Tuning Bragg wavelength by writing gratings on prestrained fibers

Bragg gratings at a specific wavelength are made using an excimer KrF laser and a phase mask. The wavelength can be varied for fine tuning and multiplexing applications by straining the optical fiber during UV illumination. When the strain is removed, the grating formed is at a smaller wavelength than that dictated by the phase mask for the unstrained fiber. This technique was demonstrated by writing two gratings located at the same point in the optical fiber. The transmission from the first grating was used as a means for in situ absolute wavelength tuning. The second grating made with approximately 0.2% axial strain was at 1534.54 nm. Once the grating was made, the strain was removed from the fiber leaving the second grating tuned to 1532.04 nm, a wavelength shift of 2.5 nm     

弯曲长周期光子晶体光纤光栅传感器的研究

为了研究弯曲长周期光子晶体光纤光栅传感器谐振波长漂移量与光栅弯曲形变的关系,采用耦合模理论和计算机模拟方法进行了理论计算和仿真研究,推导出弯曲光子晶体光纤长周期光栅谐振波长表达式,设计了一般弯曲长周期光子晶体光纤光栅传感器系统模型,分析了弯曲长周期光子晶体光纤光栅传感器的基本工作原理,并计算了长周期光子晶体光纤光栅弯曲曲率、光栅有效折射率和谐振波长与弯曲应变的关系。结果表明,随着光栅弯曲形变的增加,光栅的曲率会增加,光栅传感器的谐振波长漂移量会增加,光栅每发生1变化,光栅谐振波长的漂移量变化0.014nm。     

Chirped fiber-optic Bragg grating interrogator in a multiplexed Bragg grating sensor configuration

This paper presents a chirped grating interrogator for fiber Bragg grating sensors. The interrogator uses the wavelength dependence of the phase group-delay response of a chirped fiber Bragg grating to determine the Bragg wavelength of the sensor. The sensitivity of the interrogator is determined by the selection of the grating length and the bandwidth. The experimental results demonstrated strain measurements over a range of more than 10 000 /spl mu/m per meter. Multiplexing can be achieved by using an arrayed-waveguide grating that allows the interrogation of more than one grating sensor with a single chirped grating.     

声光调Q CO2激光器波长调谐理论分析与实验研究

采用旋转光栅法实现了声光调Q CO2激光器可调谐脉冲激光输出。理论分析了CO2激光波长调谐特性,发现调节各支谱线腔内损耗是实现激光波长调谐的有效方法。进而理论计算了特定设计波长闪耀光栅的衍射效率与激光波长间的关系,结果显示光栅调谐的激光谱线自准直角与光栅闪耀角一致时具有最高的衍射效率。采用闪耀角分别为31.97（闪耀波长10.59 m）和28.71（闪耀波长9.60 m）的光栅实验研究了声光调Q CO2激光器波长调谐特性,分别获得了65条和75条激光谱线。实验结果显示:光栅设计闪耀波长处于弱激光增益分支时可获得更多条激光谱线,该实验与理论计算结果相符。在脉冲重复频率为1 kHz时,获得10.59 m激光脉冲宽度为160 ns,平均功率4.2 W,脉冲峰值功率26.25 kW,且稳定性良好。     

Semiconductor laser with external resonant grating mirror

A resonant grating composed of an ion exchanged slab waveguide on a glass substrate with a corrugation grating at its surface is shown to perform as a wavelength selective external mirror of a semiconductor laser. Preliminary wavelength tuning is demonstrated.     

