基于超导纳米线单光子探测器深空激光通信模型及误码率研究

发布时间：2018-11-22 12:44

【摘要】：超导纳米线单光子探测器(SNSPD)作为一种新型单光子检测器,兼具有灵敏度高、噪声低和速度快等优点,在空间激光通信领域已经获得最新的应用,并取得了突破性的成果。本文系统介绍了 SNSPD的工作原理和发展过程,展示了其优异的性能和发展潜能,并详细介绍了 SNSPD在深空激光通信的重要应用实例—NASA激光通信演示实验。在对传统器件进行性能表征的基础上,测试了特殊功能的器件:对于并联电阻的光子数分辨器件,我们采集到了6种幅值的输出脉冲波形,还观察了计数器鉴别电平对计数率的影响,都证明了器件具有6光子分辨能力;对于使用高折射率材料Si制备的偏振不敏感器件,我们使用宽波段光源和偏振控制器,测得偏振态对器件效率的影响得到很大程度的抑制,在1550 nm处,平行极化时效率为61%,垂直极化时为56%,实验结果和仿真结果能够吻合。单光子条件下的激光通信不仅需要考虑传输环境的影响,还需要考虑实际单光子探测器性能和光子数量子态的分布。本文在不考虑大气湍流影响的情况下,以光电探测模型为基础,引入超导纳米线单光子探测器(SNSPD)系统探测效率和暗计数,建立了反应系统差错性能的数学模型,提出了系统误码率的计算公式。对公式中的两个因素,光强和激光脉冲重复频率对误码率的影响进行仿真,再通过实验结果验证仿真模型。模拟激光通信光电探测的实验结果表明,光强对误码率的影响最明显,随着光强从0.01光子/脉冲到1000光子/脉冲的增加,误码率从10-1到10-7量级明显下降;激光脉冲重复频率对误码率的影响受到不同光强的制约,但都随着脉冲重复频率的增加呈下降趋势。与此同时,当增加光强或者提高速度时,误码率高于仿真结果,约在10-4量级,其原因可能是实际通信中调制光信号的消光比不足和光纤引入背景噪声提高了系统暗计数。该模型和实验结果,为进一步开展基于SNSPD的月球-地球、火星-地球等高速深空激光通信奠定基础。
[Abstract]:As a new type of single-photon detector, superconducting nanowire single photon detector (SNSPD) has many advantages, such as high sensitivity, low noise and high speed. This paper systematically introduces the working principle and development process of SNSPD, shows its excellent performance and development potential, and introduces in detail the demonstration experiment of NASA laser communication, which is an important application example of SNSPD in deep space laser communication. On the basis of the performance characterization of the traditional devices, the special function devices are tested. For the photonic digital resolution devices with parallel resistance, we have acquired six kinds of output pulse waveforms with amplitude. The effect of counter discriminant level on the counting rate is also observed. It is proved that the device has a 6-photon resolution. For polarization-insensitive devices fabricated with high refractive index material Si, we use a wide band light source and a polarization controller to measure that the effect of polarization state on device efficiency is greatly suppressed. At 1550 nm, the efficiency of parallel polarization is 61%. The vertical polarization is 56 and the experimental results are in good agreement with the simulation results. In the case of single-photon laser communication, not only the effect of transmission environment should be considered, but also the performance of the real single-photon detector and the distribution of the number of photon substates should be considered. In this paper, on the basis of photoelectric detection model, the detection efficiency and dark count of (SNSPD) system of superconducting nanowire single photon detector are introduced, and the mathematical model of error performance of reaction system is established without considering the influence of atmospheric turbulence. A formula for calculating system bit error rate (BER) is presented. The effects of two factors, light intensity and laser pulse repetition rate, on the error rate are simulated, and the simulation model is verified by the experimental results. The experimental results of simulating photoelectricity detection in laser communication show that the influence of light intensity on BER is the most obvious. With the increase of light intensity from 0.01 photon / pulse to 1000 photon / pulse, the BER decreases obviously from 10 ~ (-1) to 10 ~ (-7). The effect of laser pulse repetition rate on bit error rate is restricted by different light intensity, but all of them decrease with the increase of pulse repetition rate. At the same time, when the light intensity is increased or the speed is increased, the bit error rate is higher than the simulation result, which is about 10-4 order of magnitude, which may be due to the deficiency of extinction ratio of modulated light signal in actual communication and the increase of the system dark count caused by the introduction of background noise from optical fiber. The model and experimental results lay a foundation for the further development of high-speed deep space laser communication based on SNSPD, such as the Moon Earth, Mars Earth and so on.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2018
【分类号】：TN929.1

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