The high precision fiber optical Mach-Zehnder interferometer is suitable for the measurement of refractive index fluctuations in turbulent atmosphere. However,the variation of polarization state,called polarization noise,in low birefringence single mode optical fiber causes the phenomenon of signal fading. The expressions of interferometer's output power,fringe visibility and phase noise are obtained through the method of Poincare sphere analysis. Angle of polarization between input light and optical fiber interferometer must be controlled at about zero by adding mechanical polarization controller. So polarization fading and phase noise can be restrained. Furthermore,manipulative principle of polarization controller is showed. It is an indispensable method to construct optical fiber interferometer of stabilization for optical turbulence.