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| 10.3 |  | Examining Fiber Optic Transports |
| 10.3.5 |  | Defining DWDM and CWDM |

Dense wavelength division multiplexing (DWDM) employs multiple light wavelengths to transmit signals over a single optical fiber. Today, DWDM is a crucial component of optical networks because it maximizes the use of installed fiber cable and allows new services to be quickly and easily provisioned over existing infrastructure. Flexible add/drop modules allow individual channels to be dropped and inserted along a route. An open-architecture system allows a variety of devices to be connected, including SONET terminals, ATM switches, and IP routers.

Coarse wavelength division multiplexing (CWDM) employs multiple light wavelengths to transmit signals over a single optical fiber. CWDM technology is a crucial component of Ethernet LAN and MAN networks because it maximizes the use of installed fiber infrastructure at a very attractive price point.

CWDM technology is based on the same WDM concept as DWDM technology. The two technologies differ primarily in the spacing of the wavelengths, number of channels, and the ability to amplify signals in the optical space.