CWDM is a fiber optic technology that combines multiple optical signals, each using a different light wavelength, onto a single fiber strand. ”Below, ETU will provide a detailed analysis of CWDM, including its definition, operating principles, key characteristics, wavelength planning, application scenarios, advantages, and limitations. Definition and Core Principles of CWDM 1. ” This simplicity is the. One key method of visual identification is the color of the transceiver's pull tab, which corresponds to its wavelength.