1.0um band single frequency seed laser are based on Connet low noise CoSF-D or CoSF-R narrow linewidth single frequency fiber laser, which is the best choice for LiNbO3 phase modulation spectrum broadening. Up to a few tens of GHz linewidth phase modulated light signal helps to greatly increase the threshold of stimulated Brillouin scattering (SBS) during high power fiber amplification. Single frequency fiber laser has much higher optical signal noise ratio (OSNR) and narrower linewidth compare to other single frequency lasers, this is important to realize a few kW level narrow linewidth fiber amplifier output.