Unmixing Data Lanes in Mode-Division Multiplexing Optical Fiber Transmission Using an Integrated Photonic Processor

Mode-Division-Multiplexing in few-mode fiber (FMF)/multi-mode fiber (MMF) offers an attractive approach for multi-lane data communications. The selective manipulation of modes in MMFs also has potential for use in optical sensing and MMF imaging. Typically, the coupling interface between the MMF and the optical receiver causes a mixture of different optical modes. Fiber strain or temperature fluctuations can result in the mixing of different data lanes among various spatial modes in the MMF. We show that the mixed spatial channels can be separated in the optical domain, and the mixed data channels can be simultaneously detected with negligible crosstalk, even if they share the same wavelength and polarization, and even with unknown arbitrary mixing at the receiver. The kernel of the adaptive multi-mode receiver presented in this work is a programmable integrated photonic processor that is coupled to a high-efficiency multimode waveguide grating coupler. We demonstrate experimentally the robust separation of two different spatial channels or two polarization beams coming from one spatial channel of a fiber-based photonic lantern (PL) with unknow mixing/crosstalk introduced during the coupling and fiber transmission. The integrated photonic processor is an attractive technology that can enable the practical use of mode division multiplexing in MMF.