cleanability, wear), and cable limitations (bend radii, wavelength range).
3. SPECIFIC TO EVTOL AIRCRAFT System redundancy is required for certification. Fiber optics can serve as a completely independent “fly-by-light” alternative to “fly-by-wire” systems with the bonus of zero EMI. DIFFERENT FLAVORS OF OPTICAL-FIBER ROBUSTNESS The connectors that couple the fiber optic cable to the light source, receiver, and other components come in two types: • Physical contact (PC) technology physically mates the two ends of optical fibers together. • Expanded beam (EB) technology uses lenses at fiber end faces to expand and re-focus light within a small air gap in the optical pathway. PC and EB technology differ in how they handle environmental issues (exposure to water, dust, vibration), termination factors (insertion loss, return loss, misalignment, angularity), maintainability (repair,
PC CONNECTIONS FOR SATELLITE APPLICATIONS
PC interfaces use precision ferrules and alignment mechanisms to minimize optical losses between fiber ends. It’s simply a matter of cleaving, polishing, and joining fiber ends in a butt contact. Ends may be flat polished for digital optical traffic or angle polished for optical sensing applications. It’s a one- and-done process with no need to touch it again — exactly what a mission in space requires. High- quality installation can be performed on the ground, and high optical continuity can be maintained during the vibration, shock, and temperature extremes of spacecraft launch and orbit. EB CONNECTORS FOR EVTOL AIRCRAFT APPLICATIONS EB interfaces employ a design that expands the light beam across a small gap in the optical pathway. A lens expands and collimates the beam emitted from the launch fiber. The beam remains collimated across the gap until a receiving lens focuses it onto the receiving fiber with an achievable insertion loss below 1.0 dB, just slightly higher than a PC contact. Thanks to the gap, EB interfaces are minimally affected by contamination, misalignment, vibration, and wear. Multiple connections and disconnections can occur with little measurable insertion loss even after hundreds of mating cycles — exactly what eVTOL maintenance crews require. EB connectors are usually terminated on robust military tactical, and, for eVTOL, avionics/flight-grade cable.
OUTGASSING, THE RELEASE OF GAS OR VAPOR BY MATERIALS IN A VACUUM ENVIRONMENT, IS A CONCERN FOR COMPONENTS USED IN SPACE APPLICATIONS.
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