Network Speed and Bandwidth

In distributed avionics, a large number of links are shorter than 83 meters and are suitable for 10 Gigabit Ethernet. In these cases, Cat 6a copper cabling can be used for flight control, avionics, and cabin-management systems. For links less than 60m, 26 AWG cables may be used, resulting in smaller and lighter harnesses. Cat 6a cable can be terminated with small, high-speed ARINC-compliant circular connectors.

Two TE connector families are relevant:

TE’s new lighter-weight MiniMRP composite enclosure
  • CeeLok FAS-T circular connectors use a true 100-ohm impedance design that is compatible with Cat 6A cable. The compact size 8 shell reduces SWaP (size, weight, and power) requirements. Crimp-snap contacts allow easy termination and field repairability. An integral backshell enables easy 360-degree shield termination. A T-shaped contact pattern provides noise cancellation and decoupling to minimize crosstalk and increase signal integrity.

  • CeeLok FAS-X circular connectors come in a small size 11 shell in a M38999 profile for one 10 Gb/s Ethernet channel (size 25 shell for four channels). CeeLok FAS-X contacts employ a proven AS39029 design for rugged environments. A patented shielding arrangement shields each pair through the connector to provide improved impedance matching and also eliminates crosstalk. TE’s CeeLok FAS-X Connector is qualified to a new Military Standard MIL-DTL-32546.

Distributed architecture supporting TE’s MiniMRP avionics packaging

To provide higher speeds over longer distances, MiniMRP accommodates fiber optic cabling. A multimode fiber can transmit 10 Gigabit/sec up to 550 meters. Optical fiber can also be used for avionics backbones that can support 40G and even 100G links. Moreover, compared to a Cat 6a counterpart, fiber optic cable is 78 percent lighter. Optical fibers also excel in noise immunity. They neither emit nor receive electromagnetic interference (EMI). They are made of dielectric materials and cable shielding is not required.

Despite its benefits, fiber optic cable has a reputation for being fragile and hard to use. Once again, technological advances have developed fiber optic cables that are crush and pinch resistant during installation. Fiber preparation during termination is now simplified in ways that significantly reduces labor and installation time.

Designers specifying optical connectors have two main choices:

  • Physical Contact (PC) types with mating termini that physically touch. PC termini are further distinguished by ceramic ferrules for single fibers and MT ferrules of multiple fibers. Ceramic ferrules yield the highest performance as well as lowest insertion loss and return loss. Multifiber MT ferrules offer the highest fiber density.

  • Expanded Beam (EB) types with a non-contacting interface for the termini. By avoiding physical contact, EB is more tolerant of vibration, shock, and other mechanical hazards. Wear and tear on the fiber/ferrule face is practically non-existent during vibration. Lensed MT ferrules leverage the EB benefits along with offering increased density.

Functionally, EB connectors expand and refocus light at the fiber end-faces and allow an air gap in the optical pathway. The EB concept uses optical lenses to expand and collimate the beam emitted from the launch fiber. The expanded beam remains collimated across the mechanical interface until the receiving lens focuses the beam onto the receiving fiber. Because the ferrule end-face is enclosed and protected behind the lens, the fiber does not require cleaning. Although EB exhibits higher insertion loss than PC, its longevity and consistency are superior.

In MiniMRP applications, copper and fiber can easily coexist. Each medium brings specific advantages, from the comfortable familiarity of copper to the high-bandwidth capabilities of fiber over longer distances. Avionics designers who are challenged to handle demanding data, IFE, and other bandwidth-hungry processes can employ both optical fiber and copper for an array of high-speed connectivity needs, from box to box, box to backbone, and box to server in the electronics bay.

For an end-to-end optical solution, the TE ParaByte transceiver uses a robust parallel optical design capable of achieving 10+ GB/s while also meeting MIL-SPEC standards for robustness. The small and dense design allows multiple transceivers to fit easily inside a single MiniMRP module.

A relatively new development that can push heavy data loads through active optical fiber networks is technology that features extremely small, low cost 10 GbE transceivers for MiniMRP units that are the end or drop nodes of these large networks. These transceivers are packed with GbE switches internal to the MiniMRP that require 10G optical ports.

In an end-to-end solution, the MiniMRP concept empowers designers with standardized, thin boxes packed with embedded computing power that can be distributed as intelligent nodes on an ultra-high-speed network within an airframe. As a result, designers, systems integrators, and avionics OEMs can quickly add and remove capabilities throughout the cabin, using MiniMRP to realize the full potential of IMA today.

This article was written by Russ Graves, Global Aerospace Business Development Manager, TE Connectivity (Berwyn, PA). For more information, visit here .