The pulse propagation at optical wavelengths (0.4--10.0 μm) through the fog-filled medium has been studied considering the effects of differential attenuation and phase dispersion on the spectrum of the propagated signal. The pulse distortion, in terms of percentage change in the width of a Gaussian pulse, has been obtained using a closed solution of Fourier integral for the time domain representation of the pulse. This technique, initially developed by Forrer <1958>, approximates the propagation constants by a truncated Taylor series. It has been found that the pulse distortion can be quite severe for pulses of width 0.001 ns or smaller, depending on wavelength, fog type, pulse width, and path length. Both broadening and compression of pulses can occur according to the values of second derivatives of the propagation constants. ¿ American Geophysical Union 1996