REFLECTION TYPE METHOD AND INSTRUMENT FOR MEASURING BRILLOUIN SPECTRUM DISTRIBUTION

摘要

PROBLEM TO BE SOLVED: To highly accurately measure the positional distribution of a Brillouin spectrum with a distance resolution not larger than 1 m, without cross talk, or without increasing the width of the Brillouin spectrum intrinsic to a measured medium. SOLUTION: A plurality of beams are obtained, being referred to as first and second beams, by branching an incoherent continuous oscillation beam having a line width larger than the width of the Brillouin spectrum of the measured medium. The first beam is launched from one end of the medium and a beam rearward Brillouin-scattered in the medium is made to flow together with the second beam. The confluent beam is converted into an electric signal by a photo-detector to measure the frequency and power of an electric beat signal caused by an interference of a rearward Brillouin-scattered beam included in the electric signal with the second beam. Relative delay timeτ12between the first beam rearward Brillouin-scattered in the medium and the second beam or the other branched beam is changed to make the relative delay timeτ12concerning the beam rearward Brillouin-scattered from a desired scatter position z0T in the medium substantially zero. COPYRIGHT: (C)2004,JPO