New breakthroughs in optical communications using a single laser

With the latest trend in communication, data rates up to 26 trillion bits per second can be achieved using only one laser or transmitter. This type of communication could reduce energy consumption and thereby establish a new framework for optical data transmission standard.

Juerg Luethold, a professor at the Karlsruhe Institute of Technology in Germany, and his colleagues have devised approach for increasing data rates in wireless communications using OFDM (orthogonal frequency-division multiplexing) modulation techniques. The advantage of this modulation is better utilization of available frequency spectrum and procedure is implemented by coding the data carrier signal using overlapping frequencies. When adding and extracting useful information from the waveforms the FFT transform (Fast Fourier Transform) is performed, and on the receiver side, a new waveform is decoded. When increasing transfer speeds, electronic receivers show problems with decoding the information. A team of German researchers has solved the problem by designing optical FFT device which uses interferometer that separates the light signal into the beams and then recombines them. The consequence of recombination is a stronger signal in one place and lighter in another, creating a series of mirror coded bits. With this method the data is transferred up to 50 kilometers trough the optical fiber. Luethold refers that the use of better equipment could increase the transmission distance. Another group of scientists from the NEC labs at Princeton University managed to convey more information through a single optical fiber and to the longer distances, but using up to 370 lasers. They believe that transmission using a larger number of lasers leads to better utilization of spectrum. The work also refers to other solutions which use WDM (Very dense wavelength-division multiplexing) modulation method that can achieve terabit transfer speeds, but optical solution still holds the advantage in simplicity of implementation. More information can be found at ieee spectrum web site.