A beam combiner configured to spectrally combine multiple beams includes at least one pair of identically configured TVBGs. The TVBGs are spaced apart along a light path and aligned at respective "+" and "-" Bragg angles. The upstream TVBGs diffracts a first beam, which is incident thereon at one of the Bragg angles, so that spectral components of this beams diverge from one another defining thus a fan-shaped beam at the output of the upstream TVBG. Upon launching the diffracted first beam to the downstream TVBG at the other Bragg angle, its spectral components again are diffracted but in the direction opposite to that provided by the upstream TVBG. Thus, the dispersion effects in respective TVBGs cancel out each other. Another beam is incident on and transmitted by the downstream TVBG which combines the twice diffracted and transmitted beams into a collimated combined beam.