【作者】 李敏；

【导师】 牟宏谦；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2021， 硕士

【摘要】 任意波形产生(Arbitrary Waveform Generation,AWG)技术在超宽带通信等领域应用广泛。与其它AWG技术相比,光生AWG方案具有体积小、重量轻、抗电磁干扰能力强、可产生超高速率、超大带宽信号等优势。其中,基于空间光谱整型器和频率-时间映射的AWG方案的可重构特性好,是光生AWG技术的研究热点之一。近年来,基于啁啾光纤光栅同时实现光谱整形和频率-时间映射的AWG方案,因可打破空间谱整型器插损高、稳定性低、成本高等局限而备受关注。已报道的基于啁啾光纤光栅和频率-时间映射的AWG方案中光栅反射谱的设计方法复杂,仅用于产生啁啾微波脉冲和脉冲编码信号,难以真正实现任意波形产生。本文提出具有任意形状反射谱的啁啾光栅简化设计方法,基于啁啾光纤光栅的色散特性引入频率-时间映射,实现了用户定义的任意波形产生。在此研究基础上,结合光纤非线性效应,研究了三角波和锯齿波的全光波长变换。全光波长变换技术在码型变换、时分复用等领域应用广泛,已报道的全光波长变换系统结构复杂、体积大、成本高。本文提出的基于啁啾光纤光栅和频率-时间映射的任意波形产生方法,结合光纤非线性效应实现全光波长变换方案的系统结构简单、易于集成、成本较低。主要的研究内容和创新点如下:(1)研究了基于频率-时间映射理论的AWG方案的系统结构和实现原理,推导频率-时间映射理论的相关公式。分析基于啁啾光纤光栅同时实现光谱整形和频率-时间映射的可行性。研究表明,啁啾光纤光栅由于其反射特性和色散特性可同时用作光谱整形和色散器件。在满足频率-时间映射的条件下,通过设计啁啾光纤光栅反射谱的形状可以产生相应形状的输出脉冲。(2)基于啁啾光纤光栅任意形状反射谱的简化设计和频率-时间映射理论实现了用户定义的任意波形。首先,提出基于传输损耗公式的啁啾光纤光栅任意形状反射谱的简化设计方案。引入变量因子实现了光栅反射谱形状的优化,在保证高反射率(≥0.9)的条件下,将设计误差降低在10%以下。其次,结合啁啾光纤光栅的色散特性实现了任意形状的脉冲产生,以多种波形(三角形、锯齿形、矩形、梯形、高斯型、抛物型)脉冲的成功产生为例验证了方案的可行性。此外,仿真分析了系统参数对输出脉冲的影响。研究表明,通过改变光栅长度和脉冲源频率可以得到输出脉宽可控、频率可调的输出脉冲。(3)本文提出的基于啁啾光纤光栅和频率-时间映射的任意波形产生方法,结合光纤非线性效应研究了全光波长变换方案。以三角脉冲为泵浦脉冲,对比强度调制的单频连续光生成三角波与本文设计的任意波形发生器生成三角波的波长变换结果,理论研究基于自相位调制和交叉相位调制的波长变换,仿真分析各参数对波长变换的影响。研究表明,在相同系统参数下,基于本文设计的任意波形发生器的自相位调制波长变换值更大。此外,还对比研究了不同形状(高斯型、三角形、锯齿形)泵浦光脉冲对交叉相位调制波长变换的影响。与高斯型脉冲相比,三角形和锯齿形脉冲作为泵浦光时对应的波长变换边带的信噪比更高。更多还原

【Abstract】 Arbitrary waveform generation(AWG)technology is widely used in UWB communication and other fields.Compared with other AWG schemes,the optical AWG technology has the advantages of small size,light weight,strong anti-electromagnetic interference ability,which can generate signals with ultra-high speed and ultra-large bandwidth.As one of the hot technologies of the optical AWG,the scheme based on space spectral shaper and frequency to time mapping theory has good reconfigurability.In recent years,the AWG scheme based on the chirped fiber Bragg grating to realize spectral shaping and frequency-time mapping simultaneously has attracted much attention,which can break the limitations of high insertion loss,low stability and high cost of space spectral shaper.In the reported AWG scheme based on chirped fiber grating and frequency to time mapping theory,the design method of grating reflection spectrum is complex,and it is only used to generate chirped microwave pulse and pulse-coded signal,which is difficult to achieve arbitrary waveform generation.In this paper,a simplified design method of chirped fiber Bragg grating with arbitrary reflection spectrum shape is proposed.Based on the dispersion characteristics of chirped fiber Bragg grating,frequency-time mapping is introduced to generate user-defined arbitrary waveform pulse.The all-optical wavelength conversion of triangular and sawtooth pulse is studied combined with the fiber nonlinear effect.The all-optical wavelength conversion technology is widely used in code conversion,time-division multiplexing system and other fields.The reported wavelength conversion systems have complex structure,large volume and high cost.In this paper,the method of AWG based on chirped fiber Bragg grating and frequency to time mapping theory,combined with the fiber nonlinear effect to realize all-optical wavelength conversion has the advantages of simple system structure,easy integration and low cost.The main research contents and innovations are as follows:(1)The system structure and implementation principle of AWG scheme based on frequency to time mapping theory are studied,and the relevant formulas of frequency-time mapping theory are theoretically deduced.The feasibility of using chirped fiber Bragg grating to realize spectral shaping and frequency-time mapping simultaneously is analyzed.The results show that chirped fiber Bragg gratings can be used as spectral shaping and dispersion element because of its reflection and dispersion characteristics.When satisfying the frequency-time mapping condition,the shape of the output pulse can be designed by changing the shape of the chirped fiber Bragg grating reflection spectrum.(2)User-defined AWG is realized based on the simplified design of arbitrary shape of chirped fiber Bragg grating reflection spectrum and the frequency-time mapping theory.Firstly,a simplified design scheme of arbitrary shape reflection spectrum of chirped fiber Bragg grating is proposed based on the transmission loss formula.Variable factors are introduced to optimize the shape of the chirped fiber Bragg grating reflection spectrum,and the design error was reduced to less than 10% with high reflectivity(≥0.9).The AWG is realized combining with the dispersion characteristics of chirped fiber Bragg grating.The feasibility of the scheme is verified by the successful generation of various waveforms(triangular,sawtooth,rectangular,trapezoidal,Gaussian,and parabolic).In addition,the influence of system parameters on the output pulse is analyzed.The results show that the output pulse with controllable pulse width and adjustable frequency can be obtained by changing the grating length and pulse source frequency.(3)In this paper,the all-optical wavelength conversion scheme is studied by combining the AWG with the nonlinear effect of fiber and the design of the AWG is based on the chirped fiber Bragg grating and frequent-time mapping.Triangular pulse is used as the pump pulse,and wavelength conversion results of the triangular pulse generated by intensity modulated single-frequency continuous light source and arbitrary waveform generator designed in this paper are compared.The wavelength conversion based on self-phase modulation and cross-phase modulation is studied theoretically,and the influence of various parameters on wavelength conversion is analyzed by simulation.The results show that the self-phase modulated wavelength conversion results of the designed arbitrary waveform generator are larger than that of the intensity modulated single-frequency continuous light source under the same conditions.In addition,the effects of pump pulses with different shapes(Gaussian,triangular and sawtooth)on the wavelength conversion of cross-phase modulation are also studied.The results show that the signal-to-noise ratio of the wavelength conversion sideband of the triangular and sawtooth pulses is higher than that of the Gaussian pulse.更多还原