Fiber Fabry-Perot interferometer (FFPI) sensor using vertical cavity surface emitting laser (VCSEL)

This research represents the first effort to apply vertical cavity surface emitting lasers (VCSELs) to the monitoring of interferometric fiber optic sensors. Modulation of the drive current causes thermal tuning of the laser light frequency. Reflection of this frequency-modulated light from a fiber Fabry-Perot interferometer (FFPI) sensor produces fringe patterns which can be used to measure the optical path difference of the sensor. Spectral characteristics were measured for 850nm VCSELs to determine the combination of dc bias current, modulation current amplitude and modulation frequency for which single mode VCSEL operation and regular fringe patterns are achieved. The response characteristics of FFPI sensors were determined experimentally for square, triangular, saw-tooth waveforms at frequencies from 10kHz to 100kHz. The dependence of VCSEL frequency on the dc bias current was determined from spectral measurements to be ~165GHz/mA. An independent measurement of this quantity based on counting fringes from the FFPI sensor as the laser modulated was in good agreement with this value. The effect of optical feedback into the laser was also studied. By observing the fringe shift as the FFPI sensor was heated, a fractional change in optical length with temperature of 6.95 X 10-6/ðC was determined in good agreement with previous measurements on a 1300nm single mode fiber. The performance of 850nm VCSEL/FFPI systems was compared with their counterparts using 1300nm distributed feedback (DFB) lasers. The results of these experiments show that the 850nm VCSEL/FFPI combination gives regular fringe patterns at much lower bias current and modulating current amplitudes than their 1300nm DFB/FFPI counterparts

Simultaneous measurement of humidity and vibration based on a nanowire sensor system using Fast Fourier Transform technique

This paper presents a new sensor system for vibration and relative humidity measurements based on its interaction with the evanescent field of a microwire. The interrogation of the sensing head is carried out by monitoring the fast Fourier transform (FFT) phase of one of the FFT peaks of the microwire transmission signal. This technique is not dependent of the signal amplitude and also eludes the requisite of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency ...This work was supported in part by the Spanish Comisión Interministerial de Ciencia y Tecnología within project TEC2013-47264-C2-2-R and SUDOE ECOAL-MGT and FEDER funds from the European Union

Novel approaches to the construction of miniaturized analytical instrumentation

This paper focuses on the design, construction, preliminary testing, and potential applications of three forms of miniaturized analytical instrumentation. The first is an optical fiber instrument for monitoring pH and other cations in aqueous solutions. The instrument couples chemically selective indicators that were immobilized at porous polymeric films with a hardware package that provides the excitation light source, required optical components, and detection and data processing hardware. The second is a new form of a piezoelectric mass sensor. The sensor was fabricated by the deposition of a thin (5.5 micron) film of piezoelectric aluminum nitride (AIN). The completed deposition process yields a thin film resonator (TFR) that is shaped as a 400 micron square and supports a standing bulk acoustic wave in a longitudinal mode at frequencies of approx. 1 GHz. Various deposition and vapor sorption studies indicate that the mass sensitivity of the TFR's rival those of the most sensitive mass sensors currently available, though offering such performance in a markedly smaller device. The third couples a novel form of liquid chromatography with microlithographic miniaturization techniques. The status of the miniaturization effort, the goal of which is to achieve chip-scale separations, is briefly discussed

Recent Advances in Lossy Mode Resonance-Based Fiber Optic Sensors: A Review

Fiber optic sensors (FOSs) based on the lossy mode resonance (LMR) technique have gained substantial attention from the scientific community. The LMR technique displays several important features over the conventional surface plasmon resonance (SPR) phenomenon, for planning extremely sensitive FOSs. Unlike SPR, which mainly utilizes the thin film of metals, a wide range of materials such as conducting metal oxides and polymers support LMR. The past several years have witnessed a remarkable development in the field of LMR-based fiber optic sensors; through this review, we have tried to summarize the overall development of LMR-based fiber optic sensors. This review article not only provides the fundamental understanding and detailed explanation of LMR generation but also sheds light on the setup/configuration required to excite the lossy modes. Several geometries explored in the literature so far have also been addressed. In addition, this review includes a survey of the different materials capable of supporting lossy modes and explores new possible LMR supporting materials and their potential applications in sensing

Optical fiber sensors: a route from University of Kent to Portugal

In this work the authors first summarily describe the main topics that were the subject of their post-graduate activity in fiber sensing at the Applied Optics Group of University of Kent in the late 1980s and early 1990s. After their return to Porto, Portugal, the know-how acquired during their stay at Kent and the collaboration paths that followed between the University of Porto and University of Kent were instrumental in the start-up and progress of optical fiber sensing activity in Portugal. The main topics addressed in this field, the description of some of the relevant developments achieved in recent years, the present situation and the guidelines for the future research and development activity in Portugal in fiber sensing will be the core of this work.info:eu-repo/semantics/publishedVersio

Temperature and Pressure Sensors Based on Spin-Allowed Broadband Luminescence of Doped Orthorhombic Perovskite Structures

Systems and methods that are capable of measuring pressure or temperature based on luminescence are discussed herein. These systems and methods are based on spin-allowed broadband luminescence of sensors with orthorhombic perovskite structures of rare earth aluminates doped with chromium or similar transition metals, such as chromium-doped gadolinium aluminate. Luminescence from these sensors can be measured to determine at least one of temperature or pressure, based on either the intense luminescence of these sensors, even at high temperatures, or low temperature techniques discussed herein

Development of high-speed fibre-optical laser scanning system for defect recogntion

High-speed fibre-optic laser scanning systems are being used in automated industrial manufacturing environments to determine surface defects. Recent methods of surface defect detection involve the use of fibre-optic light emitting and detection assemblies. This thesis deals with the design and development o f a new high-speed photoelectronic system. In this work, two sources of emitting diode were examined, LED (light emitting diode) and laser diode. A line of five emitting diodes and five receiving photodiodes were used as light sources and detectors respectively. These arrays of emitting diodes and photodectectors were positioned opposite each other. Data capture was controlled and analysed by PC using Labview software. The system was used to measure the dimensions of the surface defects, such as holes (1 mm), blind holes (2 mm) and notches in different materials. The achieved results show that even though this system was used mainly for 2-D scanning, it may also be operated as a limited 3-D vision inspection system. This system furthermore showed that all the metal materials examined were able to reflect a signal of the infrared wavelength. A newly developed technique o f using an angled array o f fibres allows an adjustable resolution to be obtained with the system, with a maximum system resolution of approximately 1 0 0 |im (the diameter o f the collecting fibre core). This system was successfully used to measure various materials surface profile, surface roughness, thickness, and reflectivity. Aluminum, stainless steel, brass, copper, tufnol, and polycarbonate materials were all capable of being examined with the system. The advantages of this new system may be seen as faster detection, lower cost, less bulky, greater resolution and flexibility

Integrated optics technology study

The status and near term potential of materials and processes available for the fabrication of single mode integrated electro-optical components are discussed. Issues discussed are host material and orientation, waveguide formation, optical loss mechanisms, wavelength selection, polarization effects and control, laser to integrated optics coupling fiber optic waveguides to integrated optics coupling, sources, and detectors. Recommendations of the best materials, technology, and processes for fabrication of integrated optical components for communications and fiber gyro applications are given