We propose a new integrated method which covers addition of any two signed digit numbers in all-optical domain. To implement this scheme we have exploited some photo-refractive characters of optical non-linear materials,which may experience 0.1-0.2dB attenuation loss as silica is used as non-linear medium. Moreover,the attenuation loss may be reduced to 0.001 dB/m if we consider the use of slow light at 1.56μm.