Suppression of stimulated Brillouin scattering in high power fibers using nonlinear phase demodulation

We demonstrate a modulation approach that relaxes the limitations imposed by stimulated Brillouin scattering (SBS) on amplification and propagation of narrow-linewidth light in fibers. By imposing synchronous amplitude and phase modulation on an input field, the optical spectrum after high-power fiber transmission is compressed using nonlinear self-phase modulation. This effectively reduces the SBS interaction length and increases the SBS threshold, enabling narrower linewidths. Using this technique, we demonstrate >2 × increase in SBS-limited spectral brightness from a kW-class amplifier. We show that SBS suppression becomes more effective for higher powers and longer fibers.