Spectral evolution and stimulated Brillouin scattering suppression in phase-modulated fiber amplifier

Abstract

The model combining power balance equations, coupling amplitude equations and stimulated Brillouin scattering (SBS) equation is established to simulate the spectrum evolution and SBS threshold in the amplifier stage. Four typical phase modulation seeds are employed to calculate the SBS spectrum evolution in fiber amplifier. The spectrum evolution results show that the top-hat shaped spectrum seed is optimal to suppress the SBS effect and scale the SBS threshold. The SBS threshold is studied in co-pumped and counter-pumped amplifiers. Simulation results show that counter-pumped amplifier is capable of generating about 2.5 times more output than co-pumped amplifier. The results provide theoretical basis on the design and experiment of continuous wave high power narrow linewidth fiber laser.

A 2 kW, 8 GHz-Linewidth Yb-Doped Polarization-Maintained Fiber Laser with Quasi-Flat-Top Pseudo Random Binary Sequence Phase Modulation for SBS Suppression

“…In order to suppress the SBS effect, various approaches have been reported, such as applying a thermal gradient [7][8][9], designing a special fiber with acoustic layers [10][11][12], metal-coated fibers [13], and employing a phase-modulated laser source. Nowadays, there are several methods for obtaining a phase-modulated laser beam as a seed source, including sine-wave phase modulation [14,15], white noise signal (WNS) phase modulation [16][17][18][19], pseudo-random binary sequence (PRBS) phase modulation [20][21][22], and so on. In order to mitigate TMI effect, low-NA fibers [23], tight coiling [24], shifting the pump wavelength [25,26], pump modulation [27], and bi-directional pumping schemes [28,29] are among the approaches that have been proposed and adopted.…”

Widely linewidth tunable lasers through cascaded four-wave mixing based phase modulation amplification

“…However, stimulated Brillouin scattering (SBS) limits the power scaling of such lasers [3]. SBS mitigation is achieved through various methods such as laser linewidth tuning through phase modulation [4][5][6][7][8][9], large mode area fibers, and gain competition [10]. SBS is also controlled by straining the fiber [11] and the application of a thermal gradient along the fiber [12].…”

“…Among these, linewidth tuning has the advantages of simplicity, reliability, and robustness. Various phase modulating sources such as sinusoid [4], white noise [4][5][6][7], pseudo-random binary sequence (PRBS) generators [4], * Authors to whom any correspondence should be addressed. and arbitrary waveform generators (AWG) [13] have been demonstrated for linewidth tuning.…”