With the development of optical communication, optical communication components are also growing rapidly. As one of the components of optical communication, the optical transceiver module plays the role of photoelectric conversion. There are many types of optical modules. Common ones are QSFP28 optical transceiver modules, SFP transceive optical modules, QSFP + optical transceive modules, CXP optical modules, CWDM optical modules, DWDM optical modules, and so on. Each optical transceive module has different application scenarios and functions. Here UnitekFiber will briefly introduce what is CWDM optical module.