基于零差相干光通信的激光噪声抑制技术研究

发布时间：2018-01-02 09:03

本文关键词：基于零差相干光通信的激光噪声抑制技术研究　出处：《电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：零差相干光通信技术是解决未来星地通信带宽瓶颈的重要途径,该体制对光源的强度噪声、线宽和功率均提出很高的要求。固体激光器具有易获得窄线宽、高功率输出的优点,使其成为零差相干光通信的一种优质备选光源。现在零差相干光通信中较普遍采用1.06μm的Nd:YAG NPRO(非平面环形腔)激光器的光源方案,其在噪声、线宽和功率方面的性能日臻完善。与1.06μm波长相比,1.55μm处于第三通信窗口,能与现有光通信器件和设备更好的兼容,因而在激光测距、光通讯等领域都有着很广泛的应用与发展空间,迫切需要开展1.55μm激光光源的噪声抑制技术研究。本文用光电负反馈方法,对Nd:YAG NPRO激光器和Er:Glass单频激光器进行噪声抑制研究。主要研究内容包括四个方面:(1)基于低折射率介质Er:Glass设计了NPRO,获得足够大的本征偏振态损耗差,可实现稳定的单频行波振荡。对输出噪声谱进行仿真计算,优化谐振腔的增益和损耗等参数,降低自由运转状态下的输出强度噪声。(2)采用三能级系统的噪声的全量子理论分析模型,分析三能级固体激光噪声的理论特性,克服传统速率方程理论定量分析不准确的缺陷。求解自由运转下和负反馈下的噪声传递函数和输出噪声谱。(3)为了更好地补偿高频相位延迟,对比分析了不同阶次反馈控制环路对噪声抑制效果。采用高阶相位超前电路设计了反馈控制环路,以改善噪声抑制效果,完成了反馈控制电路的研制。(4)在实验方面,搭建了Nd:YAG NPRO激光器,实现了单频激光运转,完成了对输出光束的准直、偏振控制和光纤耦合。对Nd:YAG NPRO激光器进行噪声抑制实验,采用一阶相位超前电路进行反馈控制后,相对强度噪声(RIN)峰值抑制了约24dB,但峰值会向高频方向移动;采用二阶相位超前电路进行反馈控制后,RIN整体抑制了约32dB;采用三阶相位超前电路进行反馈控制后,整体抑制了约42dB,整体RIN水平低于-145dB/Hz,验证了高阶相位超前电路可改善对四能级激光器的噪声抑制效果。还搭建了平凹腔Er:Glass单频激光器,通过腔内的标准具选模实现了单纵模运转。然后对此激光器进行了噪声抑制实验,采用一阶相位超前电路没有明显噪声抑制效果,而三阶相位超前电路在RIN峰值处噪声被抑制了12.2dB,证明高阶相位超前电路也可改善三能级激光器的降噪效果。
[Abstract]:Homodyne coherent optical communication technology is an important way to solve future satellite communication bandwidth bottleneck, the light source intensity noise on the system, line width and power are high demands. To obtain solid laser with narrow linewidth, has the advantages of high power output, the homodyne coherent optical communication is an excellent alternative source now homodyne coherent optical communication is widely used in 1.06 m Nd:YAG NPRO (non planar ring cavity laser light source), the noise performance of the power line width and improving. With 1.06 m wavelength, 1.55 m in the third communication window, can be compatible with existing optical communication devices with better equipment, thus in laser ranging, optical communication and other fields have a wide range of application and development, it is urgent to carry out the research of noise suppression of 1.55 m laser source. The optoelectronic negative feedback method for Nd:YAG NPRO Er:Glass laser and single frequency laser on noise suppression. The main research contents include four aspects: (1) the design of NPRO Er:Glass based on low refractive index, enough polarization eigenstate loss difference, single frequency traveling wave oscillation can realize stable. The output noise spectrum of the simulation, optimization of gain and loss the resonant cavity parameters, reduce the output intensity of noise free running state. (2) by means of the quantum theory of three level system noise analysis model, theoretical analysis of the properties of the three level solid state laser noise analysis, overcome the defects of the inaccurate rate equation theory. The traditional quantitative calculation of free running noise and negative feedback condition the transfer function and the output noise spectrum. (3) in order to compensate the high frequency phase delay, comparative analysis of different order feedback control loop suppression effect on noise. Using the high order phase advance circuit design The feedback control loop to improve the noise suppression effect, and complete the development of the feedback control circuit (4). In the experiment, Nd:YAG NPRO laser was built up, to achieve a single frequency laser, the collimation of the output beam, polarization control and fiber coupling. Noise suppression experiment of Nd:YAG NPRO laser, the first order phase advance circuit feedback control, the relative intensity noise (RIN) peak suppression by about 24dB, but the peak moves to the high frequency direction; the two order phase advance circuit feedback control, the overall RIN inhibited about 32dB; using the three order phase advance circuit feedback control, the overall suppression of about 42dB overall, RIN level is lower than the -145dB/Hz, verify the high order phase lead circuit can improve the noise suppression effect of four level laser. Also build a flat concave cavity single frequency Er:Glass laser by intracavity etalon The mode selection of single longitudinal mode operation. Then the laser noise suppression experiment, using the first-order phase advance circuit has no obvious effect on noise suppression, and the three order phase lead circuit in RIN peak noise is suppressed by 12.2dB, prove the high order phase advance circuit can also improve the noise reduction effect of three level laser.

【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN929.1

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