Ms. Salisbury et al., OPTICAL-FIBER PREAMPLIFIERS FOR LADAR DETECTION AND ASSOCIATED MEASUREMENTS FOR IMPROVING THE SIGNAL-TO-NOISE RATIO, Optical engineering, 33(12), 1994, pp. 4023-4032
In an effort to increase achievable postdetection signal-to-noise rati
os (SNRs) of continuous-wave, 1-mu m all-solid-state radar systems, a
prototype rare-earth-doped optical-fiber amplifier has been included i
n the optical return signal path of both a heterodyne and a direct det
ection ladar system. We provide numerical predictions for SNR increase
s according to our previously developed theory. We also detail our exp
erimental efforts and provide the results of SNR measurements for four
distinct cases: direct radar detection with and without a fiber ampli
fier, and heterodyne ladar detection with and without a fiber amplifie
r. Experimentally measured increases in SNRs for ladar systems incorpo
rating an optical-fiber amplifier are then compared with our earlier p
redictions. Specifically, we have found that for direct detection with
a fiber amplifier in place, the predicted SNR increase is 42.0 dB, an
d we have measured an increase of 36.5 dB. Similarly, for heterodyne l
adar detection with a fiber amplifier, the predicted SNR increase is 3
.8 dB, and we have measured an increase of 8.0 dB.