一种新型光纤光栅无啁啾调谐方法

分析了基于弹性梁的光纤光栅调谐原理，引入了轴向直变传递系数的概念，提出利用部分纯弯曲调谐方法，可实现光纤光栅宽带无啁嗽调谐。在实验中，利用部分纯弯曲调谐法，获得了20．1nm的光纤光栅无啁嗽调谐范围，调谐线性拟合度为0．9996，调谐过程中光栅反射谱的3dB带宽变化小于0．07nm，峰值反射率变化小于0．2dB，基本无啁嗽现象产生，实验结果和理论分析一致。

一种制作掺Yb相移光纤光栅激光器的实验方案

采用遮挡法引入相移制作了掺Yb相移光纤光栅(PS-FBG)。在制作光栅的过程中,将其作为激光器的谐振腔,通过监测激光器的输出功率来确定相移大小。当激光器的输出功率开始下降时,停止曝光,此时引入的相移为π/2。为了使光栅的特性尽快稳定下来需要对光栅进行退火,这将导致引入的相移小于π/2。为了弥补退火过程中引起的相移降低,需要对退火后的光栅进行二次曝光,以使光栅的相移恢复π/2。利用该方法制作了一只光纤光栅激光器。当抽运功率为100 mW时,获得了25 mW的输出功率,信噪比(SNR)为60 dB。在1 h内

High-performance multiplexed vibration sensor system based on fiber lasers - art. no. 683019

This paper describes a high-performance multiplexed vibration sensor system using fiber lasers. A serial vibration sensor array consists of four short cavity fiber lasers. The system employs a single, polarization-insensitive, unbalanced Michelson interferometer to translate individual laser wavelength shifts induced by vibration signals into interferometer phase shifts. A dense wavelength division demultiplexor (DWDM) with high channel isolation is inserted to demultiplex each laser signal as a wavelength filter. Finally, a digital phase demodulator based on the phase generated carrier technique is used to achieve high-resolution interrogation. Experimental results show that no observable crosstalk is measured on the output channels, and the minimal detectable acceleration of this system is similar to 200ng/root Hz at 250Hz, which is fundamentally limited by the frequency noise of the lasers.

Ultra-compact silicon-on-insulator optical filter based on sidewall Bragg grating

Micro-cavity structure composed of silicon wire with 240nm square cross section and two symmetrical sidewall waveguide Bragg gratings is fabricated and studied for the operation under telecommunication wavelengths. Optical filter of quasi-TE mode was realized based on this cavity. In such micro-cavity, optical quality factor (Q) was measured up to 380 with a 4.8nm free spectral range (FSR) and 12dB fringe contrast (FC). The measured group index of silicon waveguide with only 240nm square cross section was between 3.80 and 5.43. It is the first time group delay of silicon wire waveguide with such small core dimension is studied. Larger group delay can be expected after optimizing the design parameters and the fabrication process.

Four-wave mixing self-stability based on photonic crystal fiber and its applications on erbium-doped fiber lasers

The analytic solutions of coupled-mode equations of four-wave mixings (FWMs) are achieved by means of the undepleted approximation and the perturbation method. The self-stability mechanism of the FWM processes is theoretically proved and is applicable to design a new kind of triple-wavelength erbium-doped fiber lasers. The proposed fiber lasers with excellent stability and uniformity are demonstrated by using a flat-near-zero-dispersion high-nonlinear photonic-crystal-fiber. The significant excellence is analyzed in theory and is proved in experiment. Our fiber lasers can stably lase three waves with the power ripple of less than 0.4 dB. (c) 2005 Elsevier B.V. All rights reserved.

Ultra-narrow dual-channel filter based on symmetrical sampled fibre Bragg grating

A kind of ultra-narrow dual-channel filter is proposed in principle and demonstrated experimentally. This filter is designed by means of two sampled fibre Bragg gratings (SFBGs), where one is periodic 0-pi sampling and the other is symmetrical spatial sampling. The former can create two stopbands in the transmission spectra and the latter can produce two ultra-riarrow passbands. Our filter has the 3-dB bandwidth of about 1 pm, whose value is two orders of magnitude less than the bandwidth of the traditional SFBG filters. The proposed filter has a merit that the channel spacing remains unchanged when tuning the filter.

Room-temperature dual-wavelength erbium-doped fibre laser based on a sampled fibre Bragg grating and a photonic Robin Hood

With the assistance of a kind of photonic Robin Hood that is originated from four-wave mixing in a dispersion-flattened high-nonlinearity photonic-crystal fibre, a novel dual-wavelength erbium-doped fibre (EDF) laser is proposed and demonstrated by using a sampled fibre Bragg grating. The experiments show that, due to the contribution of the photonic Robin Hood, the proposed fibre laser has the advantage of excellent uniformity, high stability and stable operation at room temperature. Our dual-wavelength EDF laser has the unique merit that the wavelength spacing remains unchanged when tuning the two wavelengths of laser, and this laser is simpler and more stable than the laser reported by Liu et al. [Opt. Express, 13 142 (2005)].

