Unlocking Ultra-Fast Internet: The Power of 50G PON

In the digital era, 10G PON technologies, marking the advent of F5G (fifth-generation fixed networks), have laid the foundation for the digital economy's evolution. With emerging applications like generative AI and metaverse demanding higher bandwidth, lower latency, and increased reliability, the industry recognizes the pivotal role of 50G PON in transitioning access networks from gigabit to 10Gbps. This technology is crucial for meeting the escalating requirements of the 10Gbps era, ensuring efficient support for advanced digital applications.

PON Evolution and 50G PON Introduction

The advancement of PON technologies is driven significantly by standard organizations like ITU-T/FSAN and IEEE. Currently, GPON and EPON dominate with widespread deployment, offering users up. Emerging 10G PON technologies (10G GPON and 10G EPON) have seen extensive commercial deployment, providing up to 10 Gbps bandwidth to meet the demands of 4K/8K videos and early-stage VR/AR integration. Positioned as the next-generation choice, 50G-PON follows XGS-PON, employing time-division multiplexing-passive optical network (TDM-PON) to coexist with previous PON technologies. Officially standardized by the ITU-T in September 2021, 50G-PON supports asymmetric rates, dual-generation coexistence (10G-PON or GPON), and, later, symmetric 50G-PON (50Gb/s downstream and upstream) with three-generation coexistence (50G-PON, 10G-PON, and GPON) added a year later.

From a broader perspective, PON undergoes a significant evolution approximately every 8 to 10 years. Presently, gigabit broadband, utilizing 10G PON fiber access technology, has become the prevailing standard. In contrast to 10G PON, 50G PON elevates the bandwidth by five times while offering attributes like low latency, minimal jitter, and heightened reliability. Capitalizing on substantial bandwidth, minimal latency, and advanced computing capabilities, 50G PON delivers an unparalleled service experience, introducing a plethora of new applications and services. This positions it well to meet the diverse application requirements in realms such as digital homes, industrial digital transformation, and urban digital infrastructure during the 10G era.

Important Technologies of 50G PON

• Wavelength Selection: Currently, 50G PON utilizes a limited portion of wavelengths in the O band. The ITU-T has defined specific wavelengths and continues discussions on additional wavelengths.

• Line Coding: Various line coding schemes were considered, including PAM-4 and duobinary modulation. The ITU-T opted for NRZ code due to its superior signal receiving performance, essential for the high optical power budget in PON systems.

• Line Rate: ITU-T specifies the rate requirements for 50G PON, supporting a mix of symmetric and asymmetric rates with one downstream rate and four upstream rates.

• FEC (Forward Error Correction): The increased line rate in 50G PON necessitates improved receiver sensitivity. To achieve this while reusing ODN (Optical Distribution Network) resources, 50G PON employs the LDPC scheme for FEC, lowering specifications requirements for optical components.

• Common Transmission Convergence: 50G PON achieves low latencies through technologies like DAW (Distributed Antenna System), CO-DBA (Centralized Dynamic Bandwidth Allocation), and shortening the bandwidth allocation interval. DAW introduces new wavelengths, CO-DBA optimizes upstream service transmission, and shortening intervals reduces service data cache time in the ONU (Optical Network Unit).

• PHY Components: Key optoelectronic devices in 50G PON include optical transmitter and receiver modules, laser device drivers (LDDs), burst-mode TIAs (Transimpedance Amplifiers), and clock-data recovery (CDR) chips. The OLT (Optical Line Terminal) can use EML (Electroabsorption Modulator Laser) or integrated SOA-EML components as the transmitter, and APD (Avalanche Photodiode) or integrated SOA-PIN components as the receiver. The ONU driver supports burst function, and the ONU receiver does not require burst-mode CDR. Industry experiments show that a 50G EML transmitter and APD receiver enable a single-wavelength rate of 50 Gbps in 50G PON.

