Efficiency and Crosstalk in Demultiplexing Orbital Angular Momentum Modes using a Geometrical Transformation-based Mode Sorter

There is a continuing growth for reaching higher communication bandwidth and multiplexing the information of independent channels to increase the channel capacity as much as possible. Orbital Angular Momentum (OAM) beams which are a subset of the Laguerre-Gaussian beams can be created by passing Gaussian beam through a Spiral Phase Plates (SPP). Their property that can be harnessed to be a candidate in Mode Division Multiplexing (MDM) systems have gained interest. OAM beams as carriers for multiple streams of input information can enhance the spectral efficiency and system capacity in an optical communication link. Analytical formulas for calculating efficiency and crosstalk of OAM modes passing through an OAM mode sorter is derived. With the help of these metrics, the channel capacity of the system and techniques for increasing it is discussed.