Wideband tunable linear-cavity fiber laser source using strain-induced chirped fiber Bragg grating

A novel wideband tunable linear-cavity fiber laser source using strain-induced chirped fiber Bragg grating (FBG) and erbium–ytterbium co-doped fibers is proposed and demonstrated for the first time. The strain-induced chirped FBG, which acts as a partial-reflecting mirror, is achieved by bending a uniform FBG bonded at a slant onto the lateral surface of a simply supported beam. A single wavelength lasing with a maximum wavelength tuning range of 17 nm has been achieved experimentally.     

光纤光栅选频掺Yb3+双包层光纤激光器

利用相位掩模法，在D形内包层掺Yb3+双包层光纤一端直接写制出Bragg光栅，用作双包层光纤激光器的输出腔镜.试验得到了线宽为0.196nm，波长为1058.2nm，最高输出功率为570mW的稳定激光输出，解决了激光器中模式竞争造成的输出不稳定现象.从速率方程出发，对激光器的输出功率与抽运功率、光栅反射率的关系以及最佳光纤长度进行了理论分析，结果与实验符合很好. 关键词： 双包层光纤光栅 掺Yb3＋双包层光纤激光器 相位掩模 速率方程     

光纤光栅选频掺Yb3+双包层光纤激光器

利用相位掩模法 ,在D形内包层掺Yb3 双包层光纤一端直接写制出Bragg光栅 ,用作双包层光纤激光器的输出腔镜 .试验得到了线宽为 0 196nm ,波长为 10 5 8 2nm ,最高输出功率为 5 70mW的稳定激光输出 ,解决了激光器中模式竞争造成的输出不稳定现象 .从速率方程出发 ,对激光器的输出功率与抽运功率、光栅反射率的关系以及最佳光纤长度进行了理论分析 ,结果与实验符合很好     

Dual-wavelength high-power Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating

We report a high-power dual-wavelength Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating (FMFBG). The FMFBG was fabricated by using a piece of fiber in a length of fiber with a cutoff wavelength of 1225 nm, which supported two modes at 1060 nm. The laser was pumped by a fiber pigtailed laser diode working at 915 nm. Single-wavelength, dual-wavelength and triple-wavelength laser oscillations were observed when the fiber laser operated under different low pump powers. However, stable dual-wavelength operation was achieved at higher pump power of 3.9 W and remained unchanged until the output power reached 5.67 W under the maximum available pump power of 10.7 W. The laser wavelengths were centered at 1059.12 and 1060.80 nm with a full-width at half-maximum of 37 and 43 pm, respectively. The signal-to-noise-ratio was greater than 50 dB and the beam quality factor (M²) was about 1.9.     

Dispersion effects in a highly birefringent fiber laser sensor with fiber Bragg grating reflectors

The effects of dispersion in the highly birefringent fiber Bragg grating reflectors of a polarimetric elliptical-core fiber laser sensor are experimentally and theoretically investigated. The laser sensor is designed to measure fluid pressure. It is experimentally and theoretically shown that the wavelength-dependent phase shifts in the gratings can be employed to remove the near degeneracy of the polarization mode beat frequencies of a given order, which substantially improves the resolution of the sensor. A resolution of a few parts in 10(6) of the free spectral range of the laser is demonstrated.     

差动式光纤Bragg光栅沉降仪

研制了一种测量地表沉降变形的差动式光纤Bragg光栅沉降仪。等强度悬臂梁的底部固定于工地上的固定平台,顶端通过刃口、挂钩和连杆与沉降墩连接。在该测量中,沉降仪将沉降墩的地沉降量转换为悬臂梁的挠度。悬臂梁作用粘贴于其上下表面的光纤Bragg光栅产生应变,即传感光栅的Bragg波长产生了移位。对粘贴在悬臂梁上、下表面的传感光栅的Bragg波长进行差动运算,实现温度补偿,减小人为和气候因素的影响。在挂钩和沉降敦之间采用了螺旋结构连接,可通过调整螺旋或更换不同长度的挂钩来调节传感器的测量范围。荷载实验表明,该沉降仪的测量精度为0.004mm,低于变形测量中的科研级测量精度0.01~0.05mm。     

A novel fiber Bragg grating high-temperature sensor

A novel fiber Bragg grating (FBG) sensor for the measurement of high temperature is proposed and experimentally demonstrated. The interrogation system of the sensor system is simple, low cost but effective. The sensor head is comprised of one FBG and two metal rods. The lengths of the rods are different from each other. The coefficients of thermal expansion of the rods are also different from each other. The FBG will be strained by the sensor head when the temperature to be measured changes. The temperature is measured basis of the wavelength shifts of the FBG induced by strain. A dynamic range of 0–800 °C and a resolution of 1 °C have been obtained by the sensor system. The experiment results agree with theoretical analyses.     

