【作者】 冯勇；

【导师】 张汉一；

【作者基本信息】 清华大学 ， 电子科学与技术， 2010， 硕士

【摘要】 数字相干光检测是高速光通信的一个重要发展方向,它结合采用相干接收和数字信号处理,具有接收灵敏度高,频谱效率高,能够完全补偿光在传输中的各种线性损伤以及部分非线性损伤等优点。国内外很多高校、研究机构都将其作为一个重要研究方向。另外,产业界也投入巨大的热情,像Nortel、U2T等光通信设备与器件商加快研制推出40Gb/s数字相干接收机,对数字相干检测技术的研究已成为抢占下一代传输技术的制高点。本论文围绕数字相干光检测关键技术及其应用展开,取得如下工作成果。利用廉价的光纤器件制作了数字相干接收机中的关键器件之一:偏振分集光学90度混频器,四路输出损耗相差小于0.3dB,延时相差小于5ps,相比于商用品而言,具有成本低、灵活可调、性能稳定等优点。在此基础上,开发完成了数字相干检测中的混频器IQ正交化、数字色散补偿、数字偏振解复用以及载波相位恢复等基本的数字信号处理算法模块,搭建了基于数字相干接收的硬件平台,进行多次实验研究。实现了20Gb/s偏振复用DPSK信号经过280km单模光纤传输实验。开发出MSP430单片机控制的采用磁光开关的光纤环路控制系统,实现了40Gb/s偏振复用QPSK信号环路传输1200km,接收误码率小于10^-3。利用数字相干检测实现监测信号产生中的调制失真,可以监测双平行调制器中母结构MZM的偏置点偏差,监测误差<5^o。利用锁模激光器输出的脉冲光作为本振,对相干光脉冲采样进行了初步实验研究,实现了对高速光NRZ、DPSK信号的强度眼图重建。本振光脉冲时间宽度为1ps,理论上可以测量高达200G symbol/s以上的高速光信号眼图。更多还原

【Abstract】 Digital optical coherent detection has been a hot topic in high-speed optical transmission. By using coherent detection, it has higher receiving sensitivity and more effective spectrum usage. With the help of digital signal processing, full of linear and part of nonlinear impairments in transmission can be compensated. Many universities and research institutes all over the world have started research in this field. Besides, the corporations like Nortel, U2T are going to release their commercial 40Gb/s coherent receivers. Digital optical coherent detection has been a key point in the next optical transmission system.In digital optical coherent detection, we have done the following work.Based on low-cost fiber passive devices, we made the key component in digital optical coherent detection—polarization diversity optical 90o hybrid, the 4 paths’insertion loss difference of which is less than 0.3dB, and the time delay difference less than 5 pico-seconds. Compared to commercial hybrids, it is cheap, adjustable and stable. Using our home-made 90o hybrid, we set up the coherent detection platform and finished several transmission experiments. The key digital signal processing algorithms are completed, including IQ phase orthogonalization, chromatic dispersion compensation, digital polarization demultiplexing, and carrier phase estimation.We carried out a 20Gb/s polarization multiplexed DPSK system with a 280km single-mode fiber transmission. Further more, we developed an optical loop transmission system controlled by a MSP430 micro-controller. Using this fiber loop, a 40 Gb/s polarization multiplexed QPSK optical signal was transmitted for 1200km, the bit-error-rate of which is less than 10^-3.Digital optical coherent detection can be used to monitor the signal distortion caused by modulators. We use it to monitor the IQ phase bias in the parallel MZM for optical QPSK signal generation, the monitoring error of which is less than 5^o.Using mode-locked laser as the local oscillator, we have done some research work in linear optical sampling. The NRZ, DPSK signal’s eye-diagram are re-constructed by optical sampling. The time width of the mode-locked laser is less than 1 pico-second, leading to a more than 200GHz sampling width.更多还原