We present coherent phase modulation detection for laser phase noise measurement via a self-heterodyne technique. Measurements have been performed for DFB and SGDBR lasers to demonstrate the technique. The results show that DFB laser phase noise is well described by the random-walk phase fluctuation while SGDBR has additional frequency fluctuation due to 1/noise below 100 MHz that significantly broadens the linewidth. © 2011 SPIE-OSA-IEEE.