Chromatic Dispersion Monitoring Method Based on Phase Shift Technique

The modulation phase shift method was used to measure chromatic dispersion in a standard single mode fiber for telecommunication. The modulation phase difference of the transmitted light at the wavelength of 1532.16 nm modulated by a radio frequency signal was measured, relative to the transmitted light at the wavelength of 1549.33 nm modulated by the same signal. By introducing a reference light at the wavelength of 1310 nm, a 1310/1550 nm wavelength division multiplexing was used instead of the high cost dense wavelength division multiplexing. In the experiment, two testing lights were coupled with the reference light to the fiber spools of different lengths, respectively. By finite difference method, the chromatic dispersion between the two testing lights was measured, and the fixed errors generated during transmission were less than 0.5 ps/(nm·km).

Microwave photonic phase shifter with spectral separation processing using a linear chirped fiber Bragg grating

A stable and broadband microwave photonic phase shifter based on the combined use of a linear chirped fiber Bragg grating and optical single-sideband （OSSB） modulation is proposed and experimentally demonstrated. The quality of the radio frequency （RF） signal is improved by the spectral separation delay processing. The theoretical fundamentals of the scheme are explained and the phase shift can be controlled linearly by the wave- length of the light source. In the experiment, a full 360° phase shift with a 10 GHz bandwidth can be achieved and tuned dynamically, continuously, and stably.

An Optical Fiber Hydrophone Using Equivalent Phase Shift Fiber Bragg Grating for Underwater Acoustic Measurement

An optical fiber hydrophone based on equivalent phase shift fiber Bragg grating （EPS-FBG） with temperature compensation package provides an improvement of sensitivity in underwater acoustic measurement at wide frequency range, from 2.SkHz to 12kHz. The acoustic pressure is transduced into elastic vibration of a circle metal disk, resulting in an intensity modulation of the reflected light wave back from fiber Bragg grating （FBG）. Experiment shows that the 500 EPS-FBG hydrophone has a minimum detectable acoustic pressure of about at 5 kHz and achieves about 18-dB improvement of acoustic pressure sensitivity compared with a regular apodized FBG hydrophone.

An interferometric phase shift fiber Bragg grating sensing system with greatly reduced background phase noise

We presented an interferometric phase shift fiber Bragg grating （FBG） sensor, which inherited the advantages of FBG sensors, and, at the same time, the greatly reduced full-width-at-half-maximum bandwidth brought longer coherent length, higher sensitivity, and lower phase noise. Experiments show that at least a 7 dB reduction of phase noise can be achieved compared to FBG sensors interrogated by interferometer with the same optical path difference.

An Adjustable Pure Dispersion Slope Compensating-Module without Center Wavelength Shift Based on Strain-Chirped Fiber Bragg Gratings

We demonstrate an adjustable pure dispersion slope compensating-module based on strain-chirped fiber Bragg gratings. The center wavelength of the module is preserved while the pure dispersion slope is tuned.

Optical pulse shaping based on a double-phase-shifted fiber Bragg grating

Based on the transfer matrix method,a detailed theoretical and numerical study on double-phase-shifted fiber Bragg grating(FBG)is investigated.Temporal responses of the double-phase-shifted FBG to optical pulse are analyzed and the influence of the two phase-shifts’position on the reflected output pulse is evaluated.Results demonstrate that very different temporal pulse waveforms can be achieved by adjusting the length ratio(α=L2/L1).Specifically,a transform-limited Gaussian input optical pulse can be shaped into flat-top square pulse(α=1.81)or two identical optical pulse sequences(α=1.93).

Tunable phase-shifted fiber Bragg grating based on a microchannel fabricated by a femtosecond laser

A phase-shifted fiber Bragg grating(PS-FBG) based on a microchannel was proposed and realized by combining the pointby-point scanning method with chemical etching. The PS-FBG is composed of a fiber Bragg grating(FBG) and a microchannel through the fiber core. The microchannel can introduce phase shift into the FBG. What is more important is that it exposes the fiber core to the external environment. The phase shift peak is sensitive to the liquid refractive index, and it shows a linear refractive index response wavelength and intensity sensitivity of 2.526 nm/RIU and-111 d B/RIU, respectively.Therefore, such gratings can be used as sensors or tunable filters.

