An active phase locking of multiple fiber channels via square wave dithering algorithm

A novel active phase locking technique base on single detector is proposed and demonstrated experimentally. Using dual-level rectangular-wave phase modulation and time division multiplexing, the proposed multi-level phase dithering technique can achieve the same phase error signal as single/multi-frequency dithering technique, but without coherent demodulation circuit. Experimental investigation on coherent beam combination of 10 fiber laser beams is successfully demonstrated, with imposing an additional phase disturbances to mimic the phase noises in the high power fiber amplifiers. The combining efficiency with modulated phase noise is achieved above 97.55% and the accuracy of phase control is improved to λ/42 rms. One of the application fields, i.e., beam steering based on coherent beam combining using square wave dithering algorithm are proposed.