Tuesday, May 27, 2014

New technology

Austin and Pat load the DTS cable onto Atoll-1

Today we deployed the first 1 km section of fiber optic cable on the Dongsha reef between the lagoon and our scaffolding tower. Though it presented some challenges, we all made it through in one piece (especially the cable). The next step is to deploy another 3 km of cable to stretch from the lagoon all the way towards the open ocean to the forereef. During the next weeks the 4 km of cable that lies on the reef will collect accurate temperatures within 0.01°C every meter at 30 second intervals. These measurements will allow us to track the cold water brought to the reef by internal waves (see the "Science" section). All of this is accomplished using a technology known as DTS.

Tom swims behind Atoll-1, carefully laying cable across 
the reef. The scaffolding tower that will hold the solar panel
and electronics is in the background.
What is DTS? Distributed temperature sensing was developed for industrial use in the oil industry, but is more commonly being applied to hydrological and environmental applications. Instead of relying on data collected from individual sensors, the DTS records a continuous profile of temperatures along the fiber optic cable. It achieves this by measuring the light reflected back on sensor through a phenomenon known as Raman scattering. The signal consists of two wavelengths, Stokes and antiStokes. Because the antiStokes particle is strongly dependent on temperature, the ratio of the two can be translated into temperature. What does this all mean? Temperature can be cheaply and effectively measured over vast distances in time, using the same type of cable that plugs into your phone or television.

Ultimately, the scaffolding will hold the DTS, a small meteorological station, and solar panels to power the whole system. Stay tuned for progress on that in the coming days!

- Austin Hall
Water Resource Engineering
Oregon State University

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