Stimulated Brillouin scattering suppression with a chirped laser seed: comparison of dynamical model to experimental data

Abstract

Arseny Vasilyev, Amnon Yariv, "Stimulated Brillouin scattering suppression with a chirped laser seed: comparison of dynamical model to experimental data," ABSTRACT When scaling CW single-mode fiber amplifiers to high power, the first nonlinear limitation that appears for narrowlinewidth seed lasers is stimulated Brillouin scattering (SBS). We present a dynamical simulation of Brillouin scattering in a Yb-doped fiber amplifier that numerically solves the differential equations in z and t describing the laser, Stokes and pump waves, the inversion, and the density fluctuations that seed the scattering process. We compare the model to experimental data, and show that a linearly chirped seed laser is an efficient form of SBS suppression; especially for long delivery fibers. The frequency chirp decreases the interaction length by chirping through the Brillouin resonance in a time that is short compared to the fiber transit time. The seed has a highly linear chirp of 10 14 -10 16 Hz/s at 1064 nm which preserves a well-defined phase relationship in time. This method of SBS suppression retains a long effective coherence length for purposes of coherent combining, while at high chirps appears to the SBS as a large linewidth, increasing the threshold. An increase in fiber length increases the laser bandwidth as seen by the SBS, leading to a fiberlength-independent SBS threshold.

Chirped Laser Seeding for SBS Suppression in a 100-W Pulsed Erbium Fiber Amplifier

“…For a cw beam, a linear chirp also yields a flat spectrum, avoiding the sharp sidebands that give rise to four-wave-mixing when seeding with a sinusoidally-phase-modulated narrow band laser. 1 Among other applications, chirped seed amplification (CSA) is being developed for high average power cw fiber amplifiers [5]. A pulsed amplifier, however, allows us to investigate the scaling behavior of the SBS suppression without requiring high average power.…”

Theoretical and experimental study of suppressing stimulated Brillouin scattering and phase noise in interferometric fiber sensing systems with phase modulation

“…Many methods have been proposed to suppress SBS in optic communications and optic amplifier systems [9][10][11][12][13][14][15]. In interferometric fiber sensing systems the phase modulation method shows great potential in practical SBS suppression for its convenience and high efficiency [16].…”