Sensors

The Nobel Prize committee, which each year awards prizes for achievements in the sciences and humanities, have this year given their recognition to the role of optics in transforming the world of information technology^†.

Fibre optic sensors really do shine. No, I don't just mean when you pass light down one end and see it come out of the other, I mean they can be made to perform some pretty clever tasks, often triumphing over their electronic rivals. A fibre sensor fabricated by splicing together three different types of optical fibre and capable of measuring temperatures up to 1000°C, has recently been demonstrated by scientists in South Korea^†.

Wasted food amounts to loss of earnings if you're a retailer selling produce. Damaged or rotting fruits and vegetables are routinely thrown out when they can no longer be sold. It is therefore imperative that the retailer buys produce with a good shelf life. But knowing which ones will stay fresh the longest is not always apparent from a visual inspection. Bruised fruit may show no signs of damage on the surface but will be the first to rot.

Optical fibres can be used in a variety of ways to perform remote sensing operations. Take the case of the Fibre Fabry-Pérot (FFP) interferometer, for example. Working on the principle of light interference produced by two parallel reflecting surfaces either side of a small cavity, they can be constructed in different ways, either with an external cavity, or with the cavity located within the body of the fibre itself. They can be used to measure pressure, temperature or strain, all by detecting changes in the optical path length of the cavity due to environmental influences. They can even be used as chemical sensors because the optical path length in the cavity is related to the refractive index of the medium inside. Researchers at the Missouri University of Science and Technology have come up with a way in which to do just that, in such a way that produces a highly robust device suitable for chemical sensing¹.

After having just reported on a new and novel use of the photo-acoustic effect for use in the printing industry (Photo-acoustics measure ink thickness), here's another story that's (cliché alert!) hot of the press: Researchers at Oak Ridge National Laboratory and the University of Tennessee have used