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.     

基于偏振光干涉的一种新型的光纤光栅解调系统

提出一种先进的基于偏振光干涉的光纤光栅解调实现方法 ,偏振光干涉仪也是一种能将布拉格波长移动转化为干涉相位变化的非平衡干涉仪。与传统的非平衡干涉仪不同 ,偏振光干涉仪是利用折射率ne 和no 的差而不是利用光路长短的差来实现非平衡干涉的。另外 ,由于偏振光干涉是发生在有着优良双折射特性的钒酸钇(YVO4)晶体中而不是在石英光纤中 ,这样就可避免石英光纤引入的干涉噪声。通过分析钒酸钇晶体的性质指出 ,利用这种方法来实现光纤光栅温度检测 ,其最小温度测量精度可达± 0 4℃。     

全光纤口腔OCT系统偏振波动自动消除方法研究

采用法拉第旋转效应自动消除伞光纤口腔光学相十层析(OCT)成像系统巾光纤Miehelson干涉仪干涉臂单模光纤中随机偏振态变化对十涉信号的影响,使得无论样品臂和参考臂光纤中光偏振态如何发生变化,干涉信号始终保持最强.介绍了该方法的基本原理、获得了离体牙齿稳定十涉信号和二维OCT图像.     

可编程波长选择与扫描全光纤行波环形腔激光器

利用可编程控制装置对光纤光栅的中心波长进行了线性调谐,在此基础上实现了可控波长行波环形腔激光器的运转,波长线性调谐范围可达5．9nm。通过精确控制,波长选择的复现性可达5．13×10-3nm,在检测仪器的精度范围内,波长调谐的线性度达R2=0.999,波长选择间限为0．156nm。     

Highly Narrow Linewidth, CW, All-Fiber Oscillator With a Switchable Linear Polarization

We present a fiber laser with a switchable state of linearly polarized output realized by inscribing point-by-point fiber Bragg gratings directly into the active core of a polarization-maintaining fiber. The compact all-fiber system exhibited a very narrow laser linewidth of ~13.5 pm (3.5 GHz), at a maximum continuous-wave output power of 188 mW. The optical signal-to-noise ratio was greater then 62 dB for both lasing polarizations. The robust system exhibited excellent long-term wavelength and laser linewidth stability.     

An all-fiber dense wavelength-division multiplexer/demultiplexerusing photoimprinted Bragg gratings

A wavelength multiplexing/demultiplexing device is fabricated and used to drop/insert a single wavelength channel from/into a multiple wavelength transmission link with 100 GHz channel-spacing at 1550 nm. The device consists of an all-fiber Mach-Zehnder interferometer with photoinduced Bragg gratings. The following performances were measured: extraction/coupling efficiency =99.4%, excess loss <0.5 dB, adjacent channel-isolation >20 dB, and return loss >23 dB     

基于光纤拉锥及相位调制的可切换多波长掺铒光纤激光器

研究了一种全光纤可切换多波长掺铒光纤激光器。该激光器利用一段缠绕在压电陶瓷上的单模光纤作为正弦相位调制器以及基于光纤拉锥的马赫-曾德尔干涉仪作为梳状滤波器,抑制由于掺铒光纤的均匀展宽效应引起的模式竞争,从而避免了在室温下不稳定的单波长激射,实现了多波长掺铒光纤激光器的稳定输出。实验中观察到稳定的5个波长的同时激射,相邻波长间隔为0.804 nm。信噪比大于40 dB,3 dB带宽约为0.023 nm,中心5个波长输出功率的平坦度为14 dB。同时,激光器具有灵活的波长可切换特性,通过调整驱动信号和偏振控制器的状态,实现了单波长、双波长、三波长以及更多波长的输出。该激光器可应用于大容量波分复用系统和光纤传感。     

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。     

单偏振双波长非保偏有源掺杂光纤激光器

利用宽带保偏光纤光栅(PFBG)、普通有源光纤和窄带普通光纤光栅构成独立的谐振腔,且窄带普通光纤光栅的中心波长分别与保偏光纤光栅的一个反射峰波长对准,可以输出稳定的双波长/单波长的单偏振激光.利用这一思想,制成了基于非保偏有源掺杂光纤的单偏振双波长光纤激光器.实验结果表明,双波长同时激射时的激光消光比为46.7 dB,单波长激光的消光比为59.6 dB,滤波出单波长测量其偏振度为98.5%.这种激光器在微波光子领域可用于在光域产生微波.     

一种新型的光纤光栅可调整偏振模色散补偿器

文章提出一种基于磁场变化对均匀周期光纤光栅(FBG)引入线性啁啾的特性来实现可调整偏振模色散(PMD)补偿的技术。这种全光型PMD补偿技术在实现调整的同时能保持中心波长固定不变，而且能够灵活方便地实现不同的微分群时延量(DGD)。针对10Gbit／s非归fig(NRZ)传输系统，采用这种技术对进行PMD补偿的模拟计算结果表明，接收信号的眼图在补偿后得到了显著改善。     

Bragg光纤光栅构成的合成光源进行位移测量的研究

给出了一种基于布喇格光纤光栅技术进行位移测量的方法.合成光源由宽带光源经不同的布喇格光栅而得到,波长稳定性由温度稳定器进行控制.合成光源的波长要比常规光源的波长长,所以允许的光程差测量范围提高了几百倍.布喇格光纤光栅的波长准确性提高了干涉仪的测量准确性.此外,本文还利用了光外差法马赫-曾德干涉仪精密测量位移变化.     

