高空间分辨率分布式光纤传感技术的研究进展

对三种基于布里渊散射的高空间分辨率分布式光纤传感技术,即布里渊光纤时域分析暗光脉冲技术、布里渊光相关域分析及布里渊光频域分析技术,进行了详细阐述.分析了每种技术的工作原理,对每种技术所采用的实验系统配置、所能达到的空间分辨率进行了介绍,并对其存在的局限性进行了说明.     

基于布里渊散射的海洋环境激光遥感技术研究进展

布里渊激光雷达是探测海洋环境参数的重要手段之一。首先介绍了布里渊激光雷达系统的基本工作原理，然后从理论基础出发，重点介绍了三种依据布里渊散射光谱特征:布里渊频移、布里渊线宽、以及综合二者与海洋环境参数之间的耦合关系建立的反演模型；其次，作为布里渊激光雷达的关键技术，介绍了多种布里渊散射光谱的测量方法:F-P扫描干涉仪探测、边缘探测、F-P标准具- ICCD探测, 以及多边缘探测。     

Applications of Optical Carrier Brillouin Processing to Microwave Photonics

We introduce the fundamentals of optical carrier Brillouin processing and discuss its applications to the field of microwave photonics. This signal processing technique is based on the control of the amplitude as well as the phase of the optical carrier of a modulated lightwave signal using the stimulated Brillouin scattering effect. Application of the technique to improve the performance of microwave/millimeter-wave fiber links is experimentally demonstrated.     

布里渊增强四波混频研究的进展

当一个布里渊频移的信号在布里渊激活介质中与两束相反方向传播的强泵浦光相互作用时,将产生一个随时间指数增长的共轭场,直到它抽空泵浦场,并且由此产生很高的反射率(大于106)。这项技术可用于共轭微弱信号(小于10-13J),或者可以用于把大部分泵浦能量转移到共轭光,对此技术作了回顾。     

Highly stable low-noise Brillouin fiber laser with ultranarrow spectral linewidth

We demonstrate an all-fiber high-power single-frequency Brillouin fiber ring laser with maximum power of 100 mW at 1.55 /spl mu/m, which is actively stabilized by using the Pound-Drever-Hall frequency-locking scheme. Significant reduction (/spl sim/20dB) of both relative intensity noise and frequency noise was observed in the Brillouin Stokes radiation as compared with those noises of its pump source, a narrow-linewidth Er-doped fiber laser. Ultranarrow spectral linewidth of the Brillouin fiber lasers was investigated by both delayed self-heterodyne technique and heterodyne beat technique between two independent Brillouin fiber lasers.     

Complex Spectrum Analysis of Modulated Optical Signals Using Stimulated Brillouin Scattering

We introduce a novel method for the measurement of the spectral phase of modulated optical signals based on double-pump stimulated Brillouin scattering interaction and direct homodyne detection. This technique is combined with Brillouin high-resolution analysis to achieve a complete characterization of the complex optical spectrum. A 10-Gb/s nonreturn-to-zero signal with a 32-bit pattern modulated with an electroabsorption modulator is measured using this technique and its time-domain information (power and chirp) is obtained by inverse Fourier transform.      

关于布里渊散射强度角分布的探讨

运用经典的电磁场理论对布里渊散射强度和散射截面进行了推导,并在此基础上结合量子电动力学理论改进了经典的布里渊散射截面公式,对布里渊散射过程经典理论和量子理论的两种描述进行了比较和讨论。     

基于光纤光栅的微波扫描单边带调制法测量光纤布里渊散射特性

利用光纤布拉格光栅(FBG)和马赫-曾德尔电光调制器实现了单边带光调制输出。基于微波扫描的单边带调制技术提出了一种测量光纤受激布里渊散射(SBS)特性的方法,可有效地将布里渊频移与布里渊增益谱的测量统一起来。对一段50m长的光子晶体光纤(PCF)的SBS特性进行了测量,得到了PCF的SBS谱的布里渊频移为9.7443GHz,布里渊增益谱线宽为22.472MHz,布里渊增益系数为7.874×10-12 m/W。     

边缘检测技术在分布式光纤传感中的应用

提出了采用双边缘技术测量光纤传感中的布里渊频移。利用边上信号对频率变化敏感的特点，提出了边缘检测技术，并通过设置最佳的工作点，使系统工作在最敏感的点上。理论分析表明，为实现0．5MHz的布里渊频移测量精度，通过测量最大信号的常规检测所需的信噪比为65．1127dB．单边缘检测所需的信噪比为37dB，双边缘检测所需的信噪比为31dB。所以，在相同信噪比下，与常规检测技术相比，边缘检测技术可以大大提高布里渊频移测量精度。     

Microwave Photonic Signal Down‐Conversion Using a Novel Two‐Frequency Bragg Grating Based Brillouin Fiber Laser

A simple technique using a novel two‐frequency Bragg grating based Brillouin fiber laser to down‐convert high frequency microwave photonic signals is presented. The mechanism of the Brillouin fiber laser and the principle of this technique for microwave photonic signal down‐conversion are analyzed. The 12GHz microwave photonic signals are experimentally down‐converted to 1.13GHz IF signal with the technique.     

