Extended range interrogation of wavelength division multiplexed fibre Bragg grating sensors using arrayed waveguide grating

A technique for interrogating multiplexed fibre Bragg grating (FBG) sensors using an arrayed waveguide grating (AWG) is described. The approach considerably extends the sensing range from that achieved previously, while providing a strain resolution of 17n/spl epsiv///spl radic/Hz at 30 Hz.     

Air-clad fibre laser with internal Bragg grating

An air-clad fibre laser using a Bragg grating written directly into the Yb/sup 3+/ doped core as the end reflector is presented. For an unsaturated output power of 12 W and slope efficiency of 34%, there is a saturated laser wavelength shift of approximately 0.4 nm.     

High-temperature fibre Bragg grating thermometer

The use of gratings written in tin-doped silica fibres as a thermometer for high-temperature applications is described. Measurements up to ~800°C show a significant advantage over conventional fibre gratings. A considerable blue-shift has been observed at high temperatures. If corrections for blue-shift are taken into account, the errors are smaller than ~2°C     

Photosensitivity measurement in optical fibre with Bragg grating interferometers

A new technique based on two low-finesse fibre Bragg grating Fabry-Perot interferometers to study photosensitivity in optical fibre is presented. Phase evaluation using the Fourier spectra allows precise determination of the evolution of the refractive index with accumulated fluence. Results are given for different germanium/boron codoped fibres and for hydrogen-loaded fibres.     

Bragg grating fast tunable filter for wavelength divisionmultiplexing

A Bragg grating fast tunable filter prototype working over a linear tuning range of 45 nm with a maximum tuning speed of 21 nm/ms has been realized. The tunable filter system is based on two piezoelectric stack actuators moving a mechanical device thus compressing an apodized fiber Bragg grating. The filter allows both traction and compression and can work in transmission and in reflection. It is designed to work with a channel spacing of 100 GHz according to the ITU specifications for wavelength division multiplexing systems     

High-speed fibre Bragg grating sensor interrogation using dispersion compensation fibre

A novel high-speed fibre Bragg grating (FBG) sensor interrogator using dispersion-compensating fibre is proposed and demonstrated. The wavelength shift measurement of the FBG sensor is converted to time-domain measurement. The high-speed potential of this scheme was investigated experimentally, demonstrating an effective sampling speed of 2.44 megasamples per second.     

Frequency noise of a Bragg grating fibre laser

The measured frequency noise spectrum of a pair of single-frequency Bragg grating fibre lasers is dominated by noise at audio frequencies peaked near 700 Hz which fades into a white noise floor above ~50 kHz. The measured white noise floor yields an estimated Lorentzian FWHM linewidth of ~61 Hz     

Dispersionless slow light with 5-pulse-width delay in fibre Bragg grating

The excitation of gap solitons in a 30 cm fibre Bragg grating using 0.68 ns pulses, which emerge with atunable delay of up to 3.2 ns, corresponding to almost five pulse widths, and without broadening, are observed. This delay is an improvement by a factor of 2 from previous experiments.     

Electrically tunable dispersion compensator with fixed center wavelength using fiber Bragg grating

We present the design and development of a novel tunable dispersion compensator with fixed center wavelength that is based on the electrical adjustment of the chirp of a fiber Bragg grating (FBG). Both temperature gradient and strain gradient are employed to adjust the chirp of the FBG jointly. The electrical current flowing through the taper on-fiber thin-film heater will introduce a temperature gradient on the FBG. The shrinkage of a negative thermal expansion coefficient (NTEC) ceramic due to the temperature rise will compress the tapered FBG mounted inside it, and this will introduce a strain gradient on the FBG. The center wavelength of the FBG will be kept fixed because the effect of temperature rise on the FBG and the effect of compression of the FBG will offset each other. Applying an electrical power of less than 0.68 W, we demonstrate a linearly chirped FBG whose dispersion can be continuously adjusted from -178 ps/nm to -302 ps/nm with a central wavelength shift of as small as 0.16 nm.     

Microwave photonic filtering using Gaussian-profiled superstructured fibre Bragg grating and dispersive fibre

Microwave photonic filtering is realised using a superstructured fibre Bragg grating. The time delay of the optical taps is precisely controlled by the grating characteristics and fibre dispersion. A bandpass response with a rejection level of >45 dB is achieved.     

