separate fibers to reduce overall cost.”
The path forward will be interesting – and certainly not the same for every carrier.
“XGS-PON will most likely be used by operators that are facing immediate competition, with initial deployments outside the U.S,” O’Byrne wrote. “U.S. operators are comparing XGS-PON to NG-PON2 to see if they need to take the XGS-PON interim step or go directly to NG-PON2.”
The standard was finalized last year, which means that products are likely to begin hitting the market toward the end of this year and in 2018.
Carl Weinschenk covers telecom for IT Business Edge. He writes about wireless technology, disaster recovery/business continuity, cellular services, the Internet of Things, machine-to-machine communications and other emerging technologies and platforms. He also covers net neutrality and related regulatory issues. Weinschenk has written about the phone companies, cable operators and related companies for decades and is senior editor of Broadband Technology Report. He can be reached at cweinsch@optonline.net and via twitter at @DailyMusicBrk.
