Analytical and numerical results are presented for the propagation of optical pulses of 1.5 μm DFB lasers in the presence of fiber dispersion. An approximate analytical model for the evolution of the pulse is given and shown to provide reasonable agreement with the numerical results obtained for digital transmission at 3.0 Gb/s. Comparison with pulse broadening and compression of Gaussian pulses is given, showing that our model, which fits the initial pulse to an asymmetrical function, describes the numerical results better. The utility of the model is for fiber dispersion compensation. Although the examples analyzed are not of practical interest, they show the benefit of the theory with respect to the Gaussian model, since it is able to predict numerical results.