正交读出方式体全息光栅通信波长衍射特性

为了寻求高质量和高密度的密集波分复用器件,采用了在双掺铟铁的铌酸锂晶体中透射式记录/正交式读出方案制作体全息光栅的方法,对体全息光栅衍射特性进行理论分析和实验验证。利用波长为532nm的激光记录尺寸比为1:1的体全息光栅,然后用中心波长为1550nm的红外通讯波长成功读出,取得了波长选择性为0.5nm的波长衍射特性数据。同时,利用2维耦合波理论的闭形式解析解得到了该体全息光栅衍射效率随波长的变化关系。结果表明,实验结果与理论预期相符合,这一方法对制作体全息光栅密集波分复用器件的实用化是有帮助的。     

双波长可调外腔半导体激光器

提出了一种基于体布拉格光栅（VBG）和横向啁啾体布拉格光栅（TCVBG）组合的双光栅外腔半导体激光器,该外腔半导体激光器采用反射率15%的体光栅和反射率17%的啁啾体布拉格光栅作为反馈元件和模式选择元件,实现特定波长的选择和调谐,实验研究了外腔激光器的功率-电流特性、光谱特性和波长调谐特性。实验结果表明:双光栅外腔半导体激光器最大输出功率为1.96 W,斜率效率为0.94 W/A,外腔效率达到78%。输出光谱为双波长,一个波长为808.6 nm,另一个波长连续可调,通过改变横向啁啾体光栅的位置,该波长可从800 nm调谐至815 nm,可调范围达15 nm,在整个可调范围内两个波长的谱线宽度（FWHM）均小于0.3 nm。     

量子阱红外探测器光栅耦合参数的优化

基于傅里叶光学的知识,分别对量子阱红外探测器的一维和二维光栅耦合模式进行了研究,得到器件的相对吸收率随波长和光栅周期之比的变化曲线,把此曲线作为优化光栅常数的依据.对于给定峰值波长的探测器,在波长与一维光栅周期之比为1时,吸收率最大;波长与二维光栅周期之比为0.7时,吸收效率最高,结果与已发表的数据相符.此外,还对刻蚀误差的影响进行了讨论,当实际刻蚀的光栅常数与优化的有偏差时,耦合效率降低.     

Electronic tracking system for multiplexed fibre grating sensors

The authors demonstrate for the first time an electronic lock-in system using an acousto-optic tunable filter (AOTF) to track the wavelength of a fibre Bragg grating. The change in the system output is proportional to the change in grating wavelength. Initial results show microstrain resolution at data acquisition rates of 10 Hz     

Programmable fiber optic delay line

This paper describes a novel programmable delay line that generates up to 50 ns of true time-delay in discrete 10 ns intervals. The delay line consists of an externally modulated wavelength tunable fiber laser and a six-element wavelength multiplexed fiber Bragg grating array, with the grating spacing set to yield the desired delay     

Fiber laser source/analyzer for Bragg grating sensor arrayinterrogation

This paper reports on the application of a calibrated, narrow-linewidth, single-frequency, continuously wavelength-tunable erbium fiber laser to the interrogation of a multipoint Bragg grating temperature sensor. The fiber laser was wavelength-tuned, through an array of three fiber Bragg grating sensors, to determine the temperature of each individual grating. The temperatures of the three gratings were measured as a function of grating Bragg wavelength. The minimum wavelength resolution, due to electro-mechanical repeatability, of the fiber laser source/analyzer was determined to be approximately 2.3 picometers. This corresponds to a frequency resolution of approximately 300 MHz     

Wavelength multiplexer based onSiO2-Ta2O5 arrayed-waveguide grating

The characteristics of a wavelength multiplexer based on an arrayed-waveguide grating are carefully investigated by using the grating theory and related experiments. A 28-channel multiplexer is designed and fabricated as SiO₂-Ta₂O₅ waveguides on a 1 cm×2 cm substrate. The designed wavelength channel spacing of 1 nm is obtained. The crosstalk to an adjacent channel is -15 dB. The measured minimum loss is 4.2 dB, which is composed of 3.4 dB excess loss and 0.8 dB grating loss     

Active wavelength demodulation of Bragg fibre-optic strain sensorusing acousto-optic tunable filter

