Abstract

We present, for the first time to our knowledge, the use of axial laser modes in distributed temperature sensing based on stimulated Brillouin scattering. One axial mode stimulates a Stokes wave¹ with a temperature dependent frequency shift in the 13-GHz range. Optical heterodyning of the stimulated Stokes wave with a second axial laser mode allows to generate and evaluate a beat signal in a lower frequency range. Using a Nd:YLF laser we have reduced the Brillouin beat frequency from the 13-GHz range to the 470-MHz range. Hence, low cost detectors and conventional signal processing techniques can be applied for beat signal processing.

© 1994 IEEE