Investigation of higher order optical multiple pulse position modulation links over a highly dispersive optical channel

This study describes a performance analysis of eight different multiple pulse position modulation (PPM) systems with 4, 7, 12, 15, 17, 22, 28 and 33 slots operating over a plastic optical fibre (POF) channel. The receiver/decoder uses slope detection and a maximum likelihood sequence detector (MLSD). As the analysis of any multiple pulse position modulation (MPPM) system is extremely time consuming, especially when the number of slots is large, a software solution was used. A measure of coding quality that accounts for efficiency of coding and bandwidth expansion was applied and original results showed that the middle systems of these MPPM families are the most efficient for a wide range of bandwidths. Although the efficient Gray coding was used for this investigation, a close to optimum mapping is presented for MPPM systems of the families mentioned above. These mappings were found to be superior to the efficient Gray codes, linear coding and a series of random mappings.