Element-by-Element Full-Rank Optical Wireless MIMO Systems Using Narrow-Window Angular Filter Designed Based on One-Dimensional Photonic Crystal

In the field of radio-frequency (RF) communications, the multiple-input multiple-output (MIMO) strategy allows us to attain a higher rate of data transfer due to the multipath-rich environment. In contrast, it is challenging to achieve the same rate in a highly correlated channel that is specific to optical wireless communications. In this paper, we propose the novel concept of an element-by-element optical MIMO system that enables the interference-free reception of parallel symbol streams; it achieves this by using an angular filter (AF) with a narrow transparent window. The AF consists of a one-dimensional photonic crystal, and the angular selectivity is obtained by using the extremely small wave vector regime. We demonstrate that the capacity of the proposed system increases linearly with the minimum number of transmit source elements and receive detectors, which is similar to conventional RF MIMO systems.