The Ethernet Alliance’s 2020 technology roadmap expects speeds of 800 Gbps and 1.6 Tbps become IEEE standard before 2025. For short reach optical interconnects using multimode fibers VCSEL based transceivers have been the workhorse for many years.  VI Systems launched its first set of ultrahigh speed VCSEL chips for 50 Gbps at 850 nm and 910 nm two years ago. The next generation of VCSEL chips allows a serial speed of 100 Gbps. This opens up technology options for short wavelength multiplexing (SWDM) with 4 wavelengths by adding 880 nm and 940 nm wavelength. A capacity of 400 Gbps per fiber could be quadrupled by common parallel optics approach to 1.6 Tbps. Based on VCSEL with a serial speed of 224 Gbps two wavelength could be sufficient for 400 Gbps interconnects. As the next step beyond 400 Gbps however an 800 Gbps optical transceiver concept using 8 x 100 Gbps configuration may be expected. The IEEE 802.3 Beyond 400 Gb/s Ethernet Study Group is currently working to reach industry consensus for the physical layer specifications.