NAS Patuxent River, Md. –
The need for high-speed communication is real and critical. In an era with hypersonic weapons, sixth-generation fighters and a proliferation of autonomous systems, the ability to collect vast amounts of sensor data and make time-critical decisions faster has never been more paramount to surviving on the 21st century battlefield.
To emphasize this importance, imagine a group of hypersonic missiles are closing in on an aircraft at Mach 5. If the plane can detect hypersonic missiles at 80 miles out, the pilot has one to two minutes to respond versus 15 to 20 seconds to respond at 20 miles out. For Naval Aviation, response time can mean maneuvering, employing electronic or physical countermeasures, or firing a missile. Keep in mind the response does not happen instantaneously, nor does it have a 100% chance of being effective (if only there was sufficient time for multiple response attempts to maximize the probability of survival).
To maximize response time in varying mission situations, aircraft are employing more powerful sensor solutions to detect threats at longer distances. These sensors include various forms of electro-optical, radar and electronic warfare suites. To detect threats at longer ranges while maintaining the same coverage area, aircraft must capture significantly more raw data by either increasing sensor resolution, capture rates or number of sensors. Increasing the amount of sensor data an aircraft captures is not as easy as it sounds and creates a variety of secondary technological challenges. These secondary challenges involve the processing and transporting of the raw sensor data in the same or faster time interval so the pilot can then respond appropriately. The first secondary challenge—processing—can be sped up through a combination of improved hardware, parallelized computing and developing more efficient processing approaches. The other secondary challenge involves transporting data around the aircraft. Raw sensor data is not inherently useful by itself; it is merely a collection of structured numbers. Further processing is needed to extract meaning from the raw sensor data. The challenge is that this raw sensor information is not always captured by the same avionics system that processes the sensor information. The sensor data must be transported by some means from the sensor to an avionics computer that can be located up to tens of meters away from a given sensor.
Fiber Optic Versus Electrical Signaling
There are two primary ways of transporting the raw sensor information around naval aircraft: electrical and fiber optics. Electrical signaling has been the incumbent approach on aircraft since digital avionics systems became available in the 1960s. For more than 50 years, this approach has worked well and still does for many applications. However, to better understand the need for fiber optics, transporting information around an aircraft can be divided into two types of problems: 1) transporting information within an avionics system (short distance); and 2) transporting information out of an avionics system to a physically separated avionics system (long distance). When signals are transported at a short distance or when the data rate is low, electrical signaling is the preferred signaling method.
As the amount of data to be transported between avionics systems further increases, it becomes increasingly difficult to send a higher volume of data more than a short distance using electrical signaling while maintaining signal integrity.
Additional factors like signal attenuation, crosstalk, signal reflections, electro-magnetic interference, and environmental elements become increasingly difficult to overcome. The key is to be combat effective, in that an aircraft must operate reliably over a wide range of austere conditions. This can include freezing arctic environments, a corrosive saltwater environment or scorching desert conditions. In addition, there can be a large amount of electric noise in and around the aircraft that makes reliable high-speed electric communications challenging. Electronic noise can come from generators, AC power lines, motors, RF signals and adjacent electrical cables. Fiber optics has the advantage of being high speed as well as immune to electromagnetic interference (EMI). And when ruggedized, it can operate over the range of needed environmental conditions. These qualities, in addition to others like reduced size, weight, power and longer lifespan, make fiber optics the ideal candidate for high data rate system-to-system avionics communications.
How Fiber Optics Meet Naval Aviation Mission Needs
While fiber optics is the optimum solution for high-speed system-to-system communications for military aircraft, there have been some challenges slowing its adoption and implementation. Over the last several years, the needs of data centers and the aerospace industry have diverged. The drive for higher speeds and lower cost fiber optic components has led to a series of compromises on the structural and environmental robustness of a sizable percentage of these components. This is due to most of the fiber optics market being aimed toward indoor usage, i.e., in data centers where a far lower range of temperatures and environmental extremes are present. For military aircraft to meet future system-to-system high speed data transmission needs—that of advanced fiber optics technologies that can operate at high speed (25 gigabytes per second [Gbps], 100 Gbps or more) and meet harsh environment requirements—it must be matured and ruggedized.
The Navy is supporting multiple efforts through small business innovation research (SBIR) to develop digital avionics high speed and high-power optical components. This includes transmitters, receivers and transceivers operating at 100 Gbps or more, as well as wavelength division multiplexing technologies and fiber optical cables for avionics high-speed applications. In addition, the Navy has been funding the development of innovative fiber optic packaging methods, fiber optic components that meet the operating environment per military specification, and fiber optic components with improved power budget. It also includes improved fiber optics system architectures, methods for fiber optic component qualification, improvements in the fiber optic installation and installation verification process, and various types of fiber optic support equipment.
The current and future investments in fiber optics technologies are critical to maturing and ruggedizing industry fiber optic technologies. They also advance the supporting technologies required to maintain capabilities of the fiber optics components throughout the long lifecycle of military aviation platforms. The Navy continues to be involved in open standards development to provide better guidance and specification requirements for the technologies under development.
Overall, current and future focused dedication into ruggedized fiber optic high-speed technologies is essential for enabling faster system-to-system communications on military aviation platforms. This more rapid communication capability can be leveraged to enable enhanced capabilities for maintaining technological dominance well into the 21st century and provide our warfighters the edge they need to succeed.
From the Air Combat Electronics Program Office Avionics Architecture Team. 