Such optical sensors are used to monitor temperature, pressure or magnetic field along their lengths to, for example asses the stability of a bridge or detect a pipeline leak.
“We have no trouble getting a million measurement points from one optical fibre, for a resolution of 1cm over 10km,” said Luc Thévenaz, director of EPFL’s group for fibre optics (GFO). That’s 100 times more precise than current techniques.
The trick is a signal-to-noise ratio boosting technique, using a technique borrowed from graphic arts.
“The values collected from these measurement points on the fiber can be represented as a matrix of pixels – a two-dimensional image,” said Thévenaz. “By applying standard graphic filters to this image, like those found in Photoshop, we were able to reduce the noise inherent in this measurement technique very effectively and identify the desired values more precisely.”
His teams also transformed more complex measurements, which take into account several parameters simultaneously, into video sequences. “Here again, the magic of ‘standard’ video filters was at work,” said the university.
The work is described in articles appearing simultaneously in Light: Science & Applications – Nature and Nature Communications.