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新型光调制和光复用技术研究
Study on Novel Optical Modulation and Multiplexing Techniques
【作者】 吕亮；
【导师】 文爱军；
【作者基本信息】 西安电子科技大学 ， 光通信， 2010， 硕士
【摘要】 为了满足不断增长的信息传输量需求,需要采用40Gbit/s甚至100Gbit/s的高速数字光传输系统。随着单信道传输速率的提升,系统的色散、非线性效应等问题对信号的影响也更加严重。采用新型的光调制和光复用技术可以有效地抑制这些传输损伤的影响,成为高速光传输系统的关键技术之一。由于商用化的光放大器主要是在C波段,有限的传输通道使得人们对于频谱效率的要求越来越高,于是,多进制调制和全光OFDM技术开始进入人们的视野。本文针对40Gb/s高速光传输系统中的新型IRZ调制技术、IRZ-DQPSK的幅度相位调制技术以及100Gb/s高速光传输系统的全光OFDM技术进行研究。首先研究了四种产生IRZ信号的调制原理,提出了一种占空比可调且相位连续的IRZ调制新方法,仿真分析了各方法产生的IRZ信号的色散和非线性性能;然后研究了采用提出的IRZ调制方案产生IRZ-DQPSK信号的调制、解调原理,仿真分析了色散、非线性对IRZ-DQPSK幅度支路和相位支路的传输性能影响,结果表明调整占空比可以平衡幅度支路和相位支路性能。接着仿真分析了单信道40Gbit/s长距离传输(>1000km LEAF)时,自相位调制(SPM)对ASK-DQPSK与IRZ-DQPSK两种信号的影响,结果表明IRZ-DQPSK具有更好的抗SPM性能;最后研究了全光OFDM的调制、解调原理,并仿真实现了两路NRZ的20Gb/s背靠背系统以及四路DQPSK的100Gb/s全光OFDM系统。
【Abstract】 40Gb/s and even 100Gb/s high-speed digital optical transmission systems are the ideal choices to satisfy the requirement of increasing information transmission quantity. However, with the increase of transmission rate in a single channel, the quality of the signal would be more affected by dispersion, non-linear and so on. Novel modulation and multiplexing techniques are key technologies which could mitigate the transmission impairments in optical transmission system. As the gain bandwidth of commercial optical amplifiers is primarily in C-band, the requirement of high spectrum efficiency is increasing in the limited transmission channel. As a result, multilevel modulation and all-optical OFDM techniques are coming into view. This paper studies on two novel modulation formats named as IRZ, IRZ-DQPSK and the principle of all-optical OFDM transmission technique. Firstly, four kinds of schemes to modulate IRZ signal are studied and a novel way to generate IRZ modulation format is introduced. The dispersion and non-linear tolerance of them are compared. Secondly, with the IRZ scheme we proposed, the modulation and demodulation principles of IRZ-DQPSK are presented. The performance of 40Gb/s IRZ–DQPSK transmission against fiber nonlinearities and residual dispersion are simulated. Results indicate that to balance the performance of amplitude tributary and phase tributary, the duty cycle of IRZ-DQPSK must be adjusted properly. Furthermore, IRZ-DQPSK and ASK-DQPSK in a 40Gb/s single channel long distance (over 1000km LEAF) transmission link is compared by simulation. Results show that IRZ-DQPSK offers much better performance against SPM. Finally, the principle of multiplexing/demultiplexing in all-optical OFDM technique is studied and a 20Gb/s all-optical OFDM back to back system using NRZ modulation and a 100Gb/s all-optical OFDM transmission system using DQPSK modulation are demonstrated successfully.