基于铒镱共掺光纤光栅的M-Z干涉型全光开关

提出了基于铒镱共掺光纤光栅的马赫-曾德尔(M-Z)干涉仪结构的光控光开关,干涉仪的一臂为铒镱共掺光纤,另一臂为铒镱共掺光纤光栅.通过泵浦光来抽运铒镱共掺光纤从而调节两个臂信号光的相位差,引起干涉的变化,从而实现了光开关的作用.实验上在10 mW的泵浦功率水平下,实现了消光比为8 dB的全光开关.     

双偏振微结构光纤光栅的折射率传感特性分析

研究了微结构光纤(MOF)布拉格光栅(FBG)的双偏振折射率传感特性。利用有限元方法对保偏微结构光纤(PM-MOF)的传输特性进行了分析,计算了传输特性曲线,分析了该种光纤单模传输的范围。同时结合耦合模理论,仿真了该种光纤均匀布拉格光栅在充入不同介质时的反射谱,得到两个偏振模LP0x1和LP0y1的中心波长差与介质折射率的关系曲线,通过特性曲线拟合出相应公式。同时,仿真了该光纤光栅的温度特性,研究结果表明,两个偏振模中心波长对温度响应相似,因此利用双偏振差分的方式来探测,具有较强的抗干扰能力,这一特性为光纤生物传感器的应用提供了理论依据。     

基于单侧几何形变结构的全光纤Michelson干涉高温传感器

利用CO2激光脉冲对标准单模光纤(SMF)单向形成较小的几何形变,把部分基模能量耦合到光纤包层,制作了一种新型的在线型Michelson干涉传感器。理论分析了这种几何微扰激发的包层模特性,并利用芯模-包层模较大的热光系数差,把这种传感器应用于高温测量。实验结果表明,这种干涉传感器的温度灵敏度为0.093 7nm/℃,并且在800℃温度范围内具有良好的线性和重复性。这种制作简单、结构稳定、体积小和灵敏度高的全光纤在线型Michelson温度传感器将具有较大的潜在应用价值。     

基于马赫-曾德尔干涉仪和光纤光栅的光分插复用器

光分插复用器(OADM)是波分复用(WDM)系统中的关键器件之一。提出了一种结构新颖的基于马赫-曾德尔(M—Z)干涉仪和光纤光栅(FBG)的光分插复用器，它由两个三端口光环形器、一个光纤光栅和一个马赫-曾德尔干涉仪组成，马赫-曾德尔干涉仪起着光开关的作用。对光分插复用器的输出特性进行了实验研究，实验中调节干涉仪的臂长差，可以实现信号的上下载或直通功能，上下载时通道的隔离度大于20dB。这种结构的光分插复用器具有结构简单、体积小、价格低等优点，在波分复用技术中具有实际应用价值。     

Novel Distributed Fiber Bragg Grating Sensing System Based on M-Z Interferometer

One of the problems in using grating sensors is how to measure a small Bragg wavelength shift accurately. Nowadays demodulation techniques are mainly based on the edge filter, tunable filter, or interferometric scanning methods. Interferometric demodulation is widely accepted as the technology which can provide the high sensitivity. An interrogation system using the interferometric scanning method is presented, in which an unbalanced fiber M-Z interferometer is used as the wavelength scanner for temperature measurement. A novel fiber Bragg grating sensor system based on M-Z interferometric demodulation technique is presented in this paper. The temperature sensitivity measured in the experiment is almost consistent with that obtained from the theoretic calculation.     

基于光纤干涉环的掺Yb3 全光纤自调Q激光器

对基于光纤干涉环的包层泵浦全光纤自调Q激光器进行了实验研究。实验采用掺Yb^3 双包层光纤(DCF)为增益介质，光纤Bragg光栅(FBG)作为腔镜，以及接入5m普通单模光纤的光纤干涉环，实现了较稳定的全光纤自调Q激光器，获得了脉宽3．6ns，重复频率约1kHz，峰值功率56．7kW的光脉冲。提出其产生ns脉冲的原因是瑞利散射(RS)与受激布里渊散射(SBS)的共同作用。     

Fiber Bragg grating interrogation and multiplexing with a 3×3coupler and a scanning filter

We present a new technique for fiber Bragg grating (FBG) sensor interrogation and multiplexing. The technique combines a scanning bandpass filter used to multiplex by wavelength multiple gratings in a single fiber, and an unbalanced Mach-Zehnder fiber interferometer made with a 3×3 coupler to detect strain-induced wavelength shifts. A demonstration system interrogates four gratings in a single fiber at a sampling rate up to 20 kHz, with a noise floor measured at less than 10 nϵ/√(Hz) above 0.1 Hz     

Chromatic Dispersion Measurement for Multichannel FBG Based on a Novel Asymmetrical Sagnac Loop Interferometer

A novel all-fiber asymmetrical Sagnac loop interferometer is proposed to measure the chromatic dispersion of a multichannel fiber Bragg grating (FBG). This method has the advantages of simple configuration, low cost, and high tolerance for the characteristics of FBG as well as the ability to uniquely determinate the phase delay.     

Simultaneous Strain and Temperature Measurement With Fiber Bragg Grating and Multimode Fibers Using an Intensity-Based Interrogation Method

A new all-fiber sensor capable of simultaneous measurement of strain and temperature is presented. The sensor system is formed by a fiber Bragg grating and two sections of multimode fibers (MMFs). One section of the MMF is isolated from strain and acts as a temperature-dependent edge filter, while the other is isolated from both strain and temperature changes. By monitoring the optical power changes, it is feasible to obtain information that permits simultaneous measurement of strain and temperature with a low-cost and simple structure.