Applications of 50G PON

Here are the three main applications scenarios of 50G PON:

Home Ultra High Broadband Access

As home business traffic surges, users demand higher bandwidth and lower latency for broadband access. The proliferation of services like cloud VR, online gaming, and smart homes underscores the need for substantial bandwidth (200Mbps~4Gbps) and low latency (10~5ms). 50G PON presents various low-latency solutions to meet these specific business requirements.

High-Quality Enterprise/Campus Informatization

50G PON delivers nearly 50Gbps of access bandwidth, making it versatile for enterprise dedicated access and campus network development. With enhanced low latency and channelized assurance capabilities, 50G PON provides enterprises and industrial sectors with low-latency, deterministic access network capabilities, facilitating their digital transformation.

New Options for Mobile Backhaul/Wi-Fi Backhaul

In the realm of mobile backhaul, 50G PON demonstrates advantages in power consumption, size, and cost, achieving a remarkable 100µs latency. Aligned with the widespread adoption of Wi-Fi 6 and the imminent deployment of Wi-Fi 7, Wi-Fi networks are rapidly evolving from hundreds of megabits to gigabit coverage. The swift progress of Wi-Fi networks necessitates higher standards for their backhaul access. With its ample bandwidth, 50G PON can deliver close to 50Gbps of symmetrical bandwidth, meeting the high-speed requirements of Wi-Fi network backhaul.

Bright Future of 50G PON

50G-PON will become the next generation of PON technology. The main reasons are as follows:

• Network Evolution and Standardization: 50G-PON aligns with the pace and bandwidth requirements of PON network evolution. Global user bandwidth demand grows by about 20% annually, doubling every 4 years. Typically, operators upgrade to the next-generation PON every 8-10 years, and 50G-PON, providing 5 times the bandwidth of 10G-PON, fits this evolution. Commercial availability is expected by 2024, with existing 10G-PON meeting user requirements until then.

• ITU-T Standardization: 50G-PON is the next-generation PON standardized by the ITU-T, a pivotal factor for successful commercialization. ITU-T's history of leading PON industry evolution includes the widely deployed GPON. Other proposed PONs, such as 25G-PON or 100G-PON, faced challenges and were not agreed upon, making 50Gb/s PON the only higher-speed PON standardized by ITU-T.

• Operator Support: Mainstream operators globally, including tier-1 operators from North America, Europe, and Asia, actively support and participate in 50G-PON standardization. Leading operators like AT&T, Verizon, Orange, Vodafone, China Telecom, China Mobile, and others, covering about 70% of the world's PON networks, choose 50G-PON as the next generation. More mainstream operators express support for 50G-PON, indicating widespread industry adoption.

• Supply Chain and Maturity: 50G-PON enjoys broad support from the PON industrial supply chain, ensuring maturity and commercialization in the near future. Mainstream equipment manufacturers, chip suppliers, and device suppliers globally back 50G-PON. Post-standardization, manufacturers have released technical prototypes, and component suppliers are developing necessary chips and optoelectronics. This strong support ensures the maturity of key technologies, paving the way for commercial use from 2024.

• Cost-Effectiveness: 50G-PON stands out as the most cost-effective solution in optical access. Leveraging digital signal processing (DSP), 50G-PON utilizes 25G-grade components to achieve required optical loss budgets. This cost-effective approach positions 50G-PON as a faster system, delivering increased bandwidth at twice the speed of a 25G system for the same cost.

Conclusion

50G PON, a pivotal technology in the digital era, marks the evolution to 10Gbps access networks. Standardized by ITU-T, it provides five times the bandwidth of 10G PON, ensuring low latency, reliability, and cost-effectiveness. With support from global operators and a mature supply chain, 50G PON is set to be the next-generation technology, with commercial availability expected by 2024. Its applications in ultra-high broadband access, enterprise informatization, and mobile/Wi-Fi backhaul position it as a key driver in digital transformation.