34-GBd Linear Transimpedance Amplifier for 200-Gb/s DP-16-QAM Optical Coherent Receivers

Abstract

High spectral efficiency offered by the coherent optical communication links makes them attractive for the nextgeneration optical communication links. Using advanced modulation schemes such as dual-polarization quadrature-amplitude modulation (DP-QAM) data rates beyond 200 Gb/s can be achieved. A key component of such links is the wide-bandwidth and high-linearity coherent optical receiver. In this paper, we present a fully differential (FD) optical receiver architecture consisting of a variable-gain transimpedance amplifier (VG-TIA) followed by a VG amplifier (VGA). The proposed optical receiver employs a dual-feedback automatic gain control (AGC) loop that controls both the front-end VG-TIA and the following VGA to achieve both low-noise and high-linearity operation. A new photodiode (PD) dc current cancellation scheme is developed and implemented for the full differential front-end TIA. A prototype dual-TIA chip is fabricated in a 0.13-μm SiGe BiCMOS √ process. The presented TIA achieves 20-pA√Hz input-referred noise (IRN) density, 27-GHz, 3-dB bandwidth, and 1.5% total harmonic distortion (THD) at 1-mApp input PD current and 500-mV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> output voltage swing. This enables the 34-GBd operation with the bit error rate (BER) of 10-10 and 5.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> using DP-QPSK and DP-16-QAM formats at optical signal-tonoise ratios (OSNRs) of 25 and 30 dB, respectively, demonstrating the 100and 200-Gb/s single wavelength optical coherent receiver operation. The dual-TIA chip occupies an area of 1.4 mm × 1.6 mm and consumes 313 mW per channel at 34 GBd from a 3.3-V supply.