两种用于色散补偿的取样非线性啁啾光纤光栅的参数选择

本文对采用取样非线性啁啾光纤光栅用于补偿光通信系统中的动态色散进行了研究。提出了二进制取样非线性啁啾光纤光栅所产生信道个数的计算方法。对不同长度的取样光栅的一阶啁啾系数c1和二阶啁啾系数c2 的取值范围进行了研究，并进行了数值仿真。     

用于色散补偿的非线性啁啾光纤光栅

提出了采用可调谐的非线性啁啾光纤光栅来补偿光通信系统中动态的非线性色散。分析了非线性啁啾光纤光栅的光谱及时延特性 ,并对其进行了数值仿真。设计了二类 PZT制作非啁啾光纤光栅的方案     

取样啁啾光纤光栅的时延抖动抑制

研究了用于多通道色散补偿器的取样啁啾光纤光栅时延抖动问题,分析了产生时延抖动的腔效应及抑制时延抖动的切趾技术,分析、比较了切趾前后取样啁啾光纤光栅的时延抖动情况,研究结果表明:取样啁啾光纤光栅的时延抖动与其折射率包络调制形成的外腔效应有关,与取样调制形成的多腔效应无关,对取样啁啾光纤光栅进行包络切趾能够有效地抑制时延抖动.     

取样啁啾光纤光栅传输特性的研究

运用传输矩阵理论，对一种新型色散补偿光纤光栅——取样啁啾光纤光栅的传输特性进行了模拟研究。研究了光栅反射谱特性随光栅参数的变化规律。作为应用实例，本文给出了适合于对10Gb／s WDM系统进行色散补偿的8通道取样啁啾光栅的相关参数。     

增益开关DFB激光器啁啾消除技术的研究

对线性啁啾光纤光栅消啁啾技术进行了理论和数值分析,给出光纤光栅设计中的一些重要参数,并与Ｆ－Ｐ光谱窗消啁啾法和正常色散光纤消啁啾法做了比较。研究结果表明,光纤光栅的啁啾消除效果要好于其他两种方法,尤其是在消除非线性啁啾方面效果更为突出。     

用于10Gb／s WDM系统色散补偿的波长取样啁啾光纤光栅

研制出一种新型色散补偿光纤光栅--波长取样啁啾光纤光栅,它具有10个周期性为0.8nm的波长结构,每个周期的反射特性和色散特性都基本相同,其带宽为0.6nm、峰值反射率为90%、色散量为1300ps/nm、时延抖动小于50ps,光栅长度为10cm.利用此波长取样啁啾光纤光栅,在8×10Gb/s波分复用(WDM)系统中,进行了NRZ码140km标准单模光纤的色散补偿实验,补偿效果良好.     

线性啁啾光纤光栅变迹函数的研究

文中利用传输矩阵法对我们构造的四种变迹函数所描述的线性啁啾光纤光栅的光学特性进行了数值计算,并与常用的高斯型变迹线性啁啾光纤光栅的最佳光学特性进行了比较和分析,得出了一些有意义的结论,为设计和制作合适的线性啁啾光纤光栅用作色散补偿器提供了一定的理论依据。     

偏振模色散和时延抖动对啁啾光纤光栅色散补偿特性的影响

对存在偏振模色散(PMD)和群时延(GD)抖动的非理想线性啁啾光纤光栅的色散补偿特性进行了研究。实验测量了啁啾光纤光栅的群时延谱和偏振模色散光谱，理论分析和实验测量表明，啁啾光纤光栅差分群时延(DGD)抖动与其时延抖动密切相关。通过数值模拟方法，计算了线性啁啾光纤光栅偏振模色散眼图代价与入射到啁啾光纤光栅色散补偿器的光信号的偏振方向的关系，计算结果表明在使用啁啾光纤光栅色散补偿器时应对光信号的偏振方向进行调整，以获得最佳补偿效果。另外结合实验数据，模拟计算并讨论了非理想线性啁啾光纤光栅群时延抖动和偏振模色散引起的信号的展宽和脉冲形状的劣化。     

利用线性啁啾光纤光栅进行脉冲压缩的研究

利用光纤－线性啁啾光纤光栅进行光脉冲的压缩,首先讨论了线性啁啾光纤光栅的色散特性,并给出耦合系数为反高斯函数的线性啁啾光纤光栅的色散特性;然后利用此种光纤光栅与正常色散光纤结合进行光脉冲的压缩,通过理论和数值分析,得出一简单设计规则;最后利用此规划设计一个压缩因子为１０的光纤－线性啁啾光纤光栅压缩器。     

光纤Bragg光栅的优化设计

提出了一种优化设计变迹啁啾光纤Bragg光栅的方法。在优化设计过程中，利用四阶五阶Runge-Kutta方法来计算光纤光栅的反射谱，利用非线性最小二乘法来对光纤Bragg光栅的啁啾和变迹参数进行优化，以获得不同反射谱要求下的变迹啁啾光纤Bragg光栅的最佳参数。     

Phased-only sampled fiber Bragg gratings for high-channel-count chromatic dispersion compensation

Binary and multilevel phase-only sampling functions are proposed for the sampled fiber Bragg gratings (FBGs) with high channel count, which require significantly less refractive-index modulation than that does the sampled grating with amplitude sampling. The design using the new simulated quenching optimization with temperature rescaling results in high channel uniformity and minimum energy in the out-of-band channels. The technique can be applied to the sampled FBGs with very high channel count. A five-channel nonlinearly chirped multilevel phase-only sampled FBG for tunable chromatic dispersion compensation is demonstrated.     

