Adjustable dispersion-compensation devices with wavelength tunability based on enhanced thermal chirping of fiber Bragg gratings

We demonstrate a dispersion compensation device based on thermal chirping of a glued fiber Bragg grating. The device can change the group velocity dispersion (GVD) while maintaining a center wavelength or change the center wavelength while preserving a GVD value. The GVD can be tuned from -122.5 to -57 ps/nm with a center wavelength at 1552.9 nm. On the other hand, the center wavelength can be shifted by 2.2 nm with a GVD value around -105 ps/nm.     

宽带可调谐光纤光栅色散补偿器系统设计

文章提出一种在光纤光栅自身热膨胀效应产生啁啾的基础上,利用铝片热膨胀系数比较高的特点产生应力来增强光纤光栅啁啾,从而实现了宽带、大范围色散调谐的新型光纤光栅色散补偿器。该色散补偿器能够分别对群速度色散及中心波长独立调谐。实验结果表明,在中心波长为1 551.25nm处,能够实现>1.5nm的色散补偿带宽,-350～-690ps/nm的群时延色散调谐范围;在色散为-660ps/nm情况下,能够实现中心波长1nm的偏移。     

基于均匀光纤光栅的DWDM系统PMD补偿方法

提出一种基于均匀光纤Bragg光栅(FBG)的透射型密集波分复用(DWDM)系统多信道偏振模色散(PMD)补偿方案。当FBG受到横向挤压时，会产生双折射现象。当一波长的光信号从光栅带隙附近透射时，就会在快轴和慢轴之间产生时延差(DGD)。通过改变外力的大小来调节DGD的大小可以实现对PMD的补偿。通过将多个补偿光栅级联，就可以实现对DWDM系统多信道PMD的补偿。在100N外力作用下，5cm长的光栅最大可以补偿121ps的PMD，而对相邻0．8nm的信道，只引入0．2ps的DGD。     

Tunable fiber Bragg grating filters realized by chirp rate tuning with a cantilever beam

An efficient scheme to change the chirp rate of a fiber Bragg grating (FBG) has been developed based on a specially-designed cantilever beam with the beam-bending method. It allows, to date, the largest tuning range of 36 nm in reflection bandwidth of a chirped-FBG (CFBG) while keeping the center wavelength nearly fixed during the tuning process. Using this method, bandwidth-tunable fiber grating filters with tunable chromatic dispersion or differential group delay have been demonstrated. Channel spacing-tunable multi-wavelength filters based on both sampled- and superimposed-CFBGs have also been realized. Moreover, tuning of the bandwidth and channel spacing is continuous with this scheme that makes the achieved devices more flexible.     

宽带FBG与自相关算法提高CCD解调精度的研究

为提高光纤光栅解调算法的精度,设计了3 dB带宽在1~3 nm之间的宽带布拉格光栅与自相关算法解调系统,使用线阵CCD检测光谱,进行波长寻峰分析与实验验证。线阵CCD离散像素点之间波长间距固定,宽带布拉格光栅可得到更多有效像素数据点;自相关算法只考虑传感测量时光谱的偏移程度,可抵消背景噪声,消除光栅刻写或封装过程中操作不当引起光谱异常的影响,从而提高光栅中心波长解调精度。温度测量结果表明,使用自相关算法解调啁啾光栅与宽带光栅,误差较高斯算法分别减少54.05%和40.87%,此算法可以使啁啾光栅达到正常光栅的解调精度。并且,使用宽带光栅的解调误差仅为啁啾光栅的50%。     

基于弯曲压杆的光纤光栅可调谐线性啁啾化

提出利用镍钛合金压杆弯曲应变引入到光纤布拉格光栅(fiber Bragg grating,FBG)实现无中心波长漂移可调谐线性啁啾化方法并进行了实验验证。设计一种镍钛合金压杆结构,理论计算并有限元分析验证了应变分布情况。将光纤光栅粘贴在镍钛合金压杆上,弯曲压杆将线性拉伸与压缩应变引入到栅区,利用光谱仪记录反射谱。实验结果表明,当压杆移动距离达到12.5 mm时,反射谱带宽增大到1.57 nm,中心波长漂移量仅为0.11 nm。利用光纤光栅啁啾化理论,结合传输矩阵法和龙格库塔法实现啁啾光纤光栅光谱重构。实验结果与仿真结果吻合。该方法制作的啁啾光栅可以实现带宽可调谐且基本无中心波长漂移,在光纤传输和传感领域均具有一定的应用前景。     

