Flex Plane Fiber Optic Circuitry

Flex plane fiber optic circuitry is a cost-effective option for high-density routing on 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 the fiber in engineered plastic sheets, which greatly reduces weight and cross-sectional area. Other key savings are derived from lighter weight and less costly methods for adhering fiber to aircraft surfaces. Heavier copper cables require heavier fixtures, while ribbon fiber can be easily attached in a manufacturing plant or in the field without requiring additional mechanical fixtures.

Board space and airflow are factors in OEM design requirements for space-constrained aircraft cabins. Traditional fiber optic flex circuits are routed on a single substrate. Providing almost a 50 percent substrate size reduction compared to standard fiber optic cabling, the 3D style of flex circuitry routes the fiber on multiple stacked substrates to achieve a compact routing area. Custom flex fiber optic circuitry is available in single-mode, multi-mode, or hybrid versions.

Optical fibers are routed on a thermally stable polymer substrate and are locked into place with flame-resistant conformal coating. The adhesive coating holds the fiber securely in place. Substrates are engineered for proper bend radius to ensure long lifetimes and no impact on optical performance. Circuit shapes can be customized to the exact mechanical requirements of new or retrofit aircrafts.

The addition of ribbonized fiber leads, generally ranging a meter or two long, can eliminate the need for splicing the fiber. Ribbon-fiber-based interconnects are best suited for connecting the flex to other systems within the cabin. A variety of blind-mate interconnects can be used to connect the optical circuits to individual cards for passenger connectivity. Suitable for virtually any routing scheme, flex optical circuitry can be routed point-to-point or in a shuffle for crew equipment — and in a logical linear pattern for aircraft rows and seats. Direct or fusion spliced fiber terminations help to eliminate additional insertion loss well below the insertion loss associated with copper connections. In addition, to aid troubleshooting, 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.

This article was written by Thomas Heller, Account Manager, Aerospace and Defense, for Molex, Central European Region, in Waldorf, Germany. For more information, Click Here.