Fiber-optic sensors are monitored 253 km away without amplification

March 27, 2015
Such sensors are useful for monitoring concrete and asphalt, as well as oil pipelines.

Mikel Bravo-Acha, a PhD student at the NUP/UPNA-Public University of Navarre (Pamplona, Spain), has conducted a laboratory experiment in which he monitored the output from sensors at the other end of a 253-km-long optical fiber without fiber amplification. Such sensors can be embedded in concrete, for example, to measure strain. The sensor required no local electrical power to operate.

"What is interesting is that the measurement was remote, all the information arrived through the fiber, and we didn't need to fit any sockets to power the sensor," says Bravo-Acha. "This would be very useful, for example, to monitor an oil pipeline crossing the desert where fitting electrical power supply systems for the sensors is not feasible."

Such compact, electrically passive sensors embedded in optical fiber are usually immune to electromagnetic interference (EMI).

For the thesis, various sensor networks were developed with locally and remotely located sensors. Optoelectronic devices were remotely powered by a photovoltaic cell and remotely controlled to distances of 100 km via the optical fiber.

Next, the laboratory experiments were transferred to a real environment in which optical-fiber sensors were used to monitor the structural health of concrete and asphalt. Deformation and temperature sensors were fitted to a concrete beam on which a load was increased until it broke. "We monitored the information provided by our sensors, and comparing it with that of electrical sensors we found that the optical fiber ones offered much better resolution," says Bravo-Acha.



1. Mikel Bravo et al., Journal of Lightwave Technology, p. 99, IEEE, 30 March, 2015.

2. Daniel Leandro et al., Journal of Lightwave Technology, p. 354, IEEE, 6 January, 2015.

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