Currently, the three main center wavelengths for commonly used optical modules are the 850nm band, 1310nm band, and 1550nm band. To illustrate, we can use an analogy. Imagine a courier needing to transport a package during rush hour. Various lasers, including those of the same kind, may have different center. The center wavelength is the wavelength measured at the midpoint of a half-amplitude line in the transmit spectrum. Variants include Coarse WDM (CWDM), Dense WDM (DWDM). Even the same laser may have.