Starting from the Huygens-Fresnel diffraction integral,the spectral shifts and spectral switches of femtosecond optical pulses in Young′s interference experiment are studied and analyzed numerically.It is shown that the spectral shifts and spectral switches,which take place in Young′s interference experiment,depend on the pulse width,carrier frequency,obscuration ratio and the position of field points in general.The number of the spectral switches decreases with decreasing obscuration ratio,and the relative spectral shifts at the spectral switches increases with decreasing carrier frequency and pulse width.The spectral switches studied in this paper belong to the phenomenon of singular optics because the minimum at the spectral switches Smin=0.The information encoding and transmission can be achieved by a suitable variation of the obscuration ratio.