QwikConnect Vol 8 Num 4 October 2001



Glenair: A Great Source of Fiber

And You Thought All We Did Was Make Backshells and Connector Accessories


Figure 1
Click here for more information

Glenair is pleased to introduce its expanded fiber optic interconnect product line. The components are designed for use in highreliabilty applications in military aerospace, naval, avionics, and land warfare applications as well as in high performance commercial installations such as high-speed railways and communications satellites.

Glenair has developed a full-spectrum fiber optic product line which includes MIL-DTL-38999 style composite fiber optic connectors, MIL-T-29504/ 4 & 5 Qualified termini, special-purpose backshells and conduit fittings, extruded cable, and termination and test tooling. Glenair is also able to offer harness assembly services which integrate Glenair fiber optic technologies into turnkey overmolded cable harnesses, conduit systems and junction box assemblies.

This issue of QwikConnect presents an overview of the fiber optic products and technologies now available from Glenair. We invite you to discover the unique packaging options Glenair provides: from simplex pigtails to off-the-shelf multichannel jumper cables. We think you'll agree that Glenair now offers one of the most complete fiber optic solutions available for flight deck equipment, weapon systems, surveillance cameras, sensors, and other high-reliability systems. In many applications of this caliber, fiber optics are being employed to replace or upgrade existing copper conductor cable harnesses servicing existing black box equipment. Here are six principal reasons behind this upgrade trend to fiber optics:


Six Reasons to Upgrade to Fiber Optics:


Figure 2

Click here for more information

    1. Reduced Weight
    Compared to copper, optical fiber is relatively small in size and light in weight-a major advantage in interconnect systems servicing airborne avionics. As a practical matter, fiber is simply easier to install -especially in retrofit programs-because the smaller cable diameters can fit comfortably within the footprint or layout of existing electrical conduits and harnesses.
    2. Reduced Size
    Smaller size and weight also make it possible to run multiple backup cables for each electronic system or device. The ability to provide complete redundancy for all critical cabling is a major motivating factor driving the use of fiber optics in missioncritical systems.
    3. EMI Immunity
    Optical fiber is particularly useful in high-reliability applications due to its electromagnetic immunity. Since fiber optic media uses light to transmit signals, it is not subject to electromagnetic interference, radio frequency interference, or voltage surges, and so provides greater transmission reliability.
    4. Spark/Arc Immunity
    The total electrical isolation of fiber also makes it a safer, spark-free media for use in hazardous environments, such as aircraft fuel cells.
    5. Enhanced Security
    This characteristic also provides for enhanced transmission security, as light pulses, unlike electrical signals, are almost impossible to intercept or monitor.
    6. Huge Bandwidth
    Fiber can transmit a mind-boggling quantity of data with extremely good transmission quality. Two strands of optical fiber, both no thicker than a human hair, can transmit the equivalent of 24,000 telephone calls simultaneously. By way of comparison, two strands of copper wire can transmit but a single phone conversation-in a much heavier and larger cable.
    The smaller and lighter fiber strand has over 150 times the data carrying capacity of the bulkier copper cable! Additionally, data is typically transmitted digitally (the natural form for computerized equipment) which reduces translation errors and bottlenecks. Simply put, fiber can transmit signals over the longest distance at the lowest cost.


Fiber Optic Interconnect ing


Figure 3

Click here for more information

The packaging and layout of a fiber optic system can vary widely depending on the application environment. Fiber optics deployed in military avionics, for example, may take the form of a simplex pigtail connector assembly when fiber is used to interconnect the optical transmitter/receiver inside an equipment enclosure to the outside world via a panel mounted receptacle connector or feed through adapter (see figure 1). Rugged, environmental applications, such as a weapon interconnect cable intersecting a fuel tank may require more ruggedized cable construction (figure 2).

Specialized interconnect technologies, including unique backshells, conduit transitions, fiber alignment grommets and so on are regularly employed by Glenair to insure the fiber optic media is protected from environmental and physical damage, and meets the installation and repairability requirements of the application. The following guide to fiber optic interconnect packaging provides an overview of the most common layouts used in high-reliability applications:


Packaging Solutions for Inside the Box


Figure 4

Click here for more information

When fiber leads are used within equipment enclosures or other protected environments, the interconnect assembly generally looks something like figure 1: a wall mount or jam nut mount receptacle connector ("A") with simplex fiber leads. This receptacle connector is used to penetrate the enclosure and mate to the external environmental plug connector

Typical 'Inside-the-Box' Fiber Optic Assembly
Figure 1: A typical "inside-the-box" fiber optic cable assembly-now available as a standard off-the-shelf catalog product from Glenair.