Tilted fiber Bragg grating sensors

Optical fiber gratings have developed into a mature technology with a wide range of applications in various areas, including physical sensing for temperature, strain, acoustic waves and pressure. All of these applications rely on the perturbation of the period or refractive index of a grating inscribed in the fiber core as a transducing mechanism between a quantity to be measured and the optical spectral response of the fiber grating. This paper presents a relatively recent variant of the fiber grating concept, whereby a small tilt of the grating fringes causes coupling of the optical power from the core mode into a multitude of cladding modes, each with its own wavevector and mode field shape. The main consequence of doing so is that the differential response of the modes can then be used to multiply the sensing modalities available for a single fiber grating and also to increase the sensor resolution by taking advantage of the large amount of data available. In particular, the temperature cross‐sensitivity and power source fluctuation noise inherent in all fiber grating designs can be completely eliminated by referencing all the spectral measurements to the wavelength and power level of the core mode back‐reflection. The mode resonances have a quality factor of 10⁵, and they can be observed in reflection or transmission. A thorough review of experimental and theoretical results will show that tilted fiber Bragg gratings can be used for high resolution refractometry, surface plasmon resonance applications, and multiparameter physical sensing (strain, vibration, curvature, and temperature).     

A gain-clamped S-band erbium-doped fiber amplifier using fiber Bragg grating

We propose and investigate experimentally a gain-clamped S-band erbium-doped fiber amplifier module, employing a fiber Bragg grating to serve as a reflected element to lase a saturated tone injected into the module, by forward optical feedback method. In addition, different injected powers of the saturated tone are used to realize the performances of gain and noise figure for the proposed amplifier over the effectively wavelength range of 1478-1520 nm.     

A simple temperature-insensitive fiber Bragg grating displacement sensor

The study on fiber Bragg grating (FBG) displacement sensor based on monitoring the back-reflected power from an array of novelly embedded FBG sensors is presented. The sensor is a uniform FBG with three sections that are embedded in different layer in a composite lamina. Its bandwidth is displacement dependent and hence its reflected power varies almost linearly with displacement and it is insensitive to temperature variation. Thus, only low-cost photodetector (PD) is required to monitor displacement. This study demonstrates a novel fiber sensor, a method of fabricated the same, and a method to achieve simultaneous multi-sensor measurement.     

Novel grating couplers for diode-bars multi-point side-pumping double-clad fiber

Three grating couplers for diode-bars single-point and multi-point side-pumping double-clad fiber (DCF) are presented. The principles, characteristics and coupling efficiencies of these grating couplers are described and computed by a rigorous electromagnetic theory. We show computationally that the optimized gratings can couple the high-power TE- or TM-polarized pump lights with 94.7% and 79.7% into the DCF, respectively. For an un-polarized pump light, 72.4% efficiency can be reached. We also have analyzed the leakage of pump powers for diode-bars multi-point side-pumping DCF. Besides, the fabrication tolerances and other performances of the grating couplers are analyzed.     

一种新型温度自适应光纤光栅动态传感系统

 研究了采用温度控制光纤Bragg光栅（FBG）作为信号解调器件的自适应光纤光栅动态传感系统。系统利用半导体制冷器件对滤波用FBG进行温度控制,以改变FBG的窄带滤波波长,使之在合适的滤波波长工作,以适应测量环境温度变化,实现对传感器环境温度变化的自适应。通过采用参考信道,去除系统噪音,提高测量精度。系统动态应变传感精度达到9.745×10^-10(Hz^-1/2。     

A high sensitive fiber Bragg grating cryogenic temperature sensor

At cryogenic temperature, a fiber Bragg grating （FBG） temperature sensor with controllable sensitivity and variable measurement range is demonstrated by using bimetal configuration. In experiments, sensitivities of -51.2, -86.4, and -520 pm/K are achieved by varying the lengths of the metals. Measurement ranges of 293 - 290.5, 283 - 280.5, and 259 - 256.5 K are achieved by shortening the distance of the gap among the metals.     

