空间光混频器分光比调整与90°相位差补偿方法

Power Ratio Adjustment and 90° Phase Difference Compensation Method of Space Optical Hybrid

对空间光混频器的90°相位差补偿的几种方法进行了比较分析,并在此基础之上提出了两种新方法.第一种方法采取旋转本振光支路的1/4波片来补偿相位差,旋转信号光支路的第一个1/2波片来调整I路与Q路分光比;第二种方法通过旋转本振光支路的1/2波片和1/4波片到计算出来的角度来实现预定的相位差和分光比.对两种方法进行仿真分析和系统实验.采用第一种方法时,1/4波片快轴与x轴的夹角在-10°~10°变化时,相位差补偿范围为-14°~29°,分光比在0.7~1.4范围内变化;当1/2波片的快轴与y轴的夹角在35°~55°变化时,分光比在0.47~2.1范围内变化.采用第二种方法求解出I/Q路相位差分别为80°、85°、90°、95°、100°,I/Q路分光比分别为0.5、0.75、1、1.5、2时,1/2波片的快轴和1/4波片的快轴的位置.采用这两种方法均可以简单而精确地实现设定的相位差和分光比,有利于光锁相环的相位锁定以及解调出的信号强度的提高.

Based on the comparation and analysis of phase compensation methods of 90° space optical hybrid,two new methods were proposed.The first method is that 1/4 wave plate on the local oscillator laser branch is rotated to compensate for the phase difference and the first 1/2 wave plate on the signal laser branch is rotated to adjust the power ratio of I/Q branchs.The second method is that 1/2 wave plate and 1/4 wave plate on the local oscillator laser branch are rotated respectively to the calculated angle to achieve a predetermined phase difference and power ratio.The simulation analysis and system experiment of the two methods were carried out.The results of the first method show that when the angle between 1/4 wave plate fast axis and xaxis varies from -10° to 10°,the phase difference ranges from-14° to 29° and power ratio ranges from 0.7 to 1.4;when the angle between 1/2 wave plate fast axis and yaxis varies from 35° to 55°,the power ratio ranges from 0.47 to 2.1.The positions of 1/2 wave plate fast axis and 1/4 wave plate fast axis were solved by the second method when I/Q phase difference is respectively 80°,85°,90°,85° and 100° and the I/Q power ratio is 0.5,0.75,1,1.5 and 2.Either of this two methods can set the phase difference and power ratio simply and precisely,which is advantageous to the phase locking of the optical phase-locked loop and the enhancement of the intensity of the demodulated signal.