Development of an Extrinsic dual-cavity Fiber Fabry-Perot interferometer : Applications to periodic and non-periodic vibration measurements

Le travail présenté dans cette thèse concerne le développement et la caractérisation d'un interféromètre extrinsèque à double cavités de type Fabry-Perot (EFFPI) en vue de l'analyse de vibrations périodiques et non périodiques. Cette thèse est divisée en 5 chapitres. Dans le chapitre I, nous donnons un panorama des mesures de vibration et de leurs techniques associées de type optique ou non-optique. Nous fournissons une description générale des caractéristiques des interféromètres à fibre optique. Nous justifions le choix du système de type Fabry-Perot par ses propriétés de mesure sans contact, sa flexibilité géométrique, ainsi que sa facilité d'utilisation. Le chapitre II présente le principe de fonctionnement du EFFPI. Le système comprend une cavité virtuelle pseudo-duale obtenue par l'introduction d'une optique de polarisation dans le chemin optique de la cavité de mesure. Cette configuration permet d'obtenir deux signaux d'interférence en quadrature, ce qui élimine l'ambiguïté de direction. Les propriétés générales de l'interféromètre telles que la réflectance et la visibilité de franges ont été caractérisées expérimentalement. En particulier, les états de polarisation des faisceaux d'entrée et de sortie ont été étudiés pour mieux comprendre l'atténuation induite dans les signaux d'interférence afin de pouvoir minimiser ce phénomène. Dans le chapitre III, nous proposons une technique de démodulation de franges de type passage à zéro modifiée pour obtenir l'information de déplacement. La résolution obtenue dans cette technique de démodulation est déterminée par le nombre de sous-niveaux de décomposition des signaux d'interférence. Dans ce travail, une résolution de λ/64 s'est avérée suffisante pour des applications à des vibrations périodiques de relativement grande amplitude. Différentes excitations de type sinusoïdal, carré et triangulaire ont été testées. Les erreurs provoquées par la variation de température de la source laser ainsi que celles apportées par la variation d'orientation de la cible durant la mesure de déplacement ont été étudiées. Dans le chapitre IV, nous décrivons une technique de démodulation à poursuite de phase pouvant opérer sur une cible soumise à un déplacement non-périodique. Le développement d'un programme de simulation et de démodulation a permis l'analyse des erreurs de phase, l'effet du bruit aléatoire et du bruit de quantification, etc. Les erreurs de phase peuvent être corrigées par le démodulateur alors que les erreurs dues au bruit peuvent être réduites par une méthode de correction d'amplitude. Des tests expérimentaux réalisés à partir d'excitations de type carré avec un transducteur piézo-électrique (PZT) muni d'un capteur capacitif ont montré un très bon accord sur les mesures (différence de quelques nanomètres seulement). Nous avons utilisé le EFFPI pour deux applications spécifiques. En sismométrie, nous avons montré son aptitude à la mesure d'amplitude et de vitesse des vibrations. Dans une seconde application, le système a permis de mesurer de façon précise les variations de niveau d'un liquide dans un système d'inclinomètrie optique basée sur le principe des vases communicants. Le dernier chapitre donne les conclusions sur le travail réalisé et propose des perspectives afin d'améliorer les performances du capteur développé. ABSTRACT : The work involved in this thesis principally concerns the development and characterization of a dual-cavity Extrinsic Fiber Fabry-Perot Interferometer (EFFPI), with the specific aims of analyzing both periodic and non-periodic vibrations. This thesis is divided into five chapters. In chapter I, we provide a brief overview of vibration measurements and their associated techniques, both optical and non-optical. A general description of the characteristics of fiber optic interferometers most suited for this application is next included. The emphasis on non-contact measurement, geometrical flexibility, accessibility to the mesurand in question and the ease of deployment orientates our choice towards the fiber Fabry-Perot device. Chapter II presents the operating principles of the EFFPI. The device contains a “virtual” pseudo-dual-cavity which is generated due to the introduction of polarization-controlling optics into the optical path of the sensing cavity. This configuration enables two sets of “quadrature phase-shifted” interference signals to be obtained, hence eliminating the problem of directional ambiguity. The general properties of the interferometer, such as its reflectance and fringe visibility, have been characterized. More importantly, the polarization states of the injected and output lightwaves have been studied to further understand polarization-induced signal attenuation with the aim of reducing this parasitic effect. A modified zero-crossing fringe demodulation technique is described in chapter III for processing the interference signals from the dual-cavity EFFPI sensor into useful displacement information. The resolution of the demodulation scheme is determined by the number of sub-levels into which the interference fringes can be divided. In this work, a λ/64 resolution is deemed sufficient for application in periodic vibrations with relatively large amplitudes. Various signal types, such as sinusoidal, square, and triangular excitations have been applied and experimentally verified. Possible errors due to temperature variation of the laser source as well as the target orientation during displacement measurements are also investigated. In chapter IV, a phase-tracking technique is described for demodulating the interference signals into the required/desired displacement of a target subjected to non-periodic vibration. The development of a simulation and demodulation program enables the analysis of out-of-quadrature phase errors, random noise effects, quantization noise, etc. The detected phase errors can subsequently be corrected by the demodulator while the noise can be reduced via an amplitude correction method. Experimental tests under squarewave excitation carried out with a PieZo-electric Transducer (PZT) incorporating a capacitive sensor demonstrated excellent agreement (difference of only a few nanometers). The EFFPI sensor is next employed for two specific applications. In seismometry, the possibility of our sensor for detecting both vibration amplitudes and velocities is aptly demonstrated. In addition, the fiber sensor is also shown to be relatively accurate in measuring liquid level variation in an optical inclinometry set-up based on two communicating short-base vases. The final chapter concludes the work carried out in this thesis and proposes perspectives for further enhancing the performance of the developed senso

