The capacity of fiber-optic telecommunication systems can be increased by higher data rate signaling. We present key analog and digital circuits which find application as building blocks in future very high data rate systems. The circuits are fabricated in our indium phosphide (InP) double-heterojunction bipolar transistor (DHBT) technology. The physical properties of the InP material system, notably high breakdown and high electron mobility, enable functions that are not accessible with current silicon-based high-speed technologies, including SiGe. Device and circuit results are presented, and we report on transmission system experiments conducted with these InP DHBT circuits. © 2009 Alcatel-Lucent.wider basis, and 100 Gb/s systems are beginning to emerge as the next generation in Ethernet networks, attractive for packet-switched architectures [7]. This progress has been made possible due to various microelectronics developments, using different materials, such as well-known silicon, but also III-V compound materials such as indium phosphide.To date, a wide choice of high-speed electronic technologies is available to the circuit and system designer. RF CMOS can handle all functions necessary for fiber-optic electronic front ends [22] at 10 Gb/s, and most functions at 40 Gb/s [15]. SiGe BiCMOS technologies [9] with device cutoff frequencies around 300 GHz provide enough speed to realize MUX, DEMUX, and CDR up to 100 Gb/s. The 45 nm