640 Gbps FSO data transmission system based on orbital angular momentum beam multiplexing employing optical frequency comb

Orbital angular momentum (OAM) beams are basically twisted beams with infinite number of possible orthogonal OAM states. A 640 Gbps (4 × 16 × 10 Gbps) data transmission over 180 m FSO link, implemented by multiplexing of 4 OAM modes, each containing 16 wavelength channels has been proposed and demonstrated. An optical frequency comb generator, containing a single laser source is used as broadband laser source. Low power penalty of 2.91 dB at a BER value < 10 –9 with very good Q-value (> 5.5) and open eye diagrams have been achieved, which reveal the potential of the proposed system for free space communication.