Photosensitivity measurement in optical fibre with Bragg grating interferometers

A new technique based on two low-finesse fibre Bragg grating Fabry-Perot interferometers to study photosensitivity in optical fibre is presented. Phase evaluation using the Fourier spectra allows precise determination of the evolution of the refractive index with accumulated fluence. Results are given for different germanium/boron codoped fibres and for hydrogen-loaded fibres.     

光纤光栅传感技术在隧道火灾监控中的应用

分析了国内现有的隧道火灾监控系统现状,介绍了光纤光栅传感技术的原理,阐述了这一新技术在工程应用中的优点,并提出了基于光纤光栅感温探测器的隧道火灾报警监测系统,并结合工程实例介绍了该系统在隧道火灾监控中的应用。     

DWDM全光网络及光纤光栅在其中的应用

介绍了DWDM网络的结构特点及以及光纤光栅在其中的一些应用。     

动态可调谐光纤光栅单/双信道滤波的实现

阐明了应力引起光纤光栅布拉格波长漂移的机理；分析了应力对光纤光栅的反射谱的影响。采用施加应力的方法，实现了基于动态可调谐的光纤光栅的单／双滤波。     

光纤光栅钎焊嵌入金属梁及传感性能研究

为了实现金属结构内部温度和应力实时监测,以SnAg共晶合金为钎料将光纤光栅钎焊嵌入了钢质简支梁。分析了嵌入金属梁的光纤光栅温度、压力传感特性;试验监测了简支梁温度、压力与光纤光栅中心波长变化。结果表明,嵌入的光纤光栅中心波长和温度变化与梁所受压力大小都成线性关系,温度传感灵敏度比裸光栅提高了约一倍。     

Sagnac fiber interferometer with the population grating for fiber Bragg grating dynamic strain sensing

A Sagnac fiber interferometer with the population grating formed in saturable erbium-doped fiber (EDF) for fiber Bragg grating (FBG) dynamic strain sensing is proposed. In this configuration, a semiconductor optical amplifier (SOA)-based fiber ring laser with an FBG reflector is employed in the sensing part and a Sagnac interferometer based on transient two-wave mixing (TWM) via dynamic population gratings in single-mode polarization maintaining erbium-doped fiber (PM-EDF) is used in this detecting part. Experimental results show that the Sagnac fiber interferometer detection system can stably respond to dynamic strains at high frequencies. As an example of application, the response of the sensor system to continuous sinusoidal ultrasonic signals is presented. The proposed simple and robust configuration has an all-fiber design based on commercially available elements, which makes it promising for applications in fiber optic ultrasonic sensors.     

A high-resolution compact optical true-time delay beamformer using fiber Bragg grating and highly dispersive fiber

A high resolution optical true-time delay (OTTD) beamformer constructed by fiber Bragg grating (FBG) and highly dispersive fiber (HDF) is presented. It can produce the true time delay with the resolution of 1 ps. Besides the proposed system has compact structure and light weight even when a large number of antenna elements are present in a practical antenna array, this is because the used FBG fibers and HDFs are short and independent of the antenna element number. Theoretical analysis and numerical simulations are made. Proof-of-concept experiment results that demonstrate the feasibility of the system are presented.     

Fiber Bragg grating based shear-force sensor: modeling and testing

This paper presents the design and fabrication of a novel shear-force sensor using fiber Bragg grating (FBG) as the sensing element. The basic design consists of layers of carbon composite material (CCM) with an embedded FBG. A deformable layer of silicon rubber between the layers of CCM allows the applied shear force to change the grating periodicity and, hence, the reflected Bragg wavelength. The shift in the reflected Bragg wavelength shows a linear variation with the applied shear force. A theoretical model is established to study the shear sensing ability. In addition, numerical modeling is also carried out by the finite-element method (FEM). The experimental results are found to be in good agreement with the theoretical predictions as well as the FEM results. In this paper, the basic concept of shear-force measurement using FBG and related theoretical model and FEM simulation results are discussed together with experimental verification.     

