Moving from 100G or 200G to 800G per wavelength cuts the number of wavelengths, ports and transponders needed for the same capacity. It also changes how the optical line has to be planned. This article walks through the parts of an 800G link and the questions worth answering before equipment is ordered.
1. The transponder: client side and line side
A transponder maps client Ethernet onto coherent wavelengths. On the DCI5800-T8E2 board, the client side accepts 8 × 100G QSFP28 or 4 × 400G QSFP112, carrying 100GE, 100GE FlexE (unaware) and 400GE services. The line side uses two pluggable CFP2-DCO coherent modules that run at 400G or 800G.
Two 800G line modules do not automatically mean 1.6T of usable throughput on one board. Supported port combinations depend on the transmission mode, so confirm them for your configuration instead of assuming every port runs at full rate at the same time.
2. Modulation, FEC and channel plan
- 800G uses 16QAM; 400G can use 16QAM-PCS or QPSK, trading capacity for reach.
- oFEC (open forward error correction) is used on the line side.
- The line is C-band DWDM with 96 tunable channels at 50 GHz spacing.
Higher-order modulation needs more optical signal-to-noise ratio, so 800G links are usually shorter or need better amplification than 400G links over the same fiber. Reach and OSNR per mode should be confirmed for the modules in your design.
3. The open optical line system
An open line system (OLS) is the shared optical layer: multiplexing, amplification, wavelength switching and monitoring. Keeping it open lets you add transponders from more than one source over time. Useful building blocks include:
- EDFA booster, line and pre-amplifiers to balance span loss.
- WSS (wavelength selective switch) to add, drop and route individual wavelengths.
- OCM (optical channel monitoring) to see per-wavelength power and keep the line balanced.
- OLP line protection and OTDR fiber monitoring to protect the link and locate faults in service.
The DCI5800 platform includes built-in OCM and supports WSS, so it can serve as an OLS white box as well as a transport platform.
4. Planning checklist
- Span lengths, fiber type and measured loss for every span.
- Target capacity now and in three to five years, and which client rates (100GE or 400GE) you need.
- Protection model: OLP 1+1 on the fiber, SNCP 1+1 on the path, or both.
- Which transponders or pluggables must share the line, and who manages the optical layer.
- Management integration with your existing network management system.
Send us this information and we will propose a configuration and confirm the optical figures that apply to it. Engineering samples of the T8E2 board are available for project-based evaluation.