Integrated Fiber Optics for Mission-Critical Systems 

By Contributed Article | April 27, 2018

Molex examines the benefits of integrated fiber optics vs. copper cable assemblies in mission-critical systems. 

Thomas Heller, Account Manager, Aerospace and Defense, Molex

The world’s most complex technologies are deployed in critical mission command, control, communications, computer, intelligence, surveillance, and reconnaissance systems. Military and civil aerospace markets cover a spectrum of high-bandwidth fiber optic applications ranging from manned and unmanned aircraft to ground and naval systems, including battlefield networks, night/thermal vision systems, radar, and computer/data networks to complete in-cabin networking solutions.

Figure 1: High-reliability, high-bandwidth fiber optic interconnect solutions are critical to the successful operation of a variety of military and aerospace applications, including drone technology. (US Air Force photo by Senior Airman Cory D. Payne)

Demand for ruggedized computing and networks is growing — and mandatory for secure integration with ground command centers, soldiers, and other military personnel. For example, active guidance electronics are integrated into land, sea, and air-based ordnance, requiring GPS and ground control systems. Integrated vehicular systems require flexible and redundant network architectures to support data communications to control centers. Aircraft missile electronics include: flight and targeting sensors, engine control units, and fuzing and ordnance systems. Networked airframe management systems run the gamut from fuel monitoring to power, water, oxygen, and waste monitoring, and manned aircraft systems include: black-box applications, pilot command controls, radar and cockpit communications, and integration with ground networks, navigation, and flight management. Even civil aviation manufacturers are increasingly revamping cabin interiors with high-bandwidth fiber optic networks to enable in-flight entertainment (IFE) systems.

Military and civil aircraft engineers strive to reduce weight and control costs while optimizing performance, safety, and functionality. Military-grade (Mil-Spec) copper has earned its stripes as a mainstay connectivity technology. However, copper is not without limits, especially as bandwidth requirements trend upward. Higher transmission rates over longer distances are challenging on bases and in data control centers used to support applications in military theaters worldwide.

Fiber Optics Outrank Copper

New technological developments have yielded advancements in ruggedized fiber optics designed for military applications. Fiber optics outrank copper in size, weight, power, and cost (SWaP-C) characteristics. Weighing a fraction of copper, fiber is dimensionally smaller with comparable or higher transmission rates.

Copper cable assemblies can cause data transmission bottlenecks in military base networks and aircraft applications. Very little signal loss occurs during light transmission over fiber, so data can move rapidly, delivering performance of 10Gb/s and up. Unlike copper cabling, non-conductive fiber optics are dielectric and immune to EMI and RFI — a performance and security advantage that protects sensitive communications and data transmissions between theater surveillance or monitoring systems, command centers, and land, sea, and airborne radar systems.

Network modules and components and in-flight electronics box units do not always have direct access to a controlled environment and cooling systems. Copper components create heat, so thermal management can become an issue, as excess heat build-up can degrade reliability and boost maintenance costs. Alternately, data transmission over fiber is extremely reliable and immune to the environmental factors that negatively affect copper cable transmissions. Dirt, dust, mud, humidity, moisture, oil, and other contaminants that fiber can withstand can further degrade copper, resulting in system performance problems.

Figure 2: FlexPlane™ optical assemblies from Molex meet harsh-environment application requirements.

Cyber and physical security are always high priorities. Hacking into a fiber network is extremely difficult even under ideal circumstances, and can be more swiftly detected and prevented within a fiber network than a copper network. There are ways to breach the security of copper network architectures using hard connections or antennas, so fiber optic networks provide a more cyber-resilient architecture.

Additionally, the cost for fiber is steadily decreasing, and fiber reduces overall systems costs over time. Pre-spliced fibers, connector options, and other field termination technologies also simplify installation and maintenance requirements, which can make a significant difference in time-sensitive missions.

Flex Fiber Optic Circuitry: Faster, Lighter Weight, Cost Effective

In harsh environment, high-density routing applications in ground-based networks, battlefields, and aircraft PCBs or backplanes, versatile flex circuitry delivers high fiber-count in a substrate for fiber routing from card-to-card or shelf-to-shelf. Fiber optic flex planes embed fiber in engineered plastic sheets, which greatly reduces weight and cross-sectional area. Heavier copper cables require heavier fixtures, while ribbon fiber can be easily attached in a manufacturing plant or in the field without additional mechanical fixtures.

Adding ribbonized fiber leads, generally in the range of a meter or two long, can eliminate the need for splicing fiber. Ribbon-fiber-based interconnects are best suited for connecting flex fiber to other systems. A variety of blind-mate interconnects can be used to connect optical circuits. Suitable for virtually any routing scheme, flex optical circuitry can be routed point-to-point or in a shuffle or a logical linear pattern. Direct- or fusion-spliced fiber terminations help to eliminate additional insertion loss, and each fiber optic flex plane circuit can be fully tested down to the per-port insertion loss and return loss much more readily than testing copper circuitry.

 Benefits of Fiber Optics vs. Copper

  • Higher bandwidth
  • Eliminates data transmission bottlenecks
  • Improved cyber resilience and detection
  • EMI/RFI immunity
  • Weight and space savings
  • Design flexibility
  • Cost-effective new builds and incremental migration
Figure 3: Optical FlexPlane™ assemblies from Molex provide compact and manageable high-density fiber routing solutions.

FlexPlane™ High-Fiber Count Optical Circuitry

Flex fiber optic solutions are excellent performers in rugged military, aerospace, and civil avionic applications. Each delivers exceptional quality, efficiency, and reliability to ensure seamless connectivity.

As military and aerospace telecommunications and networking systems increasingly call for optical backplanes with high fiber counts and cross-connect systems, Molex FlexPlane™ optical circuitry provides one of the most versatile, highest-density interconnects on the market today. Ideal for high-density (high-fiber-count) optical routing on PCBs or backplanes and cross-connect systems, FlexPlane provides manageable fiber routing from card-to-card or shelf-to-shelf on a flexible, flame-resistant substrate. Optical fibers routed to a polymer substrate are locked into place with flame-resistant conformal coating, and — engineered for proper bend-radius to ensure no impact on optical performance — thermally stable substrate materials meet or exceed UL-V1 flame ratings.

PCB real estate and thermal management are vital design requirements in demanding applications. Standard fiber optic flex circuits are routed on a single substrate, while Molex 3D FlexPlane optical backplane circuits route fiber on multiple stacked substrates to achieve improved airflow and a more compact routing area, enabling an almost 50% substrate size reduction compared to standard FlexPlane.

Trusted, Quality-Driven Partner

Quality drives every decision for every subsystem in military, aerospace, and civil aviation. Molex combines high-quality fiber optics with in-house capabilities to design customized solutions to satisfy specific design criteria. From PCB-to-PCB, Molex total system solutions integrate transceivers, harnesses, connectors, and optical flex, and are reliability tested in the US. Molex facilities provide: product evaluations, simulations, material consultations, failure analysis, approval agency services, and testing for EMI and SI for verified assurance of frontline quality.

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