WDM technology (Wavelength Division Multiplexing) is to simultaneously allow two or more optical wavelength signals to transmit information through different optical channels in the same optical fiber, multiplexing the tight spectral spacing of a single optical fiber, to achieve the best transmission performance (such as the minimum degree of dispersion or attenuation). In this case, the number of fibers will be required less under the specified information transmission capacity.
CWDM technology is one of the applications of WDM technology. CWDM(Coarse Wavelength Division Multiplexer, also known as dilute wavelength division multiplexing) uses optical multiplexers to multiplex the wavelengths transmitted in different optical fibers. The transmission technology in an optical fiber is a low-cost WDM transmission technology for the access layer of the metropolitan area network.
The wavelength of CWDM is between 1270nm-1610nm, there are 18 bands in total and each band is separated by 20nm. In order to distinguish between conventional wavelengths and CWDM wavelengths, the related organizations shifted the channel center by 1nm which is 1271nm-1611nm. Since the 1271nm-1471nm band has obvious attenuation, the commonly used bands for CWDM are 1471nm-1611nm bands.
CWDM is compact and cost-effective for short-distance transmission. The cost is mainly in filters and lasers. Due to the 20nm wavelength interval, CWDM has low requirements on the technical indicators of the laser, which simplifies the structure of the optical multiplexer/demultiplexer and then reduced the cost.
