Deep Unfolding-Aided Design for Optical MIMO Signal Detection Circuit

In this paper, we study an optical MIMO (Multiple-Input Multiple-Output) signal detection circuit based on the projected gradient method. The projected gradient method is an iterative algorithm that iteratively performs a gradient descent step and a projection step. In the proposed optical MIMO signal detection circuit, the gradient descent step is implemented by an optical analog circuit in the optical domain, and the projection step is implemented by a nonlinear processing circuit in the electrical domain. The system noise due to the optical amplifier significantly degrades the detection performance of the optical MIMO detection circuit, which is a crucial issue for the optical implementation. In order to mitigate the effect of the system noises, we present how to apply deep unfolding, a technique for improving the performance of iterative algorithms, to the design of an optical MIMO signal detection circuit. The results of numerical experiments show that the proposed deep unfolding-based design achieves improved convergence performance and reduces the influence of the system noises.