Electronics Components World - Fiber Optic Sensors In Aircraft Manufacturing http://www.electronicscomponents world.com/articleView~idArticle~72780_7633216152032007.html 1 von 9 10.05 … … 2007 11:48 Home About Us Contact Us News Buyer’s Guide Search Advertise News Newsletter Industry News New Products Industry People Events Diary Products Buyer’s Guide Articles Tech Articles Archives Recruitment Jobs (New) Fiber Optic Sensors In Aircraft Manufacturing Publication date: 20 March 2007 Fiber Optic Sensors In Aircraft …

News Newsletter Industry News New Products Industry People Events Diary Products Buyer’s Guide Articles Tech Articles Archives Recruitment Jobs (New) Fiber Optic Sensors In Aircraft Manufacturing Publication date: 20 March 2007 Fiber Optic Sensors In Aircraft Manufacturing Fiber Bragg gratings increase the reliability of future Airbus generations (Bob Grietens, XenICs, Leuven, Belgium and Marc Voet, FOS&S, Geel, Belgium) New fiber reinforced composite materials and integrated sensors are converging to form smart structural components. They excel by their higher reliability, lead to more economical maintenance procedures and contribute significantly to reducing the cost of operating air fleets. The economics of aircraft operation…. Fiber optic sensors It is quite obvious that fiber-based sensors and sensor arrays are a good choice to monitor fiber composites. Fiber optic sensors, in contrast to traditional electrical sensors, offer significant advantages which suit them for component monitoring in vehicles of all types: . They are robust and corrosion-free passive components, and excel by a high life expectancy of more than 20 years. . Their measurement function is based on a special location-based property of glass fibers, which enables signal transmission over more than a several kilometers. . Fiber optic sensors are not impacted by electromagnetic radiation. They function under extremely harsh usage conditions, which regular sensors would not survive. . Neither sensor function nor data transmission require electrical signals or metallic conductors. They are intrinsically safe and suited for EX applications. . Multiple fiber optic sensors can be operated within one fiber as a multiplex configuration. . They can be made thinner than a human hair and thus functionally embedded in multi-layer… Optical fiber embedded in an 8-ply carbon-epoxy laminate (Courtesy of Ghent University) Fiber Bragg grating as a sensor base Among the currently most important fiber optic sensors are fiber Bragg gratings. They have a refraction index that periodically varies over a certain fiber length. Bragg gratings are made by exposing a fiber to UV light through a micro-lithographic mask that carries a specific bar pattern: the UV-exposed areas show a lowered refraction index, while unexposed areas retain the fiber’s original refraction index. Thus, within the fiber core, multiple areas with lower index are followed periodically by ones with higher index. Any light coupled into the fiber is partly reflected at each of those boundaries. The reflected waves superimpose each other. At a certain wavelength, called Bragg wavelength and dependent on grid period as well as refraction index, all of them are in sync and therefore get amplified. This effect, called Bragg condition, is shown in Figure 3. At the Bragg wavelength, the reflected spectrum is at a maximum, whereas, in the transmission spectrum, it disappears. Since the grid can be made with high precision and repeatability and, most importantly, it doesn’t change over time, this enables the production of sensors which show no offset or zero-point drift. Figure 3: The principle of a fiber Bragg grating.

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