Page 59 - 2019 Mil/Aero eBook
P. 59

The benefits of optical interconnects are many, including durability, and expanded beam technology is a key development in this respect. This technique uses lenses located at the end of an optical fiber to expand the signal to better protect it from harsh environmental hazards, as dust particles as small as 9μm in diameter can block a conventional single-mode fiber optic connection. The signal is then collimated through an air gap and received by a corresponding lens that focuses the light back into the receiving fiber.
 Expanded beam technology allows contaminant-sensitive fiber optic cables to be employed in harsh-environment applications. In addition to resisting environmental contamination, Cinch Connectivity Solutions’ QPL-certified Fibreco MIL-DTL-83526 Expanded Beam Connectors (right) enable the in-field replacement of damaged expanded beam inserts without having to re-terminate the fibers and are widely employed in military tactical communications equipment.
The general benefits of expanded beam technology include greater resilience to both contamination and misalignment and compatibility with simple wipe-and-mate cleaning, negating the need for specialized cleaning tools and supplies that are not readily available in harsh environments. The connectors protect the fiber cable, and include the protection offered by the lens itself, and the lenses provide a greater active transmission surface, which increases reliability and protects the fiber from dirt and debris. Expanded beam connectors designed for use in harsh environments provide the necessary level of protection and alignment to return insertion losses of less than 1.5dB.
   Comparing conventional and expanded fiber optic beam sizes to average dust particle sizes makes it easy to see how dust particles as small as 9μm (nine millionths of a meter) in diameter — which is roughly only a sixth to a tenth the size of a human hair in diameter — can block a conventional single-mode fiber optic connection.

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