JOHN WILLIAMSON XGS-PON
that steps towards disaggregation and open-ness can be made using pluggable optics and ONUs from specialist providers other than the Network Equipment Manufacturer, and that these specialist providers can help with the integration of components in to the network to ensure that operation is not inferior to a solution provided by a single vendor. LOOKING AHEAD None of the forgoing is to imply, in a re-hash of Francis Fukuyama, that XGS- PON represents the end of PON history. Although Nokia reckons XGS-PON will provide enough capacity for residential services for many years, the group is looking at a progression to 25 Gbps PON on account of the mature eco-system of 25G optical technologies massively used in data centres. It’s also involved in 50G standardisation, which needs a new generation of laser technologies, and in February 2021 Nokia Bell Labs and Vodafone showcased a 100 Gbps PON. Likewise, Thomas is confident that this year the BBF’s Broadband Acceleration Seminar (BASe) series will feature news of work and trials already started on the future successors to XGS-PON, including 25G, 50G and 100G PON solutions. Given the different innovation cycles of PON and Wi-Fi, at the customer premise end Golja sees a trend towards a two-box solution, with the ONT function separated from the residential gateway. Additionally, he anticipates the wider adoption of cloud technology in the optical access network. Meantime, Clarkson suggests ONU- on-a-stick solutions could play a large part in achieving open-ness, and it should be possible to connect a radio node directly to an XGS-PON using an ONU-on-a-stick – negating the need for a dedicated ONU device. Clarkson also looks to the potential of white box PONs. “In a ‘modular’ white-box solution, one could add OLT blades alongside switching and routing blades for flexible functionality,” he concludes. “By integrating an OLT into a pluggable optic, it is possible to create a PON network without any dedicated OLT or ONU hardware – simply by using pluggables at all ends of the ODNs and integrating these pluggables into existing switches/CPE, be it white-box or not.”
a variety of ONUs and once certified, vendors can deploy their ONU products with greater interoperability to existing OLT equipment already deployed,” states Thomas. “Attaining XGS-PON market readiness with the BBF.247 certification ensures that vendors’ products are trusted and proven, and therefore operators and equipment manufacturers have the confidence that the products will provide their end-users with the seamless service they require.” OPEN SAUCE? Standardisation and conformance certification lead on to considerations of further open standards, software- defined access, virtualisation and the disaggregation of network pieces. “As more vendors and operators seek to accelerate the time-to- market of new services and unlock new revenue streams, industry open standards will continue to play a huge role in ensuring ease of deployments, network interoperability and helping the broadband ecosystem thrive,” asserts Thomas. Pesovic describes how operators are increasingly considering software defined access network introduction to benefit from simplified, automated networks and open multi-vendor environments, or to implement network slicing to deliver different services and traffic types over one network in a smarter way. “Introducing XGS-PON in the network is also a good opportunity to introduce virtualisation,” she says, but cautions that it should not be a ‘must’ but should be dictated by an individual service provider’s business priorities, operational goals and migration strategy. Clarkson thinks ‘yes’ and ‘no’ is the answer to the question: do the moves towards open and disaggregated network architectures and virtualisation complicate XGS-PON deployment? “On the one hand there is the drive towards development of open OLTs and ONUs, particularly with white-box hardware becoming increasingly available,” he comments. “On the other hand, the software for these open solutions is still relatively immature. The complete solutions offered by the Network Equipment Manufacturers are the easiest ways for service providers to roll out XGS-PON with the minimum of effort.” However, Clarkson concedes
running now, XGS-PON will take the form of an upgrade, but initially it may be one line card per location to see how many subscribers will upgrade,” he ventures. Iskratel’s head of Broadband Marketing Tomo Bogataj opines that, as well as past technology history, current access to outside investment funding can be a critical component in the XGS-PON deployment story. He notes that interest should be higher in the case of operators in receipt of subsidies from local, national or regional development bodies. Greenfield networks are also prime candidates for XGS-PON roll-outs. “There you’re trying to build networks that will last longer,” says Bogataj. Pesovic agrees, remarking that the overall cost difference between GPON and XGS-PON is small, because the biggest part of the cost – typically 70% - is in the outside plant, digging the streets and laying the optical cables. “So in greenfield deployments it makes sense to invest immediately in XGS- PON and avoid upgrade cycle any time soon,” she reasons. “The recent examples include Ireland, which is deploying XGS for 0.5 million users in rural areas.” In addition, Golja describes how XGS- PON deployment options can vary by service provider type with, for example, classic, vertically integrated telcos in urban markets maybe preferring chassis-based solutions, while rural and sub-urban service providers may choose lower bandwidth ‘pizza box’ OLTs. UP TO SPEC Standardisation is one thing. Conformance certification is another, and is viewed by experts such as Craig Thomas, the Broadband Forum’s VP of Strategic Marketing and Business Development, as essential to mass market, commercial deployment of new technology. In 2011, the Broadband Forum (BBF) initiated the BBF.247 G-PON Certification Program to verify the conformance of G-PON products and their adherence to the ITU-T G-PON standard and to Broadband Forum specifications. In mid-2020 the BBF announced that it had expended the BBF.247ONU Certification Program to include XGS-PON. “The Certification Program addresses
Craig Thomas, Broadband Forum
Mitja Golija, Iskratel
Tomo Bogataj, Iskratel
Anthony Clarkson, Precision Optical Transceivers Inc
Ana Pesovic, Nokia
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Q1 2021
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