Abstract

Stimulated Brillouin scattering (SBS) is one of the most dominant nonlinear effects in coherent transmission through single-mode fibers. The gain of SBS is always accompanied by a nonlinear phase shift in accordance with the Kramers-Kronig relations between the real and imaginary parts of the nonlinear index of refraction. Such a phase shift may lead to distortion of signals in a coherent transmission line. We investigated the frequency-to-amplitude modulation conversion of a frequency modulated signal counterpropagated by a strong pump wave. For a frequency separation between pump and signal wave corresponding to the frequency of the acoustic phonons (~20 GHz at a wavelength of 820 nm) a strong AM signal was detected. This AM signal was measured as a function of the frequency separation for different pump intensities and parameters of the modulation. Results for fibers with different index profiles leading to a different Brillouin interaction bandwidth are presented. These results are in good agreement with an exact analytical model.

© 1987 Optical Society of America