The Orbital Angular Momentum Encoding System With Radial Indices of Laguerre–Gaussian Beam

Orbital angular momentum (OAM) in optical vortices (OV) beams offers a new dimension of space mode because coaxially propagating OV beams with different azimuthal OAM states are mutually orthogonal. As a result, the beams can be efficiently multiplexed and de-multiplexed to potentially increase the capacity of the optical communication system. Therefore, up to now, the azimuthal indices of the transverse spatial mode has been investigated for many times. This paper focuses on another mode, which can be called as radial indices of Laguerre–Gaussian beam. A novel OAM encoding system with high-order radial indices is established by simulation for the optical communication system. At the transmitter, a series of holograms of the Laguerre–Gaussian mode with different radial indices are used to achieve coaxial transmission of multiplexing beams, where each beam represents one data bit. At the receiver, we use the superposition of a conjugate light field corresponding to the transmitted beams for de-multiplexing the multiplexed beams. Meanwhile, the combination of the phase-shift factor and centroid algorithm can realize the simultaneous detection of the radial indices in each channel and efficient decoding of information. We also analyze the measurement deviation on the performance of an encoding system and give the corresponding discussions.