1. Passive WDM
Composed only of passive devices like Mux/Demux — no power, no O&M, low cost, but limited capacity/reach and no management visibility.
2. Active WDM / OTN
Includes Transponder/Muxponder, EDFA, OTN switching and NMS — supports high capacity, long reach, protection and O&M, at higher cost and with power/maintenance needs.
3. Comparison
- Cost: passive is far lower.
- O&M: active offers monitoring and protection; passive is a black box.
- Capacity/Reach: active wins.
4. Selection
Short reach, few services, low budget (e.g. point-to-point DCI): passive. Multi-service, long reach, SLA-driven: active OTN. They can also be layered.
