LAUSR

Abstract Imperfection of coherent receiver frontend can rapidly degrade system performance in coherent optical transmission systems. Those imperfection, including in-phase/quadrature (I/Q) gain and phase imbalance, and voltage mismatch between the output of integrated coherent receiver (ICR) and the full scaling range of analog-to-digital converter (ADC), become increasingly important, especially when high symbol rate, high modulation order, and low roll-off pulse shape are used. A low-complexity, training symbol-free and double feedback structured imperfection compensation algorithm is proposed and experimentally demonstrated online in a field-programmable gate array (FPGA)-based 2.5-GBaud 16QAM transmission hardware platform. The proposed algorithm, relied on the general assumption that I and Q tributaries are statistically independent, would be a useful tool for modulation format independent imperfection compensation. Compared with conventional method, the number of hardened multipliers is reduced by 66.6%, while no extra circuit is required.