Investigation of stimulated Brillouin scattering spectra of an optical fiber with use of a frequency modulated laser

We demonstrate a method to characterize the gain spectrum of Stimulated Brillouin scattering in an optical fiber by using two tunable CW laser sources. Brillouin amplifier configuration is used, in which one laser is used to create SBS in the fiber and frequency modulated light from a second laser is launched from the other end of the fiber in order to extract the SBS gain spectrum. Experimental results are presented to demonstrate the gain bandwidth and the Brillouin frequency shift. Experiments at larger pump powers indicate the invocation of second-order Brillouin scattering in the forward direction. This method discussed to extract the gain spectrum of the fiber does not warrant the use of high-speed modulator or detectors, and does not use heterodyne measurements.