Error performance of preamplified optical PPM systems with finite extinction ratios

•Analysis of the error performance in optically preamplified M-ary PPM communication systems with finite extinction ratios.•Theoretical expression for bit error rates and numerical computation for different symbol sizes and extinction ratios.•Power penalties due to finite extinction ratio for both coded and uncoded systems.•In certain cases, lower symbol sizes may yield an error performance similar to that achieved by higher symbol sizes.

In this paper, we present an analytical study of the error performance in optically preamplified, M-ary pulse position modulation, in free-space optical communication systems with finite extinction ratios. We derive a theoretical expression for the probability of bit error and compute it numerically for different symbol sizes and extinction ratios. We also provide the power penalty due to a finite extinction ratio for both coded and uncoded systems. The study shows that, in certain cases and for a given extinction ratio, lower symbol sizes may yield an error performance similar to that achieved by higher symbol sizes.