Dissipative vector Bragg solitons in a birefringent optical fiber

Motionless dissipative vector solitons are found numerically in a birefringent polarization-conserving optical fiber with a longitudinal Bragg grating and nonlinear amplification and absorption in the polarization capture regime. It is shown that dissipative vector Bragg solitons exist and are stable even if the birefringence is comparatively strong.     

基于色散补偿光纤的高速光纤光栅解调方法

本文提出并论证了一种光纤光栅高速解调的新方法, 利用色散补偿光纤的色散效应, 将光纤光栅的波长漂移信息转换成时域信息. 采用脉冲激光器作为光源, 仅需一个光脉冲可获取单根光纤上所有光纤光栅的反射光脉冲, 再根据各个光栅反射回光脉冲的延时变化即可实现波长的解调. 本方法可用于准分布光纤光栅传感网络解调, 系统采用全光纤结构, 无需波长扫描, 大大提高了解调速度. 本文搭建了测试系统进行实验验证, 对3个光纤光栅组成的准分布式传感网络进行了解调, 实验结果表明, 解调出的光纤光栅布喇格波长线性度好, 解调速度最高可达1 MHz, 采样数据取10次平均后解调线性度可达0.9969, 解调误差约为27.8 pm.     

温度不敏感的光纤布拉格高压传感技术研究

 为了实现单一光纤光栅对压强精确测量,设计了一种温度不敏感的光纤布拉格高压传感器。对该传感器的温度特性及压强响应特性进行研究。给出了该传感器的结构及封装方法。从理论上分析了该传感器的温度去敏原理,推导了该压强传感器的光纤布拉格光栅中心波长与压强的关系,得到了该传感器的压强响应灵敏度的解析表达。通过实验分析传感器的温度特性及压强响应。实验结果表明,在21℃～260.8℃的范围内,实现了温度补偿,平均波长漂移量为0.75 pm/℃,在0～44 MPa的范围内,获得了-0.054 8 nm/MPa的压强响应灵敏度,是裸光纤布拉格光栅压力响应灵敏度的18.27倍。该传感器的压强响应具有很好的线性和重复性,实验值与理论值吻合得很好,该传感器能够通过一只光纤布拉格光栅实现压强的精确测量。     

光纤布拉格光栅及其应用

近年来新型的紫外激光写入的光纤布拉格光栅元件（ＦＢＧ）以其具有直接写人光纤芯区、插入损耗小、易于全光集成及波长选择性好、传感信息对波长绝对编码等优点,成为国内外光纤技术领域的研究热点。该论文综述了ＦＢＧ制作技术的进展,介绍和比较了各种制作方法的优缺点,对ＦＢＧ在光纤通讯、光纤传感器等方面的应用前景进行了分析和说明,结果表明ＦＢＧ将对整个光纤技术领域产生重要的影响。     

自锁紧式光纤Bragg光栅管式应变传感器

为了便于实现应变传感器两端铠装光缆与传感器自身牢固的连接,提高其在工程中抗拉拽等能力,研制了一种由不锈钢管、法兰盘和自锁紧螺帽等元件制作的自锁紧式光纤Bragg光栅管式应变传感器。光纤光栅通过限位堵头内的环氧树脂固定于不锈钢管内,应变作用于拧在不锈钢管上的法兰盘,带动不锈钢管和粘贴在上面的光纤光栅发生形变,检测出光纤光栅的波长变化量就可以反算出应变的大小。使用万能拉力试验机对其进行拉力荷载试验,结果表明,该传感器的灵敏度为0.45pm/με,线性度为3.71%FS,重复性为7.43%FS,迟滞性为3.85%FS。     

Four-element fiber Bragg grating acceleration sensor array

A four-element fiber Bragg grating acceleration sensor array is presented in this paper. The system combines an unbalanced Mach–Zehnder interferometer and three coarse wavelength division multiplexers (WDMs). The totally passive scheme has the advantages of high operation frequency and loose requirements for the working environment. An acceleration resolution of better than for the four channels is achieved.     

Interrogation unit for fiber Bragg grating sensors that uses a slanted fiber grating

A novel interrogation technique for fiber Bragg gratings is presented. It is based on measuring the characteristics of the outgoing near-field radiation from a tilted fiber grating. This scheme was experimentally checked and was found to offer a wide wavelength interrogation range as well as a good linearity, stability, and wavelength resolution.