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Fiber optics makes airplanes safer

28 Sep 2006

Researchers in the US have devised an optical on/off switch that could be safer and more reliable than electrical controls in airplane cockpits.

An aircraft control system based on fiber optics could save space, reduce costs and improve safety, according to researchers at Texas A&M University. One important sensor for such a system is an optical on/off switch, and Zhaoxia Xie and Henry Taylor have built a prototype device that is now ready for testing in real aircraft (Optics Letters 31 2695).

Xie and Taylor's device is an on/off switch that senses when a pilot presses a button. At the heart of the optical switch is a fiber Fabry-Perot interferometer (FFPI). A cantilever is bonded to the interferometer, and the cantilever is in turn attached to a switch. Pressing the switch causes the cantilever to bend, which changes the spacing between the mirrors in the FFPI and so alters the interference pattern.

Any change in the interference pattern indicates that a switch has been pressed, and the information can be transmitted optically to the desired part of the airplane. A network of other interferometers and lasers filter out fluctuations in temperature and other disturbances so that only the pressing of the button registers as a valid signal.

However, Xie and Taylor still need to work out how to prevent vibrations during flight from affecting the sensor's performance. "The whole system can be integrated into a box with vibration protection in the mechanical design," Xie told optics.org. "In extreme situations the system performance needs to be tested in a real airplane."

The researchers believe that replacing electrical wiring with fiber optics would save space and reduce complexity. Today's aircraft typically require more than 100 miles of wiring networks, while a control system based on a single optical fiber could sense light signals from a number of different control buttons at the same time. It could also improve aircraft safety, with the US Federal Aviation Authority estimating that at least 26 accidents since 1983 have been caused by electrical fires or failures within the electrical system.

Lockheed Martin has been among the supporters of this research. The next step is to test the system on a real airplane, although there are no specific plans right now. "First we must develop the technology and proved it works, then we can implement the system in the real world," says Xie.

According to Xie, the technology could also be used to measure the weight of commercial trucks while they are moving. In this case, the optical sensors would be bonded in a groove of metal bars, and would measure the strain induced by the passing truck's wheels.

"Current weighing systems using slow and cumbersome static scales aren't a viable option," says Xie. "There's a strong demand for an economic, effective and reliable 'weigh-in-motion' system."

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