Highly-Integrated Quad-Channel Transimpedance Amplifier for Next Generation Coherent Optical Receiver

Abstract

This paper presents a highly integrated, high performance four channel linear transimpedance amplifier (TIA) RFIC with a footprint of 2mmx3.5mm towards next generation 100G/400G miniaturized coherent receivers. A TIA of such form may become indispensable as the size, complexity and cost of receivers continue to reduce. The design has been realized in a 130nm SiGe BiCMOS process for a low cost, high performance solution towards longhaul/metro applications. The TIA is capable of providing control functions either digitally through an on-chip 4-wire serial-peripheral interface (SPI) or in analog mode. Analog mode is provided as an alternative control for real-time control and monitoring. To provide high input dynamic range, a variable gain control block is integrated for each channel, which can be used in automatic or manual mode. The TIA has a differential input, differential output configuration that exhibits state-of-the-art THD of <0.9% up to 500mVpp output voltage swing for input currents up to 2mApp and high isolation > 40dB between adjacent channels. A high transimpedance gain (Zt) up to ~7KΩ with a large dynamic range up to 37dB and variable bandwidth up to 34GHz together with low average input noise density of 20pA/√Hz has been achieved. To the authors' knowledge, these metrics combined with diverse functionality and high integration have not been exhibited so far. This paper intends to report a state-of-the-art high-baud rate TIA and provide insight into possibilities for further integration.