The capacity of the optical communication infrastructure in backbone networks has increased 1000-fold over the last 20 years. Despite this rapid progress, internet traffic is continuing to grow at an annual rate of 40%. This means that in 20 years, we will need petabit/s or even exabit/s optical communication. In this paper, we present recent challenges and efforts toward achieving a hardware paradigm shift to overcome the capacity limitation imposed by the current optical communication infrastructure. We will overview the latest advances on the three "multi" technologies, i.e., multi-level transmission with ultrahigh spectral efficiency, space division multiplexing in multi-core fibers, and mode division multiplexing with multiple-input multiple-output (MIMO).