Avionics Digital Edition
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How Fiber Optics Will Propel Future Avionics

The use of fiber optics is gaining momentum in modern avionics because it helps solve the size, weight and power (SWaP) challenges in next generation system designs. Fiber optics can handle high-bandwidth applications, weigh less than copper wire, are more immune to Electro Magnetic Interference (EMI) and are more reliable. Fiber optic connectors and components manufacturers are innovating to enhance cockpit management and revolutionize aircraft cabin design.

Fiber optics offer many benefits compared with traditional copper wiring including supporting higher bandwidth, lighter weight, better signal integrity, and immunity from EMI.

  • Fiber optics support bandwidth over 60 Tbps, while copper wiring tops out at 10 Gbps.
  • Fiber optics are lightweight and have a smaller diameter. Typically, a fiber cable weighs approximately 4 lbs. per 1,000 feet, while copper wiring typically weighs 39 lbs. per 1,000 feet.
  • Fiber optics have better signal integrity. Repeater use is needed only approximately every 30 miles, as compared with every three miles for copper wiring, thus minimizing equipment and weight for an aircraft’s onboard network.
  • Fiber optics are immune from EMI. Therefore, electrical noise generated by other equipment will not affect fiber optics, allowing close proximity to equipment and saving space. More important, by preventing signal leakage fiber optics also increase security, as there are no leaks for hackers to tap.

Connector and Interconnect Innovations Enhance Avionics Design

Many avionics applications require high-speed operation. For example, a military fighter is equipped with high-performance radar to detect both targets and incoming missiles. A 4K or 8K high-resolution radar image display in the cockpit requires high-speed processing.

Video cameras onboard the fighters use digital compression to preserve system bandwidth, but at the cost of latency and delayed image display. These trade-offs will be unnecessary in avionics using fiber optics. Instead, with its high bandwidth capability, a fiber-optic based system will be able to deliver real-time imaging without digital or video compression. Doing away with such compression better supports split-second, heat of battle decisions by the pilot based on radar and camera images.

Bill Weeks, senior fellow, TE Connectivity, envisions that the need for higher speed interfaces, such as 4k/8K video, LIDAR, and other target acquisition and avoidance systems, will drive the demand for fiber optics. He said that the next-generation military fighter platforms will need to transport 100 terabits of data with extremely low latency and process that information in sub second intervals.

“In commercial air, the ability to eliminate miles of service specific, dedicated parallel wires by integrating these services onto a common high speed bus, will also drive the need for fiber optics and greatly reduce the time it takes to design, install and replace complex wiring harnesses,” commented Weeks.

According to Paul Hart, Chief Technology Officer and Technical Fellow at Curtiss-Wright, situational awareness will be further enhanced with ADS-B In and FIS-B. This would, however, create the need for improved flight displays with HD Video, ARINC 818 and avionics video data bus.

Curtiss-Wright’s COTS-based video format converter XMC-FC1 supports XMC (VITA 42) mezzanine card form factor can convert 15 different analog and digital video formats. Curtiss-Wright

Furthermore, future air data systems will be more accurate (+/-0.25 millibar), enabling aircraft to fly closer together, increasing capacity. Curtiss-Wright recently introduced the XMC-FC1 Rugged Video Gateway Format Converter module, which supports 15 different analog and digital video formats and resolutions and ARINC 818 avionics digital video bus to simplify avionics video conversion.

As more commercial planes provide faster, secure Wi-Fi and better in-flight entertainment (IFE) services, fiber optic networks on commercial flights are expected to grow quickly to support network topologies sharing data in excess of 100 Gbps. Fiber optics networks with lightweight fiber optics transceivers can support these high speeds without installing large copper-based networking systems. For example, ¬ Radiall offers an MT-based interconnect designed to withstand aerospace's harsh environments. Its Q-MTitan ARINC 846 that comes in 12 or 24 fiber channel product helps to save weight and space.

“The constant challenge is to integrate more and more fibers with limited footprint which is ruggedized and aerospace compliant. Additionally, how to provide easy-to-install turnkey solutions for system integrators is a very important factor. This is where our Q-MTitan ARINC 846 will stand out as it can be inserted inside COTS connector with a standard #8 Quadrax cavity,” says Cathy Combet, a fiber optics product manager at Radiall.

