Low-complexity blind in-phase/quadrature imbalance compensation and field-programmable gate array realization for coherent receivers

Abstract. Receiver in-phase/quadrature (I  /  Q) imbalance caused by imperfect analog receiver front end can rapidly degrade system performance in a coherent optical transmission system. These imbalances, including I  /  Q gain and phase imbalance, become increasingly important when higher symbol rate, higher modulation order, and low roll-off pulse shape are used. Here, a low-complexity blind equalization algorithm, cascaded phase, and gain imbalance equalizers, is designed to mitigate these interferences. Furthermore, a field-programmable gate array hardware realization with 128-parallel processing units is performed to demonstrate the proposed algorithm in a 32-GBaud 16-quadrature amplitude modulation off-line transmission experiment. Based on the obtained results, the proposed blind I  /  Q imbalance compensation algorithm can provide very good compensation performance with low logic element consumption, which is more suitable for high order and high baud rate transmission system.