News Feature | February 14, 2017

A Fish-Inspired Photonics Solution To The Spectrum Crunch

By Jof Enriquez
Follow me on Twitter @jofenriq

mable-fok
Mable Fok. Image courtesy of Mike Wooten/UGA

A University of Georgia researcher is turning to nature and the science of photonics to help solve the lack of sufficient wireless frequency spectrum needed to support the booming number of interconnected devices today.

Mable Fok, an assistant professor in the College of Engineering and director of the Lightwave and Microwave Photonics Laboratory at the University of Georgia (UGA), "will use photonics technologies to rapidly scan the spectrum and find frequencies that are not in use. Once identified, those gaps can be used to meet radio frequency needs of various devices," according to a news release.

Specifically, she is trying to build a photonic device that uses an artificial neural network that improves the efficiency of wireless communications. The inspiration for such a mechanism is the "jamming avoidance response" (JAR) exhibited by the glass knifefish (Eigenmannia virescens), which uses electrolocation for sensing and movement.

"They locate objects by generating an electric field and detecting distortions in the field," Fok explained. "They have a neural circuit that can effectively sense the frequency emitted by other fish, and they use this sense to regulate their own emitting frequency so they don't interfere with the others."

Such a natural anti-jamming system can be replicated to achieve automated interference mitigation for RF communication devices, and to allow dynamic use of spectrum blocks that are not in use at one given time.

"What if we can borrow the same algorithm and apply it to our radio frequency system? If someone tries to jam our signal, we'll be able to just move someplace else that no one is using," said Fok, who received a National Science Foundation (NSF) CAREER award for her research to find solutions to the spectrum crunch.

Eigenmannia, however, has a discharge frequency of only hundreds of Hz, and is only capable of operating in that frequency range.

"In our communication system, a much wider frequency band from MHz to tens of GHz is required," the researchers wrote in IEEE Photonics Society News. "Here is where photonics plays an important role in a practical JAR system."

According to them, the dynamics of biological neurons and lasers are similar, and that a number of neural algorithms can be simplified and reassembled with both linear and nonlinear photonics phenomena.

In order to demonstrate this, Fok and colleague Ryan Toole successfully designed an artificial neural model using photonics technology that mimics the fish's JAR circuit, and allows multiple wireless devices to seek an unused frequency when they detect interference from other devices. The next step is building a physical prototype of the JAR circuit.

"RF photonics-based implementation of JAR allows for frequency-independent and real-time operation based on the fact that photonics devices have a flat frequency response over a terahertz (THz) frequency range and a near-instantaneous response to inputs," the researchers concluded in the IEEE column.

Fok also is developing an educational app to create awareness on the field of photonics, and how it offers more efficient alternatives to traditional electronics technology. At least three grants from the NSF will support their efforts.