ATM Modernization, Business & GA, Commercial, Military

Product Focus: Connectors: On to Fiber Optics

By David Jensen | July 1, 2003
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When we last discussed connectors in the Product Focus section, in the November 2002 issue (page 46), we reported on the dual standard that the Airlines Electronic Engineering Committee (AEEC) New Installations Concepts (NIC) subcommittee was drawing up for copper connectors. Dan Martinec, with ARINC Industry Activities and secretary for the NIC, said the subcommittee determined that the copper-based Ethernet connector designs of Boeing and Airbus were too far along to allow the standardization of a single connector and cable design. So the NIC decided on a dual-standard approach, covering both the quadrax and twinax connectors. He also said the original equipment manufacturers (OEMs), Airbus and Boeing, and the airlines, wanted to assure that a dual standard does not result for emerging fiber optic technology.

Six months later, industry experts were working feverishly toward that goal. Driving the quest for a single fiber optic standard are the introduction of systems that could well use wider bandwidth–head-up displays, electronic flight bags, airborne file servers and new flight data recorders, to name a few–and reports that Boeing may choose to develop an about 1-gigabit/sec (1000BaseF) Ethernet backbone using fiber optics for its next new aircraft, the B7E7. Although Boeing officials say it is too soon to provide details on the B7E7, the aircraft’s systems are expected to be based on the B777’s integrated architecture and modular avionics. Boeing reportedly plans to make a decision on the B7E7’s systems architecture by the end of 2004 and would like to see a fiber optic cable and connector standard published prior to that time period.

Airbus, too, may choose to apply fiber optic technology to its jumbo A380. Although its backbone, an avionics full-duplex (AFDX) switched Ethernet bus, is copper-based, some systems on board could utilize fiber optic cable and connectors (see March 2003, page 26). Indeed, an Airbus official says the A380 will be launched with a copper-based data recording system, but the manufacturer is looking at eventually installing a flight data acquisition unit with a fiber optic interface. The unit thus would have data input via copper and output via fiber optics.

Generally, Martinec sees two "big applications" for fiber optic cable and connectors: avionics backbones and cabin display systems. "For downloading movies in seconds at passenger seats and to offer real-time Internet connection–copper simply won’t handle these applications," he explains.

Because of these developments, AEEC members made a decision during the last general session, in October 2002, to establish a working group dedicated to developing a standard for fiber optic connectors and cable. An Airbus representative and a Boeing representative co-chair this newly formed group, which has some 35 active attendees and an additional 100 industry representatives to review and comment on draft standards. Martinec is the working group’s secretary.

The AEEC is not alone in seeking a standard for fiber optics. The working group’s first meeting, on May 7 and 8, was preceded by a meeting hosted by ARINC Inc. for the U.S. Navy, which is developing a heavy-duty connector standard that is fiber-based, according to Martinec. Meanwhile, the Society of Automotive Engineers (SAE) is working on a fiber standard that would replace the mil standards, which are no longer applicable.

"We’re working together, and the common thread is the connector manufacturers, who probably will make the recommendations on the ultimate solution," says Martinec. "If they make the same recommendations–if they agree–then we may see a common approach [to a fiber optic connector standard] across the board. But if the air transport requirements are different from, say, the military’s, it will be more difficult to come up with a universal solution."

The AEEC working group’s intent is to compose two draft supplements, one for the ARINC 404A standard (for racking and connectors in older airplanes) and the other for ARINC 600 (racking and connector standard for newer aircraft, such as B757, B767 and A320). "The connector shells would be unchanged in 404A and 600," says Martinec. "But we expect different insert configurations to accommodate the fiber optic termini, or pins."

However, the working group feels the published content to standardize fiber optic cable and connectors could become so "voluminous" that it warrants developing a "whole new standard," which would complement ARINC 404A and 600. The working group, therefore, uses ARINC 6XX as the standard’s nomenclature. "We’re going beyond [ARINC] 600, in which we did only physical specs," says Martinec. "In 6XX, we’re also including design guidelines." These are to assist systems manufacturers that are anxious to finalize the designs of products using fiber optics.

"We’re also looking at active component specifications," he adds, "so when designers employ active components in the connector design, they will have a common baseline. This is a key element of the link budget–in other words, the determination of allowable signal loss in the system [aircraft wiring]." Since signal degradation can result from vibration, corrosion and wear, considerable testing of fiber optic components and the systems will be required as part of the ARINC 6XX specs.

In addition, the working group is "going beyond" standards for connectors that join cable to the black boxes. "We will establish a standard for circular and rectangular [fiber optic] connectors that do not connect to boxes but rather provide in-line connections," says Martinec. "We’re attempting to have the termini for these connectors be compatible with the termini used on box connectors."

"Ideally, we would have one terminus design, and if we do that, we could have a single cable design for consistency throughout the aircraft," he explains. "The only items that would be different are the inserts or the shells."

And then there are the maintenance guidelines, which also must be part of 6XX. Small wonder Martinec describes development of the new standard as "the single largest project the NIC subcommittee has worked on for some time." In fact, he claims 6XX could comprise two to five publications because of the volume and organization of the written material. "For example, we may want a stand-alone maintenance document," he says.

Despite the volumes of material and the impending late-2004 deadline (in part, for Boeing’s sake), the working group plans to have "substantial amount of text" for the new standard reviewed by OEMs, cable and connector manufacturers, and aircraft operators by next month.

"We’re looking at two major reviews by year’s end, one in August and another by the end of 2003," says Martinec. "At that point, we hope to have a common physical approach"–for the design of connector shells, termini, inserts and cable–which will help manufacturers as they design fiber optic products.

What about the dual standard for copper connectors? It has not been published, and Martinec says "small details" must still be resolved. However, he believes the standard will be adopted by the AEEC and published by this summer.


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