Dual-mode optical-fibre interferometric sensor

The letter describes how a dual-mode optical fibre can be used as an interferometric temperature sensor either by fringe counting or, more importantly, by analysis of the change in chromatic transmission spectrum with temperature. Such a sensor has the geometric flexibility of an all-fibre interferometric sensor as well as the advantages of a wavelength modulating device, i.e. high accuracy, noise immunity, absolute measurement capability and no need for intensity calibration.     

Integrated acoustooptic modules for interferometric RF spectrum analyzers

An integrated acoustooptic (AO) module that consists of a wideband AO Bragg cell, a wide-angle ion-milled concave Bragg grating lens, and a large-aperture titanium-indiffusion proton-exchange lens has been realized in a y-cut LiNbO/sub 3/ waveguide 1*8*16 mm/sup 3/ in size and used to perform interferometric RF spectrum analysis. This module has provided a bandwidth of 205 MHz centered at 350 MHz and single-tone instantaneous and two-tone, third-order spurious-free dynamic ranges of 50 and 40 dB, respectively, at 1.0 mW of 0.6328- mu m laser power and a drive power of 50 mW per RF signal. A pair of such basic AO modules has been integrated in a common LiNbO/sub 3/ substrate 1*10*16 mm/sup 3/ in size to facilitate measurement of the phase difference, and thus the angle of arrival, of RF signals.<>     

集成光学干涉仪光纤陀螺

简述了集成光学干涉仪光纤陀螺（ＦＯＧ）的技术优势、发展概况和采用的技术途径，介绍了适用于不同技术条件要求的三种多功能集成光学芯片结构和相应的信息处理方法。简要地概括了目前国外ＦＯＧ的发展水平。     

Transmissive serial interferometric fiber sensor array

A transmissive serial array architecture for multiplexed interferometric fiber-optic sensors based on time division addressing is discussed. The configuration gives rise to intrinsic optical crosstalk between sensor elements of the system due to multiple cross-coupling of pulses between the series of sensor elements and the output fiber bus. This crosstalk is theoretically analyzed in detail, and compared to experimental results obtained with both three- and eight-sensor networks. Phase detection sensitivities as low as ~10 μrad/√Hz at a signal frequency of 1 kHz are reported     

Integrated multisensor chip

A multipurpose integrated-sensor chip has been fabricated for the simultaneous measurement of physical and chemical variables. The multipurpose chip which measures 8 × 9 mm²contains conventional MOS devices for signal conditioning, array accessing, and output buffering along with the following on-chip sensors: a gas-flow sensor, an infrared-sensing array, a chemical-reaction sensor, cantilever-beam accelerometers, surface-acoustic-wave (SAW) vapor sensors, a tactile sensor array, and an infrared charge-coupled device imager. The multisensing functions of this chip utilize both the pyroelectdc and piezoelectric effects in ZnO thin films. Fabrication of the chip is carried out using a conventional 3-µm Si NMOS process combined with Si micromachining techniques. Compatible fabrication technology and sensor properties are described.     

Combined michelson and polarimetric fibre-optic interferometric sensor

A fibre-optic interferometric sensor utilising a highly birefringent fibre sensing element has been configured such that both Michelson and polarimetric outputs are simultaneously available. This device therefore offers the high resolution of a Michelson interferometer in conjunction with the increased dynamic range of a polarimetric device. The results of preliminary experiments in which the system was used as a temperature sensor are presented.     

Distributed fiber-optic interferometric sensor for the detection ofpressure fluctuations in reservoirs

A fiber-optic interferometric sensor for the detection of the resonant modes of reservoirs is reported. Study of the characteristics of fiber-optic hydrophones identified the ratio ΔL/Δp, i.e., the differential fiber-optic elongation due to pressure change, as the critical parameter to be enhanced in order to improve the sensor sensitivity. A model of the sensor, suitable for detecting the very-low-frequency and long-wavelength pressure changes characteristic of reservoir resonances, is proposed. The sensor is designed as a straight length of optical fiber with small masses attached at regular intervals. The dynamical analysis shows a sensitivity two orders of magnitude larger than that of the unmodified optical fiber. Use of the sensor as a resonant device is discussed. Experiments performed using the first prototype in a resonant tank are described and agree well with theoretical predictions, confirming the validity of the approach     

Polarisation-induced visibility limits in interferometric fibre-optic sensor arrays

Polarisation-induced fading is analysed in Mach-Zehnder-type interferometric fibre-optic sensor arrays. Given a sensor array configuration and the polarisation properties of individual elements, a procedure is presented to find an optimal input state of polarisation which maximises overall sensor visibility. It is shown that for both serial and parallel arrays with N sensor elements, the visibility of the worst-case sensor configuration can be maximised to a value of sin ( pi /2N).<>     

Time-domain addressing of remote fiber-optic interferometric sensor arrays

This paper describes and analyzes a particular application of high duty-cycle time-division multiplexing to the separation and identification of signals from an interferometric sensor array. Using the method discussed here, the coherence length of the laser is no longer a severe design constraint. Also, the source phase-induced intensity noise which limits some other multiplexing methods may be overcome, leading to a higher sensitivity. The arrays of all-passive remote sensors exhibit minimal crosstalk between sensors, and have downlead insensitivity. A synthetic heterodyne demodulation technique prevents environmentally induced signal fading. Analysis includes coupling ratios for all directional couplers in the system, signal and noise spectra, minimum detectable phase shift, and the effect of ac coupling on noise and crosstalk. An experimental all-fiber implementation of a two sensor array has yielded a measured sensitivity of approximately 10 μrad/sqrt{Hz}over a range of signal frequencies, and a crosstalk level of better than 55 dB.     

