A fiber amplifier system including a plurality of seed beam sources each generating a seed beam at a different wavelength and a plurality of fiber amplifiers that amplify the seed beams. The system also includes a spectral beam combining (SBC) grating that spatially combines the amplified beams and directs them in the same direction as an output beam, and a first fiber sampler and a second fiber sampler that generate a first fiber sample beam having a first intensity and a second fiber sample beam having a second intensity. The system further includes a configuration of optical and electrical feedback components that determine a difference between the first intensity and the second intensity and use the difference to control the wavelength 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.