Low-Pressure Measurement using an Extrinsic Fiber-Based Fabry-Perot Interferometer for Industrial Applications

The development of an extrinsic fiber-based Fabry-Perot interferometer (EFFPI) for low-pressure measurement in the industry applications has been studied in this work. Monochromatic light from a laser diode with a wavelength of 1310 nm is operated as a source for illuminating the EFFPI sensor. A 30 mm diameter PVC pipe is utilized as a target, of which one end is sealed with a rubber balloon and the end is connected to the air pressure flow controlling system. Furthermore, the center point of the balloon is secured with a reflective thin film, which has a reflectance of ~55%. For the performance validation of the fiber sensor, a low-pressure range from 5 to 50 mBar is released onto the target. With 12 rounds repeatability, the experimental results reported that the average measured pressure values from the EFFPI sensor are 4.915 – 50.988 mBar. When compared to the reference instrument, the maximum and average errors in percentage terms are, however, 3.77% and 1.45%, respectively. In addition, results showed that the measured pressure value is directly proportional to the number of interference fringes, giving a sensitivity in the pressure measurement of the EFFPI sensor of 0.248 mBar/fringe

A design of LED driver circuit for reducing production cost in Thailand industry

In this paper, the designing of a modified flyback converter circuit for 100 Watts LED lighting has been demonstrated. Some important factors, i.e. efficiency (ɛ), power factor (PF), and total harmonic current distortion (THDi), are considered for interpreting the performance of the proposed circuit. A commercial driver circuit which an efficiency of 94% and price of ∼2,000 THB has, consequently, been employed as a reference circuit. Two experimental setups, performance investigation and cost analysis, have been demonstrated for confirming the concept designed. However, the experimental results shown that an efficiency of the developed driver is 93.93%, while the implementation cost is 1,257 THB respectively. Compared with the reference circuit, we found that the performance of modified flyback circuit is almost equivalent in any parameters, while the cost is cheaper than the reference of 37.15%. This implies that there is a possibility to transfer the knowledge of designing concept to mass production for Thailand industry. In addition, it would thus be reduced the investment cost by the importation driver circuits from other countries and also to support Thailand industry for producing the high quality goods for exporting aboard

ระบบตรวจจับใยแก้วนำแสงชนิด ฟาบรี-เปโรต์ อินเทอร์ฟีรอมิเตอร์ สำหรับการประยุกต์ใช้งานด้านวิศวกรรมเมคคาทรอนิกส์Fiber Optic based Fabry-Perot Interferometric Sensor Applied for Mechatronic Engineering

