Papers by Keyword: Fiber Optic Sensor

Abstract: The paper deals with the experimental analysis focused on the determination of strain in wooden building structures using optical fibers with FBG sensors. Firstly, optical fibers were used to measure displacements of layers and surface strain of the lower surface of the ceiling panels made from mechanically jointed cross laminated timber (CLT). The measured displacement values of the optical fibers were compared with the results obtained from the inductive displacement sensors. Secondly, optical fibers were used for long-term monitoring of the roof structure of the sports hall. The fibers were mounted on chords of timber trusses and their correct function was verified by a load test.

Abstract: This article describes experimental research on properties of adhesive joints with embedded optical fibers. The objective was to determine whether fibers may cause a reduction of mechanical properties of joints. Specimens with single-lap joint for tensile test were made with various configurations of optical fibers in an adhesive layer. Shear strength and fatigue life tests were performed and results were evaluated using the statistical analysis methods.

Abstract: Tumor therapy using the high-energy radiation has evolved over the decades as typical non-invasive treatment method due to its advantage compared with surgery. But, the radiotherapy can damage or destroy normal cells as well as destroying tumor cells and cause side effects of treatment. Even though most side effects are temporary, these effects can be extremely fatal for patient. Therefore, the exact measurement of the exposure dose of patient during radiation therapy is very important for patient safety. In the case of the conventional fiber-optic radiation sensor that consists of a scintillator for high-energy radiation dosimetry, additional correction is necessary due to the quenching effects of the scintillator. In this study, we measured the exposure dose of the high-energy proton beam without the scintillator by using the Cerenkov radiation that generated inside the plastic optical fiber. As a result of this study, we confirmed a Bragg peak of the proton beam without a scintillator. Also it was in good agreement with the result of the ionization chamber.

Abstract: The work describes the constructions of optical fiber based minimal invasive sensing system to measure pH and dissolved oxygen using sol-gel membranes which are attached internally in any transparent container. The disposable sensing membranes are very thin size and prepared as fluorescent dye doped in silica film using simple procedures. The sensor characteristics such as response time, linearity, repeatability and reversibility are evaluated and the performance of the sensor also compared with commercial meters. The experiments such as, chemical stability and photo stability are also carried out. The detection limit of pH sensor is found between 3 pH and 10 pH, however good sensitivity is obtained for the ranges from 4 pH and 9 pH with the response time of 7 seconds. Non-linear response is obtained for dissolved oxygen sensor and it is made linear by applying Stern-Volmer equation. The oxygen sensor shows good sensitivity in the ranges from 2 mg/L to 8 mg/L.

Abstract: There are many factors that can effect on accuracy of reflective intensity-modulated fiber optic sensor (RIM-FOS). Operational object is a major element among them to fiber optic sensor, which is used in measurement of dynamic and static clearance of steam turbine, studied in this topic. For this reason, this letter researches on scattering characteristic of light on surface of medium and distributed function of outline of medium’s surface, and computes and analyzes on their effect on measuring. All of above are benefit to improve accuracy of this kind of sensors.

Abstract: For marine water pollution problems, According to the phenomenon that the refractive index of the seawater will change after been polluted .we designed a new fiber optical sensor, and completed a marine pollution monitoring automatic warning system with the sensor. One S (single mode)-M (multimode)-S-M-S structural optical fiber sensor based on the theory of M-Z Interference was made. Due to de refractive index of the fiber cladding will be affected by the environmental solution. We can determine the relationship between the movement of interference spectrum and the refractive index of the solution. With a center wavelength of 1553nm fiber Bragg grating and a coupler to obtain the change of the intensity of the light, then though the specific circuit, we can change the light intensity into the voltage values. Then enter the computer through the acquisition card, real-time reporting of environmental refractive index size, and according to the software set threshold alarms. The refractive index in the range of 1.330-1.390, the system of measurement error is less than 1%.

Abstract: As AFM tip approach speed is one of the key factors for AFM industrial on-line detection application, a sectional fast tip approach method composed of rough approach and mild approach processes is introduced here. In rough approach process, AFM tip can be approached by step motor to certain distance upon the sample surface with high speed, as a homemade dual-channel reflective intensity modulated fiber optic displacement sensor (DC-RIMFODS) can be integrated to AFM scan head easily to detect the stop position. While continued with mild approach process after rough approach, step motor can run slowly with a common PI feedback controller for Z scanner to make the tip get in touch with sample surface softly. Experimental results show that with the well-defined fiber optical sensor positioning accuracy and repeatability, the tip-sample distance can be limited in certain range after rough approach with 1mm/s high speed, and the whole AFM tip approach process can be finished in 20s by continuing with mild approach, while the initial tip-sample distance is about 10mm.

Abstract: We consider an interferometric fiber optic current sensor with a fiber coil operated in reflection and compare three different techniques to prepare the coil: thermally annealed coils, stress-free packaging of a bare low birefringent fiber in a fused silica capillary, and coils from highly birefringent spun fiber. In particular we theoretically and experimentally investigate how the fiber retarder that generates the near left and right circular light waves in the sensing fiber must be prepared for temperature compensation of the Faraday effect in the three cases. All three methods can achieve accuracy within ±<0.2% over an extended temperature range but they considerably differ in their practical challenges.

Abstract: Theoretical analysis of surface plasmon resonance ber optic sensor based on a core-shell nanoparticle layer is presented. The sensing structure consists of a standard step-indexmultimode optical ber whose bare fused silica core is coated by Ag core-shell nanoparticlemonolayer. Its optical constants were obtained using e ective media (Maxwell-Garnett) theory.Theoretical model based on thin- lm optics approach is used to compute the normalized powertransfer through the sensing part of the ber in spectral domain. The computed results areused to obtain the sensitivity and detection accuracy of the sensing scheme with respect tothe concentration of analyte components. The inuence of nanoparticle geometry on the sensorperformance is discussed.

Abstract: We outline the development and application of the Autonomous Fibre-Optic Rotational Seismograph (AFORS), which utilizes the Sagnac effect for a direct measurement of seismic rotation. The main advantage of AFORS is it complete insensitivity to linear motions as well as a direct measurement of rotational components emitted during seismic events. The presented system contains a special autonomous signal processing unit which optimizes its operation for the measurement of rotation motions, whereas applied telemetric system based on the Internet allows for a remote AFORS control. The laboratory investigation of the two such devices indicated they keep accuracy no less than 5.1·10^-9 to 5.5·10^-8 rad/s in the frequency bandpass from 0.83 Hz to 106.15 Hz with protect linear changes of sensitivity in above bandpass. The experimental results of AFORS-1 application for continuous monitoring the rotational events in the Książ (Poland) seismological observatory are also presented.