Influence of Tight Optical Filtering on Long-Haul Transmission Performance of Several Advanced Signaling Formats

In this paper, the influence of tight optical filtering (TOF) on dispersion-managed long-haul (LH) transmission performance of advanced signaling formats is analyzed through extensive numerical simulation. The investigation is performed for duobinary, carrier-suppressed-return-to-zero (CS-RZ), and duobinary CS-RZ (DCS-RZ) signaling formats, which were suggested for LH ultradense wavelength division multiplexing systems previously. The simultaneous variation of pre-, inline, and postcompensation of dispersion amounts is performed to find out the optimum dispersion map of each signaling format with and without TOF, and their dispersion tolerances. The tolerance to fiber nonlinearity of each signaling format is also analyzed. It is shown that the TOF affects differently the LH transmission performance of the three signaling formats. The TOF reduces the dispersion tolerances of the duobinary signaling format, but improves the maximum $Q$-factor and tolerance to nonlinear fiber effects due to the eye-opening improvement. It improves the tolerance to inline dispersion and fiber nonlinearity of the CS-RZ signaling format, but it reduces remarkably the eye opening leading to a significant $Q$-factor degradation. It improves also the maximum $Q$-factor and the total residual dispersion tolerance of DCS-RZ format due to the reduction of the signal spectrum width, but it worsens the tolerance to pre- and inline dispersion, and fiber nonlinearity.