Abstract: In order to understand the luminescence mechanism and modulation characteristics of distributed feedback laser(DFB), the corresponding relationship and fitting equation between modulation current and output central wavelength of FITEL laser and JDS Uniphase laser were obtained through theoretical analysis and experiment. It was proved that two DFB lasers had non-linear relationship in practical application. The results show that the relationship between 3dB bandwidth and the driving current amplitude of FITELFRL15DCWD-A82 laser is 3.715pm/mA. The available coherence length of the laser is optimized by modulation result. It is proved that the frequency change of the driving signal does not affect 3dB spectral width. The research results can provide experimental basis for drive circuit design of a coherent detection system.