基于传输矩阵法的纵向啁啾体光栅衍射特性

为了研究纵向啁啾体光栅的光谱衍射特性,采用传输矩阵方法进行了分析,研究了光栅的厚度、折射率调制系数和啁啾波长范围对纵向啁啾体光栅中心衍射效率的影响。结果表明,随着光栅厚度的增加,中心衍射效率随之增大;随着光栅折射率调制系数的增大,中心衍射效率也随之逐渐增加;而随着啁啾波长范围的增大,纵向啁啾体光栅的中心衍射效率则逐渐减小。此研究结果对大尺寸啁啾体光栅的设计制作有一定的参考价值。     

Fabrication of High Quality Broadband Type IIA Chirped Fiber Bragg Gratings

Chirped fiber Bragg gratings have found many applications in optical communication and sensing systems. High quality filters based on chirped fiber Bragg gratings with reflection bandwidth of 2.6 and 32nm and high reflectivity are demonstrated experimentally with 2 and 4cm long phase masks, respectively. These filters with flat reflection band and high reflectivity are achieved by writing type IIA chirped Bragg gratings.     

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。     

具有不同分布耦合系数的线性啁啾光纤光栅

基于模式耦合理论，推导了描述线啁啾光纤光栅的Riccati微分方程。针对光栅不同的耦合系数分布，数值分析了分布耦合系数对线性啁啾光栅频率响应特性的影响。分析表明，在光栅制作过程中通过控制光栅的耦合系数分布，将会使光栅具有不同的频响特性，从而使其具有不同的用途。     

Tunable Photonic Microwave Bandpass Filter With Negative Coefficients Implemented Using an Optical Phase Modulator and Chirped Fiber Bragg Gratings

A continuously tunable photonic microwave bandpass filter with positive and negative coefficients implemented using an optical phase modulator and chirped fiber Bragg gratings (FBGs) is proposed and experimentally demonstrated. The positive and negative coefficients are generated through optical phase-modulation to intensity-modulation conversion by reflecting the phase-modulated optical carrier from linearly chirped FBGs (LCFBGs) with positive and negative dispersions. The tunability of the filter is realized by changing the wavelength of the optical carrier such that it is reflected at different physical locations in the LCFBGs. A two-tap microwave bandpass filter with a free spectral range tunable from 1.14 to 4.55 GHz is experimentally demonstrated.     

Short multiwavelength fiber laser made of a large-band distributed Fabry-Pe/spl acute/rot structure

Multiwavelength fiber lasers are obtained by writing two superimposed chirped fiber Bragg gratings in a photosensitive Er/sup 3+/--Yb/sup 3+/ codoped optical fiber. The chirped gratings create a distributed Fabry-Pe/spl acute/rot structure in which the resonating fields of the different laser lines are spatially separated, thus, reducing cross-gain modulation. We demonstrate multiwavelength lasers emitting simultaneously over 8 and 16 lines spaced by 50 GHz. The active structure is very compact having a total active length of 8 cm. We discuss how the properties of the device are governed by the parameters of the chirped gratings giving high flexibility in the laser design.     

Calculation of the Figure of Merit of Linearly Chirped Fiber Gratings for Dispersion Compensation

1IntroductionBecauseoftheadventoferbium-dopedamplifiers,thelengthoftheophcalfiberlinksisnolongerlicitedbytheabsorphon,butratherbythechromaticdispersionofthefiber.Especially'theophcalsignalshapeissoseriouslydestroyedthatthebit-error-rate(BER)isratherhigherinthelonghaulhigh-bit-rateophcalcommunicationsystem.Sothedispersionoffibermustbecompensatedbyvariouskindsofdevices.Amongthem,thecompensatorusingthelinearlychirpedfibergratingshascausedagreatinterestindispersioncompensatingdeVices11-5].Onemus…     

线性啁啾长周期莫尔光纤光栅的理论研究

以经典耦合模理论为基础,结合线性啁啾长周期莫尔光纤光栅的结构特性,给出了线性啁啾长周期莫尔光纤光栅的耦合系数和耦合模方程,并用龙格库塔迭代法数值求解耦合模方程,对该类型光栅的光谱特性和时延特性进行了理论分析。分析结果表明,线性啁啾长周期莫尔光纤光栅的相移特性和切趾特性,使得该类型光栅在波分复用全光网中有着很好的应用前景,如可用作宽阻带带阻滤波器、宽阻带梳状滤波器、色散补偿器等。     

Design of High-Channel-Count Multichannel Fiber Bragg Gratings Based on a Largely Chirped Structure

We propose a novel technique to design a high-channel-count, multichannel fiber Bragg grating (FBG) based on a largely chirped structure. The minimization of refractive-index modulation has been widely discussed in the previously demonstrated multichannel grating designs. The complexity of the grating structure, however, is also important from the point of view of practical fabrication. In this paper, the degree of grating complexity (DGC) is defined. We show that the DGC of a multichannel grating can be significantly reduced by designing a grating with a largely chirped structure. A detailed grating design process based on this technique is discussed, by which four multichannel gratings are designed and numerically studied, for applications such as periodic and nonperiodic spectral filtering, chromatic dispersion compensation and dispersion slope compensation. The proposed theory and examples show that different gratings with high-channel-count and multichannel responses can be designed and fabricated using a single commercially available phase mask, and all the gratings can be realized by a conventional FBG fabrication facility since the gratings have a low DGC with low index modulation.      