Phase tracker for low-finesse fibre Bragg grating Fabry-Perot interferometers

Presented is a technique for the continuous tracking of interferometer fringes. The technique uses a fringe quadrature signal to keep the state of the digital tracker in balance with the interferometer state. The quadrature signal is obtained through wavelength modulation of a semiconductor laser     

Tunable multi-wavelength Raman fibre laser based on fibre Bragg grating cavity with PMF Lyot-Sagnac filter

A flexibly-tunable multi-wavelength Raman fibre laser based on the polarisation maintaining fibre (PMF) Lyot-Sagnac filter after composing fibre Bragg grating cavity is demonstrated experimentally. The number of channels and wavelength spacing of the Raman laser can be controlled readily by /spl Delta/n /spl middot/ L products of PMF segments in the intracavity PMF Lyot-Sagnac filter.     

双光纤布拉格光栅波长锁定器的设计与制备

运用耦合模理论推导了双光纤布拉格光栅的透射率和反射率的解析表达式,利用相关表达式计算和分析了双光纤布拉格光栅的反射特性,并与单光纤布拉格光栅作了比较.讨论了双光纤布拉格光栅反射特性与光栅间距、光栅长度和折射率微扰最大值之间的关系,为双光纤布拉格光栅波长锁定器的设计与制备提供了理论依据.最终获得双光纤布拉格光栅的结构和特性参数,并与实测的数据进行比较,结果表明两者较为一致.     

基于萨格纳克环与光栅的双波长光纤激光器

报道一种基于保偏光纤的萨格纳克环与级联的光纤布拉格光栅的双波长掺铒光纤激光器,该激光器采用简单的线性腔结构,所用的萨格纳克环担当了梳状滤波器,光栅组构成了波长选择器件;在偏振烧孔的作用下,通过调整偏振控制器,激光器能够输出5种不同的激发模式,其中,双波长2种,单波长3种;所有的激发线具有小于0.3nm线宽,大于24dB的光学信噪比;同时,该激光器展示了较好的波长与峰值功率稳定性.     

Fast optical wavelength interrogator employing arrayed waveguide grating for distributed fiber Bragg grating sensors

A new type of interrogator for distributed fiber Bragg grating (FBG) sensors that employs an arrayed waveguide grating (AWG) is proposed and its operating features are in detail investigated both theoretically and experimentally. The remedy for achieving the linear characteristics of wavelength detection as well as for insuring the reliable and environmentally stable operation of interrogation is proposed and its usefulness is demonstrated in good agreement with the experimental results. The developed interrogator consists of a fully passive, small, all-solid, rugged optical IC and can detect wavelengths of a great number of FBG sensors with high precision better than 0.5 pm and high speed.     

Group delay ripple in fibre Bragg grating tunable dispersion compensators

Insertion loss and group delay ripples of linearly chirped FBG-based tunable dispersion compensators are computed numerically and measured experimentally, It is shown that their magnitude depends on the dispersion level of the device.     

分布式光纤光栅传感系统的波长检测技术

波长检测技术是当前光纤光栅传感领域的重点和难点之一,光纤光栅传感系统的一个显著优点是易构成分布式传感网络系统,实现多点、多区域同时检测.文章以几个典型的解调系统为例,重点分析了分布式光纤光栅传感系统中信号解调的工作原理、特点和性能.     

光纤光栅传感器的波长解调技术研究进展

光纤布喇格光栅(Fiber Bragg grating,简称光纤光栅:FBG)波长的解调是光纤光栅传感器应用的关键技术之一.在简单介绍光纤光栅传感原理的基础上,综述了近年来国内外多种光纤光栅波长解调系统的工作原理,分析了相应解调方法的优缺点,讨论了当前光纤光栅波长解调存在的技术难点,展望了其未来的研究方向.     

Tunable wavelength filter using a Bragg grating fiber thinned byplasma etching

We studied a tunable wavelength filter using a single-mode fiber Bragg grating with a cladding thinned by reactive plasma etching. Reflection wavelength shifts were demonstrated by controlling the effective refractive index or the period of the grating. When liquid paraffin was used for additional cladding on a thinned grating fiber of 19-μm diameter, the shift rate of 0.055 nm/°C was obtained. In the case of applying the tension to the grating region, the shift rate was 3.4 nm/100 V for the fiber of 41-μm diameter