According to the encapsulation type, optical modules are classified into SFP, eSFP, SFP+, XFP, SFP28, QSFP+, CXP, CFP, QSFP28, and QSFP-DD. All optical modules are hot swappable. An optical module usually consists of an optical transmitting device (TOSA, including a laser), an optical receiving device (ROSA, including a photodetector), functional circuits,main control circuit board (PCBA), housing and optical (electrical) interface and other components. How do optical. QSFP-DD (Quad Small Form-factor Pluggable-Double Density) Optical Module: Double-density four-channel small pluggable packaged optical module, defined by the QSFP-DD MSA group as a high-speed pluggable module. Allows multiple signals to be transmitted simultaneously over a single fiber: CWDM (Coarse Wavelength Division Multiplexing): Uses wider wavelength. An optical module is a typically hot-pluggable optical transceiver used in high-bandwidth data communications applications. Optical modules typically have an electrical interface on the side that connects to the inside of the system and an optical interface on the side that connects to the outside. Optical modules are available in various types to meet diversified requirements.