By using a more complete mathematical model,the thin film Gires Tournois inteferometer (GTI) type optical all pass filter(OAPF) for tunable multi channel dispersion compensation is analyzed and designed.Particularly,influences on the reflectivity and group delay of OAPF by such factors as incident angle of light,the thin film layer structure of reflective mirrors,and the cavity length are numerically analyzed.As an analyzed result,it is clear that for a large incident angle,the polarization splitting phenomena and the amplitude irregularity in the power reflectivity spectra of OAPF will become prominent.As numerical examples,preliminary design results of the single stage GTI OAPF and the multi stage cascaded GTI OAPF with wider compensation bandwidth are provided.