A Fast and Resource-efficient GSOP Implementation for Optical Coherent Receivers

In-phase/quadrature(I/Q) imbalance compensation is an important procedure in optical coherent systems, and the Gram-Schmidt orthogonalization procedure (GSOP) is one of the most widely used compensation algorithms. However, the division and square-root operations consume a lot of hardware resources, limiting the speed of FPGA implementation. This paper proposes a fast and resource-efficient GSOP implementation by converting square-root and division operations into linear fitting. We introduce the Newton iteration method to compensate for the accuracy degradation. The FPGA implementation shows that the throughput of the 128-way-parallel GSOP is up to 100Gbps at the frequency of 392MHz.