Ultra-flat Brillouin gain spectrum via linear combination of two acoustically anti-guiding optical fibres
A novel approach to broadening and flattening the Brillouin gain spectrum is presented. A linear combination of two acoustically anti-guiding optical fibres gives rise to a Brillouin spectrum with less than 0.5 dB gain variation over>200 MHz. The fibres are selected so that they possess individual Brillouin spectra that are shifted in frequency from each other, such that a relative maximum of one overlaps with a relative minimum of the other.