Simultaneous sensing of displacement and temperature with a single FBG

A novel fiber Bragg grating (FBG) sensor with simultaneous sensing of displacement and temperature is presented. The FBG is affixed on the cantilever inclinedly. The midpoint of FBG exactly coincides with the zero strain layer of a rectangular beam. The vertical displacement can be measured by the broadened bandwidth of FBG as the bandwidth is insensitive to temperature, while the temperature can be measured by the center wavelength shift as the wavelength shift is insensitive to vertical displacement. With 0.1 nm spectral resolution of the analyzer, sensitivities of bandwidth-displacement and center wavelength-temperature are 0.48 nm/mm and 0.05 nm/°C, resolutions are 0.2 mm and 2.0 °C, and sensing ranges of displacement and temperature are up to 8.5 mm and 45°C respectively. Experimental results match theoretical analyses very well.     

Temperature Compensation for Double Fiber Bragg Grating Sensors

A novel double fiber Bragg grating(FBG) strain sensor configuration is presented. Temperature compensation method is based on double FBG moored on a rhombus frame. Through the theoretical analysis,the relation between relative shift of Bragg wavelength and the strain applied on the sensor is obtained,and the analytical expression of strain sensitivity coefficient is also given. The experiment results show that:in the strain range of 0～0.8 mm,the relation between the relative shift of Bragg wavelength and applied strain is linear,and the dispersion of double FBG wavelength at the range of -25 ℃～60 ℃ is 0～0.002 nm. The strain sensitivity of the displacement sensor configuration is 0.171 nm/με,and is nearly twice than that of single FC sensor.     

Topology and shape optimizations of substrates for chirp fiber Bragg grating spectrum tuning

A systematic method based on topology and shape optimization techniques has been developed to determine the geometry of a substrate for chirp fiber Bragg grating (FBG) spectrum tuning. The strain distribution on the FBG associated with a given wavelength spectrum is synthesized first by the application of a genetic algorithm. Then the substrate profiles determined either from topology or shape optimizations can generate the required strain distribution on FBG that responds to the required wavelength spectrum of a chirp FBG. The profile obtained from shape optimization, compared with that from topology optimization, has clear advantages in easier manufacturing and better liability. Although the strain distribution of a chirp FBG demonstrated here is simple in this study, it should be emphasized that this methodology also can be easily applied to determine other substrate profile whose strain distribution is regarding to a more complex wavelength spectrum of an FBG.     

基于非线性色散补偿光栅的可调谐光电振荡器

为实现光电振荡器(OEO)输出频率的连续可调,提出一种新型的基于非线性色散补偿光栅(FBG)实现可调谐OEO方案。本文方案不需要电滤波器,且振荡频率随着光源的波长变化而变化。其中,三阶色散补偿FBG可以采用FBG重构算法设计。当光源波长从1 550.6nm变化到1 551.4nm时,相应的色散为340～1 460ps/nm,输出频率的调谐范围为6.5～13.5GHz,实现了振荡频率的大范围可调谐。     

纯弯梁无啁啾光纤光栅调谐方法

利用简支梁和悬臂梁调谐光纤光栅布喇格波长将造成光纤光栅啁啾。提出了一种新型的纯弯梁调谐方法 ,并进行了理论和实验研究 ,实现了光纤光栅无啁啾调谐 ,用于光纤光栅外腔半导体激光器获得了± 1nm的激光波长稳定连续调谐     

啁啾管理调制格式中光谱整形滤波器优化

讨论了啁啾管理调制中光谱整形滤波器的作用及对直接调制激光器输出啁啾的影响,并对光谱整形滤波器种类、带宽、中心频率、阶数及滤波器在系统中的位置等进行了系统性的优化。结果表明优化后带宽为8.4 GHz、中心频率为193.1237 THz的1阶高斯型滤波器在滤波器前置无色散补偿啁啾管理光纤传输系统中性能最好,其1dB眼开度代价所对应的色散容限为5047 ps/nm。     

