Since 1980’s, optical fibers have revolutionized the way we communicates, allowing us to transmit voice, data, and video signals at the speed of light, along a thin glass wire. We got so well acquainted in communicating, that at the end of this year, the global Internet traffic will reach a staggering multi Zettabytes increase. To support this tremendous growth, optical fiber communication systems are required to dramatically escalate their capacity, reaching Petabit/s transmission speed. Since the fiber capacity is not as limitless as it had been thought in the past, a coming capacity crunch is worldwide foreseen. Therefore, researchers and scientists are now struggling to fully exploit the overall available optical bandwidth in the most effective way, time or frequency multiplexing independent channels. In fiber optics, time division multiplexing (TDM) requires synchronized transmitter and receivers, and the system performances are is mainly limited by the speed of the electronic devices in the terminal equipment, that is less than 100 Gigabit/s. On the other hand, using the frequency-division multiplexing (FDM) approach, the total bandwidth is divided in a set of subbands, that can be separately optically or electronically multiplexed. There are pros and cons in both approaches, mainly related to the fiber impairments and the availability of commercial devices, but in both cases Terabit/s transmission speed has been demonstrated over a single wavelength.
Within the Japanese STARBOARD project, has demonstrated that the use of the time and frequency domains for optical multiplexing is not as rigidly fixed as it may be thought. Recent experimental results on a field-trial fiber installation showed that it is possible to switch from time to frequency multiplexing and viceversa, allowing to the combined used of both approaches and fully exploiting the physical resources. This revolutionary technique introduces ultimate flexibility in light multiplexing, selecting the best approach depending on system requirements or transmission impairments.