Integration calculations for the absorption spectrum of PPQ polymeric cast film, by means of the Kramers Kronig relation, were performed for a serial number of wavelengths. An existence of an region of anomalous group velocity dispersion (GVD) span near (550￣700) nm band was evidently indicated. The dispersion parameter β 2 is relatively small, |β 2|<1.2 ps 2/m, so that a dispersion neglected nonlinear Schordinger equation was used to described the propagating behavior of femtosecond colliding pulse mode locking (CPM) laser pulses in planar optical waveguide of PPQ film, and consequently, the obtained nonlinear refractive index coefficient n 2 was in a good agreement with the reported value.