Comparison and optimisation of optical single sideband transmitters

A detailed comparison and optimisation of three different techniques to generate optical single sideband (OSSB) signals is presented. Three techniques are investigated: phase-shift (PS), optical filtering and Weaver´s method (WM). The conventional binary and alternate mark inversion (AMI) coding formats are used to assess the transmitter performance for signals with different spectral properties. Different duty-cycles are considered for each format to analyse the generation of OSSB signals from signals with enhanced tolerance to inter-symbol interference. The optimisation of each transmitter parameter is carried out by maximising the amount of accumulated dispersion, using 40 Gb/s bit rate signals, for a specific eye opening penalty. With the binary format, an increase by more than 150 ps/nm of the accumulated dispersion is observed using the WM and NRZ pulses, compared to a reference double sideband signal with NRZ pulses. The optical filtering and PS techniques present lower accumulated dispersion improvements, although the PS allows significant sideband suppression near the carrier frequency. With the AMI format, an increase of 35 ps/nm is achieved by most OSSB transmitters and considerable high sideband suppression is observed using the optical filtering technique