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. What is Fiber optic connector? What is Digital Diagnostic Monitoring (DDM)? Expanded Knowledge: What are CWDM and DWDM modules? What is CWDM? What is DWDM ? Expanded Knowledge: What are Optical fibres ? What is an optical module? The optical module serves as a crucial component in optical fiber. That is, metal medium communication represented by coaxial cables and network cables is gradually being replaced by optical fiber media. Optical modules are a core component of optical fiber communication systems.