Group delay ripple reduction and reflectivity increase in a chirpedfiber Bragg grating by multiple-overwriting of a phase mask with anelectron-beam

The phase errors in electron-beam-written step-chirped masks can be reduced by using a method based on the continuous movement approach and overwriting a pattern at the same place on the substrate several times. The group delay ripple of chirped fiber Bragg gratings fabricated by a four-times-overwritten phase mask is comparable with that of gratings obtained using a holographically written chirped phase mask     

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。     

平方型啁啾光纤光栅高阶色散补偿器的理论设计

对周期保持恒定,而其有效折射率大小随其长度按平方律变化的啁啾光 纤光栅提出了一个理论设计模型,从该模型出发,得到了光栅有效折射率分布函数与光栅色散量之间的关系,最后将该模型的计算结果与传输矩阵法的计算机模拟结果进行了比较,二者基本上一致。     

Investigation on reflection spectr a of chirped and phase-shifted fiber Bragg gratings

The characteristics of chirped and phase-shifted fiber Bragg gratings have been investigated by the use of transfer matrix formulation. While the characteristics of a chirped and phase-shifted fiber Bragg grating are the same as those of non- chirped one in some important aspects, both the reflection and transmission windows of a chirped and phase-shifted fiber Bragg grating can be broadened in a wide range. Therefore, chirped and phase-shifted fiber Bragg gratings will have applications in WDM or DWDM optical communication systems. The work in this paper can be used to design the new devices based on chirped and phase-shifted fiber Bragg gratings.     

Azimuthal mode discrimination in radially chirpedconcentric-circle-grating distributed feedback lasers

We report a theoretical investigation analyzing the threshold modes of a concentric-circle-grating (CCG) distributed feedback laser with a radially chirped first-order Bragg grating. A numerical coupled-mode analysis of a chirped CCG laser shows improved azimuthal mode discrimination for chirped gratings with linear, quadratic, and square-root radial dependence. Negatively chirped gratings, in which the grating period decreases with radius, result in improved threshold discrimination between the circularly symmetric fundamental mode and higher order modes; positively chirped gratings, in which the grating period increases with radius, result in decreased threshold for higher order modes in general. Also, the intensity for the fundamental mode at the grating center can be reduced by an order of magnitude using linearly chirped gratings     

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。     

利用动态相位掩膜板法制作光纤光栅

在相位掩膜板法光纤Bragg光栅(FBG)制作系统中,通过高精度陶瓷压电(PZT)促动器对相位掩膜板进行运动控制,实现对光栅折射率交流调制量和相位的任意调制,从而实现相移、切趾和啁啾等FBG的制作,从而提高FBG制作工艺的灵活性。     

利用均匀光纤光栅进行色散补偿的数值分析和实验研究

介绍了利用均匀光纤光栅的透射色散特性进行色散补偿的机理 ,对其色散补偿效率作了数值模拟 ,并进行了利用均匀光纤光栅补偿色散的实验。通过与传统的啁啾光纤光栅色散补偿方案比较 ,得知利用均匀光纤光栅的透射色散特性进行色散补偿是一种行之有效的色散补偿方案     

Chirped Microwave Pulse Generation Using a Photonic Microwave Delay-Line Filter With a Quadratic Phase Response

We propose an optical approach to generating chirped microwave pulses using a photonic microwave delay-line filter (PMDLF) with a quadratic phase response. If a chirp-free broadband microwave pulse is inputted into the filter, a chirped microwave pulse is generated thanks to the quadratic phase response of the filter. To design a PMDLF with a quadratic phase response, complex tap coefficients are required, which is hard to implement in the optical domain. In this letter, a PMDLF with equivalent complex coefficients implemented based on a nonuniformly spaced delay-line structure is demonstrated. Since only positive coefficients are required, the filter is easy to implement. A design example is provided. A five-tap PMDLF to generate a chirped microwave pulse with a chirp rate of 13.2 GHz/ns is then experimentally demonstrated.     

光纤光栅的制作方法

介绍了各种周期性光栅的制作方法,包括纵向驻波干涉法、横向全息曝光法、点光源写入法、位相母板复制法,以及非周期性光纤光栅的制作方法,并分析比较了各种制作方法的优缺点。     

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。