The effect of signal pulse shape on the transmission performance is studied for an optical fiber communication system with cascaded in line optical phase sensitive amplifiers (PSA′s) having phase shifting between pumping and signal light. Computer simulation shows that at different phase shifting the eye pattern degradation of high speed signal increased rapidly with the accretion of fiber dispersion, and changed with signal pulse shape for given fiber dispersion. From the simulating results, it is known that signal pulse shape also affect the system performance. The system transmission performance of using super Gaussian pulse is superior to that of using Gaussian pulse, and super Gaussian pulse has an optimum pulse exponent for best transmission performance.