An optical detection system for a capillary electrophoresis instrument is disclosed. The system includes an ultraviolet (UV) source and an absorption measurement optical path. In an embodiment, the optical path comprises a first plurality of optical elements arranged to obtain a plurality of respective UV beamlets from a UV beam emitted by the UV source and to direct the respective UV beamlets transversely through respective capillaries of a plurality of capillaries and to an absorption detector positioned to detect respective signals for use in obtaining respective UV absorption measurements corresponding to the respective capillaries.