KATIA SAFONOVA PASSIVE OPTICAL NETWORKS
One of the reasons for the increased use of XGS-PON is the need for more upstream speed. With more people working remotely and the increased use of technologies like cloud computing and artificial intelligence more people are uploading more massive amounts of data than ever before. The previous GPON with an upstream of 1.2 GB/s can’t keep up with the demand. Instead, symmetrical PON with a higher upstream is the most sought after technology making every second new installed PON an XGS-PON in 2023. Additionally, operators tend to use the more recent XGS-PON
GPON + XGS-PON: External or MultiPON Module (MPM) with internal CEX. (Image: Corning Optical Communications)
because it is possible to have a split ratio of 1:128 without sacrificing the quality of the service, making it more cost-effective and resulting in a much higher ROI. GPON offers in direct comparison only a split rate of 1:64. In order to achieve the higher 1:128 XGS-PON split ratio an additional splitter is included before the OSP Cross Connect as shown in Figure 1. This example by a European operator shows how they combine GPON and XGS- PON to connect more people with high upstream and downstream rates without the need for more optical fibres. Another technology, the 10G-EPON (Ethernet PON), is an IEEE standard that uses the same wavelengths as XGS-PON. China has embraced Ethernet PON, as well as the North American CATV industry, due to its backward compatibility with DOCSIS via DPOE. Additionally, the 25G-PON is not an IEEE or ITU standard, but rather a MSA formed in 2020 and led by Nokia. With over 20 members now, the technology leverages the need for enterprise and mobility requirements based on mature 25G optics technology. WILL WE BE GOING DIRECTLY TO 50G? With the move past 10G to 50G+, several technologies have emerged, including 25G-EPON evolving from 10GEPON, 50G-PON, which requires expensive dispersion compensation with integrated Digital Signal Processors (DSPs) or 50G-EPON which doesn’t require DSP for dispersion compensation. Prior to 50Gbps-PON becoming available, 25Gbps-PON will achieve market traction between 2022 and 2026, primarily in enterprise and 5G transport applications. This technology will allow service providers to deliver high bandwidth and low latency for cloud services and applications. However, beyond 2026, the future of 25G-PON remains in question due to the split among vendors and standards bodies between 25G-PON and 50G-PON. The timeline for 50G-PON component and equipment availability is uncertain, with general availability likely to occur in 2026. Until then, service providers
will continue to rely on XGS-PON for their large-scale residential PON deployments and 25G-PON for their 5G transport and enterprise networks. As the deployment of 5G networks increases, service providers are looking for efficient ways to transport traffic from small cell units to the core network. 25Gbps-PON is expected to be a suitable technology for this requirement, especially for operators who have experience using standards for transport in existing LTE networks. With the high bandwidth and low latency that 25Gbps-PON can provide, service providers will be able to address the growing demand from large enterprises that rely on cloud services and applications. It is expected that cable operators will also partially rely on 25 Gbps EPON for the delivery of enterprise services, as well as the aggregation of their remote PHY and remote MACPHY nodes, especially those that are being used to deliver DOCSIS 4.0 services and bandwidth. However, and as mentioned before, the future of 25Gbps- PON beyond 2026 is uncertain due to a split among vendors and standards bodies between 25Gbps-PON and 50Gbps- PON. There is an industry consensus that 50Gbps-PON equipment could possibly be ready by 2024 or 2025. Still, general availability is more likely in 2026. Until then, service providers will need to continue using XGS-PON for large-scale residential PON deployments and 25Gbps- PON for their 5G transport and enterprise networks.
XGS-PON can use their own fibres in the same sheath. To achieve coexistence, an External or MultiPON Module (MPM) with an internal CEX can be used. This approach allows for a smooth transition to XGS-PON without disrupting the existing GPON service, which can continue to operate until it is phased out over time. Overall, the smooth migration to XGS-PON is crucial for service providers looking to upgrade their networks while minimising disruption and maximising efficiency. WHAT’S NEXT AND IN THE FUTURE? In conclusion, the deployment of PON technologies is rapidly evolving to meet the growing demand for high-speed broadband services. XGS-PON is currently the preferred technology for most operators, with trials already moving to production deployments. However, 10G-PON technologies are queued up to overtake GPON as the dominant PON solution, while the 50G-PON is expected to be the next major ITU PON standard. The future PON technologies will gain momentum after 2024, with 25G-PON expected to gain traction as operators seek future-proof solutions that are backward compatible with existing PON deployments. Ultimately, 50G-PON is expected to dominate in the long term due to its ability to deliver unprecedented bandwidth, and Chinese telcos’ adoption of the technology is expected to decrease equipment prices. While 100G-PON lab tests have started in 2022, the technology is not expected to see widespread adoption until after 2027. Overall, the PON industry is continuously innovating to meet the ever-increasing demand for faster and more reliable broadband services. This leaves providers in need to invest in PON today to ensure the needed speeds for the Gigabit Society and because users are deciding on their contracts based on factors like upstream and downstream speeds, low latency and the associated costs. And they will always decide in favour of the most attractive combination of price and service level provided.
NETWORK SCENARIOS: SMOOTH MIGRATION
Because of this, they have to make sure that the migration to XGS-PON is smooth. It can be achieved through two ways of deployment. The first is through Greenfield deployment, where XGS OLT’s are deployed on day one without any changes to the existing OCS business. This deployment scenario is most suited for competitive carriers (OTTC). The second deployment scenario involves using the existing ODN with spare feeder fibres. In this scenario, both GPON and
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ISSUE 37 | Q2 2024
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