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The nonlinear properties of NRZ, RZ50, RZ33, CSRZ, and DPSK in 40 Gbit/s 1000 km single fiber and DMF systems are analysed. We find that DPSK provides 1.3 dBQ nonlinear tolerance advantage over RZ in both optical links. We show that RZ formats tolerate 2 dBm higher power per channel than NRZ, further increasing their advantage in linear receiver sensitivity. We find that smaller duty cycle formats exhibit better performance due to suppression of sXPM and sFWM and CSRZ nonlinear tolerance to sFWM is enhanced due to the intermittent phase of the signal. In addition, we determine linear cross-talk penalties for MF from WDM back-to-back simulations. With respect to NRZ performance of RZ33 is offset by 0.9 dBQ, RZ50 by 1.5 dBQ, CSRZ by 0.7 dBQ, and DPSK by 0.2 dBQ.