Shining an appropriate light on such a wire from the outside would alter its refractive index (a measure of how fast light travelling inside the wire can move).
Deutsche Bank has chosen to use the Reuters NewsScope database which contains data from 2003 on and applies natural language processing algorithms to the wire stories to measure sentiment.
Some Lib Dems believe that there is not much depth of support for the bill among the Conservatives and they will not go to the wire to save the measure.