The requirements for higher bandwidth and speed and lower weight and power use are driving expanded use of fiber optics in the aircraft cabin and cockpit. The technology, increasingly being used to connect in-flight entertainment systems and video-rich cockpit displays, is now being looked at to play a more significant role in aircraft control operations. In the meantime, connector developers are crafting components for current and newer, more capable optics technologies — some of which are still in development.
The use of fiber in aircraft is up “big time,” said Donald Stone, fiber optic design engineer at Kitco Fiber Optics. The Virginia Beach, Va.-based company provides fiber optic connectors, training and field services to the military and commercial users, such as FedEx. “A lot of the systems that are being back-fit on aircraft … are fiber-optic-driven cable systems.”
A key reason for this growth is fiber optics helps address the industry’s number one concern: reducing size, weight and power “without compromising bandwidth and performance,” said Earle Olson, business development manager at TE Connectivity.
In fact, along with delivering much higher bandwidth than copper, there are no electromagnetic and radio frequency interference issues associated with fiber and less weight since there is no shielding, said Stone.
Even as interest in the technology grows, Olson offers a cautionary note to those who are beginning to claim the end of copper wire on aircraft: “Frankly I don’t see it. I see it as a blending. The two have to collocate; they have to interoperate.”
However, the use of fiber on aircraft has been on the rise for several decades with the military taking the lead using it as early as 1976 on the A-7 Corsair IIs, said Stone. It is used now on most major platforms including F-18, F-15, F-35 and F22, for the cockpit technologies, such as heads up displays and enhanced vision systems, said Stone, noting these systems are now also being deployed the commercial flight decks.
In the military, “imaging is the number one — whether that imaging is visual or thermal or IR” — driver for the use of fiber optics, said Wes Morgan, director, Americas product management at ITT Interconnect Solutions. The upgrade from standard to higher resolution imaging systems or enhanced imaging systems on older platforms is an ongoing trend that is creating a lot of work for fiber optics companies, he said. From their military experience, connector developers learn to build to harsh exposure criteria and observe via recurring maintenance the effect of stress and strain at an accelerated pace on the fiber and its connections compared to commercial operations, Morgan said. For example, “you learn (quickly) what is happening with fretting at the end of the termini” or the impact of “long cycles of vibration.” This experience helps you fine-tune your product for use in the commercial world, Morgan said.
In the commercial market, the prime mover is not imaging, but in-flight entertainment and connectivity and its requirement for higher throughput to provide a growing menu of offerings from satellite-based mobile and Wi-Fi communications and on-demand video. In this case, the harsh environment is the cabin of a commercial airliner. Addressing this environment, “we see multiple fiber optic implementations being deployed,” said Larry Paterson, associate technical fellow with the Boeing Engineering, Operations & Technology unit. Those implementations involve the use of fiber along with copper, especially for the last link or loop to the seat, but “in some instances, fiber optic cabling is routed all the way up to the video display in the passenger seat,” he said.
A prime example of the latter is Irvine, Calif.-based Lumexis’ Fiber to the Screen (FTTS) system, which was developed with TE Connectivity based on an ARINC 801 fiber optic connector interface. The company has landed “three, soon to be four, announced customers as they continue to gain data on their reliability,” including flydubai and Transaero, said Olson.
In addition, Lumexis continues to improve its reliability and can, on average, fit out a single aisle 737-800 in two and half days, said Olson. The company is working on the modernization of Transaero’s 777s and 747s, he added.
On a more fundamental level, industry is exploring “proposals to change … (the) architecture on the aircraft from copper to fiber optic control and to use … an Ethernet-type fiber optics network to send aircraft control signals off to various components around the aircraft, such as flight and engine controls,” Morgan said. This change to the aircraft architecture “reduces the amount of the spaghetti of wiring that is going out to these various spots from the central avionics or cockpit,” with signals instead traveling on a common network.
“Of course, you still have to run power out there, which can be done by copper or possibly aluminum wiring,” said Morgan. From an architectural point of view, this will require transceivers out at each user of the signal … to bring that signal in and translate it” to ensure “the control does what your signals are asking it to do,” he said.
Unlike with IFE, the key concern is not bandwidth since “control systems signaling is very low bandwidth typically; even if you take all of the controls and put them on a common Ethernet loop the signaling bandwidth requirements are still fairly low,” he said. Instead, the stress is on reliability; therefore, the dependability of the connectors will be critical.
While challenging, these changes or potential changes offer key opportunities for vendors and developer. “Our aerospace training has really been picking up big time, especially as these new aircraft start rolling out like the 787 and A350 and A380,” said Stone. “Also, in retrofit area we have been training a lot of companies I have never heard of that have to install fiber on different types of platforms.”
