The nonlinear phase change accompanying the gain induced by stimulated Brillouin scattering is investigated in single-mode fiber. A frequency-modulated signal, when counterpropagated by a strong pump wave, is converted to an amplitude-modulated signal owing to this nonlinear phase change. The measured amplitude modulation is in good agreement with the theoretical predictions. It is at its maximum for a frequency difference between the pump and signal waves that corresponds to the Brillouin Stokes shift ±0.5 full width at half-maximum of the Brillouingain bandwidth (90 MHz at λ = 820 nm). This conversion may lead to distortion in coherent transmission systems and Brillouin amplifiers.
© 1988 Optical Society of America
R. G. Waarts, A. A. Friesem, and Y. Hefetz, "Frequency-modulated to amplitude-modulated signal conversion by a Brillouin-induced phase change in single-mode fibers," Opt. Lett. 13, 152-154 (1988)