Performance and optimal presynchronisation filtering for direct-detection optical fibre PPM

Abstract

A thorough performance analysis is presented for a self-synchronised direct-detection optical fibre pulse position modulation (PPM) system. A new hybrid erbium-doped fibre amplifier (EDFA) PPM system is analysed. Sensitivity results are presented for a system operating at 622 Mbit/s and lambda =1.53 µm. These results indicate that EDFA PPM offers 7.9 dB sensitivity improvement over a comparable PCM system and is beyond the PCM fundamental limit. An original expression is presented for the PPM power spectral density under jitter. Original results are given for the extracted-slot clock timing variance and the resultant jitter wrong-slot error probability. The sensitivity penalty associated with self synchronisation is investigated and shown to vary between 0.15 and 1.9 dB for the range of parameters considered. An original presynchronisation filtering strategy is proposed and results are presented demonstrating its effect. The sensitivity penalty was bound to about 0.1 dB when the proposed presynchronisation filter was utilised.