Abstract
In this study, we compare the end-to-end performance of optically pre-amplified 16-ary and 64-ary pulse position modulation (PPM) systems for the use in free-space optical communications. Simulations were carried out to evaluate the bit-error-ratio (BER) versus Eb/N0 for several scenarios where Eb is the energy per bit and N0 is the effective single-sided power spectral density of the noise at the amplifier input. For the optimum full width half maximum (FWHM) of the Fabry-Perot filter combined with the optimal 3-dB bandwidth of the butterworth electrical filter in the presence of dual polarized amplifier noise and no extinction ratio, the required Eb/N0 = 8.37 dB for 16-ary and Eb/N0 = 7.1 dB for 64-ary at BER=10-4. At extinction ratio of 15 dB, the 16-ary PPM system outperforms the 64-ary PPM system with Eb/N0 = 10.8 dB for 16-ary and Eb/N0 = 12.64 dB for 64-ary since the orthogonality of the M-ary PPM is not maintained any further. The results also indicate that 16-ary PPM systems are more suitable than 64-ary PPM systems for 10 Gbps inter-satellite optical links.
Published Version
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