They are devices that amplify an incoming optical signal directly, without the need to convert it to an electrical signal first. These units are designed for PDH, SDH, SONET and optical Ethernet transmission applications and has been developed to. Among the various types of amplifiers, optical Booster Amplifier (BA), optical Line Amplifier (LA), and optical Pre-amplifier (PA) are each with unique functions. After reading this article, we can understand what they are and what the differences are between them. What is the optical Booster. Booster (power) amplifiers: Boost power into transmission fiber, low NF, high Psat. Typical fiber cables experience a loss of about 0.