温控体布拉格光栅外腔单管半导体激光器

为了研究铷蒸气激光中的线宽匹配技术,基于半导体制冷片(TEC)的温度控制技术设计了窄线宽可调谐单管半导体激光器.利用半导体激光器的温度漂移特性,使LD的激光光谱中心波长在780 nm附近(工作温度-6℃),采用体布拉格光栅(VBG)外腔结构改善了LD的激光光谱,获得了功率1.448 W线宽0.13 nm的激光输出.通过调节VBG的温度,LD波长可从779.28 nm调谐至780.13 nm,调谐范围达850 pm.     

光纤光栅型平面冲击信号方向识别的小波包分析

介绍了光纤光栅传感器检测平面冲击信号的方向识别技术的重要性;构建了基于小波包分解的能量谱特征向量,说明了能量谱特征向量用于诊断系统参数改变或损伤故障的原理;搭建了基于非平衡M-Z干涉仪和PGC相位解调技术的光纤光栅平面冲击信号检测系统;测试了与光纤光栅传感器轴向夹角为0°,30°,45°,60°,90°等方向的平面冲击信号;通过Fourier分析表明不同方向的冲击信号频谱的能量随冲击方向变化而改变;描绘了基于小波包分解构造的能量谱特征向量与冲击信号方向的关系,结果显示两者具有理想的余弦关系;实验表明基于小波包分解的能量谱特征向量能很好的识别平面冲击信号的方向。     

Narrow-stripe distributed reflector lasers with first-order vertical grating and distributed Bragg reflectors

Narrow-stripe 1.55-/spl mu/m wavelength distributed reflector lasers consisting of both distributed Bragg reflectors and vertical grating of the first Bragg order were fabricated. A low threshold current I/sub th/ of 2.8 mA, a differential quantum efficiency /spl eta//sub d/ of 28% from the front facet, and a submode suppression ratio of 44 dB were obtained for structures with a stripe width of 1.3 /spl mu/m and a cavity length of 150 /spl mu/m.     

光孤子系统的传输与控制技术

介绍了光孤子传输用的基本部件，分析了光纤孤子通信传输和控制技术的研究进展，指出了现阶段有待解决的问题，最后展望了光孤子通信发展前景。     

Design and analysis of widely tunable sampled grating DFB laser diode integrated with sampled grating distributed Bragg reflector

A new widely tunable laser diode structure that requires only two tuning currents is proposed. The laser diode consists of a sampled grating distributed feedback (SGDFB) laser diode monolithically integrated with a sampled grating distributed Bragg reflector (SGDBR). The phase control sections are properly inserted between the grating bursts of the SGDBR and SGDFB sections for the discrete and continuous tuning. To confirm the feasibility of the new structure, the split-step time domain model is used. The simulation result for a particular design shows that the tuning range as wide as 27 nm is possible with side-mode suppression ratio exceeding 35 dB. Furthermore, the output power is larger than that from SGDBR laser diodes with similar parameters.     

Technological implementation of Bragg grating reflectors in Ti:LiNbO/sub 3/ waveguides by proton exchange

The authors propose and demonstrate a simple and novel method for fabrication of efficient Bragg grating reflectors at telecommunication wavelengths in titanium-indiffused lithium niobate single-mode channel waveguides. This technique is based on the patterned proton-exchanged process. The validity of the method is verified by the good agreement of the spectral responses and the Bragg phase-matching condition. Reflectivity as high as 94% at 1546 nm was measured with 4-mm distributed parameter waveguides in z-cut lithium niobate.     

