The photorefractive index generated inside the photorefractive crystal has a very small change and is not easy observed in real time,resulting in the failure to characterize the quality of the writing lattices.In order to observe the temporal and spatial variation of the photorefractive index caused by the writing of photorefractive photonic lattice,we propose amplified Fourier transform method based on Mach-Zehnder optical path.The resolution of the measurement is greatly improved.This method can observe t...