基于单侧几何形变结构的全光纤Michelson干涉高温传感器

利用CO2激光脉冲对标准单模光纤(SMF)单向形成较小的几何形变,把部分基模能量耦合到光纤包层,制作了一种新型的在线型Michelson干涉传感器。理论分析了这种几何微扰激发的包层模特性,并利用芯模-包层模较大的热光系数差,把这种传感器应用于高温测量。实验结果表明,这种干涉传感器的温度灵敏度为0.093 7nm/℃,并且在800℃温度范围内具有良好的线性和重复性。这种制作简单、结构稳定、体积小和灵敏度高的全光纤在线型Michelson温度传感器将具有较大的潜在应用价值。     

Miniature Fabry-Perot interferometric sensor for temperature measurement based on photonic crystal fiber

A novel miniature Fabry-Perot interferometric (FPI) temperature sensor is proposed and demonstrated experimentally. The modal interferometer is fabricated by just splicing a section of photonic crystal fiber (PCF) with a single-mode fiber (SMF). The air holes of the PCF are fully collapsed by the discharge arc during the splicing procedure to enhance the reflection coefficient of the splicing point. The transmission spectra with different temperatures are measured, and the experimental results show that the linear response of 11.12 pm/°C in the range of 30–80 °C is obtained. This sensor has potential applications in temperature measurement field.     

基于涡旋光的光纤干涉型应力传感器

为了进一步增大光纤应力传感的测量范围,设计了一种基于涡旋光束与平面波光束干涉的光纤马赫-曾德尔干涉型(MZI)应力传感器,提出一种新型应力解调模型。利用主成分分析法提取了叉状干涉图样集的主要特征,得到两光束间相位差与其对应干涉图样对于主要特征的相关系数之间的关系,并根据应力-相位差关系,进而得出了应力与相关系数之间的关系;搭建了基于涡旋光束与平面波光束干涉的应力传感实验系统,研究了系统的应力传感响应特性。实验结果表明:该传感器的应力响应灵敏度为0.25694 rad/MPa,最大应力测量量程为3392με。     

High-resolution fibre-grating based strain sensor with interferometric wavelength-shift detection

A technique for the detection of dynamic strain induced wavelength shifts in fibre Bragg grating sensors is reported that is based on an unbalanced-interferometer wavelength discriminator, which is capable of subnanostrain resolution (0.6 n in / square root (Hz) at 500 Hz) sensing.<>     

适用于大功率光电芯片散热的一体化平板热管

为解决大功率光电芯片散热问题,构造了一种新结构一体化平板热管。利用超轻多孔泡沫金属作为毛细吸液芯,以水、丙酮和乙醇为工质,在不同充液比、加热功率和倾角条件下对新结构热管的热性能进行了研究,结果表明,这种新结构平板热管不仅消除了热管与散热片间的接触热阻,而且使整个散热翅片也处于均温状态,当功率达到380W、热流密度超过445 W/cm2时,热管仍具有较好的均温特性,且热阻较小,可达0.04℃/W。在3种工质中,水是最佳工质选择,且当充液比为30%时具有较好的效果。实验表明,以泡沫金属为吸液芯的新结构一体化平板热管具有很好的传热性能,并扩展了承载大热流密度的能力。     

Integrated bistable optical device using mach-zehnder interferometric optical waveguide

An integrated mirrorless bistable optical device based on the Mach-Zehnder interferometric optical switch has been proposed and demonstrated experimentally using a Ti: LiNbO3 waveguide. The resulting device is capable of combining more than two of them to realise multifunctional optical devices such as optical multivibrators.     

Integrated astable optical multivibrator using Mach-Zehnder interferometric optical switches

An integrated astable optical multivibrator has been analysed and demonstrated experimentally for the first time using a couple of Mach-Zehnder interferometric optical switches with crossed and straight electronic feedback. Fairly good agreement is found between experimental and analytical results.     

Choosing relative optical path delays in series-topology interferometric sensor arrays

We consider the problem of selecting relative optical path delays for a chain of Mach-Zehnder interferometric sensors which are to be multiplexed using a frequency modulated source (FMCW multiplexing) or a short coherence-length source (coherence multiplexing). Possible sets of delays which do not lead to crosstalk are described for two different series topologies. It is shown that the rapid growth of required delay with sensor number can be ameliorated if some cross-talk is allowed.     

Fibre-optic interferometric sensor utilising low coherence lengthsource: resolution enhancement

A fibre-optic interferometric sensor is described based on a low-coherence source. A novel form of homodyne signal processing is used in which the interferometer is locked to the quadrature point nearest to maximum visibility. This technique avoids the ambiguities which arise from the use of a high-coherence source in interferometers, where the transfer function is periodic     

双频干涉型光纤激光加速度传感器的指向性特性

矢量传感器可以共点、同步测量振速、加速度等矢量信息,且具有一定的噪声抑制能力,具有重要的应用价值。铒镱共掺双偏振光纤激光器已被证明可用于实现易解调、结构小巧、易于复用、高灵敏度的光纤传感器。针对此类传感器,本文提出一种加速度传感器结构,通过限制质量块的横向位移,实现了一种双频干涉型光纤激光加速度矢量传感器。除了具有双偏振光纤激光器的一系列优点外,该传感器还具有良好的“8”字形指向性,并在1 kHz以下具有平坦的频率响应特性,对于后续双频干涉型光纤矢量传感器的实现具有重要的指导意义。