High-Resolution Strain and Temperature Sensor Based on Distributed Bragg Reflector Fiber Laser

We present a high-resolution strain and temperature sensor by using a polarimetric distributed Bragg reflector fiber laser. The mean wavelength and polarization beat frequency of the laser output are utilized to determine the strain and temperature of the sensor. Experimental results show that the sensor has a capability of sensing strain and temperature simultaneously, with root mean square deviations of 9.3 mu epsiv and 0.05degC, respectively.     

一种新颖的基于预应变技术的光纤光栅应变温度传感器

报道了采用预应变技术制作的一种结构简便而新颖实用的光纤光栅传感探头及其对温度和应变的响应特性。该方法能使一根光纤光栅产生两个以上的反射峰 ,因此能解决温度和应变测量时存在的交叉敏感问题。在测量范围内 ,应变和温度响应曲线具有良好的线性。     

Multirate and Dual-Wavelength Semiconductor Fiber Laser

We demonstrate the successful operation of a multirate and dual-wavelength mode-locked semiconductor fiber laser that incorporates a multichannel nonlinear optical loop mirror (NOLM) functioning as a multichannel all-optical modulator. Each channel of the NOLM incorporates its own length of highly nonlinear fiber and can be driven by independent pump signals. Thus, the single NOLM is capable of processing multiple wavelength channels independently and simultaneously. We obtain mode-locked operation at different frequencies (5 and 10 GHz) for two wavelengths with spacing as narrow as 0.8 nm.      

Distributed Optical Fiber Sensor for Multi-point Temperature Measurement

The distributed optical fiber sensing technology is overviewed, which is based on Raman scattering light theory. Basic operation principle, structure, system characteristics and signal processing are discussed. This structure and method of the signal processing possess of certain spatial resolution, hence will ensure the practicability of system.     

Transversal Loading Sensor Based on Tunable Beat Frequency of a Dual-Wavelength Fiber Laser

Microwave signal generation by using the photonic beating from a phase-shift fiber Bragg grating (PS-FBG)-based dual-wavelength laser is proposed and experimentally demonstrated. The dual-wavelength laser is formed by a linear cavity, in which a PS-FBG is used as a dual-wavelength selective component. Transversal loading on the PS-FBG enhances the birefringence of the optical fiber and consequently makes the transmission peak of the PS-FBG splitting into two sharp transmission peaks of orthogonal polarizations. The wavelength spacing between the two transmission peaks increases with the transversal loading on the PS-FBG, thus making the polarization beating frequency increase. This property is exploited in a transversal loading sensor.      

高分辨率光纤激光传感系统

提出并实现了一种基于光纤光栅(FBG)激光器的高分辨率光纤传感系统。通过在一段高增益有源光纤写入光纤光栅形成光纤激光传感器,待测信号作用在激光器上引起激光频率变化,采用偏振无关的非平衡迈克耳孙光纤干涉仪将激光频率变化转化为干涉仪相位变化。干涉仪输出的信号经过光电转换后,用采集卡转换为数字信号输入计算机,最后利用改进的归一化相位载波(PGC)解调技术,实现信号的高分辨率解调。实验表明该传感系统的动态应变分辨率达到了5.6×10-4nε/Hz,并且解调结果与待测信号具有良好的线性关系。     

应变与温度同时测量的二阶灵敏度分析

分析了应变与温度同时测量的光纤传感器中普遍存在的二阶灵敏度问题，导出了二阶灵敏度引起的误差的一般计算公式，并将这些公式和双模椭芯光纤温度、应变扰动的理论模型结合，给出了二阶灵敏度对线性近似误差影响的定量分析结果。     

用于大型结构应变测量的光纤传感器

描述了一种梳形光纤应变传感器，从理论上导得传感器传输光功率变化和应变之间的线性关系；得到了这种传感器应变灵敏度和梳形结构参数的函数关系。实验得到的结果和理论一致．实验显示出这种传感器没有滞回特性，具有好的单值性、重复性和温度稳定性。     

