分布式光纤光栅传感网络的复用解调技术

波长编码信号解调是实现光纤光栅多参量、多点分布式传感网络的核心技术之一。本文总结了光纤光栅传感信号解调的一般原理和技术难点,分类评述了常用解调方法的工作机理、特点和性能。同时,提出了一种新型的、用宽带光源和可调谐光滤波器(TOF)构成的可调谐窄带光源,对测量光栅阵列和参考光栅进行波长扫描,借助光电探测器和信号处理系统实现复用传感系统的解调技术。     

分布式光纤光栅传感网络的复用解调技术

波长编码信号解调是实现光纤光栅多参量、多点分布式传感网络的核心技术之一。本文总结了光纤光栅传感信号解调的一般原理和技术难点，分类评述了常用解调方法的工作机理、特点和性能。同时，提出了一种新型的、用宽带光源和可调谐光滤波器(TOF)构成的可调谐窄带光源，对测量光栅阵列和参考光栅进行波长扫描，借助光电探测器和信号处理系统实现复用传感系统的解调技术。     

基于调谐滤波的光纤光栅解调技术研究

用宽带光源和自主研制的波长选择器IPD构成可调谐窄带光源, 对测量光纤光栅阵列和参考光纤光栅进行波长扫描, 借助光电探测器和DSP信号处理系统实现复用传感系统的解调.采用梳状滤波器进行波长校准,大大提高其检测精度.实验表明:该解调方案是可行的, 且可获得较高的信噪比和测量精度, 每个通道具有对15个以上FBG进行寻址解调的潜在能力.     

基于傅里叶域模式锁定的扫频光源实验研究

扫频光源是光纤传感解调的关键部件,高质量的扫频光源可提高光纤传感系统的信噪比和解调精度。研制了一种基于傅里叶域模式锁定(FDML)的扫频光源。光源采用环形腔结构,由半导体光放大器(SOA)、光纤法布里-珀罗(FP)可调谐滤波器、隔离器、光纤耦合器和光纤延迟线组成。同时设计了基于FP腔的滤波器,对输出光谱进行平坦滤波。得到扫频范围为60 nm(1506~1566 nm),扫频速度为250 Hz,平坦度优于0.3 d B,线宽小于0.16 nm,平均输出光功率为4.53 m W的扫频光源。研制出的扫频光源结构简单、成本低廉、平坦度好,在光纤传感解调系统中作为光源有一定的实用价值。     

新型大容量光纤光栅传感解调系统研究

采用自主研发的可调谐窄带光源和光波分复用联合空分复用技术研究并实现了新型大容量光纤光栅传感解调系统。实验结果表明,系统可实现32通道超过600个监测点的实时并行监测,有效提高了传感解调系统的系统容量和信噪比,可满足大型工程对光纤光栅传感系统的应用需求。     

基于可调谐激光器的复用传感系统的研究

为了克服复用传感系统中光源带宽及功率的制约,有效地扩大多点检测的范围,采用波分和时分复用传感技术,设计了可调谐光纤激光器作为传感系统的光源.基于耦合模方程的理论,对匹配光栅调谐光纤激光器波长扫描寻址解调方法进行了理论分析和实验研究.实验中采用可调谐光纤激光器对由4个光栅组成的两个光栅串成功地进行了波分和时分复用传感,实验获得的应变分辨率为2.9με/step.该传感系统具有经济实用性、信噪比高、可复用数目大等特点,对于多点检测的传感网络具有较大的实用价值.     

基于FBG的弹性波测量及其泄漏检测应用

为了利用光纤布喇格光栅(FBG)实现宽带弹性波的测量,提出了基于双FBGs+压电陶瓷（PZT）的解调方案。该方案使用宽带光源提供入射光,通过改变PZT的驱动电压,使其上粘贴的FBG的布喇格波长处在传感FBG的半峰宽处,形成FBG对。该方案具有成本低及工作点可动态调整等优点。通过实验验证了基于双FBGs+PZT的系统调节最佳工作点的方法,及利用该系统进行了连续弹性波测量和泄漏检测的实验。实验结果表明,该系统可以检测出8 kHz,58 kHz,98 kHz, 200 kHz的弹性波,且可以成功检测到气体管道泄漏产生的弹性波信号。     

