1,721,020 research outputs found
Optical characterization techniques for the characterization of semiconductor devices and materials
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Multifunction fiber optic sensing system for smart applications
No full textThe end of the twentieth century was witness to the merger of several technological disciplines that could eventually revolutionize engineering design philosophy and lead to the creation of intelligence within otherwise inanimate structures. This new technology will endow a structure with senses and the ability to react to its environment and change its state, shape and geometry. The key point for the practical realization of the so-called smart materials is the availability of robust and reliable structurally integrated sensors able to monitor the state of the structure. To this aim, a fiber optic multiparameter sensing system for process and structural health monitoring in concrete structures is presented. The reflectometric technique has been implemented for refractive-index measurements by using as transducer the fiber end /host interface. Results on the capability of the developed sensor to monitor the curing process of thermoset-based composites are presented. The integration with fiber Bragg gratings (FBGs) with the aim to perform temperature and strain measurements has been discussed. Two low-cost intensity-based demodulation techniques for FBGs interrogation have been developed and tested
Fiber optic sensor arrays: a new method to improve multiplexing capability with a low complexity approach
No full textIn this paper, we show some preliminary numerical results in order to increase the multiplexing capability of a multipoint fiber Bragg grating (FBG) sensor network without increase the system complexity. We base the new approach on the possibility of exploiting the chirped-pulsed frequency modulation technique (C-PFM). This technique, extensively used in radar applications, is based on the amplitude modulation of the emitted signal (pulsed) by a chirped frequency signal and on the demodulation of the reflected signal by means of adaptive filter. FBG sensors are instrumental to obtain cheap and easy handling multipoint sensing arrays
SYSTEM FOR REAL-TIME MONITORING OF THE STATE OF OCCUPATION OF RAILWAY LINES
No full textAxle-count automatic-block system for monitoring the state of occupation of a section of railway line by means of sensors designed to count the number of axles of railway vehicles that enter the section of line, the system comprising two optical-fibre Bragg-grating sensors, which are mounted at a distance from one another in positions corresponding to end portions of a section of railway line to be monitored and identify a block section, connected by means of an optical fibre to a querying system, which is able to send a light radiation to the sensors and process the radiation back-reflected by each of the sensors in order to acquire the information on the direction of travel of the railway vehicles and on the state of occupation of the block section
NUOVE CONFIGURAZIONI DI MODULATORI DI AMPIEZZA ULTRA VELOCI PER COMUNICAZIONI IN FIBRA OTTICA PER RETI DI TELECOMUNICAZIONI A LARGA BANDA.
No full textNUOVE CONFIGURAZIONI DI MODULATORI DI AMPIEZZA ULTRA VELOCI PER COMUNICAZIONI IN FIBRA OTTICA PER RETI DI TELECOMUNICAZIONI A LARGA BANDA.
No full textChirped-pulsed frequency modulation (C-PFM) for fiber Bragg grating sensors multiplexing
No full textIn this paper, we present experimental demonstration Of using chirped-pulscd frequency modulation technique (C-PFM) in order to increase the multiplexing capability of a multipoint fiber Bragg grating (FBG) sensor network without. increasing the hardware complexity of the acquisition system. This technique, extensively used in radar applications, is based on the amplitude modulation of the emitted signal (Pulsed) by a chirped frequency signal and on the use of an adaptive filter for the demodulation of the reflected signals. Here, the same principle has been used to develop a FBG multisensor interrogation system by employing a proper frecquency chirped modulation. The optical signals reflected from the FBG sensors are first interrogated by using an in-fiber edge filter and discriminated by a novel adaptive numerical filtering. The potentiality and limitation of such technique are discussed. Preliminary experimental results are presented
Characterization of long period gratings in hollow core fiber fabricated via electrode arc discharge
No full textIn this paper we report on the fabrication and characterization of Long Period Gratings (LPGs) in hollow-core air-silica photonic bandgap fibers (HC-PCFs). The fabrication procedure is based on a pressure assisted Electrode Arc Discharge (EAD) technique. It relies on the combined use of EAD step, to locally heat the HC fiber, and of a static pressure (slightly higher than the external one) inside the fiber holes, to modify the holes. Here, the experimental fabrication of LPG prototypes with different periods and lengths are discussed. And, the sensitivity of LPGs in HC-PCF to environmental parameters such as strain, temperature and static pressure are presented and discussed. © 2014 AEIT
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