As illustrated in typical SFP internal structure diagrams, the module's core components include an optical transmitter assembly (TOSA), laser driver, optical receiver assembly (ROSA)—some high-sensitivity modules (like L16. 2) use APD receivers, which require an additional booster. Optical modules are key components in fiber optic communication systems, responsible for electro-optical conversion, meaning the conversion of electrical signals to optical signals or vice versa. The internal structure of an optical module is complex but can be divided into several main parts.