Nonlinear tolerance of 112 Gbit/s polarization-multiplexed differential quadrature phase-shift keying signal over long-haul transmission with different types of neighboring channels, and with a cascade of 50-GHz grid is increased. The result indicates considerable tolerance to nonlinear effects is observed and proves the feasibility of 112 Gbit/s overlaying existing 10 Gbit/s or 43 Gbit/s commercial systems despite the presence of strong cross-phase modulation.