New milestone: 661 TBit / s data rate over a fiber optic cable reached


Researchers have created a fiber optic cable with an impressive 661 TBit / s transmission rate by developing a combination of different techniques in the development of energy-saving optical fiber systems.

Lyngby (Denmark). Fiber optic cables are an indispensable part of modern life. But even if they have many advantages over old copper cables, they still have a major shortcoming: their operation requires an incredible amount of power. For example, about nine percent of the world’s energy resources come from the Internet, and fiber optic cables are an integral part of the system. For this reason, Hao Hu and his colleagues from the Technical University of Denmark have started a research project that will make so-called fiber optic systems much more energy-efficient and also significantly increase the data transmission rate.

The result was a fiber-optic cable, which achieves a data transfer rate of 661 TBit / s from a combination of different and already established techniques, such as time division multiplexing or wavelength division multiplexing, for example, and only requires a fraction of the energy.

Different light spectra

Wavelength division multiplex or time division multiplexing is a technique that is used, for example, in copper-based Ethernet or in WLAN. Dividing the data rate into different light spectra, however, requires a lot of energy. For example, a typical laser consumes about 70 mW and is no more than 30 percent more efficient on a worldwide average. The researchers have calculated that their method in theory requires only about five percent of the energy.

The researchers used several lasers for their project in order to be able to cover as many color spaces of the light as possible. A wire just 300 nanometers thick amplifies the light sources and helps to break the light into other spectra.

This created several pulsating lasers that created a mixture of different colors within the fiber optic cable, resulting in only one color at the end. In addition, the researchers used two different polarizations of the electromagnetic fields within the optical waveguide with a conductor and 30 fibers for the data transmission in order to further increase the data rate.

Theoretically 750 TBit / s possible

The transmitted data are also divided into four time intervals, which is possible by the pulsing of the laser. Hao Hu researchers achieved a data transfer rate of 25 TBit / s per fiber. They report in the journal Nature that theoretically 750 TBit / s would be possible with 30 fibers. However, redundancy in coding the signal leaves only 661 TBit / s.

Current technology is a long way off

Previous fiber optic cables are distinguished in singlemode and multimode cables. The essential difference between singlemode and multimode is the structure of the respective fiber optic cable. While both cables are approximately the same thickness, a singlemode fiber has a much thinner core, but a thicker cladding glass. For a multimode fiber, however, it is the other way round. Both cable systems have different advantages and disadvantages.

For comparison, a modern submarine cable, such as the 1.3 billion TAT-14, which connects Europe and North America, currently comes to only about 1.3 TBit / s.

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