Realisation of an effective dual-parameter sensor employing a single fibre Bragg grating structure

A novel technology for simultaneous and independent measurement of dual parameters is proposed and experimented. The length of a single fibre Bragg grating (FBG) is divided into two parts. The temperature variation and another measurand can be measured independently and simultaneously, and the thermal effect can be erased with great ease. © 2005 Elsevier Ltd. All rights reserved.

Refractometer based on a liquid core FBG device

A 1.2X500μm slot was engraved across a fiber Bragg grating (FBG) using femtosecond laser patterning and chemical etching. liquid core FBGs were constructed and their sensitivity to refractive index of up to 10-6/pm was measured.

Single-reflection-band fiber Bragg gratings with channelized linear and nonlinear dispersion and their applications

We present a new class of multi-channel Fiber Bragg grating, which provides the characteristics of channelized dispersion but does so with only a single reflection band. Such gratings can provide pure phase control of optical pulses without introducing any deleterious insertion-loss-variation. © 2006 Optical Society of America.

First order optical differentiator based on an FBG in transmission

Optical differentiators constitute a basic device for analog all-optical signal processing [1]. Fiber grating approaches, both fiber Bragg grating (FBG) and long period grating (LPG), constitute an attractive solution because of their low cost, low insertion losses, and full compatibility with fiber optic systems. A first order differentiator LPG approach was proposed and demonstrated in [2], but FBGs may be preferred in applications with a bandwidth up to few nm because of the extreme sensitivity of LPGs to environmental fluctuations [3]. Several FBG approaches have been proposed in [3-6], requiring one or more additional optical elements to create a first-order differentiator. A very simple, single optical element FBG approach was proposed in [7] for first order differentiation, applying the well-known logarithmic Hilbert transform relation of the amplitude and phase of an FBG in transmission [8]. Using this relationship in the design process, it was theoretically and numerically demonstrated that a single FBG in transmission can be designed to simultaneously approach the amplitude and phase of a first-order differentiator spectral response, without need of any additional elements. © 2013 IEEE.

Acousto-optic effect in microstructured polymer fiber bragg gratings:simulation and experimental overview

A fine control of the microstructured polymer fiber Bragg grating spectrum properties, such as maximum reflected power and 3-dB bandwidth, through acousto-optic modulation is presented. For simulation purposes, the device is modelled as a single structure, comprising a silica horn and a fiber Bragg grating. For similar sized structures a good correlation between the numerical results and the experimental data is obtained, allowing the strain field to be completely characterized along the whole structure. It is also shown that the microstructured polymer fiber Bragg grating requires less effort from the piezoelectric actuator to produce modification in the grating spectrum when compared with a silica fiber Bragg grating. This technique has potential to be applied on tunable optical filters and tunable cavities for photonic applications.

Highly sensitive liquid level sensor using a polymer optical Bragg grating for industrial applications

A novel and highly sensitive liquid level sensor based on a polymer optical fiber Bragg grating (POFBG) is reported for the first time. The sensitivity of the sensor is found to be 57 pm/cm of liquid, enhanced by more than a factor of 5 when compared to an equivalent sensor based on silica fiber. © 2015 OSA.

Proposal and design of phase-modulated fiber gratings in transmission for pulse shaping

A novel approach to pulse shaping using a phase-modulated fiber Bragg grating (FBG) in transmission is proposed and designed. We show that phase-modulated FBGs can provide transmission responses suitable for pulse shaping applications, offering important technological feasibility benefits, since the coupling strength remains basically uniform in the grating. Moreover, this approach retains the substantial advantages of FBGs in transmission, such as optimum energy efficiency, no requirement for an optical circulator, and robustness against fabrication errors.

Design of high channel-count fiber Bragg gratings using tailored group delay

A novel method of fiber Bragg grating design based on tailored group delay is presented. The method leads to designs that are superior to the previously reported results. © OSA 2012.

Effect of Rayleigh-scattering distributed feedback on multiwavelength Raman fiber laser generation

We experimentally demonstrate a Raman fiber laser based on multiple point-action fiber Bragg grating (FBG) reflectors and distributed feedback via Rayleigh scattering in a ∼22 km long optical fiber. Twenty two lasing lines with spacing of ∼100 GHz (close to ITU grid) in C-band are generated at Watts power level. In contrast to the normal cavity with competition between laser lines, the random distributed feedback cavity exhibits highly stable multiwavelength generation with a power-equalized uniform distribution which is almost independent on power. The current set up showing the capability of generating Raman gain of about 100-nm wide giving the possibility of multiwavelength generation at different bands. © 2011 SPIE.

