空间相干光通信外差效率及天线像差的影响

Heterodyne Efficiency and the Effects of Aberration for Space Coherent Optical Communication

空间相干光通信中接收天线像差会使光外差效率下降。对本振光为高斯分布,信号光为爱里斑分布的光外差效率进行了研究,给出了无像差时外差效率的解析表达式。当焦平面上爱里斑半径与本振高斯光束光腰半径之比为1.71时,有最大外差效率81.45%。然后以本振光为理想的高斯光束,信号光受像差的影响,研究了倾斜、离焦、球差、彗差、像散等像差引起的光外差效率损失,给出了存在像差时外差效率的一维积分表达式。研究表明即使在采用离焦校正后,一个波长的球差引起的附加外差效率损失仍可达0.9dB。因此对于爱里斑位于光轴上的接收天线,在设计时需仔细处理球差的影响。

Heterodyne efficiency is reduced by aberration of receiving antenna for space coherent optical communication On the assumption that local oscillator wave is Gaussian distribution and signal wave is Airy distribution, a simple analytic expression of heterodyne efficiency is given for an aberration-free system. When the ratio of signal Airy disk radius to local oscillator Gaussian 1/e field radius at focal plane is 1.71, maximum heterodyne efficiency of 81.45% can be obtained. The effect of signal wave receiving antenna＇s tilt, defocus, spherical, coma and astigmatism aberration on heterodyne efficiency is analyzed by assuming that local oscillator wave is perfect Gaussian distribution. One-dimensional integral expression of heterodyne efficiency including aberration effects is given. The result shows that one wavelength spherical aberration could induce 0.9 dB heterodyne efficiency loss even by using defocus adjustment. So spherical aberration should be carefully considered in designing an on-axis receiving antenna.