一种基于ASE光源的边缘滤波解调技术的研究

研究了一种利用放大自发辐射(ASE)光源线性段做边缘滤波器进行光纤Bragg光栅(FBG)解调的新方法,可实现在传感波长变化3 nm范围内的波长解调。系统采用了全光纤结构,无需机械部件调谐,提高了光纤传感系统的解调速度及稳定性,具有反应迅速快、性能价格比高等优点,应变测量范围可达2 500με。     

光纤光栅振动传感信号解调技术的研究

研究了一种基于掺Er超荧光光源(EDSFS)的滤波解调方法,分析了光源的输出功率谱形状。利用光谱中光功率密度与波长的线性关系,实现了光纤光栅传感信号的动态解调。建立振动测试系统,采用高精度差分变压器式位移传感器作为参考,对比讨论了两种传感器输出的时域波形和频谱。结果表明,在相同的条件下,二者的动态响应特性具有很好的一致性。由于系统的光源和解调部分合为一体,无机械调谐元件,很适合高速动态测量。     

光纤光栅传感的解调方法

介绍了光栅传感系统的组成,分析了常用的三种光源:LD、LED和掺铒光源的性能.描述了在光栅解调中常用的滤波法、干涉法、可调谐激光扫描法、啁啾光栅检测法、光栅色散法等几种信号解调技术并进行了简要的评述.     

Dynamic power-equalized EDFA module based on strain tunable fiberBragg gratings

An adaptive power-equalized erbium-doped fiber amplifier (EDFA) module is proposed and experimentally demonstrated by using strain tunable fiber Bragg gratings (FBGs). In a demonstration for a five-channel wavelength-division-multiplexed (WDM) system, the EDFA module can effectively reduce the power variation from 11 dB to 0.3 dB. Measured power penalty for 2.5-Gb/s data is less than 0.5 and 1.1 dB for 5 and 17 dB of signal attenuation by tunable FBGs, respectively. The power-equalized EDFA module can find wide applications in WDM lightwave transmission systems     

FBG-based bidirectional optical cross connects for bidirectional WDM ring networks

This paper proposes a new bidirectional optical cross connect (BOXC) using fiber Bragg gratings (FBGs) and optical circulators for bidirectional wavelength-division-multiplexing ring networks. Dynamic and independent wavelength routing is achieved by employing cascaded tunable FBGs. The proposed BOXC requires a small tuning range equal to wavelength channel spacing for tunable FBGs. Therefore, the wavelength count of the proposed BOXC could be increased easily without imposing constraint on the tuning range of FBGs. Coherent and incoherent crosstalk arising in the proposed BOXC and their impact on the power penalty are studied in detail. The Monte Carlo simulation is used to characterize the probability distribution of the power penalty due to both coherent and incoherent crosstalk under various conditions. The specification requirements are then obtained for the FBGs used in BOXC nodes with a different number of wavelengths. The study in this paper reveals that the requirement for the isolation of FBGs is more stringent than that for the reflectivity of FBGs at the Bragg wavelength. It is also shown that a large BOXC can be built based on the Benes network structure, and a method to reduce the complexity is also presented.     

光码分多址系统可调谐编/解码器研究

介绍了光码分多址(OCDMA)系统和常用的几种编/解码器(E/D).研究了基于光纤延时线(OFDL)和基于光纤布拉格光栅(FBGs)的可调谐编/解码器,讨论了两种基于光纤延时线的可调方案,对它们的结构和性能进行了分析.讨论了基于光纤布拉格光栅(FBGs)的编/解码器,介绍了光纤布拉格光栅编/解码器的原理和利用压电陶瓷(PZT)调谐光纤布拉格光栅的参数选择.给出了一种基于光纤布拉格光栅阵列的可调谐二维编/解码器结构,并分析了它的主要优点.介绍了基于超结构光纤布拉格光栅(SSFBG)的二进制相移键控(BPSK)编/解码器和可调谐四进制相移键控(QPSK)超结构光纤布拉格光栅编/解码器的构造方法,探讨了光码分多址系统编/解码器的发展前景.     