Study on the Characters of Phase-Shifted Fiber Bragg Grating in Asymmetric Perturbation and Its Application in Fiber Laser Acoustic Sensor

A n-phase-shifted fiber Bragg grating theoretical model is established, and the effects of an asymmetric and symmetrical perturbation field on a phase-shifted fiber Bragg grating are investigated in this paper. The trends of wavelength shifting caused by effective refraction index of phase shift grating in symmetric and asymmetric acoustic field are investigated in detail. Then, the fiber laser acoustic sensors packaged in asymmetric and symmetrical structures are designed and tested, respectively. The results show that the acoustic response of the wavelength of the distributed feedback （DFB） fiber laser （FL） in an asymmetric packaging structure is much more sensitive than in that in the symmetrical structure. The sensor packaged in the asymmetrical structure has a better low frequency （0Hz-500Hz） performance and a higher sensitivity than that in the symmetrical structure, and the sensitivity is improved about 15dB in average and 32.7dB in maximum. It provides a new method to improve the sensitivity of the fiber acoustic sensor.

Computer-Generated Holograms for Recording Multiple-Phase-Shifte Fiber Bragg Grating Corrugations

A new method of fabricating multiple-phase-shifts fiber Bragg grating by CGHsis proposed . The authors present an example of such CGH by which a section multiple-phase-shiftefiber Bragg grating with twoπ/2 phase shifts and grating length L = 21.2 μm was produced. Theauthors describe the production process and finally give an example of a reconstructed fiber gratingwith two phase-shifts.

长周期光纤光栅的分析和优化设计

利用传输矩阵法对相移和变迹长周期光纤光栅的传输特性进行了计算和分析 ,提出长周期光纤光栅传输谱的相移优化设计方法 采用非均匀相移的设计思想 ,优化长周期光纤光栅的传输谱 和传统的均匀相移和变迹长周期光纤光栅相比 ,可以有效消除长周期光纤光栅谐振波长附近的旁瓣 ,并保证其传输性能 计算和分析结果表明

动态色散补偿技术的研究进展

概述了光通信网中动态色散补偿技术。对常见的几种动态色散补偿技术的机制。

优化二元相位取样光纤布喇格光栅及对色散和色散斜率补偿的应用

利用粒子群算法对二元相位取样光栅的周期相位调制进行优化设计,在此基础上提出了基于二元相位取样光纤布喇格光栅的色散和色散斜率补偿技术.通过光栅周期啁啾可以调整每个信道的带宽,色散量由子光栅长度决定,调整取样函数的啁啾系数可以改变色散斜率,因此可以设计出用于波分复用系统的多信道色散补偿器件.

光纤光栅技术的进展及其色散补偿

光纤光栅在远程光通信系统中有着重要的现时和潜在的应用。文章介绍了制造具有复杂结构的光纤光栅的技术的最新进展以及它们在色散补偿中的应用，并指出了其发展趋势。

自放大结构分布反馈光纤激光器输出特性

在光敏性掺铒光纤上制作了45mm长非对称相移结构光纤光栅,构成前后向功率输出比大于100∶1的分布反馈光纤激光器.利用一定长度的掺铒光纤吸收有源相移光栅后的剩余泵浦光,实现了对前向输出激光信号的放大,并采用OptiSystem软件模拟了掺铒光纤长度与增益的关系.为了保持输出激光的窄线宽和低噪音特性,利用布喇格波长与激光相同的光纤光栅和光纤环行器构成光窄带滤波器,对放大后激光信号的ASE噪音进行滤除.研究表明:所设计的激光器结构充分利用了泵浦光,在300mW的(980nm)泵浦功率下获得了功率为32.5mW,线宽为11.5kHz,相对强度噪音为-87dB/Hz的激光输出.

