1,720,974 research outputs found
A Fiber Optical Sensor For Non-Contact Vibration Measurements
Full text linkThis paper describes an intensity based optical sensor for the evaluation of accelerations from non-contact displacement measurements. Plastic optical fibers are used to collect the reflected light from several points on the vibrating surface, allowing the reconstruction of the vibration distribution. Two compensation techniques to reduce systematic effects due to the target reflectivity are also described and compared: one is based on the spectral analysis of the received optical signal and the other takes advantage of a reference displacement sensor. Experimental results in real conditions during vibration tests have demonstrated the capability to measure sub-micrometer vibration amplitudes up to about 40 kH
A fiber optic sensor for displacement and acceleration measurements in vibration tests
Full text linkThe paper describes a plastic optical fiber sensor for the evaluation of accelerations from non-contact displacement measurements and highlights the issues concerning its calibration in practical applications, like vibration tests of printed circuit board assemblies. A procedure to contemporaneously calibrate several optical sensors to allow mapping the vibration amplitude and acceleration distributions in a simple and low cost way is also disclosed. The proposed calibration procedure requires just one reference accelerometer, which is actually already available in typical vibration test facilities. Experimental results obtained in real conditions during a sinusoidal vibration test are also provide
Issues concerning intensity-based fiber sensors for non-contact vibration monitoring
No full textThe paper describes a simple fiber optic sensor for non-contact vibration measurements. The sensor is based on a couple of optical fibers placed in front of a vibrating target and derives the vibration amplitude from the changes of the reflected light intensity. A model of the optical sensor is introduced to predict the sensor behavior in different working conditions and for different sensor configurations. Then, issues concerning the sensor calibration in the presence of arbitrary targets, the choice of the sensor working distance, the strategies for sensitivity enhancement and the noise effects are investigated
Static Characterization of Curvature Sensors Based on Plastic Optical Fibers
Full text linkSensors able to measure curvature changes are emerging as an effective alternative to the more common strain gauges for structural health monitoring applications. Particularly interesting is the all-optical fiber implementation for its unique properties and the possibility of being embedded. This paper, after a brief description of curvature sensors using plastic optical fibers, focuses on their characterization in applications where high sensitivity is required, and compares their performance with commercial strain sensors based on fiber Bragg gratings. The choice of plastic optical fibers allows the realization of simple, compact and cheap sensors. A characterization setup to test different sensor typologies is proposed and the main uncertainty contributions are investigate
Optical fiber sensors for long- and short-term crack monitoring
No full textThis paper describes a fiber displacement sensor and analyzes its performance in evaluating the evolution of cracks for structural health monitoring applications, both over short and long time periods. The sensor is based on plastic optical fibers, a choice that allows having all the advantages typical of optical fibers, but with costs comparable to the more common electro-mechanical systems. Two sensor topologies have been realized and some experimental results about laboratory and in field tests are reported to assess the effectiveness of the proposed solutio
Plastic optical fiber sensor for displacement monitoring with dual-wavelength compensation of power fluctuations
No full textThe paper describes the use of a dual-wavelength technique for compensating power fluctuations in intensity-based plastic optical fiber sensors for displacement measurements. The sensor consists of a fiber that collects the reflected light from a target and retrieves its distance from the signal attenuation. Besides a measurement signal at 450 nm that travels back and forth the displacement region and is attenuated according to the target position, a compensation signal at 650 nm propagates along the fiber and is back-reflected at the fiber tip by a dichroic filter. The compensation signal undergoes power fluctuations due to environmental stress of the fiber and is therefore used as a reference to correct the measurement signal. A demonstrator, which includes a sensor, the acquisition circuitry and signal processing software, was built and tested in laboratory and proved that the measurement signal is capable of monitoring displacements in the range (0 ÷ 10) mm even at low power, while the reference signal is not influenced by the position of the reflecting target and can therefore be used as reliable referenc
Assessment of a Dual-Wavelength Compensation Technique for Displacement Sensors Using Plastic Optical Fibers
Full text linkThe paper analyzes the performance of a dual-wavelength technique devised to compensate power fluctuations in intensity-modulated plastic optical fiber sensors, which were specifically conceived for the measurement of displacements in industrial and civil applications. These sensors retrieve the displacement from the variation of the attenuation along the light path and use two signals at different wavelengths to compensate for the effects of parasitic quantities, such as temperature and strains along the fiber. The theoretical behavior of the compensation technique is presented, and the results of experiments carried out with different combinations of signal wavelengths and plastic fibers are reported. The experimental setup has proved that, by proper choice of the compensation signal wavelength, it is possible to monitor displacements in the range (0 to 10) mm, even for low received power and under severe perturbation conditions, thus significantly improving the long-term stability of the sensor
An Intensity Based Fiber Accelerometer
No full textThe paper presents a low cost, compact, fiber optic sensor for measuring acceleration in environmentally harsh industrial applications. The sensor is based on the deformation of a cantilever measured through the variation of the propagation loss of a plastic optical fiber fixed on its surface. In order to enhance the sensitivity to bending, the fiber surface has been modified with grooves extending to part of the core. Preliminary experimental results have confirmed the feasibility of the proposed approach and the possibility to use the sensor both as an accelerometer and as a seismomete
- …
