1. What are CWDM and DWDM
CWDM (Coarse WDM) and DWDM (Dense WDM) both transmit multiple wavelengths over a single fiber. The core difference is channel spacing.
2. Wavelength and Channel Spacing
- CWDM: 20nm spacing, covering 1270-1610nm, up to 18 channels; typically 8-16 channels are used.
- DWDM: 0.8nm/0.4nm spacing (100GHz/50GHz), concentrated in C-band (1525-1565nm) and L-band; up to 40/80/96 channels.
3. Transmission Distance
CWDM is typically used within 80km without amplifiers; DWDM with EDFA and coherent modules can reach 1000km+ long-haul.
4. Cost and Applications
CWDM is low-cost and simple — ideal for enterprise private networks and access. DWDM offers high capacity and long reach — ideal for metro/backbone and DCI.
5. Selection Guide
Choose CWDM for short reach, low cost, few channels; choose DWDM for high capacity, long reach, scalability. A hybrid (CWDM access + DWDM backbone) is also common.