Compact high frequency true-time-delay beamformer using bidirectional reflectance of the fiber gratings

A compact high frequency true time delay (TTD) beamformer using bidirectional reflectance of the fiber gratings (FGs) is proposed. The FGs can be a set of fiber Bragg gratings (FBGs) or chirped fiber gratings (CFGs). The number and the length of the time delay lines are greatly reduced compared to the previous systems. A phase array antennas system using this TTD beamformer has many advantages including being compact, low requirement on the bandwidth of the tunable laser source and working at high microwave frequency. The proof-of-concept experiment results demonstrated the feasibility of the proposed scheme.     

L-band fiber laser with wide tuning range based on dual-wavelength optical bistability in linear overlapping grating cavities

A new mechanism to tune an erbium-doped fiber laser in the L-band is presented. The technique is based on the dual-wavelength bistability in overlapping linear cavities, which allows two lasing lines to be switched from one to another by a triggering pulse superimposed to the dc bias current applied to the pump source. The two wavelengths can be independently tuned to give the laser a total tuning range of 33 nm that covers the whole L-band, while the tuning range of either of the tunable fiber Bragg gratings (FBGs) used is only half of that range. An output dynamic range of 7 dB, and a maximum output power of up to 11 dBm with high optical signal-to-noise ratios are obtained. A study of the switching transient responses shows that the typical switching time is about 4 to 12 ms, depending on the dc bias current applied to the pump source. Moreover, our wide tuning technique is implemented by only applying ordinary commercial tunable FBGs which normally would have given rise to only about half of the tuning range; no additional filtering mechanisms are required to achieve almost uniform outputs.     

Time-Division Multiplexing Fiber Grating Sensor With a Tunable Pulsed Laser

A novel time-division-multiplexing fiber Bragg grating (FBG) sensor with a tunable pulsed laser is proposed and demonstrated. A tunable pulsed fiber laser based on a matched FBG is applied. The wavelengths of the sensing FBGs are obtained by detecting maximum voltages with a photodiode, which avoids a complex demodulation process. The advantages of the sensor include simple structure, high signal-to-noise ratio, and the sensing signals obtained by detecting the maximum voltages     

Modeling and performance analysis of a fiber Bragg gratinginterrogation system using an acousto-optic tunable filter

The performance of a fiber grating interrogation system using an acousto-optic tunable filter (AOTF) is analyzed. An equivalent linear circuit is presented to describe the system, which tracks the wavelength of a fiber Bragg grating (FBG) sensor in a FBG sensor array. From the model, the tracking resolution of a shot-noise-limited system has been determined for both transmissive and reflective interrogation of FBGs. An optimum ratio between the bandwidths of the FBG and the AOTF has been derived. Experimental results of a tracking system are presented to validate the theoretical predictions. The theory should also be suitable for interrogation systems using other forms of tunable bandpass filters for tracking the FBG wavelength     

Tunable Photonic Microwave Bandpass Filter With Negative Coefficients Implemented Using an Optical Phase Modulator and Chirped Fiber Bragg Gratings

A continuously tunable photonic microwave bandpass filter with positive and negative coefficients implemented using an optical phase modulator and chirped fiber Bragg gratings (FBGs) is proposed and experimentally demonstrated. The positive and negative coefficients are generated through optical phase-modulation to intensity-modulation conversion by reflecting the phase-modulated optical carrier from linearly chirped FBGs (LCFBGs) with positive and negative dispersions. The tunability of the filter is realized by changing the wavelength of the optical carrier such that it is reflected at different physical locations in the LCFBGs. A two-tap microwave bandpass filter with a free spectral range tunable from 1.14 to 4.55 GHz is experimentally demonstrated.     

基于重叠多光栅的动态应变传感特性研究

利用重叠多光纤布拉格光栅(FBG)反射谱的时间同 步性,实现了动态或静态应变信号的高速传感与解调。给出了基于光纤F-P 可调谐滤波器(FFP-TF)的重叠多FBG解调系统及其时域重构的实现方法,重叠多FBG在FFP- TF 三角波扫描电压与动态应 变信号测量时产生时域上等间隔分布的传感脉冲,解调系统采用质心法硬件解算并结合平滑 滤波的方法可满足速度与解调精 度的同时测量需要。在重叠双FBG与500Hz FFP-TF扫描速率条件下 可产生2kHz的传感脉冲,动态应变信号的测量 带宽相对于单FBG解调系统提高了4倍,静态条件下的波长偏移小于±4pm。给出了影响重叠多FBG动态应变信号解调结果失真度的影响因素。