บทคัดย่อบทความนี้นำเสนอการพัฒนาระบบตรวจจับใยแก้วนำแสงชนิด ฟาบรี-เปโรต์ อินเทอร์ฟีรอมิเตอร์ (Fiber optic based Fabry-Perot interferometer: FFPI) สำหรับวัดว่าความเครียดขนาดเล็กของวัตถุ คานอะลูมิเนียม (Cantilever beam) ที่ติดตั้งอยู่กับตัวกระตุ้นแบบไดนามิกส์ (Mechanical vibrator) ถูกเชื่อมต่อเข้ากับเครื่องกำเนิดรูปคลื่นสัญญาณ (Function generator) เพื่อใช้ในการทดลอง นอกจากนั้นตัวตรวจจับความเครียดอ้างอิง (Reference strain gauge) ยังถูกนำมาใช้เพื่อหาค่าความผิดพลาด (Measurement error) ที่เกิดขึ้นจากการวัด โดยการดำเนินการวิจัยสามารถแบ่งออกได้เป็น 2 การทดลองหลัก ๆ คือวัดค่าความเครียดจากการป้อนความถี่กระตุ้น และแอมปลิจูดกระตุ้นแบบซ้ำคาบ และไม่ซ้ำคาบ ตามลำดับ ผลการทดลองพบว่าเมื่อกำหนดให้ความถี่กระตุ้นของสัญญาณแบบซ้ำคาบรูปสามเหลี่ยม (Triangular waveform) มีค่าเท่ากับ 200 เฮิรตซ์ และเปลี่ยนค่าแรงดันกระตุ้นในช่วง 0.25 - 6 โวลต์    ค่าความเครียดที่วัดได้จากระบบตรวจจับใยแก้วนำแสงมีค่าเท่ากับ 0.164 µe - 4.179 µe ขณะที่ค่าความเครียดที่วัดได้จากตัวตรวจจับความเครียดอ้างอิงมีค่าเท่ากับ 0.158 µe - 3.519 µe ตามลำดับ ซึ่งจะมีค่าเปอร์เซ็นต์ความผิดพลาดเฉลี่ยเท่ากับ 2.46% นอกจากนั้นเมื่อดำเนินการป้อนความถี่กระตุ้นวัตถุทดสอบใช้ช่วง 30 - 180 เฮิรตซ์ ระบบตรวจจับ ใยแก้วนำแสงสามารถอ่านค่าความเครียดได้ในช่วงตั้งแต่ 0.158 µe ถึง 3.519 µe ขณะที่เปอร์เซ็นต์ความผิดพลาดเฉลี่ยมีค่าเท่ากับ 2.74% ตามลำดับAbstractThis paper presents a development of a fiber optic based Fabry-Perot interferometer (FFPI) for strain measurements. A cantilever beam with connected to a mechanical vibrator has been interfaced to a function generator for the experiments studying. In addition, a reference strain gauge has, also, been employed for studying the measurement errors. However, the experiments have been divided into 2 main parts; using the amplitude excitation, and also frequency excitation in terms of periodic and non-periodic for strain investigations respectively. By choosing a triangular waveform with an excitation frequency of 200 Hz and varying the excitation amplitude from 0.25 V to 6 V, the output strain obtained from the FFPI sensor has been indicated in the range of 0.164 µe - 4.179 µe, while the output from the reference sensor are 0.158 µe - 3.519 µe, leading to an average percentage error of 2.46% occurred. Moreover, the second experiment has been investigated by inputting the excitation frequency in the range of 30 - 180 Hz driven to the vibrator. The experimental results shown that the fiber optic sensor has been detected the strain value in the range of 0.158 - 3.519 µe, with an average error of 2.74% respectively

