Channelmania! – future proof your DWDM network topology while keeping it flexible for 1.6T#

Thomas Weible (FLEXOPTIX)

• Why: A pragmatic design approach for DWDM networks moving to 400GHz channels and coherent-only superchannels — directly relevant to DC/WAN interconnect planning, especially for operators who don't want ROADMs.
• What: Argues for moving from 50/100GHz DWDM grids to 400GHz channels (12×400GHz in C-band vs 96×50GHz), leveraging coherent detection's "blindness" to non-own wavelengths to build filterless or simplified-filter topologies. Shows how to use cheap PLC 1×4/4×1 splitters and regular 50GHz DWDM MUX/DeMUX to combine/split subbands, enabling colorless architecture without ROADMs.
• How: Coherent receivers use phase- and polarization-diversity intradyne detection, making them robust to adjacent-channel interference. By running a 400GHz subband through standard 50GHz MUX/DeMUX and using PLC splitters, you get flexible bandwidth reassignment without active ROADM infrastructure. 800G Coherent ZR+ in OSFP form factor is available today for this approach.
• Where applicable: Medium-scale DCI operators, regional DWDM networks. Requires coherent transceivers (400G-ZR+ class or above). The 400GHz filter approach trades spectral efficiency for flexibility and simplicity — best for networks that don't need maximum fiber capacity but want to avoid ROADM capex. FLEXOPTIX-branded but content is physics/standards-based.