The paper discusses the evaluation of displacements and accelerations from non-contact displacement measurements using a low-cost plastic fiber optic sensor.Issues about the sensor calibration in the presence of nonuniform targets, a situation occurring in many practical applications like vibration tests of printed circuit board assemblies, are analyzed. Furthermore, 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 is particularly effective since it 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 provided.

The paper analyzes the performance of a dualwavelength 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 sensors.

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Sensors able to measure curvature changes are emerging as an effective alternative to the more common strain gauges in structural health monitoring. Particularly interesting is the optical fiber implementation of such sensors and this paper discusses the design and characterization of a simple, cheap, and compact curvature sensor based on plastic optical fibers. A characterization setup is also proposed in order to test the sensor performances with dynamic deformations.