Fibre-optics are becoming increasingly more important in space applications. Here Mike RessL, director of development & design engineering at Molex, explains why.
Space initiatives run on data. Satellites and spacecraft depend on high-resolution sensors, advanced imaging payloads, onboard analytics, guidance and communication systems to operate. With each advancement, the quantity of information generated and processed onboard modern space programs steadily increases.
Meanwhile, the number of private and public space initiatives continues to grow. Constellation launches, such as the Space Development Agency’s (SDA) Proliferated Warfighter Space Architecture, comprise hundreds of optically interconnected satellites designed to collect, share and relay critical defence and security data across orbital networks and back to Earth. Industry leaders are eyeing space as the next frontier for data centre locations, while efforts are already underway to deploy a 2,800-satellite constellation designed to deliver space-based real-time computing at an unprecedented scale.
Moving Data in Space
In each of these examples, reliable high-bandwidth data mobility is essential. But, these are not like terrestrial networks – they must endure some of the most demanding operating environments. Exposure to cosmic and solar radiation, extreme thermal swings (from +120˚C in direct sunlight to -170˚C in Earth’s shadow), the vacuum of space, vibration, shock and electromagnetic interference (EMI) make designing resilient electronic systems a daunting task. These challenges are only compounded by the strict size, weight and power (SWaP) constraints demanded by space programs.
Fibre-optic technologies have become increasingly important in addressing performance and survivability requirements. Active optical cable (AOC) technology is among the most promising. Already proven in terrestrial data centres and supercomputers, and with space mission heritage, AOCs pave the way for expanding space-based applications.
Beyond Copper
Traditional copper coaxial cables have been an industry staple for years. Copper remains the most cost-effective choice for short-distance, EMI protected installations. However, as data rates climb to multi-gigabit territories across expansive installations, copper faces inherent physical limitations. Prone to signal attenuation over longer distances and EMI, and burdened by weight and bulk constraints, copper struggles to meet the high-bandwidth requirements of modern systems.
Fibre-optic cables present a viable alternative. Addressing many of these challenges, they transmit light rather than electrical signals. This makes them immune to EMI, supports higher bandwidths over long distances and minimises attenuation. However, fibre is not without its own challenges.
Conventional fibre interconnect assemblies require precise splicing, polishing and termination, as well as proper cleaning and inspection. This avoids the risk of exposure to foreign object debris (FOD) and cable damage, two of the most common causes of performance problems in terrestrial data centres. Understandably, this poses a significant hurdle for any space-based infrastructure.
What Is an Active Optical Cable?
AOCs combine the advantages of both copper and fibre into a single solution. They do so by integrating optical fibre and electrical interfaces into a single interconnect assembly. While traditional transceiver solutions require fibre-optic cables employing optical connectors, AOCs are optical fibre assemblies with only electrical connectors at each end. They convert electrical signals to optical signals and then back again, all within the cable assembly.
There are no optics to clean or maintain. This allows them to accept the same electrical inputs as traditional copper cables while using optical fibre between the connectors. This approach supports longer transmission distances and improved signal integrity without sacrificing compatibility with standard electrical interfaces.
From a system design perspective, this effectively makes AOCs a plug-and-play replacement for copper connections. There is no need to redesign connect points. Engineers can use AOCs to gain the benefits of fibre while maintaining standard electrical interfaces. This provides flexibility to use either copper or fibre according to application requirements.
AOCs also eliminate the FOD exposure and cleaning challenges present in traditional fibre installations. Their fibre terminations are housed within the unit and carried out in cleanroom environments during the manufacturing/assembly process. This prevents the fibre from ever being exposed to any potential contamination, alleviating problems associated with cleaving, polishing and termination, thus eliminating the main cause of 80% of link failures as reported for terrestrial data centres. Space-rated AOCs support aggregate bandwidths of up to 50Gbps over distances
of up to 35m. Designed for multi-lane data communication and interconnect applications, they are protocol agnostic, an important advantage in applications where proprietary protocols are common.
Compared with copper cables, AOCs also weigh less and have smaller diameters, simplifying installation and routing in space-constrained environments, while directly supporting SWaP optimisation.
Engineering Considerations for AOCs
While AOCs offer significant advantages, deploying them in space programs requires comprehensive design and testing.
One of the primary challenges AOCs face is radiation-induced attenuation (RIA). Exposure to ionizing radiation causes the gradual darkening
of optical materials. These effects compound as total dosage and distances increase, making it increasingly difficult for light to pass through the fibre. As such, appropriate shielding and housing must be used along with radiation-tolerant optical materials. As with any high-reliability network architecture, error-correction mechanisms and redundant circuits may also be required.
Designer engineers must also carefully manage power consumption, vibration levels, thermal behaviour and radiation exposure throughout the mission lifecycle. These factors can contribute to radiation-induced embrittlement within the interconnect, conductivity loss and atomic oxygen erosion.
Fortunately, AOCs are typically simpler in design than traditional transceivers, featuring fewer parts. This reduces the number of potential failure points along with inventory stock-keeping units (SKUs).
Space: The Next Data Frontier
Space is emerging as a major data frontier, where data mobility is becoming an increasingly important design priority. With the global space economy projected to grow significantly by 2040 and large-scale initiatives already underway, organisations will need to make scalable design choices that support long-term performance and reliability.
Supporting the next generation of space-based computing will require technologies that can perform effectively under extreme constraints. AOCs can play an important role in this evolution by combining the simplicity of electrical interfaces with the high performance of fibre optics to deliver a balance of bandwidth, reliability, SWaP efficiency and integration simplicity.
More broadly, high-reliability connections are fundamental to system performance in these environments. As system complexity increases and operating conditions become more demanding, there is a corresponding need to strengthen quality and resilience across the interconnect stack. This includes expanding capabilities in ruggedised solutions such as custom connectors, contacts, RF components and optical transceivers designed for harsh environments. The recent acquisition of Smiths Interconnect by Molex reflects this focus.
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