High-resolution measurement of stimulated Brillouin scattering spectra in single-mode fibres

A new technique is introduced for stimulated Brillouin scattering spectral characterisation. It provides accurate measurements of the amplitude and phase of the Brillouin gain and loss spectra with high frequency resolution and stability. Furthermore, only narrow-electrical-bandwidth electro-optical components and instruments are needed in its experimental implementation. The measurement principle is based on translating the Brillouin spectral information from the optical to the electrical domain. This leads to frequency resolutions of the measurements in the kilohertz range because the Brillouin spectra are scanned by sweeping an electrical rather than optical carrier, The experimental setup relies on a Brillouin-erbium fibre laser to generate the optical signals needed to perform measurements, so that problems related to optical frequency drift are avoided. Measurements of Brillouin gain and loss spectra in a 25 km reel of standard single-mode fibre are presented demonstrating the capabilities of the technique.