An acousto-optic tunable based active wavelength demodulation system for intracore Bragg grating fibre-optic sensors has been demonstrated. The system uses an intensity self-referenced edge-locking technique to track the reflected signal of the Bragg sensor. A strain resolution of 2.2 με was achieved with a Bragg fibre-optic strain sensor operating at ~1324 nm. Corresponding to a wavelength resolution of 2.6 pm. The potential for high resolution measurements over wide wavelength ranges is particularly attractive for wavelength multiplexing of Bragg grating sensors     

DWDM技术在新型波长解调方法中的应用

为实现光纤传感器的波长解调,以8通道50 GHz密集型波分复用器作为光纤光栅压力传感器中的解调工具,依据各个通道的中心波长作为波长的标定基准,利用从各通道中获得的光功率输出值获得光纤光栅反射光谱分布曲线的包络,并以高斯多项式拟合法作为光纤光栅波长寻峰算法,最终获得光纤光栅反射光谱的中心波长的准确位置,从而实现结构简洁、成本低廉、全光纤的波长解调系统,系统压力与波长的线性拟合度为0.996 5,实验测得的波长分辨率可达0.3 pm,最大引用误差为2.6%,测量精度为0.16 MPa。     

利用光栅实时测量大视角入射激光波长的方法

本文探讨了利用光栅实时测量大视角入射激光波长和方位的理论依据，并进行了误差分析；尝试并实现了利用光栅实时测量大视角入射激光波长和方位的方法；预见到光栅是实时测量大视角、宽频带、脉冲激光波长的有效元件。     

主动锁模光纤环形激光器的悬臂梁调谐法

利用悬臂梁来对光纤光栅的Bragg波长进行调谐,并将可调谐光纤光栅用于主动锁模光纤环形激光器中,获得了5.24nm的波长调谐范围。同时,在1547.883nm处,获得了脉宽为55ps,谱宽为0.017nm锁模脉冲输出。     

环形腔光纤激光器波长选择技术

用波分复用 (WDM)光栅串作环形腔端镜 ,调节F P滤波器透过的共振波长 ,实现对应光栅波长的稳定激光输出 ,其斜率效率在 0 0 9左右 ,实验表明光栅反射率以及所处波长处的增益影响激光阈值的大小。用全反镜替代光栅串 ,在 15 30～ 15 75nm范围内可对输出波长进行连续调节。     

连续调谐输出的多周期极化铌酸锂晶体光学参量振荡器

对基于多周期极化铌酸锂晶体(PPLN)的信号光单谐振准相位匹配光学参量振荡器(QPM—OPO)，进行了温度调谐的理论和实验研究。以激光二极管(LD)端面抽运的声光调Q Nd：YVO4全固态激光器为抽运源，获得了1369．7～1678．8nm无重叠波段连续可调谐输出。给出了1064nm Nd：YVO4激光器抽运下，由PPLN的极化周期和温度直接计算输出信号光波长的公式，以及由信号光波长和极化周期计算相应的晶体温度的公式。这样就可直接计算实现无重叠波段连续可调谐输出时不同极化周期所对应的温度调谐范围，而不必联立能量守恒和动量守恒公式，逐点进行尝试。另外，周期极化晶体的极化周期不可避免地较理想值有一定的偏移，且具有不均匀性，给出了利用实验获得的温度调谐曲线，对极化周期进行修正计算的方法。     

Highly tunable Bragg gratings in single-mode polymer optical fibers

A Bragg grating in a single-mode polymer optical fiber (POF) has been created. The novel grating has a length of 1 cm with a reflectivity of 80% and a linewidth of about 0.5 nm. The wavelength tunability of the POF grating by stretching was investigated and a wavelength tunable range of 20 nm has been achieved. Based on the properties of the polymer, we believe that this kind of grating has a wavelength tuning potential of more than 100 nm     

基于弹性梁的光纤光栅波长调谐原理及技术

光纤光栅波长调谐在光纤通信和光纤传感器领域中具有重要意义和实用价值。从理论上分析了基于弹性梁的光纤光栅波长调谐的基本原理,阐述了几种典型的简支梁、悬臂梁及扭梁调谐技术及其特点,展望了波长调谐方法的未来发展。