A fiber amplifier system (10, 70, 90, 100) comprising: a plurality of seed beam sources where one source is provided in each of a plurality of fiber wavelength amplification channels, each seed beam source generating a seed beam at a wavelength that is different than the wavelength of the seed beams generated by the other seed beam sources, wherein each seed beam source includes a beam wavelength tuning capability; a fiber amplifier provided in each amplification channel that receives the seed beam in that channel and provides an amplified beam; an emitter array responsive to all of the separate amplified beams and directing the amplified beams into free space as diverging uncombined beams; beam collimating optics responsive to the diverging uncombined beams and redirecting the diverging uncombined beams as collimated uncombined beams; a spectral beam combining, SBC, grating responsive to the collimated uncombined beams and spatially combining the collimated uncombined beams at the different wavelengths so that all of the separate amplified beams in the collimated uncombined beams are directed in the same direction as an output beam; a beam sampler responsive to the output beam and providing a sample beam therefrom that includes a wavelength portion of all of the amplified beams; a far-field optic responsive to the sample beam and generating a far-field image of the sample beam; a detector assembly responsive to the far-field image of the sample beam, said detector assembly including a first fiber sampler and a second fiber sampler spaced apart from each other and being positioned relative to a dispersive axis of the SBC grating, said first fiber sampler generating a first fiber sample beam having a first intensity and including a wavelength portion of all of the amplified beams, and said second fiber sampler generating a second fiber sample beam having a second intensity and including a wavelength portion of all of the amplified beams; and a configuration of optical and electrical feedback components responsive to the first and second fiber sample beams, said feedback components determining a difference between the first intensity of the first fiber sample beam and the second intensity of the second fiber sample beam, said feedback components using the differences between the intensities of corresponding wavelength portions of said first and second fiber sample beams to control the wavelengths of all of the seed beams so that all of the amplified beams are spatially aligned and propagating in the same direction in the output beam. a plurality of seed beam sources where one source is provided in each of a plurality of fiber wavelength amplification channels, each seed beam source generating a seed beam at a wavelength that is different than the wavelength of the seed beams generated by the other seed beam sources, wherein each seed beam source includes a beam wavelength tuning capability; a fiber amplifier provided in each amplification channel that receives the seed beam in that channel and provides an amplified beam; an emitter array responsive to all of the separate amplified beams and directing the amplified beams into free space as diverging uncombined beams; beam collimating optics responsive to the diverging uncombined beams and redirecting the diverging uncombined beams as collimated uncombined beams; a spectral beam combining, SBC, grating responsive to the collimated uncombined beams and spatially combining the collimated uncombined beams at the different wavelengths so that all of the separate amplified beams in the collimated uncombined beams are directed in the same direction as an output beam; a beam sampler responsive to the output beam and providing a sample beam therefrom that includes a wavelength portion of all of the amplified beams; a far-field optic responsive to the sample beam and generating a far-field image of the sample beam; a detector assembly responsive to the far-field image of the sample beam, said detector assembly including a first fiber sampler and a second fiber sampler spaced apart from each other and being positioned relative to a dispersive axis of the SBC grating, said first fiber sampler generating a first fiber sample beam having a first intensity and including a wavelength portion of all of the amplified beams, and said second fiber sampler generating a second fiber sample beam having a second intensity and including a wavelength portion of all of the amplified beams; and