Ukraine And Russia Battle To Defeat “Un-jammable” Fiber-Optic Drones

In the ongoing war between Russia and Ukraine, innovation in drone and counter-drone technology has become a defining feature of the battlefield. Since many counter-drone systems work by jamming the radio signals controlling the drones, both Russia and Ukraine are increasingly using “jam-proof” drones that communicate over lightweight fiber-optic cables. The lightweight cable is wrapped onto a spool mounted to the drone. It unspools as the drone flies, allowing the drone operator to maintain a communication connection even in the presence of jamming. Regardless, in the cat-and-mouse game of drone and counter-drone technology, even these drones have inherent vulnerabilities that both countries will soon exploit.

The challenge of countering these tethered drones goes beyond their immunity to jamming. Since jamming is ineffective, Ukrainian and Russian forces have to use kinetic methods to counter them. However, many kinetic counter-drone systems rely on the radio signal from the drone, which includes the video feed, for detection. This signal is then triangulated to determine the drone’s precise position. With fiber-optic drones, these feeds are transmitted to the operator over the cable, leaving no detectable signal.

Although these fiber-optic controlled drones cannot be detected through their radio signature, there are other methods for detection. A recent article by Business Insider indicated that Kara Dag, a Ukrainian technology company, has proposed using acoustic and visual signatures, combined with advanced processing techniques, to detect these tethered drones. Once detected, the Ukrainians can counter the drone through a series of kinetic methods. Meanwhile, the Russian Ministry of Radioelectronic Industry is soliciting information from the defense community on how to detect and potentially defeat these drones. Many of their proposals are similarly focusing on acoustic and visual detection of these drones.

The acoustic detection of drones is a well-established technique that relies on an array of microphones to identify the distinctive noise produced by drone propeller blades and motors. Fiber-optic drones are louder than similar non-tethered drones because their propellers must generate more thrust to support the added payload of the cable spool. Regardless, the primary challenge with this approach has traditionally been range. Noise levels attenuate with distance, and most microphones struggle to distinguish drone noise from ambient sounds at distances greater than approximately 100 meters. To address this limitation, arrays of directional microphones are commonly used. These arrays focus on specific portions of the sky, significantly reducing the interference from ambient noise. By sweeping the sky, they can enhance the likelihood of detecting the acoustic presence of a drone.

The visual detection of drones is similarly well-established but also has its own challenges. Small drones often appear as tiny specks against the sky, making them difficult to distinguish from aircraft or birds. Moreover, tethered drones typically fly closer to the ground, which limits the line of sight required for visual detection. However, several proposed techniques are using the fiber-optic cable to aid in the detection. Although the cable is thin and difficult to see in the visible spectrum, it reflects light in the infrared range. A drone detection system can exploit this property by using a diffuse infrared laser to sweep the sky and an infrared camera to detect reflections from the cable. The infrared cameras could also be able to detect the heat signature from the drone’s motors as they heat up during operation.

Both acoustic and visual detection methods must identify very small signals within a large amount of noise, the proverbial needle in a haystack. Advances in processing techniques, including machine learning and artificial intelligence, have the potential to make this task easier. Additionally, when the two detection techniques are combined, they reinforce each other, increasing the likelihood of detecting a drone. Kara Dag is developing such a system for Ukraine, leveraging the country’s strong technical expertise in advanced processing techniques.

Despite these potential methods for countering fiber-optic-controlled drones, such systems are not currently available. As a result, whichever side develops a counter-drone solution first will gain a distinct advantage on the battlefield. While Russia possesses expertise in drone technology, Ukraine has the ability to rapidly innovate and field new solutions. Once one side implements a solution, the other is likely to quickly follow with its own, and drone warfare will continue to evolve.