An optical module typically consists of an optical transmitter (TOSA, Transmitter Optical Sub-Assembly, containing a laser diode), an optical receiver (ROSA, Receiver Optical Sub-Assembly, containing a photodetector), functional circuits, and optical (electrical) interfaces. Its primary function is to achieve optoelectronic conversion by converting electrical signals into optical signals and vice versa. Today, when we talk about optical modules, we usually mean. Integrated circuits and reference designs help you create a smaller and faster optical module design used in high-bandwidth data communication applications. The source drive circuit intensity modulates the opt cal source by varying the current through the source.