This paper presents a 4-channel VCSEL driver array operating up to 8 Gb/s per channel for the applications of active optical cables. Implemented in a 0.13-mu m CMOS technology, the proposed 4-channel array chip directly drives four common-cathode VCSEL diodes with bias currents of 3.0 mA and modulation currents of 6.0 mA(PP) in maximum. Each channel consists of an input buffer for impedance mathching, an equalizer for wide bandwidth, a modified Cherry-Hooper amplifier for optimizing the design tradeoff between switching speed and device size, and a main driver with pre-emphasis for fast rising time. Particularly, a constant bias circuit is exploited to acquire stable bias voltages for current-sources. Measured results of the proposed 4-channel VCSEL driver array demonstrate wide and clean eye-openings for up to 8-Gb/s operations. The driver array dissipates only 47.6 mW per channel and the chip core occupies the area of 0.15x0.1 mu m(2).