一种有源型光纤水听器原理与实验分析

分析了一种有源型光纤水听器的水声传感原理,在一段掺铒光纤中写入具有π相移的光纤光栅构成光纤激光器,水声压力作用在激光器上引起激光波长的移位,采用干涉法检测出波长移位引起的相位变化即得到声压的信息.水声探测实验表明,有源型光纤水听器的声压灵敏度为-166.5 dB(参考值1 rad/μPa).将不同工作波长的四元光纤水听器串接于一根光纤内组成水听器阵列,使用带通波分复用器将阵列发出的激光分离至各独立通道后检测出相应的声压信号,测得水听器之间的级串扰小于-60 dB,且单元水听器水声响应的动态范围不受影响.     

干涉型全保偏光纤水听器阵列研制

报道了干涉型全保偏光纤水听器阵列的研究结果。在详细介绍全保偏光纤水听器基元结构和性能基础上,描述了四基元阵列结构和特性,给出了光纤水听器基元相对接收灵敏度的频率响应和阵列指向性的测量结果。同时指出光纤水听器与传统压电换能器在性能指标、信号传输和处理等方面的差异。     

采用频分多路复用方案的干涉型光纤水听器阵列研究

从系统设计的角度,在介绍干涉型光纤水听器阵列采用基于相让产生载波（ＰＧＣ）技术的频分多路复用方案时的阵列构型、调制解调技术的基础上,通过对阵列输出信号频谱进行理论分析入手,重点揭示了在Ｊ×Ｋ阵列中阵列单元数Ｎ、可测信号幅度Ｄ和可测信号频率ωｓ之间的相互关系,以及制约Ｎ、Ｄ、ωｓ增大的关键因素。特别分析了最大可检测光相移及其随频率变化的规律。并用实验验证了有关理论分析得出的结果。     

光纤传输系统中互相位调制和受激拉曼散射串扰噪声的比较研究Ⅱ--级联传输系统

在具有级联光放大器的密集波分复用强度调制一直接检测光纤系统中，导出了包含互相位调制和受激拉曼散射共同作用的强度／相位矩阵表达式。在计算强度噪声谱的基础上，研究了互相位调制和受激拉曼散射的相互耦合并用于密集波分复用系统的噪声分析。在带色散补偿的密集波分复用级联光纤传输系统中(如80信道，信道间距50GHz)，受激拉曼散射引入的串扰噪声功率可能超过互相位调制。最后，给出了密集波分复用系统分析与设计的若干建议。     

对称结构光纤光栅耦合器及其应用

光纤光栅耦合器(FGC)具有光纤光栅良好的波长选择特性和光纤耦合器的多端口特点，易于实现全光纤的光波分插复用。光纤光栅耦合器主要有4种结构：基于M Z干涉仪的分离型、基于100％耦合器的非对称型、基于0耦合器的非对称型和基于100％耦合器的对称型。着重介绍对称结构光纤光栅耦合器的结构、工作原理和研究现状。提出了测试方案，并探讨了这种器件在大规模波分复用光纤传感器阵列中的应用。     

光纤马赫—陈德尔干涉型8波分超窄波分复用器的研制

报道了采用７个单模光纤马赫－陈德尔干涉仪进行三级串联而组成的８波分复用器，既保留了干涉型光纤波分复用器超窄波分复用间隔的优点，又消除了其复用路数少的缺点。文中介绍了这类波分复用器的原理、设计方法和制造技术。实验样品的使用波段为１．５μｍ，波长复用间隔为２．４ｎｍ，整个器件的附加损耗约为１．５ｄＢ。     

二维复用半导体激光器线性调频光纤位移传感器的研究

利用半导体激光器线性调频外差干涉原理和频域多路复用原理,研究了光纤位移传感器多路复用技术,制作了两路复用光纤位移传感器,研究和解决了多路复用时信号串话问题.实验证明,各路之间串话引起的误差小于±0.02μm,每路测量误差小于±0.05μm.     

蚀刻衍射光栅波分复用器件的设计与模拟

近年来光通信飞速发展,波分复用技术(WDM)是满足要求的有效手段.密集波分复用技术已经得到成功商用,其扩展信息传输容量的能力也在不断增强.作为波分复用中最关键的器件,蚀刻衍射光栅(EDG)是平面波导密集波分复用器件中很有发展潜力的一种.本文分析了EDG器件的解复用原理,参量设计,工艺过程.文章最后,建立了一个光栅干涉的简单模型,对设计好的器件参量进行模场形状、谱响应、色散等光栅性能的模拟,得到基本的器件解复用特性,并加以分析.     

