Orthogonal coding-based spatial channel switching: breaking the dimensionality barrier in optical multiplexing systems

In multi-channel wavelength-division multiplexing (WDM) and space-division multiplexing (SDM) optical communication systems, spatial channel-switching devices play a critical role. Here, we propose an optical orthogonal coding (OC) mode construction method based on phase-gradient coding and establish a mapping with dispersed spatial channels of a fiber array to develop a spatial channel-switching device. The device consists of a multi-channel fiber array, a mode converter, and a channel-switching plane. We experimentally demonstrate a bidirectional mode converter that consists of five phase masks, enabling the switching of seven spatial channels with seven corresponding switching phase distributions. The orthogonal coding-based channel-switching devices eliminate the need for phase adjustments in predetermined spatial regions and simplify the operational complexity of the channel-switching process. This work paves the way for the simultaneous enhancement of channel scalability and system performance, thereby providing a viable pathway to overcome the dimensionality barrier in optical multiplexing systems.