Optical hydrogen sensor based on etched fiber Bragg grating sputtered with Pd/Ag composite film

A novel fiber optical fiber hydrogen sensor based on etched fiber Bragg grating coated with Pd/Ag composite film is proposed in this paper. Pd/Ag composite films were deposited on the side-face of etched fiber Bragg grating (FBG) as sensing elements by magnetron sputtering process. The atomic ratio of the two metals in Pd/Ag composite film is controlled at Pd:Ag = 76:24. Compared to standard FBG coated with same hydrogen sensitive film, etched FBG can significantly increase the sensor’s sensitivity. When hydrogen concentrations are 4% in volume percentage, the wavelength shifts of FBG-125 μm, FBG-38 μm and FBG-20.6 μm are 8, 23 and 40 pm respectively. The experimental results show the sensor’s hydrogen response is reversible, and the hydrogen sensor has great potential in hydrogen’s measurement.     

All-optical TDM data demultiplexing at 80 Gb/s with significant timing jitter tolerance using a fiber Bragg grating based rectangular pulse switching technology

We demonstrate the use of fiber Bragg grating based pulse-shaping technology to provide timing jitter tolerant data demultiplexing in an 80 Gb/s all-optical time division multiplexing (OTDM) system. Error-free demultiplexing operation is achieved with /spl sim/6 ps timing jitter tolerance using superstructured fiber Bragg grating based 1.7 ps soliton to 10 ps rectangular pulse conversion at the switching pulse input to a nonlinear optical loop mirror (NOLM) demultiplexer comprising highly nonlinear dispersion shifted fiber (HNLF). A 2-dB power-penalty improvement is obtained compared to demultiplexing without the pulse-shaping grating.     

Temperature and strain sensing characteristics of the tilted fiber Bragg grating

Theoretical and experimental studies on the tilted fiber Bragg grating (TFBG) temperature and strain sensing characteristics are conducted. The TFBG is stuck to the surface of the beam along the axis direction. When the free end of the beam is forced, both the strain and temperature will induce wavelength shifts. The temperature characteristic of TFBG cladding modes is similar to that of the core mode while the strain characteristics of TFBG core mode and cladding modes are different. A novel method to discriminate the temperature and strain simultaneously is put forward based on TFBG sensing characteristics.     

应用等效规则优化法设计光通信光栅

基于光栅电磁场理论,应用光栅等效规则计算光栅槽形初始值、结合衍射效率等高线法优化设计光栅槽形,给出了具有几何对称中心的任意槽形光栅.以全息工艺上易于制作的正弦、矩形和两种梯形典型槽形光栅为例进行优化设计,结果表明,正弦槽形光栅C波段TM波衍射效率理论峰值为95%,测量值为92%.较互易定理优化方法,等效规则优化法拓宽了光通信光栅的制作方法、降低了制作难度,为全息方法制作光通信光栅提供了理论依据.     

Structural and optical properties of InAlN/GaN distributed Bragg reflectors

Structural and optical properties of InAlN/GaN distributed Bragg reflectors grown by MOCVD on sapphire substrates are studied. The influence of growth conditions and thicknesses of the InAlN layers on structural properties of distributed Bragg reflectors is studied. It is shown that optimization of the conditions of epitaxial growth makes it possible to design InAlN/GaN distributed Bragg reflectors with a reflectance of more than 99% and a reflection maximum in the wavelength range of 460–610 nm.     

Optical DPSK demodulator based on /spl pi/-phase-shifted fiber Bragg grating with an optically tunable phase shifter

We propose and demonstrate a novel optical differential phase-shift keying (DPSK) demodulator with an optically tunable phase shifter. The proposed DPSK demodulator is implemented by using a /spl pi/-phase-shifted fiber Bragg grating and an Yb/sup 3+/-Al/sup 3+/ codoped optical fiber. A 10-Gb/s DPSK signal was successfully demodulated by the proposed demodulator, showing clearly open eye diagrams as well as bit-error-free performance. Moreover, the phase of delayed optical signal can be tuned by the phase shifter that is controlled by a pumping light at around 980nm.