It is given mathematical models and analyze the performance of polarizers and coupler in an all polarization maintaining fiber (PMF) Michelson interferometer. The optical coherent signal to noise ratio (CSNR) of the interometer is calculated by means of the Jones matrix with cross coupling matrix elements. It is mathematical model and analyze the performance of polarizers and coupler in an all polarization maintaining fiber (PMF) Michelson interferometer. The optical coherent signal to noise ratio (CSNR) of the interometer is calculated by means of the Jones matrix with cross coupling matrix elements.