Single-Sideband Differential Phase-Shift Keying Asynchronous Carrier-Suppressed Return-to-Zero – A Novel Signaling Format Optimized for Long-Haul UDWDM Systems

In this paper, a novel single-sideband differential phase-shift keying asynchronous carrier-suppressed return-to-zero (SSB-DPSK-ACS-RZ) format is proposed for long-haul ultradense wavelength-division multiplexing (UDWDM) systems with 43 Gbit/s/channel and 50 GHz of channel spacing. The time delay between the DPSK and clock signals is optimized to achieve higher eye-opening and improved group velocity dispersion tolerance. Furthermore, the tight SSB filtering performed by the multiplexer is used to convert the DPSK-ACS-RZ signal from phase- to amplitude-shift keying, allowing using a lower-cost direct-detection receiver and improving its spectral efficiency. The single-channel and UDWDM transmission performance of the novel format is numerically investigated and compared to the SSB duobinary carrier-suppressed RZ, bandwidth-limited duobinary, phase-modulated duobinary transmission, and bandwidth-limited DPSK formats. The SSB-DPSK-ACS-RZ format shows similar Q-factor and tolerances to pre- and in-line dispersion compensations and fiber nonlinearity to the ones of other investigated direct-detection formats. Significant total residual dispersion tolerance improvement is achieved by the SSB-DPSK-ACS-RZ format relative to the other formats due to the signal chirp. Moreover, the SSB-DPSK-ACS-RZ format shows higher Q-factor than the one of the bandwidth-limited DPSK for long-haul UDWDM transmission systems. In ultra-long-haul UDWDM transmission systems, SSB-DPSK-ACS-RZ and bandwidth-limited DPSK formats show similar performance.