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

Thomas Weible (FLEXOPTIX)

• Why: A pragmatic design approach for DCI/metro DWDM that trades narrow-grid spectral efficiency for flexibility and cost — directly relevant to DC/WAN interconnect planning for coherent-only, filterless topologies.
• What: An argument for moving from 50/100GHz DWDM grids to 400GHz channels (12×400GHz across the C-band vs 96×50GHz) as per-channel bandwidth grows to 800G and 1.6T. Coherent detection's "blindness" to anything but its own wavelength enables filterless topologies; 400GHz filters retain flexibility for legacy ≤10G signals while allowing easy bandwidth reassignment.
• How: Coherent receivers use phase- and polarization-diversity intradyne detection, tolerating adjacent-channel interference. The proposed architecture runs a 400GHz subband through regular 50GHz DWDM MUX/DeMUX and uses cheap PLC 1×4/4×1 splitters to combine TX/split RX, achieving colorless functionality without ROADMs. 800G Coherent ZR+ in OSFP form factor is available for this approach. Emphasis on thinking in THz/GHz frequency plans per span rather than nm/channel numbers.
• Where applicable: Medium-scale DCI and regional DWDM operators who want flexible bandwidth without ROADM capex. Requires coherent transceivers (400G-ZR+ class or above); trades spectral efficiency for flexibility. FLEXOPTIX-affiliated speaker, but the physics and standards grounding is general.