Transmission in wavelength division multiplexing (WDM) optical communication system is mainly impaired and ultimately limited by group velocity dispersion (GVD) and cross-phase modulation (XPM). In this paper, we analytically determine and compare the impact of XPM in a WDM system in presence of first- and second order GVD for standard single mode fiber (SSMF) and dispersion shifted fiber (DSF). Even at high bit rate in a first order GVD compensated system, the second order GVD plays a critical role in limiting the distance of optical signal. The results show that XPM crosstalk penalty due to second order GVD is 16 dB more in DSF than that of SSMF for 0.8 nm channel spacing at 10 GHz modulation frequency. It is also found that the spectral characteristics are strongly dependent on the channel spacing and dispersion of the fiber.