3.05 kW, 13.7 GHz linewidth fiber amplifier based on PRBS phase modulation for SBS suppression

In this paper, we establish a multi-stage fiber amplifier with pseudo-random binary sequence (PRBS) phase modulation. The stimulated Brillouin gain spectra of the main amplifier with both the unmodulated and pseudo-random binary sequence phase modulated configuration are measured (with corresponding output power), and the stimulated Brillouin scattering (SBS) threshold is investigated experimentally and theoretically. The pseudo-random binary sequence phase modulation parameters are optimized by theoretical simulation. With a two-stage preamplifier chain and a counter-pumping main amplifier stage, a maximum 3.05 kW output power with a slope efficiency of 85.9% is obtained experimentally. The central wavelength of the fiber amplifier is 1050 nm, associated with a full-width at half-maximum linewidth of 13.7 GHz. The stimulated Brillouin scattering reflectivity is below 0.01% at 3.05 kW at 13.7 GHz, which indicates that stimulated Brillouin scattering can be suppressed efficiently at this power and linewidth level.