Researchers at the University of California have successfully deciphered information in lab experiments after it travelled a record-breaking 12,000 kilometers through fiber optic cables with standard amplifiers and no repeaters, which are electronic regenerators.
This increased maximum power and distance at which optical signals can be sent through optical fibers, has the potential to increase the data transmission rates for the fiber optic cables that serve as the backbone of the internet, cable, wireless and landline networks.
The research is published in the June 26 issue of the journal Science.
The new study presents a solution to a long-standing roadblock to increasing data transmission rates in optical fiber: beyond a threshold power level, additional power increases irreparably distort the information travelling in the fiber optic cable.
The new findings effectively eliminate the need for electronic regenerators placed periodically along the fiber link. These regenerators are effectively supercomputers and must be applied to each channel in the transmission. The electronic regeneration in modern lightwave transmission that carries between 80 to 200 channels also dictates the cost and, more importantly, prevents the construction of a transparent optical network. As a result, eliminating periodic electronic regeneration will drastically change the economy of the network infrastructure, ultimately leading to cheaper and more efficient transmission of information.
The breakthrough in this study relies on wideband “frequency combs” that the researchers developed. The frequency comb described in this paper ensures that the signal distortions — called the “crosstalk” — that arises between bundled streams of information travelling long distances through the optical fiber are predictable, and therefore, reversible at the receiving end of the fiber.
In an optical fiber, information is transmitted through multiple communication channels that operate at different frequencies. The electrical engineers used their frequency comb to synchronize the frequency variations of the different streams of optical information, called the “optical carriers” propagating through an optical fiber. This approach compensates in advance for the crosstalk that occurs between the multiple communication channels within the same optical fiber. The frequency comb also ensures that the crosstalk between the communication channels is reversible.
The frequency comb ensured that the system did not accumulate the random distortions that make it impossible to reassemble the original content at the receiver.
The laboratory experiments involved setups with both three and five optical channels, which interact with each other within the silica fiber optic cables. The researchers note that this approach could be used in systems with far more communication channels. Most of today’s fiber optic cables include more than 32 of these channels, which all interact with one another.
The same research group published a theoretical paper last year outlining the fact that the experimental results they are now publishing were theoretically possible.
The University of California has filed a patent on the method and applications of frequency-referenced carriers for compensation of nonlinear impairments in transmission.