高斯切趾非线性啁啾光纤光栅特性的研究

根据耦合模理论，采用分段均匀的传输矩阵法数值分析了不同啁啾系数对非线性啁啾光栅光谱响应和时延的影响，进而讨论了非线性啁啾光栅在色散补偿中的应用。     

System-Performance Analysis of Optimized Gain-Switched Pulse Source Employed in 40- and 80-Gb/s OTDM Systems

The development of ultrashort optical pulse sources, exhibiting excellent temporal and spectral profiles, will play a crucial role in the performance of future optical time division multiplexed (OTDM) systems. In this paper, we demonstrate the difference in performance in 40- and 80-Gb/s OTDM systems between optical pulse sources based on a gain-switched laser whose pulses are compressed by a nonlinearly and linearly chirped fiber Bragg grating. The results achieved show that nonlinear chirp in the wings of the pulse leads to temporal pedestals formed on either side of the pulse when using the linearly chirped grating, whereas with the nonlinearly chirped grating, pedestals are essentially eliminated. In an OTDM system, these pedestals cause coherent interaction between neighboring channels, resulting in intensity fluctuations that lead to a power penalty of 1.5 dB (40 Gb/s) and 3.5 dB (80 Gb/s) in comparison to the case where the nonlinearly chirped grating is used. Simulations carried out with the aid of Virtual Photonics Inc. verify the results achieved.     

相位掩模板接缝相差对光栅时延纹波的影响

电子束刻蚀啁啾相位掩模板采用的是分步啁啾法,而掩模板制造过程中分步之间的接缝误差是啁啾光纤光栅产生时延纹波的一个重要因素。该文以分步步长1 mm,总长度140 mm的相位掩模板为例,理论分析和比较了不同接缝误差对啁啾光纤光栅时延纹波的影响。分析表明,最大相位误差为0.05 rad和0.08 rad时,光栅时延纹波的统计平均分别为14.491 ps和22.38 ps。进行相关试验研究以上相位掩模板写入光栅的时延特性,得出结论与理论分析一致。     

电子束刻蚀分步啁啾相位掩模板的优化

掩模板制造过程中采用的是分步啁啾方法,分步间长度容易出现误差,这种接缝误差是引起啁啾光纤光栅（CFBG）时延纹波的系统误差。理论分析了相位掩模板的接缝误差对CFBG时延纹波的影响。分析表明,对长度为140mm的掩模板采用1．4mm的步长,接缝误差影响最小。并进行了实验验证。     

用于色散补偿的NLCFBG的参数选择

分析了不同长度情况下非线性啁啾光纤光栅(NLCFBG)的一阶啁啾系数c1、二阶啁啾系数c2的取值范围,并对其光谱及时延特性进行了数值仿真.分析了调制度与一阶啁啾系数c1之间的限制性.     

Chirped RF Pulse Generation Based on Optical Spectral Shaping and Wavelength-to-Time Mapping Using a Nonlinearly Chirped Fiber Bragg Grating

Chirped radio-frequency (RF) pulse generation based on optical spectral shaping and nonlinear wavelength-to-time mapping in a nonlinearly chirped fiber Bragg grating (NLCFBG) is investigated. In the proposed approach, the spectrum of a femtosecond pulse generated by a mode-locked fiber laser is shaped by an optical filter that has a sinusoidal frequency response. The spectrum-shaped optical pulse is sent to the NLCFBG, to implement nonlinear wavelength-to-time mapping. A chirped electrical pulse with the central frequency and chirp rate determined respectively by the first- and second-order dispersions of the NLCFBG is then obtained at the output of a high-speed photodetector. An approximate model that describes the chirped RF pulse generation is derived, which is verified by numerical simulations. Chirped pulse generation with a pulse compression ratio as high as 450 is demonstrated. The key device in the chirped RF pulse generation system is the NLCFBG, which is investigated in detail with an emphasis on the influence of its group delay ripples on the performance of the pulse generation system. Techniques to design and fabricate the NLCFBG are also discussed. The proposed approach provides a potential solution for the generation of chirped RF pulse with a high central frequency and large chirp rate for applications in pulse compression radar systems.     

Efficient technique for increasing the channel density in multiwavelength sampled fiber Bragg grating filters

We introduce a new class of high channel count multiwavelength comb filters based on sampled fiber Bragg gratings (FBGs). Our approach exploits the spectral fractional Talbot effect in sampled chirped FBGs (S-CFBGs). For specific conditions between the grating chirp and sampling period, the channel spacing can be reduced compared to the value obtained using conventional sampling techniques. In this way, the channel density can be multiplied without needing to increase the sampling period. Moreover, despite the fact that the grating is chirped, operating under the spectral Talbot regime ensures that the resultant in-band group delay characteristics are similar to those of a sampled uniform period FBG.