湿端结构极简的低噪声低串扰光纤光栅水听器阵列

由于湿端极简化,光纤光栅水听器系统中普遍存在的偏振诱导信号衰落和随机相位衰落等关键问题仅能采用复合型调制解调手段解决;光纤光栅的双向反射特性会引起传感通道间信号串扰增加等新问题。报道了一种光纤光栅水听器阵列,水下仅采用80个光纤光栅构成64基元水听器阵列。采用相位生成载波与偏振切换调制解调方案,系统本底相位噪声达到■,等效噪声压为36 dB@1 kHz。系统采用低反射率光纤光栅,结合8空分×2波分×8时分复用结构设计,系统的时分、空分和波分通道串扰均稳定在-40 dB以下。该研究为光纤光栅水听器的工程实用化提供了重要的实践探索。     

一种耐静压分布反馈式光纤激光水听器探头设计

大深度工作环境下，静水压会引起分布反馈式光纤激光水听器反射中心波长漂出解调系统的复用窗口，使水听器无法解调目标声压信号；不同的静水压也会引起分布反馈式光纤激光水听器灵敏度的变化，影响光纤激光水听器阵列的一致性。基于电力声类比理论，提出带静压补偿的分布反馈式光纤激光水听器探头，建立结构的声压传递函数，分析各结构参数对传递函数的影响，为分布反馈式光纤激光水听器探头频率响应平坦化设计提供理论依据。加工制作了耐静压分布反馈式光纤激光水听器样品进行测试，在0 kHz～10 kHz频率范围内声压灵敏度波动范围不大于±2.4 dB，2.3 MPa内出射激光中心波长漂移量不大于0.06 nm，对深水光纤激光水听器的研究具有指导意义。     

Multiplexed fiber optic sensors matrix demodulated by a white light interferometric Mach–Zehnder interrogator

A multiplexed white light interferometric fiber optic sensors matrix system was designed and demonstrated. In this system, a Mach–Zehnder optical path interrogating technique is used to demodulate each sensor of the sensors matrix. The sensors matrix consists of M×N sensing elements linked by a 1×M star coupler. The multiplexing capacity of the sensing scheme has been analyzed and an experimental result with a 2×2 sensors matrix was presented.     

分布反馈式光纤激光水听器拖曳线列阵实验研究

为了进一步增大光纤拖曳阵的探测距离,研制了缆径为16mm的32元分布反馈式光纤激光水听器拖曳线列阵.阵元在10~2 000Hz频率范围内的平均声压灵敏度为-142.7dB(re 1rad/μPa),波动幅度小于±2dB.基于声光调制器的时分、波分联合复用技术实现了32元光纤激光水听器的多路复用,各个阵元之间以及各个通道之间的串扰均小于-40dB,并完成了静态和动态拖曳湖上实验.实验结果表明,研制的32元分布反馈式光纤激光水听器拖曳线列阵无论是在静态,还是在6~16节的动态拖曳状态,都能对目标形成稳定的波束指向,与GPS轨迹记录完全一致,展现了分布反馈式光纤激光水听器拖曳线列阵在工程上的应用前景.     

Tuning fork enhanced interferometric photoacoustic spectroscopy: a new method for trace gas analysis

A photoacoustic trace gas sensor based on an optical read-out method of a quartz tuning fork is shown. Instead of conventional piezoelectric signal read-out, as applied in well-known quartz-enhanced photoacoustic spectroscopy (QEPAS), an interferometric read-out method for measurement of the tuning fork’s oscillation is presented. To demonstrate the potential of the optical read-out of tuning forks in photoacoustics, a comparison between the performances of a sensor with interferometric read-out and conventional QEPAS with piezoelectric read-out is reported. The two sensors show similar characteristics. The detection limit (L) for the optical read-out is determined to be L _opt=(2598±84) ppm (1σ) compared to L _elec=(2579±78) ppm (1σ) for piezoelectric read-out. In both cases the detection limit is defined by the thermal noise of the tuning fork.     