Investigation of Fiber Optic-Based-Refractometer for Biogas Sensing

In this study, a fiber-based refractometer (FOR) applied for biogas sensing has been investigated. Two types of fiber, single-mode (SMF) and multimode fiber (MMF) have been proposed as sensing elements. The research aims to investigate the spot and power attenuation of both fiber types in 4 main conditions; fiber cladding, de-cladding, compound coating, and biogas feeding. The experimental results showed that the spot diameters from both fiber types are constantly at 4 and 26 mm in any conditions. This causes the difference in core diameters and also the dispersion of light characteristics within the fibers. Moreover, when the sensing element has been modified by the following conditions, the results indicated that the output intensity has proportionally changed, according to the fiber modification and the concentration of biogas absorbed into the sensing element. Besides, the power attenuation from MMF is larger than SMF. This causes the length of fiber de-cladding and dispersion of light within the MMF can easily be induced by biogas feeding. Therefore, it can be concluded that the MMF is more suitable than SMF for employment as a sensing element of the fiber refractometer

Development of an extrinsic dual-cavity fiber Fabry-Perot interferometer (applications to periodic and non-periodic vibration measurements)

Le travail présenté dans cette thèse concerne le développement et la caractérisation d un interféromètre extrinsèque à double cavités de type Fabry-Pérot (EFFPI) en vue de l'analyse de vibrations périodiques et non périodiques. Le système comprend une cavité virtuelle pseudo-duale obtenue par l'introduction d'une optique de polarisation dans le chemin optique de la cavité de mesure. Cette configuration permet d'obtenir deux signaux d'interférence en quadrature. Deux techniques de démodulation, comptage de frange de type passage à zéro modifiée et poursuite de phase, ont été développées pour démoduler les signaux interférométriques déplacement. Les résultats expérimentaux montrent le potentiel du capteur pour résoudre l'ambiguïté directionnelle du mouvement de la cible, doublant ainsi son résolution par rapport à un interféromètre classique.TOULOUSE-ENSEEIHT (315552331) / SudocSudocFranceF

Validation of Fiber Optic-based Fabry-Perot Interferometer for Simultaneous Heart Rate and Pulse Pressure Measurements

International audienceIn this work, a fiber optic-based Fabry-Perot interferometer (FFPI) developed for simultaneous heart rate (HR) and pulse pressure (PP) measurement was investigated. Particularly, the FFPI was designed with simplicity in configuration for highly precise and non-invasive arterial distension measurement whose output was then demodulated via fringe counting to simultaneously obtain both HR and PP information through fringe pattern analysis and Kirchhoff-Love’s plate theory, respectively. The sensitivity was then characterized by linear fitting of measured PP inducing a number of interference fringes, whose slope represented the FFPI sensitivity. Experiments were conducted both on a simulating device and healthy subjects, each measurement carried out at least 10 times. Obtained results demonstrated the FFPI sensitivity for PP measurement in both experiments to be ~1.916 mmHg/fringe. For HR measurements, an average difference of 1.24% was found when compared to a digital sphygmomanometer employed as reference. Analysis of the FFPI resolution revealed the impact of the fringe counting technique, interrogating wavelength, and sensing material properties on measurement accuracy. Consequently, the thickness of the transducing thin film was found to have the most impact on PP demodulation. Therefore, optimization of the aforementioned parameters could lead to the development of a more accurate FFPI for PP measurement

A software development for investment analysis of LED lighting production project using fuzzy logic technique

International audienceIn this work, an application software for investment decision-making has been developed to analyze thefeasibility level of an LED lighting production project. Particularly, the initial, manufacturing, administration, andfinancial expenses of the project, along with sales income and corporate tax, are applied as financial data. Theseinputs are then calculated into the net present value (NPV), internal rate of return (IRR), benefit-cost ratio (BCR),and discounted payback period (DPB) values, and further synthesized into the investment feasibility level usingfuzzy logic. Additionally, the software allows flexible discount rate variation throughout project duration. Theanalysis results of 5 years duration project show that the NPV, IRR, BCR, and DPB were 6,307,759.46 Thai Baht,24.04%, 1.08, and 3.38 years, respectively. Moreover, with 20% of expected profit margin, the feasibility level ofproject applying the floating discount rate of 7.12%-8.00% was “medium” at 77.89%, while project with fixed8.00% rate suggested the level of “medium” at 67.34%. The discount rate variation, further, implied that using thefloating discount rate was more attractive for the investment. Sensitivity analysis also revealed that the project wasattractive until its income was 3.1% lower and expense was 2.4% higher than original. Therefore, the developedsoftware could be suitable tool for more realistic project feasibility assessment and investment decision-making