DPSK光调制系统相位噪声分析及补偿方法

发布时间：2018-06-11 14:54

本文选题：DPSK光调制 + 相位噪声　；参考：《长春理工大学》2017年硕士论文

【摘要】：自由空间光通信是目前通信领域的研究热点和前沿,在众多适用于自由空间光通信系统的调制格式中,DPSK光调制格式最受关注。但是,DPSK光调制码型采用相位携带信息,对相位噪声很敏感,相位噪声造成信号相位的起伏会使信息失真,限制传输距离。本文重点分析DPSK光调制系统中产生相位噪声的主要因素并加以补偿,使系统中的相位噪声减小,发射性能得到提升。本文根据DPSK光信号的调制原理,完成了以下工作:(1)设计自由空间光通信DPSK调制系统,并通过光学仿真软件Optisystem验证此系统在理想条件下的可行性;(2)分析系统相位噪声的主要来源,得出系统中产生相位噪声的主要因素为:半导体激光器线宽展宽、半导体激光器频率漂移以及相位调制器半波电压随温度发生变化;(3)研究系统相位噪声的补偿方法。采用闪耀光栅外腔反馈线宽补偿技术,通过延长半导体激光器的有效腔长减小其线宽,对由半导体激光器线宽展宽产生的相位噪声进行补偿;采用声光偏频无调制频率补偿技术,通过控制激光器有效腔长的改变稳定激光频率,对由半导体激光器频率漂移产生的相位噪声进行补偿;采用数字PID半波电压补偿技术,控制调制器的驱动电压,使其峰峰值始终等于调制器半波电压,对由相位调制器半波电压随温度变化产生的相位噪声进行补偿;(4)通过仿真与实验对系统相位噪声补偿技术的可行性进行验证,最后通过相位噪声补偿前后系统输出信号星座图和眼图的对比,对系统的整体性能进行了分析。实验结果表明,在对系统中相位噪声的主要来源进行补偿之后,提高了系统输出信号的稳定性,系统误码率得到改善,发射性能得到很大提升,由此说明本设计的正确性。
[Abstract]:Free space optical communication is the research hotspot and frontier in the field of communication. Among the many modulation formats suitable for free space optical communication systems, DPSK optical modulation format has attracted the most attention. However, the DPSK optical modulation code uses phase to carry information, which is very sensitive to phase noise. The fluctuation of signal phase caused by phase noise will make the information distorted and limit the transmission distance. In this paper, the main factors that produce phase noise in DPSK optical modulation system are analyzed and compensated, so that the phase noise in the system is reduced and the emission performance is improved. According to the modulation principle of DPSK optical signal, the following work has been accomplished: 1) designing the DPSK modulation system for free space optical communication, and verifying the feasibility of the system under ideal conditions by Optisystem.) analyzing the main source of phase noise in the system. It is concluded that the main factors to produce phase noise in the system are: linewidth broadening of semiconductor laser, frequency drift of semiconductor laser and half-wave voltage of phase modulator changing with temperature) the compensation method of phase noise in the system is studied. By extending the effective cavity length of the semiconductor laser and reducing the linewidth, the phase noise caused by the linewidth broadening of the semiconductor laser is compensated by using the feedback linewidth compensation technique of blazed grating external cavity. The phase noise caused by frequency drift of semiconductor laser is compensated by controlling the effective cavity length of the laser to compensate the phase noise generated by the frequency drift of semiconductor laser, and the digital pid half-wave voltage compensation technique is adopted. Control the driving voltage of the modulator so that its peak value is always equal to the half wave voltage of the modulator. The phase noise caused by the change of the half-wave voltage of the phase modulator with temperature is compensated. The feasibility of the system phase noise compensation technique is verified by simulation and experiment. Finally, the overall performance of the system is analyzed by comparing the constellation and eye diagram of the output signal before and after the phase noise compensation. The experimental results show that after compensating the main sources of phase noise in the system, the stability of the system output signal is improved, the bit error rate of the system is improved, and the transmission performance is greatly improved, which shows the correctness of the design.
【学位授予单位】：长春理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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