Feature: Avionics
fitted with high-reliability ELIO fibre optic contacts. Te 8D range, in particular, is based on a popular derivative of the military-proven MIL-DTL-38999 circular connector style. Te connector construction provides comprehensive sealing when mated, with the circular metal shell being specified in aluminium, composite, marine bronze and stainless steel, with a range of plating finishes. Te single-mode and multi-mode Elio fibre optic contacts use a robust 2.5mm ferrule with precision alignment to provide performance and resilience in environments with high levels of shock and vibration. Features to look for in fibre optic
connectors for rugged applications include: • Low insertion loss, to ensure minimal signal loss (typically < 0.5dB for physical contact connectors and < 1.0dB for expanded beam ones);
• High return loss, in order to reduce signal reflections and maintain data integrity; • Shock and vibration resistance:
Connectors must meet military and industrial standards (e.g., MIL- DTL-83526) to withstand mechanical stress;
• Impact protection: Use of reinforced housings to prevent damage from physical impact;
• Wide operating temperature range, typically -55°C to +85°C;
• IP67- or IP68-rating for protection from water and environmental conditions;
• Stainless steel or composite plastic materials to resist exposure to fuels, oils and other harsh substances.
Expanded beam technology Another approach in these applications is expanded beam technology which uses two matching lenses, one at the end of the transmitting fibre from which the light beam is emerging, and the other at the end of the fibre it is being connected to. Te first lens expands the emerging beam and the second lens refocuses the light, reconstructing a beam in the second fibre
36 September 2025
www.electronicsworld.co.uk
of same size as the original beam. As the beam of light passing between the two lenses is expanded to have a much larger diameter than the beams inside the fibres, this means that any particle of dust or dirt will be a much smaller proportion of the transmitted light beam, thus having lesser effect on blocking the light and affecting the signal. Specifically designed expanded
beam connectors incorporate this lens technology within each mating half. Unlike physical contact technology, the expanded beam connection is contactless, with the expanded light beam passing over a small gap between the two lenses within the connector system, once mated. This significantly improves resistance to vibration and mechanical wear and can increase connector reliability and lifetime. The air gap also means that any dirt or contamination on the lenses will not damage the mating half in use. A good test for expanded beam connectors that
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