中文摘要：

通过相干合束提高光纤激光源的输出功率是目前研究的一个热门领域,其中多束激光的相位控制是提高合束效率的关键技术之一.本文基于主动相位锁定技术对传统外差探测法进行了改进,基于压电陶瓷及光纤电光相位调制器双通道伺服反馈,实现了对同一激光源输出的两路相位独立变化的1531 nm激光长时间的相位锁定.通过选择合适的PID控制参数,将反馈带宽拓展到了220kHz（受限于PID控制器自身带宽）.最终的相位锁定控制在0.88°以内,即相位控制精度为λ/400,经过160 s平均后可得到相位锁定的最佳值为0.006°,整体实验装置结构简单、运行稳定.

英文摘要：

Fiber laser can be used for fiber optic communications, laser cutting, industrial manufacture, defense security and many other fields because of its advantages of narrow output linewidth, good reproducibility, etc. However, due to nonlinear and thermal effects, only a limited output power of a single fiber can be obtained with a sharp attenuation of the output beam quality, which obstructs the applications of fiber lasers. Therefore, the research of expanding the power of a fiber laser source while maintaining its beam quality by combining coherent beam has become a hot subject at present. In this field, the performance of phase control of coherent laser beams is a key factor to influence the efficiency of combination. The phase-controlling methods mainly include stochastic parallel gradient descent control algorithm,dithering, and heterodyne detection. In this paper, based on the active phase lock technology, the traditional heterodyne detection method is improved by the use of a fiber electro-optic phase modulator（EOM） rather than an acousto-optic frequency shifter（AOFS） to avoid the complex designs of the RF driver and circuit, which makes the overall experimental setup simple and stable. Moreover, in order to achieve a stable and wide correction range of phase locking, two servo paths are designed by use of piezoelectric transducer（PZT） and EOM1 to correct the optical phase differences. Firstly,a single-frequency narrow-width fiber laser with its central wavelength of 1531 nm is split by a beam splitter to generate a signal and a reference beam, respectively. The reference beam is phase modulated by another EOM2 with a 15 MHz signal. The phase error signal is obtained by demodulating the detected heterodyne signal at the modulation frequency.After that the error signal is divided into two parts, and sent to two PID servos to control PZT and EOM1, respectively.The PZT, used in the slow feedback loop, eliminates the laser phase error induced by the ambient temperature drift,while the EOM1, in the qu