啁啾相移光纤光栅分布式应变与应变点精确定位传感研究

利用啁啾相移光纤光栅狭缝的中心波长对应变点和应变量的波长敏感性,实现应变与应变点精确定位的传感.当啁啾光纤光栅上的某一位置产生微应变时,该应变点会产生相移,其频谱则会出现一个与之对应的狭缝,且狭缝的深度和中心波长与应变的大小和位置相关.当串接不同中心波长的啁啾光纤光栅后,即可实现一定范围内的分布式应变与应变点精确定位检测.本文通过V-I传输矩阵法建立了狭缝深度和中心波长关于应变量和应变位置的理论模型,分析结果表明理论上可以实现微米量级的精确定位.搭建了级联啁啾相移光纤光栅的分布式应变传感装置,实验获得的最大应变灵敏度为0.19 pm/με.该精确定位传感装置在先进制造、精密加工、航空航天、铁路系统等高新技术领域具有重要的应用前景.

光纤光栅传输矩阵研究

利用模耦合理论给出并分析了一般坐标系下相移布喇格光纤光栅中的传输矩阵及其特性,所给出的传输矩阵具有分段不变性,而且不能被分解为一个矩阵和一个相移矩阵的乘积.利用该传输矩阵可以研究均匀、相移、啁啾、超结构等光纤光栅及光栅的级联等.计算了相移光栅的反射谱和相移量的关系,以及两个光栅级联时的反射谱.结果表明,同样相移量时的反射谱和已有文献不同,两个光栅级联时,也不同于已有文献,各自的谐振波长与光栅的级联没有关系.

非均匀应变场下相移光栅光谱特性及其实验研究

采用传输矩阵法系统研究轴向非均匀应变场下相移光栅光谱特性,对均匀应变、线性应变、二次应变以及三次应变分布下相移光栅反射谱进行仿真,分析应变分布函数各项系数对反射率、通透带宽、透射窗口对应波长以及光谱形状的影响,并得出规律性结论。基于不同形状悬臂梁组建应变调谐实验装置,利用有限元法计算固定于不同形状悬臂梁表面相移光栅栅区应变分布,结合数值计算结果进行相移光栅应变调谐实验,研究相移光栅栅区轴向在均匀应变场、线性应变场以及二次应变场下相移光栅的反射光谱,实验结果表明在不同应变场下相移光栅反射谱呈现规律性变化,与仿真结果很好吻合。

偏振控制法紫外写入Bragg光纤光栅的特性分析

结合目前常用光纤布喇格光栅制作方法 ,详述了一种更加灵活、简单而又有效的制作光纤布喇格光栅的方法 ,即偏振控制法。该方法是基于 :在紫外光s和 p偏振方向诱导而成的两个折射率调制剖面之间形成一个π相移 ,通过改变两个偏振方向上光强比例 ,就能够控制调制量和诱导相移。它的优点是写入的光栅具有多相移和不均匀切趾剖面的特点 。

基于相移超结构光栅的ROF单边带调制系统（英文）

提出了一个利用相移超结构光栅构建的典型ROF单边带调制系统。改变倾斜角,光栅就会呈现不同的传播特性。将不同的相移插入光栅的不同位置就会得到不同的透射谱特性。因此该光栅可视为滤波器应用于单边带调制系统中。反射谱的负斜率特性使得低阶边带会经历更高的衰减。所以,仅仅使用一个相移超结构光栅就可以简单地实现双边带到载波单边带的转换。与此同时,还可以通过改变光栅的倾斜角优化光载波抑制比。在实验中,60 GHz的毫米波信号产生的同时光载波抑制比也由33.02 dB优化到1.31 dB,经过30 km光纤传输后的最小误码率可以达到1.966e-44,所以仅仅通过一个相移超结构光栅就可以大大提高链路性能。

一种光纤光栅水听器灵敏度校准技术研究

为了校准光纤光栅水听器的灵敏度,开展了光纤光栅水听器灵敏度校准技术研究.本文首先介绍了光纤光栅水听器的工作原理;其次,采用可调谐激光器和带工作点控制的强度调制法,实现了光纤光栅水听器的信号解调和稳态测量;在此基础上,利用比较法建立了一种光纤光栅水听器校准系统,校准频率范围为20Hz～10kHz;最后,在该频率范围内对采用等效相移布喇格光栅研制的一只光纤光栅水听器的灵敏度进行了校准,对系统的测量不确定度进行了估算.结果表明,该系统可准确校准光纤光栅水听器的灵敏度,扩展不确定度为0.9dB(k=2).