The present invention relates to a solar concentrator for illuminating an algal suspension, which comprises: - at least one optical element (1) suitable for receiving solar radiation; - at least one optical fiber (3), having an input face (11) and an output face (12); - at least one spectrally selective optical filter (9), situated along the path between said solar radiation and said input face (11) of said at least one optical fiber (3); characterized in that said optical filter (9) transmits only the spectral portion which is most active for photosynthesis purposes, reflecting and/or absorbing the spectral portion which is of little use for photosynthesis purposes
