Mode division multiplexing in few-mode or multimode optical fibers is one of the most promising emerging technologies which can enable optical fiber interconnects to increase their data transmission capacity and bandwidth density. Current 400Gb ethernet standard optical transceivers use 4 lasers at four wavelengths, each supporting 50Gbaud PAM-4 modulation. This is not scalable to 1.6Tb/s as it becomes too expensive to use 16 lasers in a transceiver. Besides, mode division multiplexing in multimode fibers is currently impractical because of the difficulty to selectively excite different modes with the large volume produced silicon photonic transceivers.
We have developed a new type of multimode waveguide grating coupler which will enable the use of mode division multiplexing in multimode optical fibers. A direct optical interface between multimode fiber and a silicon photonic transceiver is also developed, in which will enable mode division multiplexing in multimode fibers for high capacity short-reach data communications. The technology will enable the next generation optical ethernet to attain 800Gb/s or possibly 1.6 terabit/s capacity with a single wavelength silicon photonic transceiver interfaced with multimode fibers. We have already demonstrated this technology with few-mode fibers and are currently developing advanced designs for use with standard multimode fibers.