基于光梳的奈奎斯特脉冲信号生成技术研究

发布时间：2018-10-16 16:51

【摘要】：微波光子学是融合了微波技术与光学技术的新型交叉学科,近几十年发展尤为迅速,其应用涉及到微波和光学领域的各个方面。光奈奎斯特脉冲是微波光子学信号生成中的关键技术之一。随着“互联网+”时代的到来,作为互联网和通信网基础的光传输网络面临的压力越来越大,扩容措施刻不容缓。通常人们采用增加信道带宽的办法,但是频率资源是有限的,因此人们开始研究如何提高频谱利用效率。理论上奈奎斯特信号具有最小的信号带宽,但是受到电子器件带宽及采样速率的限制,在电域很难产生高速信号,而全光奈奎斯特信号既能实现高速信号产生,又能提高频谱效率,具有极大的应用前景。此外,该脉冲在全光信号处理,光谱学,光存储等方面也有着重要的应用,所以引起了国内外学者的广泛关注。生成光奈奎斯特脉冲信号的方法有多种,一些侧重于设计结构的简单与灵活,一些侧重于生成的脉冲的参数及质量。本文主要研究的是基于傅里叶变换的时频二元性的Sinc型光奈奎斯特的直接生成方法。首先使用电光调制器生成具有窄线宽、振幅相等、相位呈线性变化的均匀光学频率梳,也称为光梳,经时频变换后,在时域直接生成序列Sinc型光奈奎斯特脉冲,简记为Sinc脉冲。本文首先研究了使用单个强度调制器(IM),单个双平行马赫曾德尔调制器(DPMZM),两个级联IM,两个级联DPMZM的方案,分别生成了满足条件的3线、5线、9线、25线不同频率间隔的光梳,经过时频变换后生成Sinc型光脉冲。并分析了级联调制器时,其参数设置应该满足的条件。在此基础上提出了使用DPMZM与IM生成Sin脉冲的方案,其频域生成的是满足上述条件的15线光梳,通过改变输入射频频率可以改变生成Sinc脉冲的重复速率及过零脉宽。并对这些方案进行了公式推导与VPI软件仿真验证,最后使用Matlab软件对比在归一化的频率下,不同的光梳线对应的Sinc脉冲。本文还研究了Sagnac环效应,利用该效应,提出了在Sagnac环中加入IM,形成S-IM方案,生成了5线光梳的Sinc型光奈奎斯特脉冲方案。然后利用级联调制原理结合S-IM环设计了级联的IM与S-IM、S-IM与S-IM结构分别生成了15线,25线光梳的Sinc光脉冲,同样使用VPI与Matlab软件进行了相关的仿真,该方案突破了IM只能生成3线的光梳的脉冲,更具灵活性;且结构简单,易于控制。另外,由于使用的是Sagnac环,沿正反两个方向传播的光在同一个光纤环路中传播,环境的影响对系统的稳定性影响是有限的,具有一定的研究价值和使用价值。
[Abstract]:Microwave photonics is a new interdisciplinary subject which combines microwave technology and optical technology. It has been developing rapidly in recent decades. Its application involves all aspects of microwave and optics fields. Nyquist pulse is one of the key technologies in microwave photonics signal generation. With the arrival of the "Internet" era, the optical transmission network, which is the basis of the Internet and communication network, is facing more and more pressure. People usually use the method of increasing channel bandwidth, but the frequency resources are limited, so people begin to study how to improve the efficiency of spectrum utilization. In theory, Nyquist signal has the smallest signal bandwidth, but limited by the bandwidth of electronic device and sampling rate, it is difficult to produce high speed signal in electric domain, while all optical Nyquist signal can produce high speed signal. It can also improve the spectral efficiency, and has a great application prospect. In addition, the pulse also has important applications in all optical signal processing, spectroscopy, optical storage and so on, so it has attracted wide attention of scholars at home and abroad. There are many methods to generate the pulse signal of Nyquist, some of which focus on the simplicity and flexibility of the design structure, some on the parameters and quality of the generated pulse. In this paper, the direct generation method of Sinc type light Nyquist based on Fourier transform is studied. At first, the electro-optic modulator is used to generate a uniform optical frequency comb with narrow linewidth, equal amplitude and linear change of phase. After time-frequency conversion, a sequence of Sinc type optical Nyquist pulses is generated directly in time domain, which is abbreviated as a Sinc pulse. In this paper, we first study the scheme of using single intensity modulator (IM), single double parallel Mach Zehnder modulator (DPMZM), two cascaded IM, cascades and two cascaded DPMZM, and generate three lines, five lines, nine lines, 25 lines with different frequency intervals respectively. After time-frequency conversion, Sinc type optical pulses are generated. The condition of parameter setting of cascade modulator is analyzed. On this basis, a scheme of generating Sin pulse using DPMZM and IM is proposed. The frequency domain of the scheme is 15-line comb which meets the above conditions. The repetition rate and zero-crossing pulse width of the generated Sinc pulse can be changed by changing the input RF frequency. The formulas of these schemes are deduced and verified by VPI software simulation. Finally, the Sinc pulse corresponding to different combs is compared with Matlab software at normalized frequency. In this paper, the Sagnac ring effect is also studied. By using this effect, the scheme of adding IM, to Sagnac ring to form S-IM is proposed, and the Sinc type Nyquist pulse scheme with 5 lines combs is generated. Then the concatenated IM and S-IMO S-IM and S-IM structures are designed by using cascade modulation principle and S-IM loop to generate Sinc pulses of 15 lines and 25 lines respectively. The simulation is also carried out by using VPI and Matlab software. This scheme breaks through the pulse of IM which can only generate 3 lines of light comb, and is more flexible, simple in structure and easy to control. In addition, because the Sagnac loop is used, the light propagating in both positive and negative directions propagates in the same fiber loop, so the influence of environment on the stability of the system is limited, which has certain research value and practical value.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN78

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