In this work we demonstrate the use of optical fiber sensors to measure temperature in thin metallic bonding wires. Temperature was measured in copper wires with diameter of 0.10, 0.28, 0.60 and 0.70 mm and for different values of the driven electrical current (0.75-10.00 A). A theoretical model for the system, which takes into account the relevant heat exchange mechanism, was developed. The results demonstrate the feasibility of the optical sensors application for the measurement of temperature in thin metallic bonding wires. (C) 2010 Elsevier Ltd. All rights reserved.

In this paper, the monitoring of an adobe structure with optical fiber sensors is reported. Static measurements were made during a destructive test on a full-scale wall, in which an in-plane cyclic force was imposed by a hydraulic jack until its collapse. The recorded data with these sensors and the force applied evolution allows to identify the two instants when the major diagonal cracks occur in the wall. Initially, before the cracking, a linear elastic response was observed, corresponding to a deformation at each monitoring point proportional to the applied lateral force, being quantified the relation between the external force and the deformation at each point. This structural test allows demonstrating the feasibility of applying static optical FBG sensors to study the behavior and performance of civil engineering infrastructures even for extreme loading events.

Structural health monitoring is a fundamental tool to guaranty the civil infrastructure lifetime. In this paper, the monitoring of an adobe structure with optical fiber sensors is reported. Static and dynamic measurements were made during a destructive test on a full-scale wall, with an optical fiber accelerometer and a network of thirteen multiplexed displacement sensors. The measured values shown a decrease of 47.8 % in the first natural frequency value, between the initial situation (structure undamaged) and after the cyclic test (structure damaged). The results show very good agreement (maximum relative error in terms of structural frequency of 2.08 %) between the results obtained using electronic sensing technology and the optical sensing technology.

Este trabalho centra-se no desenvolvimento de um sistema, baseado em tecnologia óptica, que permite a identificação das frequências naturais de estruturas especiais de engenharia e que vai de encontro às necessidades de uma monitorização eficaz e de baixo custo. O sistema óptico implementado foi validado através de testes de campo numa ponte pedonal, comparando a resposta medida com a obtida com sensores baseados em tecnologia electrónica. Os resultados alcançados confirmam a viabilidade da solução implementada nas medidas dinâmicas pretendidas para estruturas.

In this paper, the monitoring of an adobe structure with optical fiber sensors is reported. Static measurements were made during a destructive test on a full-scale wall, in which an in-plane cyclic force was imposed by a hydraulic jack until its collapse. The recorded data with these sensors and the force applied evolution allows to identify the two instants when the major diagonal cracks occur in the wall. Initially, before the cracking, a linear elastic response was observed, corresponding to a deformation at each monitoring point proportional to the applied lateral force, being quantified the relation between the external force and the deformation at each point. This structural test allows demonstrating the feasibility of applying static optical FBG sensors to study the behavior and performance of civil engineering infrastructures even for extreme loading events.

Fiber optical sensors, namely Fiber Bragg gratings, are one the most promising technologies in several sensing systems. This sensing technology could be useful and cost effective in most civil engineering infrastructures. FBG sensors take advantage of the optical fiber properties, such us low transmission losses, immunity to electromagnetic interference, light weight and electrical isolation. But also, since the information is codified in the optical domain, they can be used in hostile environments, where electrical currents of electronic devices might pose a hazard. In this work we proposed the application of optical FBG based accelerometers to monitor two structures: a reinforced concrete building and a steel footbridge. The results show that optical monitoring schemes can be used in structural health monitorization of large structures, being a low cost solution. The two implemented acceleration systems, with different interrogation techniques allow to successfully obtaining the eigenfrequencies of structures with an error, when compared with the value obtained with a reference electronic accelerometer inferior to 0.80 %.

In this work the dynamic monitoring of a self supported telecommunications tower is presented. The feasibility of an optical FBG biaxial accelerometer to obtain the structure natural frequencies is demonstrated, recurring only to natural loading.

The dynamic monitoring of a tower for mobile communications with 50 meters high using a bi-axial optical accelerometer is reported. The resonant frequencies for the first modes were obtained, being consistent with the expected values.