ABSTRACT
Space division multiplexing (SDM) is a promising technique to increase the system capacity by providing an extra degree of freedom for multiplexing parallel to the time, frequency, polarization, and quadrature. In practice, multi-input multi-output (MIMO) processing is commonly employed at the receiver side of the SDM systems to undo the mode coupling effects occurring during fiber transmission. Compared to the linearly polarized modes, the orbital angular momentum (OAM) modes have lower model interactions during fiber transmission and thus are promising for ultra-high-capacity systems with lower-complexity MIMO processing. However, multiplexing of OAM modes still relies on free-space optical devices that are bulky, expensive, and unfavorable in practice for a large channel count. Building OAM multiplexers on a silicon photonic chip provides remarkable advantages of compactness, scalability, low cost, and straight-forward integration with electronics and other photonic functions. In this chapter, we review principles and recent progress of silicon photonic OAM generators and multiplexers and discuss their future development for OAM-based SDM systems.
