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。     

啁啾光纤光栅补偿光纤色散的研究

啁啾光纤光栅被认为是目前最有实用价值的色散补偿方案之一。分析了啁啾光纤光栅补偿色散的基本原理,从简单模型出发分析了啁啾光纤光栅的色散补偿能力,用数值法研究了啁啾光纤光栅的时延及色散特性,并比较了变迹型与非变迹型啁啾光纤光栅。结果表明要获得较大的色散,要求光纤光栅有较长的长度和较小的啁啾。同时为了消除色散曲线的振荡还必须采取适当的变迹方法。     

PMD补偿系统中啁啾光纤光栅的啁啾系数和有效折射率的选择

啁啾光纤光栅是用于偏振模色散补偿的重要光无源器件。本文对基于两个啁啾光纤光栅的偏振模色散补偿系统进行了分析。重点分析了啁啾光纤光栅的一阶啁啾系数c1和两个光栅之间的有效折射率差△n变化对系统补偿特性的影响，并进行了数值仿真。     

线性啁啾型光纤光栅双稳特性的理论研究

基于非线性耦合模理论,利用逆向递推传输矩阵方法,数值研究分析了线性啁啾型光纤光栅（LC-NLBG）的双稳开关性能。研究结果表明：在NLBG中引入啁啾能扩大实现双稳的入射光波长范围,当光栅啁啾参量发生变化时,光栅双稳开关性能表现出明显的差异,此差异源于啁啾光栅内部前向波能量分布的不同。     

啁啾超结构光纤布拉格光栅的一种新研究方法

从耦合波理论出发,利用传输矩阵分析了啁啾超结构光纤光栅,得到了其反射谱的解析式,数值计算结果表明：超结构光纤光栅的光栅总长度、折射率调制深度、占空比、取样周期和啁啾系数等参数都会影响反射谱的峰值和带宽。为超结构光纤光栅的设计提供了理论依据。     

采用啁啾光纤光栅补偿带啁啾的超高斯脉冲在光纤中传输的色散

利用啁啾光纤光栅,对带啁啾的超高斯脉冲的色散补偿特性进行了理论分析和数值模拟。数值模拟结果表明,光脉冲在普通单模光纤中传输了一定距离后,由于色散的作用,脉冲发生展宽,超高斯脉冲比高斯脉冲展得更宽。若初始脉冲含有啁啾,展宽后的脉冲还出现小调制。用啁啾光纤光栅进行色散补偿后,高斯型脉冲能够较好的恢复初始脉冲形状,带啁啾的超高斯脉冲的脉宽可恢复到接近初始脉冲的宽度,但脉冲形状发生了畸变,并出现了旁瓣,脉冲峰值功率与超高斯脉冲阶数和啁啾参数有关。     

高斯脉冲在光纤中传输的光纤光栅色散补偿研究

高斯脉冲在光纤中传输一段距离后，啁啾系数和脉冲宽度均要发生变化，不同啁啾系数和脉冲宽度的高斯脉冲经过啁啾光纤光栅反射后的脉宽压缩特性也不同。本文介绍了啁啾高斯脉冲在光纤中的传输特性以及啁啾高斯脉冲经啁啾光纤光栅反射后的传输特性。理论分析和实验均表明，使用啁啾光纤光栅实现长距离色散补偿时，最佳色散补偿长度与光栅位置有关。     

啁啾光纤光栅中偏振模色散的研究

首先介绍了不同种双折射率差Δn的光纤制成的啁啾光纤光栅中偏振模色散现象 ,然后说明了光栅中偏振模色散的大小与 Δ n的相关性 ,并阐述了对用于色散补偿作用的啁啾光纤光栅中偏振模色散的消除 (补偿 )方法 ,最后指出利用啁啾光纤光栅中大的偏振模色散对高速光通信系统传输线路中偏振模色散的补偿方法。     

啁啾光纤光栅引起的系统色散功率代价

分析了啁啾光纤光栅对光脉冲信号的作用 ,计算光脉冲经过一定距离传输并由啁啾光纤光栅进行色散补偿后的脉冲展宽情况 ,同时分析啁啾光纤光栅群时延抖动对系统色散代价的影响。在系统色散功率代价一般要小于1dB的条件限制下给出啁啾光纤光栅群时延抖动的幅度、周期与系统单信道速率这三个参量之间存在相互关系     