Radiall’s Q-MTitan™ series is ARINC 846 compliant. Its contacts support off-the-shelf multipin connectors, such as MIL-DTL-38999, ARINC 600 NSX, EN4644 EPX, EN4165 connectors, Quick Fusio™.Radiall

Compared with optical transceivers used in the commercial environment, Reflex Photonics’ design used in avionics and space is rugged and must meet extended temperature, humidity, shock and vibration, and radiation (for applications in space) requirements. Products need to comply with standards such as MIL-STD 883 (shock, vibration, and thermal cycling tests), MIL-STD 202 (damp heat tests), and MIL-STD-810 (cold storage tests). Avionics optical transceivers need to be both rugged and compact.

“Physical space is a precious commodity within increasingly complex airframes and spacecraft, and reductions in dry weight improve fuel efficiency and increase payload capacity. While copper is cost-effective and well-established in avionics cabling, the size, weight, bandwidth and power advantages of replacing copper with fiber are driving new projects and existing avionics platform retrofits to adopt COTS optical transceiver and cabling systems,” says Arlen Martin, product line marketing director, Reflex Photonics.

Reflex Photonics’ optical fiber transceivers support (a) BGA electrical interface, (b) MegArray™ electrical interface, and (c) LGA electrical interface.Smiths Interconnect

Carlisle Interconnect Technologies (CarlisleIT) further suggested the importance of using fiber optics to reduce weight. It provides a full range of fiber optic cables and assemblies. Its LITEflight fiber optic cable is specifically designed to support aerospace, military, industrial and other harsh environments. With its protection, a typical fiber optic cable will weigh-in at only about 15 pounds per mile of cable much lighter than copper wire cables.

CarlisleIT provides a range of fiber optics cables. With its protection, a typical fiber optic cable will weigh-in at only about 15 pounds per mile of cable much lighter than copper wire cables.CarlisleIT

Connectors and Cable Harnesses Will be More Integrated and Modular

Instead of having one cable harness, aircraft can use a fiber optic cable harness in a modular format, much like a hardware system with multiple plug-in modules. If one module fails, a new module can be plugged in to replace the defective one. Similarly, if a cable harness problem is detected, it’s possible to replace the harness right in the aircraft instead of grounding the plane for repair work. This will increase installation and maintenance efficiency.

Samtec has developed the “Extended Temperature Optical FireFly Micro Flyover System” for military, industrial and avionics applications. The product is capable of data transfer speeds of up to 10 Gbps, operates from -40 0C to +85 0C and supports x4 and x12 configurations.

Future speed upgrade targets are within the 25 Gbps for Samtec. The module is compliant with industry-standard optical end options including MT38999, MTP, MXC, ARINC 801 and ARIB STD-B58 interfaces. As shown below, it is an example of an integrated connector and cable module which will be a trend of the future. “A modular design approach of connector and cables not only makes design easier, it also saves space and makes it attractive for most avionics applications,” says Matt Burns, technical product marketing manager of Samtec, Inc.

The rendering of the Extended Temperature Optical FireFly Micro Flyover System demonstrates that many custom and flexible design can be configured.Samtec, Inc

The fiber optics-based network speed is expected to increase to 200Gbps in the next few years. Transceivers and connectors are catching up quickly. How would this super-speed capability impact the future of avionics? Unmanned aerial vehicles (UAV) are one area that could greatly benefit from future improvements to the ultimate goal of avionics.

UAVs are already available today such as military drones which are controlled remotely. Some helicopters are also autonomous. But it is still in its infancy. Foolproof UAV is still many years away. But the high-speed capability of fiber optics networks will bring UAV one step closer.

Additionally, the custom, modular cable/connector harness will potentially change the approach of building aircrafts. Whether building a new plane, troubleshooting or routine maintenance, it will take less time. This means it will shorten the time a plane will be on the ground and together with built-in artificial intelligence, an aircraft may be able to do self diagnose. In short, fiber optics connectors and interconnects will enable higher performance, smaller and lighter designs and the aviation industry as a whole will be more efficient and profitable.