Performance of DCS-RZ single-sideband signal in 40 Gbit/s long-haul transmission systems

Optical sideband suppression (SS) by means of optical filtering is proposed for duobinary-carrier-suppressed return-to-zero (DCS-RZ) coding format. The performance of DCS-RZ with SS format generated using three different SS filters is investigated through numerical simulation. The power of the nonsuppressed sideband to the power of the suppressed sideband ratio (SSPR) is used to categorise the level of sideband suppression. A minimum level of SSPR of 20 dB is required to generate single-sideband (SSB) signals. It is shown that, for all three SS filters, an SSPR higher than 20 dB can be accomplished by choosing properly the SS filter bandwidth and detuning. Hence, the SS filter can generate single-sideband (SSB) signals. Transmission performance over different distances is assessed numerically. Results reveal that a double-sideband (DSB) modulation format shows better performance (Q-factor improvement of ∼3 dB, for optimum input power levels), even after 8 transmission spans of standard single-mode fibre, than the SSB formats. However, the optically generated SSB signals increase the DSB signal tolerance to dispersion compensation ratio variation more than three times, showing remarkable robustness to optical filter parameter variation, revealing that the DCS-RZ-SSB format is a good candidate for long-haul transmission systems.