An original scheme for the utilisation of optically preamplified (EDFA
) PPM receivers in intersatellite laser communications is presented. I
n order to facilitate high bit rate operation an analysis is presented
for a PPM system employing threshold detection. When operating at the
STM-1 bit rate of 155 Mbit/s and using conservative parameters the au
thors' model demonstrates a possible receiver sensitivity of 13.5 phot
ons/bit (at a BER of 10(-6)) in the presence of background noise, thus
indicating the impressive potential of the proposed receiver formatio
n for use in satellite communications. The authors further demonstrate
that their threshold detection PPM scheme can obtain receiver sensiti
vities up to 12.3 dB better than an equivalent EDFA OOK NRZ satellite
receiver, for which new results are also presented. Furthermore the re
sults indicate that the PPM system may perform at sensitivities beyond
the fundamental optically preamplified OOK NRZ limit of 27.3 photons/
bit.