120 Gbit/s 2 × 2 Vector-Modes-Division- Multiplexing DD-OFDM-32QAM Free-Space Transmission

We demonstrate a 120-Gbit/s mode-division-multiplexing (MDM) system based on two typical vector modes of TE01 and TM01 with direct detection orthogonal frequency division multiplexing (DD-OFDM) and 32-quadrature-amplitude-modulation (32-QAM) signal. The vector mode conversion is achieved by the key q-plate and the mode crosstalk between the converted two vector modes are both less than -20 dB. This crosstalk can be further minimized by high-quality q-plate. In this demonstration, error-free transmission has been realized with the power penalties less than 2 dB. The experimental results show that the scheme proposed in this paper can be a good candidate in large-capacity short-reach optical interconnect.