Short-distance transmission is shifting from 25G to 50G per wavelength
Dec 15, 2025|
Ethernet short-distance transmission:
| Ethernet Standard | MMF | Parallel SMF | 2 km SMF | 10 km SMF | 40 km SMF |
|---|---|---|---|---|---|
| 25 G BASE– | SR | LR | ER | ||
| 40 G BASE– | SR4 | FR | LR4 | ER4 | |
| 50 G BASE– | SR | FR | LR | ||
| 100 G BASE– | SR10 SR4 SR2 | PSM4 | CWDM4 CLR4 FR2 | DR2 FR4 LR4 | ER4 |
| 200 G BASE– | SR4 | DR4 | FR4 | LR4 | |
| 400 G BASE– | SR16 | DR4 | FR8 | LR8 |
Regarding the evolution of the technology roadmap, the earliest 100G short-distance transmission evolved from 10×10 to 4×25G, with each single channel being 25G NRZ, serving as the technological foundation.
By selecting one of the channels, we get single-wavelength 25G transmission.
The 4 channels are further multiplexed into 16 channels, resulting in 16 × 25 = 400G transmission.
Single-wavelength 25G NRZ, represented by the gray dots in the diagram below, was a hot topic of research in the industry for the past two years. Moving forward,short-distance transmission will focus on the black dots, which represent single-wavelength 50G PAM4 technology.
The dashed boxes in the table below show the various combinations for single-wavelength 50G PAM4
The dashed boxes represent technologies that will continue to evolve and mature over the next two years, while the next step after that is the single-wavelength 100G PAM4 technology shown in the solid box.