Time to enter 2019, when 400G has become a hot topic in the optical communications industry, the world's leading optical transceiver manufacturers have launched their own 400G optical modules. When we list the form-factors of these manufacturers' 400G optical modules (as shown in the figure below), we found that all the manufacturers except the Finisar (acquired by II-VI) have adopted the QSFP-DD form-factor — the market seems to have recognized QSFP-DD as the first choice for form-factors of 400G optical modules, though some manufacturers have also introduced 400G optical modules with OSFP and CFP8 form-factors. 400G Form-factors of Mainstream Optical Transceivers Manufacturers Tips: QSFP-DD is a high-speed pluggable module form-factor defined by the QSFP-DD MSA group. "The QSFP-DD MSA group has defined the next generation, high-density, high-speed pluggable module form factor that addresses the industry need for high-density, high-speed networking solution...