Resource Efficient Quadrature Imbalance Compensation Method for High Throughput Optical Coherent Receiver

In this work, hardware efficient FPGA-based implementation scheme of quadrature imbalance compensation for optical coherent receiver is proposed. A novel parallel Gram-Schmidt orthogonalization procedure (GSOP) algorithm is presented for real-time high throughput implementation and recursive average calculating method is introduced. In addition, a multiplier multiplex strategy is proposed and the hardware resource is reduced significantly. Finally, performance evaluation of the proposed algorithm is carried out via simulations and the FPGA implementation result is presented.

I. Introduction

Because of the high spectrum efficiency and sensitivity of the optical coherent communication system, it has attracted extensive attention from both academic and industrial communities. The great capacity of optical coherent communication enables its application for a wide variety of scenarios that include long-haul fiber-optical communication and free space optical communications^[1]. Coherent optical communication is a promising modulation format for high speed transmission which can achieve multi-Gbaud. Without the atmospheric turbulent effect, the satellite-ground laser link is equivalent to back to back laser links in sunny days. As a result, optical coherent transmission is a good candidate for multi-Gbaud satellite-ground station link^[2]–[4]. In addition, the development of high-speed analog-to-digital converter (ADC) and digital signal processing techniques based on field programmable gate array (FPGA) has significantly simplified the implementation of optical coherent receiver, especially the polarization multiplexing system^[5]–[6]. A series of real-time optical coherent reception has been demonstrated beyond 100Gbps in the last decades. However, it is a crucial problem to implement optical receivers for satellite application because the limitation on hardware resource and power consumption.