光纤布里渊温度和应变同时传感系统性能分析

采用基于朗道比的微波外差检测技术的布里渊光时域反射传感系统,获得布里渊散射信号的频移和强度,可以精确地测量沿光纤长度的分布式温度和应变信息。此方法在同一条光纤线路上分别测量光纤的布里渊散射和瑞利散射,且使用布里渊频谱扫描对信号进行处理。给出了这种传感方案的实验系统,并在理论推导的基础上对其性能进行了分析,该传感系统可以获得1℃的温度分辨率和100uε的应变分辨率。     

Modal Interferometer Based on ARROW Fiber for Strain and Temperature Measurement

In this letter, interferometric sensors based on antiresonance reflecting optical waveguide (ARROW) fibers were developed, and used to sense strain and temperature. Two types of solid-core ARROW fibers were considered and signal demodulation was achieved by using the white light interferometric technique. The ARROW fibers have two rings of high index rods arranged in a hexagonal structure with a lattice constant of $approx$6 $muhbox{m}$. The different sizes of the rods cause different measurand sensitivities for the two fibers. Resolutions of $pm$1.1 $mu varepsilon$ and $pm$0.07 $^{circ}hbox{C}$ were achieved for strain and temperature, respectively.      

Dual-Wavelength Mode-Locked Erbium-Doped Fiber Ring Laser Using Highly Nonlinear Fiber

We demonstrate a stable dual-wavelength actively mode-locked erbium-doped fiber laser operating at 20 GHz. A highly nonlinear fiber is used to compensate the frequency chirp caused by regular single-mode fiber in the optical cavity. Dual-wavelength pulse trains with pulsewidths $sim$1.4 ps are obtained.      

具有温度补偿的光纤生物量浓度在线测量传感器

利用光能量的吸收和散射与生物量浓度之间的关系,建立了一种基于光纤回归反射能量衰减技术的生物量浓度在线测量方法。由于在生化反应过程中常伴随着生化产热以及环境温度的改变,从而给传感器测量带来误差。为了消除温度信号对测量结果带来的误差,通过在传感器单元中引入温度补偿臂,消除温度信号对待侧信号的影响。实验表明:该传感器实现了生物量浓度的在线测量;同时,通过引入温度补偿臂消除了温度变化对生物量浓度测量的影响,从而真正实现了生物量浓度的准确在线测量。     

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.     

A Novel Dual-Wavelength DFB Fiber Laser Based on Symmetrical FBG Structure

A novel grating structure is proposed and demonstrated to obtain stable dual-wavelength (DW) distributed-feedback (DFB) fiber lasers at room temperature. The proposed grating is based on a symmetrical structure, where one half is periodically sampled by "0"-to-"pi" period and the other half is done by "pi"-to-"0" period. This structure can create two separated resonance cavities and hence achieve the stable DW lasing operation. By fabricating the proposed grating on a piece of Er : Yb-codoped fiber, we experimentally obtain a stable DW-DFB fiber laser with wavelength spacing of ~440 pm at room temperature     

双波长环形腔掺铒光纤激光器输出的稳定性

使用掺铒光纤平均反转粒子数模型推导了双波长激光器平衡振荡需满足的条件,并据此设计实验系统,对抽运功率、模式损耗以及波长间隔对输出功率的影响进行了实验研究.结果表明,可通过调节腔内损耗谱实现掺铒光纤环形腔内多波长激光输出,双模平衡振荡条件在远离阈值点情况下成立;可变衰减器的稳定性对双波长平衡的影响极大,允许的偏离值小于0.4 dB;而起振波长的偏离对双波长平衡的影响较小,大于1 nm的波长偏离才会导致平衡破坏;掺铒光纤的非均匀加宽效应允许平衡时损耗在一定范围内波动,这有助于提高激光器的输出稳定性,30 min内1546 nm和1556 nm双波长的功率波动小于0.5 dB.     

