Performance analysis of AMI-RZ single-sideband signals in 40 Gbit/s transmission systems

The performance of alternate-mark-inversion return-to-zero (AMI-RZ) signalling format with optical sideband suppression (SS) by means of optical filtering is assessed. The optimisation of the settings of the SS filter is performed numerically for three types of SS filters. A minimum level of the suppressed sideband power ratio of 20 dB is required to generate single-sideband (SSB) signals. It is shown that all three filters can generate AMI-RZ-SSB signals by imposing proper SS filter bandwidth and detuning. Transmission performance over different distances revealed that, in a post-compensation scheme, double-sideband (DSB) modulation format shows better transmission performance than the SSB formats, whereas the duobinary format shows the worst performance of the studied formats. In a pre-compensation scheme, the duobinary shows better performance than the SSB formats. However, the optically generated SSB signals nearly triplicate the DSB signal tolerance to group velocity dispersion and dispersion-compensation ratio (DCR) variation. The duobinary proved to have the best DCR tolerance, whereas the SSB formats proved higher tolerance to polarisation-mode dispersion. It is shown that the SSB formats present remarkable robustness to optical filter parameters variation, revealing that the AMI-RZ-SSB format is a good candidate for long-haul transmission systems.