一种新型光纤光栅无啁啾调谐方法

分析了基于弹性梁的光纤光栅调谐原理，引入了轴向直变传递系数的概念，提出利用部分纯弯曲调谐方法，可实现光纤光栅宽带无啁嗽调谐。在实验中，利用部分纯弯曲调谐法，获得了20．1nm的光纤光栅无啁嗽调谐范围，调谐线性拟合度为0．9996，调谐过程中光栅反射谱的3dB带宽变化小于0．07nm，峰值反射率变化小于0．2dB，基本无啁嗽现象产生，实验结果和理论分析一致。     

Recompression of pulses broadened by transmission through 10 km ofnon-dispersion-shifted fiber at 1.55 μm using 40-mm-long opticalfiber Bragg gratings with tunable chirp and central wavelength

A 40-mm-long fiber Bragg grating with both tunable chirp and central wavelength is used to recompress pulses broadened by transmission through 10.0 km of non-dispersion-shifted fiber at 1.542 μm. 4.0-ps transform-limited pulses having an optical bandwidth of greater than 1 nm were broadened to 230 ps, and recompressed to 12 ps, showing compensation of 95% of the fiber dispersion     

基于SOA啁啾管理的连续可调谐色度色散补偿的研究

提出了一种新型的可小范围连续调谐的色度色散(CD)补偿方案.该CD补偿方案包括一个半导体光放大器(SOA)和一段固定长度的色散补偿光纤(DCF).利用SOA的交叉相位调制(XPM)效应,通过调节SOA的偏置电流和控制脉冲光的强度,可以对进入SOA的光信号引入不同大小的附加啁啾量,从而可以利用固定长度的DCF得到补偿后的无啁啾光信号.实验中,实现了10 Gb/s可调谐CD补偿器,在无需替换DCF的情况下,实现了补偿范围为-40 ps/nm到60 ps/nm的连续可调谐CD补偿.     

Photonic crystal fiber with novel dispersion properties

Our recent research on designing microstruc-tured fiber with novel dispersion properties is reported in this paper. Two kinds ofphotonic crystal fibers (PCFs) are introduced first. One is the highly nonlinear PCF with broadband nearly zero flatten dispersion. With introducing the germanium-doped (Ge-doped) core into highly non-linear PCF and optimizing the diameters of the first two inner rings of air holes, a new structure of highly non-linear PCF was designed with the nonlinear coefficient up to 47 W-1·km-1 at the wavelength 1.55 μm and nearly zero flattened dispersion of ±0.5 ps/(km·nm) in telecom-munication window (1460-1625nm). Another is the highly negative PCF with a ring of fluorin-doped (F-doped) rods to form its outer ring core while pure silica rods to form its inner core. The peak dispersion - 1064 ps/(km·nm) in 8 nm full width at half maximum (FWHM) wavelength range and -365ps/(km·nm) in 20nm (FWHM) wavelength range can be reached by adjusting the structure parameters. Then, our recent research on the fabrication of PCFs is reported. Effects of draw parameters such as drawing temperature, feed speed, and furnace temperature on the geometry of the final photonic crystal fiber are investigated.     

A tunable four-channel fiber Bragg grating dispersion compensator

A tunable four-channel dispersion compensator is achieved using fiber Bragg grating technology and applying a temperature gradient along the grating. Any dispersion from -370 to -1420 ps/nm could be obtained.     

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     

An chromatic dispersion monitoring method based on spectral-shift of SOA

A remnant dispersion monitoring method based on spectral-shift of SOA in high speed optical communication system with CSRZ format and single channel speed of 40 Gbit/s is proposed. The system performance can be optimized by careful choosing bandwidth and center wavelength of the optical fiber grating filter. The dynamical monitoring range is ±60 ps/nm and the monitoring precision is about 5 ps/nm. This method can be suitable for the application in dynamical dispersion compensation of high speed optical communication systems.     

单个光纤光栅实现对位移和温度的同时测量

结合光纤光栅悬臂梁调谐的特点 ,采用一种新颖的光纤光栅悬臂梁结构 ,将光纤光栅粘贴在悬臂梁和固定端基板的结合处 ,成功地实现了对位移和温度的同时测量。基于光谱分析仪 0 1nm的光谱分辨率 ,实验可得到的位移分辨率为 0 0 8mm ,温度分辨率为 3 1℃ (位移不变时可达 0 73℃ ) ,位移测量范围可达 10 5mm。实验结果与理论分析基本一致