The latest Internet technologies require ever-more bandwidth at the highest speeds, but it shouldn’t come at the expense of greater power consumption. According to DTU Fotonik, the Technical University of Denmark, emissions linked to the total energy consumption of the Internet corresponds to more than 2% of global man-made carbon emissions—putting it on a par with the transport industry.
To that end, the High-Speed Optical Communications (HSOC) team at DTU tested a new fiber-optic technology that meets those bandwidth and power-consumption goals. By transmitting at 43 Tbits/s using a single laser source, the team broke the 26-Tbit/s record set by researchers at Karlsruhe Institut für Technologie.
The new optical fiber, borrowed from NTT, expands from the typical one core (glass thread) to seven cores. A central core transmitted a synchronization signal to the receiver, while six outer cores each carried a copy of the Nyquist wavelength division multiplexed (N-WDM) data signal. Eventually the team was able to generate 320-Gbaud Nyquist channels, and multiplexed six of the channels (in optical frequency) at different wavelengths together. The six N-WDM channels were then polarization-multiplexed, with each optical pulse carrying two bits of information in quadrature using the differential quaternary phase shift keying (DQPSK) format.
Despite the added cores, the new fiber doesn’t take up any more space than a standard fiber, yet it transfers more data while cutting down on power consumption. A key toward making this possible is what the team calls an “optical time lens,” which separates the individual data channels in the receiver. When the receiver gets the Nyquist terabit-per-second signal, the lens converts it to a spectrally parallel data signal. As a result, the direct individual channels can be passively filtered out without using more energy than that consumed by the lens.
DTU Fotonik announced the breakthrough at the international Conference on Lasers and Electro-Optics (CLEO 2014), which took place in San Jose, Calif., this past June.