Advances in distributed sensing using Brillouin scattering

Abstract
Fiber optic distributed sensors based on Brillouin scattering can measure strain and temperature in arbitrary regions of a sensing fiber. The fiber optics group at the University of New Brunswick has recently developed an automated system for strain measurements in a distributed sensing system. Under a computer control program, strain measurements are taken using Brillouin Optical Time Domain Analysis. The computer takes a series of measurements of Brillouin loss in the fiber as a function of the frequency difference between the two lasers in the system. By fitting the returned data to a predetermined model, accurate determination of the Brillouin frequency and hence strain in the fiber can be made. An experiment was conducted to test the sensor system in which fiber was stretched by use of dead weights hanging on a system of pulleys. Determination of strain to within 17 (mu) (epsilon) was realized. Spatial resolutions of better than 1 m were obtained through standard BOTDA methods and resolutions of better than 500 mm were realized using our compound spectrum analysis method.