So what will happen to a small drone mission when GPS is not reliable and the radio connection is a target?
Another recent Marine Corps over-water experiment at Camp Pendleton considered a solution that looks less like a new waveform and more like a physical workaround a first-person-view quadcopter that is operated via a fiber-optic connection. Marines tested the ability of a tethered communications route to maintain control inputs, navigation confidence, and live video in the case of jamming, spoofing, interception, or emitter geolocation by conventional small unmanned aircraft systems.
The test, which was in collaboration with Defense Innovation Unit, saw the system in a maritime environment where gusts of wind, glare, and few recovery options soon reveal vulnerabilities in managing and pilot workload. To the Marines working in littoral areas, this environment is important since it shortens the timeframes and narrows the error margin. It also puts emphasis on the video feed that FPV pilots use in fine control and accurate observation. The idea of the fiber-optic approach is simple, eliminate the command-and-control connection in the electromagnetic spectrum. A hardline connection does not radiate radio-frequency energy, so the control line is not vulnerable to jamming, and is more difficult to cue using passive detection.
That architecture has more than anti-jam resilience technical benefits. Fiber connections have the potential to provide predictable bandwidth and low latency, which are fundamental to the process of FPV control and the ability to retain usable imagery when a vehicle is performing a high-speed manoeuvre. Practically, the drone has a canister that releases a thread of optical fiber on flight, maintaining the operator connected via a closed physical circuit as opposed to using an over-the-air channel. The fiber can be bare or coated depending on the design, and the diameter of the fiber can be in the range of 200-400 microns to maintain weight, drag, and survivability depending upon the design.
The Marine Corps testing is also enclosed within a broader U.S. test to pressure systems that can still be operational in the face of electronic assault. An FPV fiber-optic aerial was one platform of the platforms exhibited in Exercise Silent Swarm 25, a Navy-led series of technology tests hosted by the Michigan National Guard at Alpena. Rob Gamberg of NSWC Crane, in an announcement related to the said event, explained the rationale: The Silent Swarm hypothesis is to find that set of systems that will be able to outsmart and make a difference even in the most demanding conditions.
The request of Marine forces, particularly reconnaissance units, operationally, is reduced to maintaining the presence of the gaze in front without making the presence of the operator known. The lack of a signal of control by a drone decreases the chances of an opponent tracking the controller using emissions. In the case of distributed littoral operations, where small groups can be spread out and can only be linked together intermittently, there the same characteristic can complement rather than substitute existing wireless fleets.
The tradeoffs are still physical and mechanical. The length of fibers places a limit on useful radius and the cable itself is a mission-critical part that could snag, get entangled or cut. The canister provides weight and influences endurance and agility whereas the line provides routing restrictions that may restrict aggressive actions around obstacles. The latter limitations are increased in water, where the plane will likely have to remain uninvolved with the surface and where there exists little room to save the plane in case the connection is lost.
Nevertheless, the theme that cuts across Marine testing and joint experimentation is the same: in case the spectrum is fought over, the resilience can be achieved by going outside of the spectrum. Fiber-tethered FPV drones represent a very specific but very timely device one that is meant to maintain control and video alive in the very circumstances that are being manufactured to render them obsolete.
