Brillouin Optical Frequency Domain Analysis (BOFDA)

A fully distributed system can be realized using Stimulated Brillouin Scattering (SBS) in silica optical fibers. The SBS describes an interaction of two counterpropagating light waves with an acousic wave. The pump beam undergo inelastic backscattering from the acoustic vibrations (wave) propagating in the same direction as the primary pump wave. The frequency shift of the backscattered light depends on strain and temperature distribution along the optical fiber.

In the method of BOFDA, the modulated pump beam and the backscattered signal are fed to a vector network analyzer, which calculates the complex transfer function by comparing both optical signals in amplitude and phase. This function is converted by the inverse fast Fourier transform, which gives the distribution of strain and temperature along the fiber.