The common optical modules are divided into short distance(＜2km）, middle distance(10~20km), long distance(＞30km). According to the typical transmission distance, optical module types are divided into SR (100m), DR (500m), FR (2km), LR (10 km), ER (40 km), ZR (80 km). What do the SR, FR that means?
Optical Passive Components 