Ms. Salisbury et al., SENSITIVITY IMPROVEMENT OF A 1-MU-M LADAR SYSTEM INCORPORATING AN OPTICAL-FIBER PREAMPLIFIER, Optical engineering, 32(11), 1993, pp. 2671-2680
In an effort to increase the SNR of a continuous wave, 1-mu m all soli
d state ladar system, a rare-earth-doped optical fiber amplifier is in
vestigated as a preamplifier for radar return signals. The experimenta
l system is detailed and a theoretical analysis of the fiber amplifier
's effect on both heterodyne and direct detection schemes is provided.
Beginning with the optical powers incident on the detector, the signa
l and noises are analyzed, through the detector electronics, to predic
t the SNR. The SNR is then plotted as a function of the return signal
power, and a SNR threshold is defined to determine a minimum detectabl
e signal power. The return signals required to attain the SNR threshol
d are then compared for four cases: direct detection with and without
the fiber amplifier and heterodyne detection with and without the fibe
r amplifier. For the direct detection scheme considered, our results p
redict a sensitivity increase of 20.6 dB with the addition of the fibe
r amplifier, yet for heterodyne detection the predicted sensitivity in
crease is only 3.1 dB.