The Future-Proofing Power of 25G PON: Preparing for Tomorrow's Demands

In the dynamic realm of fiber broadband technology, the quest for future-proof solutions is essential. This exploration dives into the transformative potential of 25G PON, illuminating its capacity to exceed the demands of tomorrow's digital era. As businesses and residences seek higher bandwidth and reliability, the forward-looking features of 25G PON position it as a cornerstone for preparing today's networks to seamlessly navigate the challenges and opportunities of the future.

PON Development and New Trend

The evolution of PON technology, originating from long-haul optics and adapting for the metro market, saw earlier generations like EPON, GPON and 10G PON enabling widespread fixed access deployment. Inspired by data center technologies, the next PON era emerges, drawing from advanced 100G Ethernet with 25 Gb/s channels. Fueled by growing data center demands, cost-effective 25G components pave the way for the transition to 25G PON, reshaping high-speed connectivity. 25G PON introduces innovative services over existing fiber networks, with operators leveraging its efficiency for small cell xHaul transmission.

Figure 1: PON Evolution

25G PON Introduction

25G PON (25 Gigabit Passive Optical Network) is an advanced fiber optic network technology that represents an evolution within the PON framework. Compared to traditional technologies like GPON and XGS-PON, 25G PON offers a higher transmission rate of 25 Gb/s, providing users with faster and more reliable internet connectivity. The development of this technology aims to meet the growing demands of networks, supporting more users and various emerging applications, including but not limited to enhanced mobile communications, the Internet of Things, high-definition video streaming, and more. The deployment of 25G PON is expected to drive the development of next-generation networks, offering users a more powerful and flexible network experience.

Why 25G PON Is Quite Urgent?

The urgency for 25G PON is propelled by two key factors. Firstly, the advent of 5G has spurred mobile operators to adopt fiber broadband for efficient mobile transport, essential for 5G densification and novel cloud network architectures. While XGS-PON can meet many 5G requirements, XGS-PON cannot reach true 10Gb/s because its capacity is limited to 8.5Gb/s due to standard specified overhead and 25G PON excels in scenarios with high-density 5G small cells, demanding throughput, and premium SLA maintenance. It not only provides the necessary bandwidth for small cell backhauling but also ensures ultra-low latency for fronthaul. Leveraging existing FTTH networks for mobile transport allows quicker 5G small cell deployment, eliminates the need for a dedicated transport network, and significantly reduces total ownership costs.

The second driving force is the escalating demand for high-bandwidth connectivity among large-scale enterprises. Consulting and research firm Analysys Mason forecasts a 30% growth in fiber-connected enterprises in the next four years, and for large enterprises, the coveted standard is 10Gb/s connectivity. Presently, this is achievable only through a costly, dedicated point-to-point connection. 25G PON emerges as a highly cost-effective alternative, meeting the increasing demands of businesses while supporting residential and 5G transport services. It opens avenues for greater efficiencies and revenues for operators.

25G PON Implementation

The core principle of 25G PON is achieving 2.5 times more bandwidth at a cost increment of less than 2.5. The cost-effective strategy includes:

• O-band wavelengths to mitigate dispersion issues at higher bit rates, ensuring downstream and upstream wavelengths in the O-band.

• Simplified transmission utilizing data center technologies, favoring non-return-to-zero (NRZ) over complex and costly modulation schemes like PAM4.

• Addressing the 5 dB power penalty of 25 Gb/s compared to 10 Gb/s through a combination of higher launch power, enhanced receiver sensitivity, and robust FEC to adhere to a 29 dB loss budget.

• Dual-rate transmission supporting both symmetrical (25/25) and asymmetrical (25/10) bitrates, enabling cost-effective deployment of 25G/10G ONTs where symmetry is unnecessary.

The 25G-PON standard prescribes a 1358 nm wavelength for downstream and provides three upstream options:

• Option 1: 1300 nm (GPON subset) for coexistence with XGS-PON.

• Option 2: 1270 nm (same as XGS-PON) for coexistence with GPON.

• Option 3: 1286 nm to facilitate triple coexistence of 25G PON, XGS-PON, and GPON. This wavelength strategy ensures a seamless evolution path in any network.

Key Benefits of 25G PON

Cost-Efficient Evolution

25G represents the most cost-effective evolutionary stride for the coming decade. Drawing on well-established data center technologies, it simplifies the technology landscape by eliminating the need for sophisticated digital signal processing, amplifiers, or tunable lasers. Unlike its predecessors, 25G PON marks a direct evolution from 10G PON, anticipating that advancements beyond 25G will necessitate a substantial technological leap, requiring years to mature.

Diverse Applications

The versatile applications of 25G PON underscore its pivotal role in the evolution of network services. From empowering enterprises with true 10G speeds for mission-critical applications to efficiently handling the demands of 5G mobile transport, 25G PON caters to diverse scenarios. Its adaptability extends to large-scale wholesale providers, meeting their bandwidth requirements through network slicing, ensuring optimal utilization, and delivering differentiated Quality of Service (QoS) for varied tenants and services. Furthermore, as the technology opens doors to next-gen services like remote surgery, Virtual Reality, and real-time digital twins, it remains a strategic consideration for operators exploring disruptive true 10G services and optimizing costs in greenfield environments with high split ratios. The multifaceted capabilities of 25G PON position it as a cornerstone for addressing present and future demands across the telecommunications landscape.

Faster Speed

25G PON stands out with impressive speed metrics, surpassing GPON by 10 times and outpacing XGS-PON by 2.5 times. This substantial leap aligns with the Ethernet market's strategy, demonstrating that a 2-2.5x speed increase yields optimal commercial results. Widely adopted by key industry players such as IEEE (25G EPON), data centers, WDM, G.metro, and 25GS-PON MSA, the 25G stride is fueled by tangible demand in enterprise services and 5G transport. Anticipating future residential needs, the technology, currently 20 times faster than 1 Gigabit connectivity (factoring in overheads), ensures ample bandwidth for the next decade. This remarkable speed proficiency positions 25G PON as a leading force in addressing the escalating connectivity demands of diverse markets.

Seamless Transition and Coexistence

Ensuring a seamless transition is vital for cost-effective and uncomplicated network upgrades. Recognizing that these upgrades unfold gradually, with both old and new technologies coexisting for extended periods, compatibility is paramount. As networks evolve towards speeds exceeding 10G, the prevalence of both GPON and XGS-PON becomes commonplace. A standout feature of 25G PON is its innate ability to effortlessly coexist with both GPON and XGS-PON. This harmonious coexistence accommodates three PON generations on the same fiber infrastructure, granting operators the flexibility to deploy the most suitable technology and speeds for each distinct service. The absence of forced migrations, restrictions, or overlay deployments further enhances the adaptability and efficiency of network evolution.

Figure2: Coexistence of 25G PON

Conclusion

In summary, 25G PON is a transformative solution in fiber broadband, exceeding future digital demands. With a rapid 25 Gb/s transmission rate and cost-effective implementation, it caters to diverse needs, from 5G transport to next-gen services. Outpacing GPON by 10 times and XGS-PON by 2.5 times, its versatility allows seamless coexistence with GPON and XGS-PON. In essence, 25G PON is pivotal, efficiently meeting current and future telecommunication demands.