1.27 kW, 2.2 GHz pseudo-random binary sequence phase modulated fiber amplifier with Brillouin gain-spectrum overlap

Abstract

We present a 2.2 GHz modulated, 1.27 kW output power, monolithic fiber amplifier based on pseudorandom binary sequence (PRBS) phase modulation. The spectral line spacing of maximizing the threshold enhancement factor (plateau of trend) was found by theoretical simulation. The spectral line spacing was adjusted to 12.7 MHz by a pattern length of n = 9, which is close to the plateau of trend in the proposed architecture. A 2.2 GHz low-pass radio frequency filter was used to control the FWHM of the seed. A four-stage Yb-doped fiber amplifier chain was established to boost a distributed Bragg reflector (DBR) laser and a distributed feedback (DFB) diode laser to 1.2 kW and 1.27 kW with a backward reflectively of <1‰, which shows a good suppression of SBS effect. open Scientific RepoRtS | (2020) 10:629 | https://doi.org/10.1038/s41598-019-57408-5www.nature.com/scientificreports www.nature.com/scientificreports/ fiber, which is used to boost a DFB diode laser and a DBR fiber laser to 1.27 kW and 1.2 kW, respectively. The backward reflectively is measured to be <1‰. To the best of our knowledge, this is the highest power level for narrow linewidth fiber amplifier based on phase control under 5 GHz spectral linewidth.

3.96 kW All-Fiberized Linearly Polarized and Narrow Linewidth Fiber Laser with Near-Diffraction-Limited Beam Quality

“…Normally, the methods of generating narrow linewidth laser seeds mainly include: narrow linewidth laser diode [ 9 , 10 ], multi-longitudinal-mode fiber oscillator [ 11 , 12 , 13 ], filtered superfluorescent source [ 14 , 15 , 16 ], and phase modulated single-frequency laser [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Among them, phase modulation has been proved to be a preferable method to acquire narrow linewidth high power fiber laser without obvious spectral broadening and high SRS threshold [ 17 , 18 , 19 ].…”

“…Among them, phase modulation has been proved to be a preferable method to acquire narrow linewidth high power fiber laser without obvious spectral broadening and high SRS threshold [ 17 , 18 , 19 ]. At present, sine-wave signal [ 25 , 26 ], pseudo-random bit sequence (PRBS) [ 27 , 28 , 29 ], and white noise signal (WNS) [ 30 , 31 , 32 , 33 , 34 , 35 ] have been regarded as typical phase modulation signals in fiber lasers. As for random polarization narrow linewidth fiber lasers, the output power had reached 5 kW power-level by using WNS phase modulation [ 31 , 32 ], and 6.12 kW output power had been realized quite recently [ 33 ].…”

Effective Brillouin Gain Spectra Broadening for SBS Suppression Based on Pseudo Random Bit Sequence Phase Modulation in Fiber System

“…Normally, the pseudo random bit sequence (PRBS) phase modulation is a promising SBS suppression candidate, which provides flexibly optical spectral line separation adjustment. By applying the lowpass filter and RF amplifier, the envelope of the phase modulated laser spectra can be modified, thus provide further SBS suppression improvement [21], [22]. In our earlier work, the dependent of SBS suppression capability on the parameters of the filtered and amplified PRBS such as pattern length, modulation depth, and the ratio of lowpass filter cutoff frequency to clock rate has been investigated [23].…”

Seeding High Brightness Fiber Amplifiers With Multi-Phase Coded Signal Modulation for SBS Effect Management

“…As the combining beamlet in CBC system, the power scaling ability of high-brightness, Yb-doped, narrow-linewidth fiber amplifier is one of the significant aspects. Along with the development of output power scaling, the brightness of this type of fiber source is to be restricted by the dual effects of nonlinear stimulated Brillouin scattering (SBS) and thermal-induced mode instability (TMI) [9][10][11][12][13][14][15]. Specifically, SBS will induce the laser light transferring into the backward Stokes light so that the output power of the fiber amplifier will be limited and the whole amplification system will be fragile [16].…”

“…Among all of them, phase modulation technique is a simple and robust approach to mitigate SBS effect and control the linewidth of fiber amplifiers to promise an excellent temporal coherence [35]. Aiming on this approach, some typical modulation signals have been proposed and applied, which mainly includes sine-wave signal modulation [9,29], white noise signal modulation [30,31], pseudo-random bit sequence (PRBS) modulation [10,32], and piecewise parabolic signal (PPS) modulation [33] and multi-objective nonlinear optimized signal (MONOS) modulation [34]. Within these modulation signals, WNS and PRBS are the two prevail phase modulation techniques in multi-kilowatt level, narrowlinewidth fiber amplifiers [10,[30][31][32].…”