We report here on the design, fabrication and characterization of 48-channel parallel optical transceivers demonstrating terabit/sec data transfer rate. The 0.48 Tb/s transmit plus 0.48 Tb/s receive throughput was achieved using a second-generation single-chip holey CMOS transceiver IC. In addition to 24 receiver (RX) and 24 laser diode driver circuits, the 5.2 mm\,\times\,5.8 mm single CMOS chip incorporates 48 through-substrate optical vias (holes), one for each transmitter (TX) and RX channel. A complete holey Optochip is formed following direct flip-chip attachment of 24-channel 850-nm VCSEL and PD arrays. The 48 optical vias enable optical access to the 24 VCSELs and 24 PDs. The holey Optochip concept provides a dense chip-scale package which is fully compatible with industry-standard top emitting/detecting 850-nm VCSELs/PDs providing optimized high-speed performance through close integration of the optoelectronic (OE) devices with their drive electronics. Furthermore, the optical vias and OE devices are arranged in a 4\,\times\,12 array on 250 \mu m\,\times\, 250 \mu m pitch to facilitate direct fiber-coupling to a standard 4\,\times\,12 multi-mode fiber array. © 1983-2012 IEEE.