Multiple-input multiple-output based high density on-chip optical interconnect
In on-chip optical interconnect, dielectric waveguide arrays are usually designed with pitches of a few wavelengths to avoid crosstalk, which greatly limits the integration density. In this paper, we for the first time propose to use multipleinput multiple-output (MIMO), a well-known technique in wireless communication, to recover the data from entangled signals and reduce the waveguide pitch to subwavelength range. In the proposed on-chip MIMO system, there is significant coupling among the adjacent waveguides in the high density waveguide region. In order to recover signals, the N×N transmission matrix of N high-density waveguides is calculated to describe the relation between each input ports and output ports. In the receiving part, homodyne coherent receivers are used to receive the transmitted signals, and obtain the signal in phase and π/2 out of phase with local oscillator. In the electrical signal processing, the inverse transmission matrix is utilized to recover the signals in the electronic domain. To verify the proposed on-chip MIMO, we used the INTERCONNECT package in Lumerical software to simulate a 10x10 MIMO system. The cross section of each waveguide is 500 nm x 220 nm. The spacing is 250 nm. The simulation verifies the possibility of recovering 10 Gbps data from the heavily coupled 10 waveguides with a BER better than 10-12. The minimum input optical power for a BER of 10-12 is greater than -18.1 dBm, and the maximum phase shift between input laser and local oscillator can reach to 73.5°.
