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). 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). First of all, the two most important parts of the optical transceiver are the optical transmitting assembly (TOSA) and the optical receiving assembly (ROSA). Among them, the optical transmitting assembly (TOSA) mainly plays the role of converting electrical signals into optical signals (E/O ). The optical module, known as Optical Transceiver in English, is a general term for various module categories, including optical receiver modules, optical transmitter modules, optical transceiver modules, and optical forwarding modules. Today, when we talk about optical modules, we usually mean. The optical module serves as a crucial component in optical fiber communication systems, operating at the physical layer, which is the lowest layer in the OSI model. An. Optical modules are devices used to connect network devices, transmit and receive data between network devices, and can be used to convert optical and electrical signals. Figure 20-27 shows how an optical module works.