光纤激光器相干合成系统中组束误差对远场光场的影响

对光纤激光器相干合成系统中组束误差对远场光场分布的影响进行了数值研究,分析了输出单元占空比、位置误差和平行度误差对远场光场分布的影响。结果表明,输出单元占空比的增加只能提高中心光斑的能量,但无法改变中心光斑的平均光强;而位置误差会使远场光场中的旁瓣能量减弱,降低光纤激光器相干合成系统的转换效率。分析发现,位置误差的这种影响可以通过增加输出单元的占空比来减弱。最后,通过分析平行度误差对远场光场的影响,对光纤激光器相干合成系统中的平行度误差控制提出了建议。

Influence of Combining Errors in the System for Coherent Combining of Fiber Lasers on the Far Field of Output

Signal aliasing is one of puzzling questions of a practical fiber-optic hydrophone system based on phase generated carrier (PGC) modulation-demodulation. The physical mechanism of signal aliasing is analyzed theoretically and simulated by computer. The results show that increasing the modulation frequency and lowering the sensitivity of the fiber-optic hydrophone cannot effectively resolve the signal aliasing induced by high-frequency interfering signal. A novel acoustic low-pass filtering scheme is proposed based on the principle of acoustic low-pass filters. A simple fiber-optic hydrophone with an acoustic low-pass filter is designed and fabricated. The acoustic pressure phase sensitivity is measured in a standard standing-wave duct. The experimental results show that the fiber-optic hydrophone has fine characteristics of acoustic low-pass filtering, and can restrain the high-frequency interfering signal strongly. The low-frequency acoustic sensitivity is about -140 dB (0 dB=1 rad/μPa), the attenuation of high frequency is bigger than 20dB. The scheme is very simple and economical, can be used to eliminate the signal aliasing in a practical phase generated carrier modulation-demodulation system effectively.