Fiber optics enable very high bandwidth over long distances with low loss. As a result, fiber optics provide nearly all data connections today, such as transoceanic cables, within and between data centers, between 5G cell towers, and fiber-to-the-home. Therefore, new technologies are required to sustain this growth in the coming decades.
To support traffic growth, future optical transport systems will have to transmit orders of magnitude more data while being able to transition to energy-efficient green networks. Modern transoceanic fiber optic cables can transmit 10 terabits of data per second per pair of fibers. These data rates are achieved through extensive parallelization of physical dimension multiplexing.
Current optical systems exploit the amplitude, phase, wavelength and polarization of laser light. Only one physical dimension remains unused: space. Spatial multiplexing is required to support future petabits per second per fiber transmission link. Space-division multiplexing uses modes such as multimode fiber to modulate data, increasing data rates by an order of magnitude or more.
To take advantage of space division multiplexing, advanced digital signal processing (DSP) is required. Light in multimode fiber experiences both linear and nonlinear effects, and the receiver sees a scrambled combination of the transmitted signal. Therefore, multiple-input multiple-output (MIMO) filtering similar to that used in WiFi and 5G needs to be used to address mode mixing in optical fiber transmission channels.