Signature analysis on wheel-rail interaction for rail defect detection

Fibre Bragg Grating (FBG) sensors have been installed along an existing line for the purposes of train detection and weight measurement. The results show fair accuracy and high resolution on the vertical force acted on track when the train wheels are rolling upon. While the sensors are already in place and data is available, further applications beyond train detection are explored. This study presents the analysis on the unique signatures from the data collected to characterise wheel-rail interaction for rail defect detection. Focus of this first stage of work is placed on the repeatability of signals from the same wheel-rail interactions while the rail is in healthy state. Discussions on the preliminary results and hence the feasibility of this condition monitoring application, as well as technical issues to be addressed in practice, are given.

一种同时测量温度和应变的光纤光栅传感器

报道了一种新型实用的用单根光纤布拉格光栅(FBG)实现温度和应变分离传感的技术。当光纤光栅一部分包层直径变小时，整个光栅可以看成由两个周期相同但直径不同的子光栅连接而成。理沦分析和实验都证实了这两个子光栅具有相同的温度敏感性和不同的应变敏感性．由此实现光纤光栅传感器中温度和应变两参数的分离测量，而且这两个子光栅的中心波长间距可以直接测量应变大小．温度变化不影响所测量的应变值。实验中光栅的一部分包层直径被HF酸腐蚀到82μm．获得了两子光栅应变响应系数分别为0．00201nm/με．0．000858nm/μ

光纤光栅滤波的瓦斯传感系统的研究

差分吸收法是进行瓦斯远距离监测的重要方法，根据瓦斯在近红外波段的吸收特性，报道了一种新型的远距离光纤瓦斯传感系统。采用1．3μm超辐射发光二极管为光源，利用光纤布拉格光栅(FBG)优良的窄带滤波特性实现了对瓦斯的差分吸收测量。和传统的干涉滤光片相比，光纤光栅滤波器插入损耗低、制备简单。系统具有全光纤化、结构简单、工作距离远、稳定性好的特点。工作距离10km，测量灵敏度为0．1％，是瓦斯爆炸极限的2％。

高分辨率光纤光栅温度传感器的研究

报道了一种具有高分辨率和高效且价廉的解调系统的光纤布拉格光栅(FBG)温度传感器。提出了光纤光栅的金属槽封装技术，以提高传感光栅的温度灵敏性。研究了金属槽封装光栅的温度灵敏性，理论分析和实验结果表明，封装光栅的温度灵敏系数比普通裸光栅提高了3．6倍。系统利用一长周期光栅(LPG)作为线性滤波器，宽带光源经此长周期光栅调制后入射到传感光栅，可解调布拉格传感光栅的波长位移。理论分析与实验结果一致，系统可达到的温度分辨率为0．02℃。

光纤光栅高温传感器的研究

提出了一种能够测量高温的光纤布拉格光栅（FBG）传感器结构。利用线膨胀系数和长度均不同的两种金属细杆和光纤布拉格光栅设计而成的传感头，能够将被测温度转化为光栅的应变，解调由应变引起的光栅波长漂移，即可得知待测的温度。目前在实验室实现了500℃的动态范围和1℃的温度分辨率，实验结果与理论分析一致。

偏振模色散和时延抖动对啁啾光纤光栅色散补偿特性的影响

对存在偏振模色散(PMD)和群时延(GD)抖动的非理想线性啁啾光纤光栅的色散补偿特性进行了研究。实验测量了啁啾光纤光栅的群时延谱和偏振模色散光谱，理论分析和实验测量表明，啁啾光纤光栅差分群时延(DGD)抖动与其时延抖动密切相关。通过数值模拟方法，计算了线性啁啾光纤光栅偏振模色散眼图代价与入射到啁啾光纤光栅色散补偿器的光信号的偏振方向的关系，计算结果表明在使用啁啾光纤光栅色散补偿器时应对光信号的偏振方向进行调整，以获得最佳补偿效果。另外结合实验数据，模拟计算并讨论了非理想线性啁啾光纤光栅群时延抖动和偏振模色