[en] (A3600GV) We propose a lightweight method for the determination of heat difusivity of silica fiber bundles based on the use of a laser and an IR camera. The fiber bundle is maintained in traction in a holder; exposition is made as a step function, followed by a laser shutdown. The movie obtained by the IR camera is then processed : frame averaging, background computation and subtraction, image smoothing, extraction of the IR signal along the fiber bundle. A 1D model has been developed. This problem admits an analytic solution that we have obtained through the use of Laplace transforms. Several identification methods are proposed and tested, and have been compared favorably with an existing method based on periodic heating. Results are in agreement with literature values.