基于高精细度光纤滤波器的双波长光纤激光器

提出了基于高精细度光纤环形滤波器的双波长窄线宽光纤激光器结构.在单波长光纤激光器的基础上,增加保偏光纤布拉格光栅(PM-FBG)和高精细度的光纤滤波器.其中保偏光纤布拉格光栅作为激光器的波长选择元件,可产生两个波长的激光输出.高精细度的光纤滤波器由两个光耦合器和一段弱抽运的掺铒光纤构成,掺铒光纤产生的增益和光纤时延使滤...     

基于光反馈的双波长光纤环形激光器有源传感

提出了一种基于光反馈的双波长光纤环形激光器有源传感的模型。通过光纤光栅对激光器的波长进行选择, 输出不同波长的两路光反馈信号, 实现光纤环形激光器的波分复用。根据光纤环形激光器的超越方程, 理论上得出系统的输出变化。系统的输出信号与自混合干涉有着相同的灵敏度, 同时可根据条纹的倾斜情况辨别物体的运动方向。系统中的激光器不仅作为传感光源, 同时也作为传感敏感元件, 实现光纤环形激光器的有源传感。模拟分析了两路不同波长信号之间的变化关系, 考虑外部靶面位移大小对系统输出的影响。实验观测的结果与模拟结果相一致。     

Dual-Wavelength DFB Fiber Laser Based on Unequalized Phase Shifts

A novel structure for dual-wavelength distributed feedback (DFB) fiber laser is proposed and experimentally demonstrated. This structure is based on a uniform fiber Bragg grating with two unequalized phase shifts, which markedly suppress the mode competition of the two lasing wavelengths; and then a 52-pm-spaced dual-wavelength DFB fiber laser operating at single-longitudinal-mode and single-polarization is achieved at room temperature. A simple method is also implemented to fabricate the phase shifts with high precision     

激光脉冲制作的长周期光纤光栅/法布里-珀罗高温-应变组合传感器

在很多高温环境应用中,诸如发动机、飞机和宇航器、复合材料的健康监测,需要精确测量应变。针对这种场合提出了一种基于激光脉冲制作的长周期光纤光栅/法布里-珀罗(LPFG/F-P)温度-应变组合光纤传感器。该传感器由长周期光纤光栅与光纤法布里-珀罗干涉传感器级联构成,其中长周期光纤光栅由高频CO2激光脉冲制作,用于监测温度;光纤法布里-珀罗干涉传感器由157nm准分子激光脉冲制作,用于监测应变。这种新型组合光纤传感器最大的特点是能承受500℃的高温并能在高温环境下实现应变的精确测量,可望在高温恶劣环境条件下的结构(如飞机发动机)健康监测、复合材料生产过程监测等应用中发挥重要作用。     

基于保偏光纤光栅的双波长掺铒光纤激光器

提出了一种基于保偏光纤(PMF)中布拉格光栅的波长间隔可调的可开关双波长掺铒光纤激光器(EDFL)。由于和光纤布拉格光栅(FBG)两个反射峰对应的不同波长的两纵模在偏振态上是止交的．从而在均匀展宽的掺铒光纤中增强了偏振烧孔(PHB)效应。这种偏振烧孔效应大大减小了不同模式之间的竞争，因此可在室温下得到稳定的双波长振荡。另一方面。通过调整偏振控制器的状态．即改变腔内的双折射状念，光纤光栅的两个反射峰强度会发生变化。基于以上原理。便形成了对激光振荡模式的选择．即通过调整偏振控制器的状态可使激光器工作在稳定的双波长状态或在两波长之间转换。通过改变加在光纤光栅上侧向应力的大小和方向．可有效控制双波长激射的波长间隔．实验中得到了0．2～1．1nm的可调间隔。