doktorska disertacija
Andraž Javernik (Author), Denis Đonlagić (Mentor)

Abstract

Sistemi za spektralno razločevanje optičnovlakenskih senzorjev so dandanes kljub hitremu razvoju optičnih senzorjev še vedno dokaj kompleksni in posledično dragi, kar preprečuje uvajanje optičnih vlakenskih senzorjev v širši spekter industrijskih in drugih aplikacij. V okviru doktorske disertacije smo raziskali in izdelali merilni sistem, s katerim lahko spektralno razločujemo optičnovlakenske senzorje, ki temeljijo na Fabry-Perotovem interferometru. Merilni sistem, ki je predmet doktorske disertacije, je bil izdelan izključno iz majhnega števila cenenih telekomunikacijskih elektro-optičnih komponent. Za nastavljiv laserski vir smo tako uporabili lasersko diodo DFB, ki smo jo vzbujali s tokovnimi sunki višjih amplitud. Pravilna oblika tokovnega sunka skozi lasersko diodo DFB, selektivno in časovno linearno segreje aktivno področje, kar povzroči linearen zamik valovne dolžine izsevanega optičnega spektra za okoli 11 nm. Pri tokovnem vzbujanju laserske diode DFB se tako generira valovno-dolžinsko zamaknjen optični sunek, s katerim razločimo dolžino Fabry-Perotovega interferometra tako, da opazujemo odbito svetlobno valovanje t.i. interferenčni vzorec, ki ima značilno kosinusno obliko. Z uporabo tehnike merjenja faze v kosinusni spektralni karakteristiki Fabry-Perotovega interferometra lahko razločimo informacijo o merjeni veličini. S predlaganim merilnim sistemom lahko zaznavamo spremembo optične poti preko zaznavanja spremembe faze v spektru Fabry-Perotovega interferometra s frekvenco vzorčenja 40 kHz in ločljivostjo zaznavanja optične poti 2,7 nm. Če uporabimo digitalno filtriranje zajetih merilnih vrednosti, pri čemer zmanjšamo pasovno širino merilnega sistema na 1 Hz, lahko zaznavamo spremembe optične poti v Fabry-Perotovem interferometru z ločljivostjo 46 pm (npr. polmer atoma vodika znaša rB = 53 pm). Zaradi naslavljanja Fabry-Perotovih senzorjev s kratkimi optičnimi sunki lahko spektralno razločujemo tudi več Fabry-Perotovih optičnih senzorjev z različnimi ali enakimi nazivnimi dolžinami. Predstavljen merilni sistem za spektralno razločevanje Fabry-Perotovih senzorjev omogoča zasnovo stroškovno ugodnega senzorskega sistema, s katerim lahko z visoko ločljivostjo izvajamo statično ali dinamično meritev poljubne fizikalne veličine. V okviru disertacije so z uporabo predlaganega sistema za razločevanje Fabry-Perotovih interferometrov prikazane visoko-ločljive meritve raztezkov, tlakov, temperature, lomnega količnika in jakosti električnega polja. V ta namen smo uskladili nekatere obstoječe senzorje s predlaganim sistemom za razločevanje oz. uporabili nove rešitve za zaznavanje električne poljske jakosti.

Keywords

optična vlakna;merilni sistemi;temperaturna kompenzacija;laserske diode DFB;generatorji tokovnih sunkov;visokoločljive meritve;senzorji električnega polja;tlačni senzorji;senzorji lomnega količnika;senzorji raztezka;temperaturni senzorji;

Data

Language: Slovenian
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UM FERI - Faculty of Electrical Engineering and Computer Science
Publisher: [A. Javernik]
UDC: 681.586.5:681.7.068(043.3)
COBISS: 296203008 Link will open in a new window
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Other data

Secondary language: English
Secondary title: High-speed Fabry-Perot sensor interrogation system
Secondary abstract: Efficient signal interrogation of fiber-based sensors still presents a major challenge that limits the introduction of these sensors into a broad span of practical applications. This is an even more pronounced problem when there is a need for measurements requiring a high-speed signal interrogation. Research conducted in our dissertation lead to fabrication of a novel interrogation system for fiber optic sensors employing Fabry-Perot interferometry (FPI). The proposed system was built out of a small number of highly cost-efficient optoelectronics and electronics components and has the potential to yield in applications, where the cost of interrogation is presently limiting, while preserving the resolution and stability of conventional spectral resolved methods. The proposed system was built around a standard Telecom distributed-feedback (DFB) laser diode, which was driven by short and high-amplitude current pulses. When a small active region diode is driven by a short and high-amplitude current pulse, rapid and selective heating occurs of the diode’s region and its immediate vicinity. Since the diode’s distributed feedback structure resides in the vicinity of the diode’s active region, this leads to a rapid and significant wavelength shift for about 11 nm of emitted optical spectrum. Produced high-power and extensive frequency-swept optical pulses were then guided to one or more all-fiber FPIs, which back-reflected part of the incoming frequency swept light. Back-reflected optical pulses were modulated over time due to the FPIs’ distinctive and periodic spectral characteristics. Real-time signal processing through multiplication of the incoming data vector with sine and cosine matrices were then utilized to extract phases of the spectral fringes of the interrogated one or multiple FPIs. The achieved FPI optical path length measurement resolution was in the range of 2.7 nm at a 40 KHz sampling rate. When the low pass filter was applied to reduce the system bandwidth to 1 Hz the resolution corresponded to about 46 pm. For comparison, the radius of the hydrogen atom (H) is 53 pm. Proposed solution presents a cost efficient, high resolution interrogation system for dynamic and static measurements, that can resolve multiple Fabry-Perot Interferometers simultaneously, which might include multiple sensors, multi-parameter sensors, or combinations of sensor(s) and reference FPIs. High-resolution interrogation was demonstrated employing fiber optic Fabry-Perot sensors for measuring a variety of physical parameters, such as strain, pressure, temperature, refractive index and electric field intensity for which a novel sensor was presented.
Secondary keywords: optical fiber;Fabry-Perot interferometer;sensors;measuring system;temperature compensation;DFB laser diode;current pulse generator;high-resolution measurements;electric field sensors;pressure sensor;strain sensors;reflective index sensor;Senzorji;Disertacije;Fabry-Perotovi interferometri;
URN: URN:SI:UM:
Type (COBISS): Doctoral dissertation
Thesis comment: Univ. v Mariboru, Fak. za elektrotehniko, računalništvo in informatiko
Pages: XXIII, 212 str.
ID: 10954616