Modified Holographic Exposure to Fabricate Varied Bragg Grating in an Identical Chip

A new fabricating method is demonstrated to realize two different Bragg gratings in an identical chip using traditional holographic exposure. Polyimide is used to protect one Bragg grating during the first period. The technical process of this method is as simple as that of standard holographic exposure

Flat Surface Plasmon Polariton Bands in Bragg Grating Waveguide for Slow Light

The formations of the surface plasmonpolariton (SPP) bands in metal/air/metal (MAM) sub-wavelength plasmonic grating waveguide (PGW) are proposed. The band gaps originating from the highly localized resonances inside the grooves can be simply estimated from the round trip phase condition. Due to the overlap of the localized SPPs between the neighboring grooves, a Bloch mode forms in the bandgap and can be engineered to build a very flat dispersion for slow light. A chirped PGW with groove depth varying is also demonstrated to trap light, which is validated by finite-difference time-domain (FDTD) simulations with both continuous and pulse excitations.

光纤光栅传感器干涉型解调仪的稳定性分析和改进

提出了一种利用两种不同温度系数的光纤光栅对来对解调仪的不稳定性进行改进的方法，并进行了理论分析，研究了影响该解调仪稳定性的几个因素。将所研制的传感器布设在东海大桥上，组成传感网络，并用改进后的光纤光栅解调系统对传感器的信号进行解调。在大桥竣工测试时，该传感解调系统表现出较好的性能。

一种闭环控制的光纤光栅动态色散补偿仪

利用啁啾光纤光栅的应变调谐特性，将色散补偿的啁啾光纤光栅斜贴于悬臂梁的侧面，通过应力实现啁啾量调整而改变其色散补偿量的大小，同时利用固定在同一悬臂梁的均匀布拉格光栅传感器，实现了闭环自动控制色散补偿量，研制出了一种新型的光纤光栅动态色散补偿仪。该色散补偿仪工作在1550nm波段，典型性能数据为：色散动态补偿范围-1000-1680ps／nm，插入损耗小于1．5dB，动态调谐步进响应时间小于50ms，基本上能满足10Gb／s光纤通信系统中色散动态补偿的要求。

基于光纤光栅的结构健康监测技术及应用研究

本文介绍了近几年来中国科学院力学研究所开展的结构健康监测(StructuralHealth Monitoring,SHM)研究的进展。主要包括:基于光纤光栅(Fiber Bragg Gratings,FBG)的SHM传感技术,涉及到系列光纤传感器(应变、温度、加速度、位移)开发、应变分布测量算法和技术、低温应变和温度测量及SHM应用;模态空间SHM理论和FBG应变模态测量技术;状态空间SHM理论和技术,如结构静载监测和非线性系统相空间损伤识别技术。此外还介绍了SHM系统的集成及在实际结构中的应用。最后对SHM的重要研究方向进行了展望。

Some engineering issues of an FBG sensor with the dual gratings parallel matched interrogation method

The key issues of engineering application of the dual gratings parallel matched interrogation method are expanding the measurable range, improving the usability, and lowering the cost by adopting a compact and simple setup based on existing conditions and improving the precision of the data-processing scheme. A credible and effective data-processing scheme based on a novel divisional look-up table is proposed based on the advantages of other schemes. Any undetermined data is belonged to a certain section, which can be confirmed at first, then it can be looked up in the table to correspond to microstrain by the scheme. It not only solves inherent problems of the traditional one (double value and small measurable range) but also enhances the precision, which improves the performance of the system. From the experimental results, the measurable range of the system is 525 mu epsilon, and the precision is +/- 1 mu epsilon based on normal matched gratings. The system works in real time, which is competent for most engineering measurement requirements. (C) 2007 Elsevier GmbH. All rights reserved.

光纤布拉格光栅传感系统在海洋平台监测中的应用研究

首先阐述了光纤布拉格光栅(FBG)传感系统的传感原理和基本组成。然后介绍了我们研制的FBG温度和应变传感器的特性以及关于它们应用于平台监测中的可靠性问题的研究结果，包括疲劳损伤、防水密封和机械防护。最后讨论了FBG传感系统在海洋工程中的其它潜在用途。Sensing mechanism of Fiber Bragg gratings (FBGs) and its sensing system are presented. Then, the performance of the FBG strain and temperature sensors we designed is described. Some results related to the reliability of the FBG sensor in the application to monitoring offshore platforms is also given, which involves fatigue damage, waterproof packing and mechanical protection. Finally, other potential applications of FBGs in offshore engineering are discussed.

光纤光栅在金属锈蚀传感中的应用

介绍了一种基于光纤布拉格光栅（FBG）应变敏感特性的金属锈蚀传感器。该器件由光纤光栅、有预应力的钢弹簧和一些机械部件组合而成。组合后的弹簧处于压缩状态。在弹簧弹力的作用下，光纤光栅的峰值波长增长了3．213m。对该器件进行了加速腐蚀实验：将其放入盐酸环境中，逐日监测光纤光栅峰值波长的变化，发现峰值波长逐渐缩短，说明弹簧的弹性系数随着弹簧的锈蚀而逐渐减小。到弹簧锈蚀断裂，整个锈蚀过程持续了1315h，平均锈蚀速率约5μm／d。实验表明了该传感器在实际应用中的可能性。同时讨论了光纤光栅的温度效应及其他影响其实