A new delayed self-heterodyne technique using an unbalanced Michelson interferometer (MI) composed of a 3×3 optical fiber coupler is proposed. The principle of the technique to measure the laser phase and frequency noise are analyzed theoretically. The experimental setup is introduced. Also, the technique is used to characterize the phase noise power spectral density (PSD), frequency noise PSD and linewidth of two typical kinds of lasers, distributed feedback (DFB) semiconductor laser (Emcore) and super-narrow linewidth DFB fiber laser (NKT). The results show that the technique can measure the noise characters of different kinds of lasers and it confirms the correction and robustness of the proposed technique.