We experimentally study the effects of cross-phase modulation and stimulated Brillouin scattering limitations in long unrepeatered transmission systems at 10.7 Gb/s. We find significant SBS suppression in wavelength-division multiplexed systems and investigate system performance for different numbers of channels and channel spacing. We find greater than 4 orders of magnitude improvement in bit error rate (BER) with a WDM system in comparison to single channel transmission due to SBS impairment mitigation. Unrepeatered transmission over 323 km with a simple system configuration using low-attenuation fiber, NRZ modulation, and only EDFA amplification is demonstrated with more than 5 dB system margin over the forward error correction (FEC) threshold.