An all-fiber unbalanced Mach-Zehnder interferometer was designed and several demodulation methods were discussed.A new quadrature signals acquisition technique and phase compensation method were used to calculate wavelength drift.The wavelength-dependent phase information was extracted by application of digital arctangent function and phase unwrapping to the quadrature signals.The sampling ratio was greatly enhanced therefore high frequency wavelength measurement was possible.An efficient wavelength demodulation was experimentally demonstrated.