Distributed sensing using stimulated Raman interaction in a monomode optical fibre

A distributed optical-fiber stress sensor with a measurement path length of 25 m and a spatial resolution of 1 m is described. The sensor, the first of its kind, uses the stimulated Raman interaction between counter-propagating pump and Stokes waves. In principle, the sensor can be extended so that stress-induced birefringence can be measured over a path of several hundred meters with a resolution of less than 0.1 m, these parameters being fixed by the pump laser pulse width and the response of the detection electronics.