Performance Analysis of Duty-Cycle Division Multiplexing over Wavelength Division Multiplexing System

Abstract

Performance optimization of a duty-cycle division multiplexing system over 8- and 40-channel wavelength division multiplexing networks is reported in this article. The modified duty-cycle division multiplexing system with optical domain multiplexing using a dual-drive Mach–Zehnder modulator is simulated with two and three users per wavelength. Using conventional dispersion compensation, the 40 × 40-Gbps system with two and three users per channel can support 240 and 160 km of transmission distance, respectively. The dispersion management technique based on a chirped fiber Bragg grating is proposed for a 40 × 3 × 13.33-Gbps duty-cycle division multiplexing/wavelength division multiplexing system that allows double the transmission distance compared to conventional technique.     

Optical Fiber Sensor Technology in Portugal

Abstract

A general overview of the R&D activity in fiber optic sensing developed over the last fifteen years in Portugal is given. Different topics are addressed, including interferometric, intensity and Bragg grating based fiber optic sensors, signal processing and multiplexing techniques, optical current sensors, together with some references to field trials and applications. Possible guidelines for present and future national R&D activity on this subject are outlined.     

Multiplexing fiber bragg grating sensors

Abstract

Bragg reflection gratings and out-coupling taps for sensors can be written holographically within the core of many commercial fibers available today. The gratings appear to be permanent and have been tested to temperatures in excess of 500°C. Quasi-distributed temperature, strain, pressure, chemical, and interferometric sensors can be made with the wavelength selective, reflection gratings, and taps. The fiber gratings, and the different types of sensors they can make, conveniently lend themselves to (wavelength-division multiplexing) WDM, (time-division multiplexing) TDM, and (frequency-division multiplexing) FDM types of multiplexing schemes. Instrumentation to detect the multiple sensors and measure their spectral shift for localized and quasi-distributed sensing is currently under development.     

Multiplexing Techniques for Noninterferometric Optical Point-Sensor Networks: A Review

This article presents a review of the strategies that have been both demonstrated and proposed for the multiplexing of multiple noninterferometric optical fiber point sensors to form a sensor network. The focus, which avoids consideration of interferometric sensor types, enables discussion of conventional multiplexing tech niques, namely, spatial, time division, frequency division, and wavelength division prior to dealing with combined or hybrid schemes, which exhibit the potential for increased multiplexing gain. Specific advantages and potential drawbacks of the different strategies are provided together with an indication of the number of point sensors that each multiplexing scheme can support.     

Optical Fiber Sensor Technology in Portugal

A general overview of the R&D activity in fiber optic sensing developed over the last fifteen years in Portugal is given. Different topics are addressed, including interferometric, intensity and Bragg grating based fiber optic sensors, signal processing and multiplexing techniques, optical current sensors, together with some references to field trials and applications. Possible guidelines for present and future national R&D activity on this subject are outlined.     

Dispersion compensation in optical transmission systems using high negative dispersion chalcogenide/silica hybrid microstructured optical fiber

In this paper, a new hybrid microstructured optical fiber (H-MOF) based upon photonic bandgap (PBG) light guiding mechanism which can be used for dispersion compensation in optical transmission systems is designed and simulated. The H-MOF core is made up of silica glass and the holes in the cladding network are filled with As₂Se₃ chalcogenide glass. By selecting an appropriate geometrical parameters for the structure, the dispersion and confinement losses of the proposed H-MOF at 1.55 µm are calculated to be ?6700 ps/nm/km and 6?×?10^?4 dB/m, respectively. Relative dispersion slope (RDS) of the H-MOF at 1.55 µm is about 0.00347 nm^?1. The proposed H-MOF is suitable for use in wavelength division multiplexing and dispersion compensating systems in optical fiber transmission networks.     

白光干涉双环传感网络理论与实验研究

构造了一种基于双环形拓扑结构的白光干涉光纤传感网络．可用于智能结构中准分布应变或温度的测量。光纤传感网络基于空分多路复用技术(SDM)．目的是增强带载能力．降低单点传感器的测量成本，并借助丁双端口问询技术．增强传感网络的抗毁坏能力。分析了环形网络结构的低相干多路复用原理．根据空分复用的光程匹配条件．推导了传感器干涉信号的强度特性。实验中对连接9个传感器的双环传感网络特征及其抗损坏特性进行了验证．并对实验结果进行了分析和讨论。