Abstract: This paper discusses an optical fiber coated with pieaoelectric AnO.,the optical fiber acousto optic phase modulator.The geometry of optical fiber using ZnO coating is firstly presented.Then,the basic theory of piezoelectric resonator of this geometry is analyzed and also the T network of electrical equivalent circuit for the optical fiber coated with piezoelectric ZnO been deduced.Finally,the experimental setup for optical phase measurement of the optical fiber acousto optic phase modulator is given.