REQUIRED ENERGY FOR A LASER-RADAR SYSTEM INCORPORATING A FIBER AMPLIFIER OR AN AVALANCHE PHOTODIODE

The transmitted energy required for an airborne laser radar system to be able to image a target at 20 km is investigated. Because direct det ection is being considered, two methods of enhancing the received sign al are discussed: (1) using an avalanche photodiode (APD) as the detec tor and (2) using a commercial fiber amplifier as a preamplifier befor e a photodetector. For this analysis a specified signal-to-noise ratio was used in conjunction with the radar range equation, which includes the effects of atmospheric transmission and turbulence. Theoretical a nalysis reveals that a system with a fiber amplifier performs nearly t he same as a system incorporating an APD.