The fabrication and performance of an electrophoretic separation chip with integrated of optical waveguides for absorption detection is presented. The device was fabricated on a silicon substrate by standard microfabrication techniques with the use of two photolithographic mask steps. The waveguides on the device were connected to optical fibers, which enabled alignment free operation due to the absence of free-space optics. A 750 mum long U-shaped detection cell was used to facilitate longitudinal absorption detection. To minimize geometrically induced band broadening at the turn in the U-cell, tapering of the separation channel from a width of 120 down to 30 mum was employed. Electrical insulation was achieved by a 13 mum thermally grown. silicon dioxide between the silicon substrate and the channels. The breakdown voltage during operation of the chip was measured to 10.6 kV. A separation of 3.2 mum rhodamine 110, 8 mum 2,7-dichlorofluorescein, 10 mum fluorescein and 18 mum 5-carboxyfluorescein was demonstrated on the device using the detection cell for absorption measurements at 488 nm.