啁啾长周期光纤光栅的滤波特性研究

基于光纤光栅耦合模理论,采用传输矩阵法对啁啾长周期光纤光栅的啁啾系数和光栅参量（光栅长度、光栅周期和折变量）对其滤波特性的影响进行分析。当啁啾系数处于-0.000008～-0.0004 nm/cm范围内时,可用于宽带带阻滤波器。当啁啾系数处于-0.05～-1 nm/cm范围内时,可用于多通道窄带滤波器。为啁啾光纤光栅滤波器的优化设计提供理论依据。     

光栅参数对线性啁啾光纤光栅偏振特性的影响

研究了单模线性啁啾光纤光栅的偏振相关损耗特性。运用耦合模理论和传输矩阵分析法推出了反射光的偏振相关损耗,并模拟了光栅的反射谱和偏振相关损耗随光栅参数和双折射量的变化曲线。模拟显示双折射值的变化对啁啾光栅偏振相关损耗的影响非常显著, 尤其是在带边比较陡峭时。啁啾光栅的偏振相关损耗也受光栅的啁啾系数和调制深度的影响。这表明线性啁啾光栅的偏振相关损耗不光依赖光栅双折射量,还依赖其啁啾系数等其他参数。实验结果与理论模拟基本吻合。     

折射率啁啾调制光纤光栅性能研究

从耦合模理论出发,详细推导出平均折射率调制啁啾系数、初始位置平均折射率调制系数和啁啾光纤Bragg光栅(FBG)周期啁啾系数之间的对应关系,并进行了数值模拟和实验研究。结果表明：通过对平均折射率调制系数进行啁啾控制,可以利用一块相位掩膜版制作出不同色散补偿量的FBG。     

Pulse evolution in a photorefractive self-pumped phase conjugatorwith transmission grating geometry

The effect of grating dispersion on pulse evolution in a photorefractive self-pumped phase conjugator is analyzed. The broadening factors and the time-dependent phases of self-pumped phase-conjugate pulses of unchirped and chirped Gaussian pulses are obtained. When the grating dispersion and the angular dispersion cancel the material dispersion, the self-pumped phase-conjugate pulse has a minimum width, which is determined by the first-order dispersion of the grating. The self-pumped phase conjugation of an unchirped Gaussian pulse broadens and is linearly chirped whereas the self-pumped phase conjugation of a chirped Gaussian pulse is compressed when the dispersion-induced chirp cancels the initial chirp     

Continuous True-Time-Delay System Employing a Novel Tunable Chirped Fiber Grating Delay Line and a Sampled Grating Based Multiwavelength Fiber Laser

A photonics true-time-delay system for phased array antenna beam steering employing a novel tunable chirped fiber grating delay line and a multi-wavelength erbium-doped fiber ring laser source based on a sampled grating filter is proposed. The tunable chirped fiber grating, which act as a continuous time-delay element, is achieved by bending a uniform fiber Bragg grating bonded at a slant onto the lateral surface of a simply supported beam. This technique allows the dynamic control of the chirp rate and spectral width of the grating without center wavelength shift. By adjusting the chirp rate of the fiber grating via bend strain, this kind of tunable chirped fiber grating could achieve very low and adjustable delay times, therefore provides higher angle resolution for scanning microwave beam, even the wavelengths of laser source are fixed and un-tunable. The true-time-delay system using proposed tunable chirped fiber grating delay element and sampled grating based laser source is constructed and demonstrated experimentally.     

Tunable Photonic Microwave Filter Using a Superstructured FBG With Two Reflection Bands Having Complementary Chirps

A tunable photonic microwave bandpass filter using a superstructured fiber Bragg grating (SFBG) with two reflection bands having complementary chirps is proposed. Being different from a regular chirped FBG, which is usually fabricated using a chirped phase mask with a fixed chirp rate, the SFBG with complementary chirps is fabricated using a uniform phase mask and a chirped sampling function. The chirp rate of the sampling function can be designed to realize specific equivalent chirp rates that are complementary in the 1st-order and the 1st-order reflection bands of the SFBG. An SFBG with complementary chirps is fabricated and characterized. The use of the SFBG to implement a photonic tunable microwave filter with a negative coefficient is experimentally demonstrated.     

Fabrication of chirped fiber grating with adjustable chirp andfixed central wavelength

We theoretically analyze and experimentally demonstrate a simple method for adjusting the chirp of chirped fiber gratings by temperature, while the central wavelength is temperature insensitive. Chirped fiber grating with tapered cross-section area is mounted under tension in a negative thermal-expansion coefficients material. The central wavelength is determined by the tension, and almost does not vary with temperature after packaging. The chirp can be adjusted by temperature. The grating in the package exhibits a linear variation in chirp of -0.00051 nm/cm/°C, and the temperature coefficient of central wavelength is -0.0018 nm/°C     

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.