基于高频微波技术的分布式光纤传感器布里渊散射信号检测

分析了布里渊分布式光纤传感技术原理,采用自行研制的光纤单纵模分布反馈(DFB)激光器结合电光调制技术,利用相干检测技术,对布里渊微弱后向散射信号进行检测。通过改进滤波放大技术,对微弱后向散射光信号进行有效放大,再用扰偏技术及信号采样平均处理,实现对光纤传感器后向布里渊散射信号在11 GHz高频段直接采集显示。结果表明,探测所得布里渊散射信号峰值功率可达50 mV,能有效降低解调系统信号检测难度,改善了系统信噪比(SNR)。初步实验结果证明了该方案的可行性。     

水中布里渊散射的边缘探测方法

提出了一种测量水中布里渊散射的新方法——边缘探测技术。分析了这种方法的原理。结合布里渊散射激光雷达在海洋监测中的应用,给出了一个基于溴和碘分子吸收池的实际探测系统,并给出了系统的响应函数。最后,讨论了边缘探测技术的特点     

Distributed fiber Brillouin strain sensing with 1-cm spatialresolution by correlation-based continuous-wave technique

This letter describes improvement in the spatial resolution of distributed fiber Brillouin strain sensing by the correlation-based continuous-wave technique, which we proposed previously. The spatial resolution of 1 cm has been achieved for a partly stretched fiber. This result shows the technique is applicable to smart structures or materials as a nervous system to monitor strain distribution     

布里渊散射法测量盐度及温度不同的海水中的声速

报道了不同盐度及温度海水中用布里渊散射方法得到的声速的实验测量结果。结果表明 ,布里渊散射方法是一种很好的海洋监测技术     

基于布里渊散射探测空间目标的计算分析

提出用布里渊散射原理探测空间目标的方法。分别对大气、空间目标材料金属涂层及隐身材料的布里渊散射特性进行了计算和对比分析。结果表明,大气布里渊散射频移与目标涂层及隐身材料布里渊散射频移之间相差至少大于一个数量级,由此得出利用分析布里渊散射光谱来探测空间目标的可行性。计算了散射频移的大小,并对探测技术作了分析,采用一种窄带量子滤光系统探测装置,对散射光谱进行了精确的探测和分辨。     

Simple distributed optical fiber sensor based on Brillouin amplification of microwave photonic signals

A simple distributed fiber sensor is proposed by Brillouin amplification and depletion of microwave photonic signals. This technique utilizes optical carrier suppression (OCS) modulation to generate two sidebands acting as the pump waves. After Fresnel reflection at the cleaved end of the fiber under test (FUT), the pump waves are converted to probe waves. By sweeping the modulated microwave frequency, the stimulated Brillouin scattering (SBS) spectra and Brillouin frequency shift (BFS) can be precisely characterized. As a result, the accurate measurement of the Brillouin frequency shift makes good determination of the distributed temperature or stain along the FUT, and the position along the FUT can be resolved and controlled by the delay of the microwave pulses. Furthermore, our proposed sensing system is implemented with a single-ended configuration which has shown many advantages such as immunity of the laser frequency fluctuation and compact setup without additional pump laser source and filters.     

Optical heterodyne carried generation using stimulated Brillouin scattering in birefringent optical fibre

An optical technique for producing a heterodyne carrier frequency suitable for electronic signal processing schemes in sensing applications is described. The technique exploits stimulated Brillouin scattering generated in birefringent optical fibre. A single fibre system is reported which produces a 10.6 MHz output carrier signal, modulated by optical chaos induced instabilities. The implications of the results for future signal processing and sensing schemes based on stimulated Brillouin scattering are then discussed.<>     

宽带可调谐双频移多波长布里渊光纤激光器

提出了一种采用高非线性光纤作为布里渊增益介质 的双倍布里渊频移间隔的多波长布里渊光纤激光器(MW-BEFL)。激光器利用两个环形器构成 双倍频移结构,将奇数阶的斯托克斯信号隔离在腔内循环,仅有泵浦 信号和偶数阶的斯托克斯信号能够耦合输出,实现了双倍布里渊频移的多波长输出。激光器 腔内没有引入 任何的有源增益介质对斯托克斯信号进行放大,消除了腔内自激模的影响。激光器的调谐范 围由布里渊泵 浦的工作波长和掺铒光纤放大器(EDFA)的增益带宽决定。实验中,在布里渊 抽运 功率为0dBm、EDFA的输出功率为20 dBm的情况下,在1536~1605nm之间得到双频移间隔的多 波长输出,调谐范围是69nm。     

Brillouin gain spectrum characterization in single-mode opticalfibers

A novel method for Brillouin gain spectrum measurements in optical fibers is presented. It is based on the pump and probe technique with the specificity to use a single laser source together with an external modulator to generate the interacting lightwaves. The high accuracy and inherent stability of the technique makes it suitable for calibration and reference measurements. Different fibers with different refractive index profiles have been tested and characterized. The problem of the evolution of the polarization of the interacting waves is addressed in the article and a polarization insensitive determination of the actual Brillouin gain coefficient is made possible through two successive measurements with different polarizations. The effects of strain and temperature on the Brillouin gain spectrum are also fully characterized     

In situ spatially-resolved thermal and brillouin diagnosis of high-power ytterbium-doped fibre laser by brillouin optical time domain analysis

An in situ spatially-resolved diagnosis of thermal and Brillouin characteristics of a double-clad ytterbium-doped fibre (YDF) laser operating at 1.09 μm is demonstrated. For this a Brillouin optical time domain analysis technique based on 1.55 μm Brillouin pump and probe beams is utilised. A 2.4 K temperature difference across the YDF laser when it was running with 6.5 W pump power has been measured and resolved. Based on the measured thermal and Brillouin characteristics of it is expected the YDF, that the effective Brillouin gain coefficient would decrease by 20% for 1.09 μm radiation if an 80 K temperature variation is built up across it, as a result of the quantumheating by the pump power.