Phase noise detection method in fiber lasers based onphase modulation and demodulation

In coherent combination of active phase control, there have existed three main phase detection techniques until now, they are heterodyne phase detection technique, multi-dithering technique and stochastic parallel gradient descent algorithm. A new phase detection method based on phase modulation and demodulation is proposed according to the principle of heterodyne phase detection and multi-dithering technique. Periodic phase modulation signal is implemented on a reference laser, and the coherent detection is carried on between the reference laser and the signal laser. With some processing of the modulation signal and the coherent detected optoelectronic signal, the phase noise is detected and the noise compensation can be realized. Numerical simulation and experimental studies are conducated. Experimental results show that the phase detection accuracy is higher than 1/50 wavelength and the average phase compensation residual error is less than 1/50 wavelength in the case of a 2 kHz sine wave phase noise with a phase region of