The invention discloses a polarization independent tunable filter based on Mach-Zehdner Interferometer (MZI). The polarization independent tunable filter includes hybrid 3 desibel primary coupler, a non 3 desibel secondary coupler, a polarization controller and a pair of polarization maintaining fiber (PMF); The input of the polarization independent tunable all fiber comb filter is an optical light source and the output is a light spectrum which has the desired wavelength shifting and spectral spacing.