Abstract
It is difficult to design small, highly sensitive LIDARs because downsizing their receiving lens degrades
their sensitivity. The main feature of our system is the utilization of optical amplifiers for both the
transmitter and the receiver, which enable us to exceed the detection limit set by thermal noise. In
conventional LIDAR systems, the detection limit is determined by thermal noise because the avalanche
photodiodes (APD) and trans-impedance amplifiers (TIA) directly detect the received signals. In our
LIDAR system, the received signal is amplified by an optical fiber amplifier before reaching the
photodiode and the TIA. Therefore, the signal level is boosted before the incoming signal is depleted by
the thermal noise. There are conditions under which the noise figure for the combination of an optical
fiber amplifier and a photodiode is superior to the noise figure for an APD.
