EPON broadband three-generation coexistence solution: the best path choice for industry evolution

With the rapid development of technologie s such as 5G, cloud computing, and AI, optical access networks are accelerating their evolution towards higher bandwidth and lower latency. As a new generation of PON technology, 50G PON has become the focus of industry attention. Currently, operators still have a large number of EPON and 10G EPON in their existing networks. How to protect existing investments to the greatest extent while upgrading the network and achieve the coexistence of three generations of EPON, 10G EPON, and 50G PON has become a major challenge in technology evolution.

1. Wavelength Conflict: The Core Challenge of EPON Evolution

The upstream wavelength range of PON is as wide as 100nm (1260nm~1360nm), while the upstream and downstream wavelengths of 50 G PON defined by ITU-T are 1286nm and 1342nm respectively, which completely overlaps with the upstream band of EPON.

This wavelength conflict makes the coexistence of the three generations of PON extremely difficult. From standard formulation to industrial practice, the industry has proposed three main solutions:

1. EPON is withdrawn from the network, and 10G EPON and 50G PON coexist in the second generation

As early as the early stage of 50 G PON standard formulation in 2018, the industry realized that broadband EPON was an obstacle to the evolution of future PON networks. As EPON is gradually withdrawn from the network, the second generation coexistence of 10G EPON and 50G PON has become the preferred solution.

Advantages:

Standard normalization: 50G PON standard has achieved compatibilty with 10G EPON, and the industry chain is mature.

Network simplification: Avoid the complexity brought by the coexistence of three generations and reduce operation and maintenance costs.

Performance improvement: After EPON is withdrawn from the network, network bandwidth and latency performance can be greatly optimized to match the needs of the AI era.

At present, operators such as China Mobile have begun to promote the withdrawal of EPON, gradually improving network capabilities to align with GPON regions, and building a more competitive access network.

2. EPON converges to narrowband to achieve coexistence of three generations

After 10G EPON was commercialized in 2017, as the cost of DFB lasers decreased, operators narrowed the EPON upstream wavelength to 1290nm~1330nm through enterprise standards, and the asymmetric 1G upstream of 10G EPON was narrowed to 1260 nm~1280nm. This adjustment laid the foundation for the coexistence of 50G PON.

In 2022, 50G PON newly defined an upstream wavelength of 1286nm. After the deployment of narrowband EPON, the three generations of EPON/10G EPON/50G PON can coexist.

Advantages:

Smooth evolution: retain existing EPON users and avoid forced network withdrawal.

Standard normalization: ITU and IEEE PON converge on wavelength, and the industry chain is more efficient.

However, the popularization of narrowband EPON still needs time, and the elimination of broadband EPON equipment requires continuous investment from operators.

3. Independently define 50G EPON wavelengths and use time-division multiplexing for upstream

Recently, the industry have proposed to achieve coexistence of three generations by independently defining 50G EPON wavelengths (such as 136x nm) and using time-division multiplexing mechanisms

However, this solution faces multiple technical bottlenecks:

Fiber attenuation problem: 136x nm is at the edge of the water peak, with large and unstable attenuation.

Dispersion limitation: High-frequency dispersion causes signal degradation, making it difficult to support 50G NRZ transmission.

Efficiency and latency: The three generations of PON share the upstream time slot, and the long preamble (us level) of EPON/10G EPON will significantly reduce the bandwidth efficiency of 50G PON and increase latency.

Industry chain cost: 136x nm optical devices cannot be reused with the GPON industry chain, and the cost is high.

Disadvantage summary:

. Low technical feasibility, great performance sacrifice.

. Continuing the standard split between IEEE PON and ITU PON, the industry chain cannot converge.

. Network competitiveness declines, making it difficult to meet future business needs.

From the perspective of long-term industry development, the best choice is to retire EPON and realize the coexistence of 10G EPON and 50G PON. This path can:

Avoid technical risks: avoid wavelength conflicts and performance defects of time-division multiplexing.

Improve network capabilities: unify PON standards, simplify operation and maintenance, and reduce TCO.

Enhance competitiveness: pave the way for the evolution of 50G PON to the next generation of PON technology in the future.

On the contrary, if the 50G EPON time-division coexistence solution is selected, it will lead to standard splits, industrial chain redundancy, network performance decline, and ultimately make the deployed network lose technical competitiveness.