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Fiber-Optic Sensors
Dejdar, Petr ; Róka,, Rastislav (referee) ; Kyselák, Martin (referee) ; Münster, Petr (advisor)
Optical networks are continuously expanding and this creating space for the use of optical fibers for non-data transmissions. One of them is the use for sensing purposes, where optical fibers can be used to measure temperature, pressure, vibration, etc. In standard conditions or in conditions where the placement of conventional sensors is not suitable (increased humidity, radiation, lack of space, etc.).This paper is devoted to the comparison of technologies comparing sensing systems and describes their principle and their possible applications. Subsequently, the different systems are built and tested. Possible improvements are then proposed based on the measurements, where for the reflectometric system the advantages of using edge detection algorithms are quantified. For the polarization detectors, improvements are made using machine learning classification algorithms with classification success rates above 97 %. Detailed measurements of the sensitivity of optical fibers to acoustic vibrations in three different environments, with different path configurations, cables, vibration-damping materials, etc. are also described. These measurements proved the possibility of intercepting optical fibers using interferometric, reflectometric, and polarization systems, where the polarization system is proven to be the least sensitive and records only lower frequencies. Based on these measurements, a system for securing the physical layer of optical networks is then proposed, which is able to accurately distinguish the quiescent and cable manipulation states from the datasets we created.
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Optical fiber sensors for measurement strain and vibration
Mikel, Břetislav ; Helán, R. ; Buchta, Zdeněk ; Holík, M. ; Jelínek, Michal ; Číp, Ondřej
We present optical fiber sensors to measurement strain and vibration. The sensors are based on fiber Bragg gratings (FBG). We prepared construction of strain sensors with respect to its implementation on the outer surface of concrete structures and with compensation of potential temperature drifts. These sensors are projected with look forward to maximal elongation and strength which can be applied to the sensor. Each sensor contains two optical fibers with FBGs. One FBG is glued into the sensor in points of fixation which are in the line with mounting holes. This FBG is prestressed to half of measurement range, than the stretching and pressing can be measured simultaneously by one FBG. The second FBG is placed inside the sensor without fixation to measure temperature drifts. The sensor can be used to structure health monitoring.
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Optical fiber sensors and optical fiber splicing
Jelínek, Michal ; Mikel, Břetislav
We present development of new methods and techniques of the splicing and shaping optical fibers. We developed new techniques of splicing for standard Single Mode (SM) and Multimode (MM) optical fibers and optical fibers with different diameters. Together with development these techniques we prepared other techniques to splicing hollow core Photonic Crystal Fiber (PCF) and theirs cross splicing methods.Development of these new techniques and methods of the optical fibers splicing are made with respect to using these fibers to another research and development in the field of optical fibers sensors.
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Optical fiber senzors to measurement length, pressure, tension, temperature and vibration
Mikel, Břetislav
We present new optical fiber sensors based on fiber Bragg gratings to measurement length, pressure, tension, temperature and vibration. We developed systems to monitoring several types of sensors. Measurement of length, tension, pressure and temperature is realized on the same principle of measurement spectral properties of sensors. We used optical filter based system to monitoring optical spectrum reflected from sensors in our system. Sensor with tilted fiber Bragg grating in tapered optical fiber we used to monitoring vibration. This ghost mode reflected from tilted fiber Bragg grating is recoupled into the fiber core in tapered prat of fiber. The measurement system can measure only optical power.
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Laser interferometry with optical fibers and fiber Bragg gratings
Mikel, Břetislav
Optical fibers and fiber Bragg grating can improve using of standard laser interferometry methods in industry applications. Especially fiber Bragg gratings can improve frequency parameters of laser diodes in the laser interferometers. These parameters increase resolution and measurement range of the laser interferometer.
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