Coarse Wavelength Division Multiplexing

Why Trust Techopedia

What Does Coarse Wavelength Division Multiplexing Mean?

Coarse wavelength division multiplexing (CWDM), a variant of wavelength division multiplexing (WDM), is an optical transmission technique used for shorter distances as compared to dense WDM (DWDM).


CWDM transmits few channels and makes use of wider spacing in between the channels for distances of up to 60 km. CWDM’s wider spacing of up to 20 nm, when compared with DWDM’s 1.6 nm, can tolerate much higher temperature fluctuations.

In 2004, IEEE standardized CWDM for 10-Gb Ethernet.

CWDM is also known as wide WDM.

Techopedia Explains Coarse Wavelength Division Multiplexing

Coarse wavelength division multiplexing (CWDM) is highly economical when compared to DWDM, as there is no need to stabilize the laser nor is there a need for an external modulator. By adjusting the drive current, the laser can be directly modulated. CWDM functions between 1265 and 1625 nm compared with DWDM’s tighter range of 1530 to 1620 nm.

Although DWDM rules the long-haul network sector, CWDM is all set to help carriers take full advantage of their network capacity in the regional, metro and access network sectors. When compared to DWDM, CWDM supports fewer wavelengths; however, it is offered at a fraction of the cost of DWDM. This makes CWDM perfect for those areas having average traffic growth projections.

CWDM highlights:

  • As many as 16 CWDM wavelengths over a single pair of fiber
  • CWDM channel spacing is 20 nm
  • Distances as high as 120 km
  • Scalable by hybrid CWDM/DWDM
  • A highly cost-effective WDM solution

CWDM applications:

  • Fiber exhaust relief
  • In LAN and SAN connections
  • Cost-effective WDM deployments in metro networks
  • Main office to client-premise interconnection

Related Terms

Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.