Breakthrough May Double Speed of Fiber Optics Networks

An engineering breakthrough by researchers at the University of California, San Diego, has the potential to double the speed of fiber optic networks. The findings, reported by a team of photonics researchers in the June 26 edition of the journal Science, could dramatically increase the maximum power capacity of signals sent through fiber optic cables.

Although not every user connects to the Internet through an optical cable, fiber optics do serve as the primary infrastructure for much of the Internet. Increasing the speed of those key connections would significantly increase speeds for all Internet users, regardless of the type of service they have.

No More Repeaters

Currently, fiber optic signals are limited in terms of the amount of power that can be used to transmit them. Beyond that limit, additional energy begins to increase the amount of distortion in the signal, making it impossible for receivers to decipher it. This power threshold limits the distance that signals can be sent, requiring communication infrastructure to include signal repeaters placed at various intervals along the network.

But the discovery at UC San Diego would potentially allow optical signals to be transmitted with far greater energy without suffering from the same level of distortion. That, in turn, would mean fewer signal repeaters would be required. The researchers were able to transmit a signal 12,000 kilometers without using repeaters and successfully decode it -- a new record.

The ability to transmit a signal that far would eliminate the need to install repeaters along the transmission path. Getting rid of repeaters would not only significantly speed up data transmission, it would also greatly reduce the cost of building such communications infrastructure in the future.

Eliminating Crosstalk

The breakthrough comes a year after the UC San Diego research team published a paper indicating that such a development was theoretically possible. The signal degeneration responsible for the current energy limit is the result of “crosstalk,” distortion between different data bundles as they travel along an optic cable. The researchers discovered that this distortion was non-random, but instead the result of fixed physical laws.

As a result, the researchers theorized last year that a signal could be pre-conditioned in such a way that when the signal eventually degraded, it would do so in a way that was predictable, allowing them to accurately reconstruct the original signal by filling in the gaps caused by the distortion.

The UC San Diego team used a device known as a frequency comb to synchronize the variations between the various communications channels present in a typical optical fiber. The frequency comb prevented random fluctuations from entering the system, ensuring that the signal would still be readable when it was eventually received. The discovery allowed the team to increase the energy output of the signal 20 fold while still resulting in a coherent transmission.