Experimental results for optimum coded digital PPM with Ge APD receiver and Gaussian noise approximated theory

Practical and theory results are presented for an optical ( lambda =1.523 mu m) digital PPM system using a suboptimum filtered Ge APD receiver. These original results show that an optimum coding level and APD gain exists for received FWHM Gaussian pulse widths of 11.3 and 35 ns. These optima compare well with those predicted by a suboptimum filter, APD model using Gaussian approximated noise statistics.