Meanwhile, the growth is good for connector vendors with ARINC 801 fiber optics standard connector products to offer like Radiall with its fiber LuxCis connectors, which can operate and multimode or the more advanced single mode range. “Current [fiber optic] interconnect designs have room for growth in terms of bandwidth,” said Jon Prouty, business development manager at Radiall. “We foresee future systems using more and more fiber, but potentially using a different type of cable — the single mode.”
The single mode, designed to carry a single ray of light, has wave guide area that is around 8.3 microns, much smaller than the 62.5 or 50 micron wave guide area on multimode systems used on commercial aircraft. In commercial uses it “tends to be more about reach, but also about capacity,” said Olson, adding “the lions share (of uses) continues to be multimode.” A key issue is cost as “single mode tends to be a little more expensive.”
Focusing on size, Positronic Industries is poised to introduce lighter, smaller and less expensive robust fiber optic connectors, said Gino F. Nanninga, vice president of sales for Positronic. Many of the existing fiber optic connectors out there now are robust but relatively large and expensive, he said.
Meanwhile, ITT is eying the changing circumstances and seeking to capitalize them. Its ARINC 600 series of connectors grew in the last few years to include next-generation avionics connector inserts that combine signal, power, Ethernet and fiber optic data transmission into a single interconnect, according to the company.
Despite all the interest, a number of concerns about fiber optics remain beginning with costs, which include “significant investment in test tools, along with the added specialized infrastructure needed to maintain them,” said Paterson. In addition, there are training requirements for cleaning, testing and handling fiber optic systems, he said.
“One of the big issues is that people aren’t being trained,” to correctly install and maintain the technology, said Stone. “If a copper guy installs a fiber optic harness, it is usually a problem. He often yanks on it and bends it too much,” he said. “Training just always seems to be at the bottom of the totem pole for funding, and people [only] want to get trained after they’ve caused $10,000 to $20,000 worth of damage.” Stone has written a training standard for ARINC on fiber optics including key information for the buyers and planners, installer and fabrication courses as well as technician level training program.
Along with training, there are also specific concerns about the ability of the fiber to survive in harsh environments, such as a commercial aircraft cabin where the fiber termini are exposed to dirt and contamination. “Moving fiber into this harsh environment is a good motivator for looking at expanded beam fiber technology, as opposed to the current ARINC standard PC [physical contact] fiber termini,” said Paterson.
A noncontact type of interface, the technology addresses a thorny issue of maintaining fiber. “The use of physical contact science in connectors requires you to use diligence and skill to clean [them],” said Olson. If you don’t, “it becomes quite expensive when ferrules get damaged, and then you have to take it apart or send it back for repair,” he said.
The enhanced beam technology has been embraced by military for ground tactical uses, and there is interest in aviation, but “we haven’t gotten to the point where it’s reached its crossover point to be as cost affordable in industrial and commercial space as it needs to be, [but] I think we are on the cusp of that.”
“There is a near-term cost penalty with expanded beam connectors, but this is quickly outweighed by the overall life cycle costs the airline’s must shoulder in maintenance and training costs associated with physical contact termini,” said Paterson, adding “there is a lot of activity in the (ARINC) Cabin Systems subcommittee right now on developing new expanded beam connectors for this passenger seat environment.”
In addition, “the Cabin Systems subcommittee and its Connector Working Group are currently evaluating requirements for a high data rate ‘OM4’ grade fiber cable,” said Paterson. “Having this fiber type in the repertoire of standard cable products will open the door for higher data rate applications in the IFE area.”
In addition, the fourth Generation Cabin Distribution System (4GCN) “development is progressing through the Cabin Systems subcommittee, said Paterson. “There are currently multiple installation options in the standard, some of which locate an active fiber optic data switch below the floor panels,” he said. “From that switch location, options range from copper Ethernet or fiber optic cabling to the passenger seat groups (which) … puts sensitive fiber optic termini … directly into a harsh environment, from a contamination and installation handling perspective.”
Next month: Antennas
Avionics Magazine’s Product Focus is a monthly feature that examines some of the latest trends in different market segments of the avionics industry. It does not represent a comprehensive survey of all companies and products in these markets. Avionics Product Focus Editor Ed McKenna can be contacted at email@example.com.
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Air Electro www.airelectro.com
Airborn, Inc. www.airborn.com
Ametek Aerospace www.ametek.com
Amphenol Aerospace www.amphenol-aerospace.com
Array Connector www.arrayconnector.com
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PIC Wire & Cable www.picwire.com
Positronic Industries www.connectpositronic.com
TE Connectivity www.te.com