The simplex leads within the protected enclosure commonly route to the transceiver optical device, and are terminated to common commercial connectors such as ST, FC, SC, LC (or other) connectors at the "B" end.

Glenair recommends that pigtail assemblies of this type be equipped with a short "FiberCon" backshell whenever possible. This lightweight composite backshell insures strict alignment of the fiber strands to the connector while providing optimum strain relief to the individual fibers.

The use of a short length of conduit and a small end-bell fitting is also sometimes called for in applications where a heat or abrasion source within the box may damage the fiber media. In both cases however, analysis of the available space is critical to insure such interconnect hardware does not interfere with the electronics package inside the box. This basic packaging is appropriate for any equipment- such as a radar, camera, shipboard console, antenna and so on-with an internal fiber wire servicing an optical transmitter/receiver.

Glenair can supply the complete interconnect assembly, including the connector, termini, fiber, optional backshell fittings and conduit. Glenair's Military-off-the-Shelf Fiber Optic Cable Sets (See Sidebar, Page 7) are specifically designed for applications of this type.

Packaging Solutions for External Point to Point Applications

Figure 5

Click here for more information


Figure 6

Click here for more information


Figure 7

Click here for more information


Figure 8

Click here for more information


While inside-the-box applications may be conveniently terminated in the field during the installation of the electronic equipment, other fiber optic interconnect cables lend themselves to factory termination and assembly. This is due to the rugged nature of the environments in which they are used. When fiber optic cables need to withstand rough handling, caustic and corrosive fluids or other sources of stress, the interconnect package needs to be extremely tough, and the cables are generally factory assembled with the appropriate protective materials.

Figure Overmolded Cable Assembly
Figure 2: Glenair high-temperature overmolded cable assemblies are ideally suited for fiber optic and hybrid fiber/copper applications in exposed, harsh environments
Factory assembly is also called for when there are no restrictions or impediments to providing a prebuilt harness or assembly, such as unpredictable distances between bulkheads or other site-specific routing problems. Factory-terminated fiber optic cables are typically multichannel, with sometimes as many as 30 fiber optic channels. Examples include ship-to-shore phone/data cables, fuel cell cable harnesses, intra-car railway cables, external ground support cables and other harsh environmental applications.



The range of performance requirements for rugged, external cables includes strain-relief, environmental sealing, high tensile pull, crush resistance and chemical resistance. Electromagnetic shielding can also be a requirement in hybrid copper/fiber cables. Packaging generally takes three forms: (1) Overmolded cable harnesses, (2) Metal-core or polymer conduit assemblies, and (3) Armored cable equipped with environmental and/or shield terminating backshells.

Overmolded Harnesses

Overmolded designs are specified when field repairability is not an anticipated requirement and harsh environmental and mechanical stress conditions warrant extra protection of the fiber media and terminations.

Conduit is also known for its excellent pull strength, high crush resistance, and relative light weight. Perhaps most important, conduit can more easily be opened for repair or to expand the number of fiber lines. Additionally, conduit assemblies make use of a wide range of existing fittings and transitions, including lightweight composite versions, to meet virtually any configuration and lay-up requirement.

Glenair offers complete in-house capabilities for the construction of fiber optic conduit assemblies. In addition to helically molded polymer materials, we also offer a metal-core conduit product which provides unmatched crush-resistance and EMI protection (for hybrid copper/fiber applications). Both styles of tubing may be outfitted at the factory with braided shielding and external jacketing. And Glenair manufactures all the necessary branched transitions and fittings for every connector and/or feed through configuration.

Reinforced Cable/Backshell Assemblies

Reinforced extruded cable provides a third packaging option for rugged application environments. Multichannel fiber optic cable is available in a broad range of designs. Depending on customer requirements for fiber type, strength members, jacketing material and other component-level options.

Glenair can extrude short-run fiber optic cable for most high-performance applications (see sidebar, Page 6). The cable becomes the backbone of this packaging solution. A ruggedized, environmental backshell is an equally key component in the armored cable assembly. Such backshells allow for the termination of overall shielding, the provision of additional strain-relief and/or environmental protection of the cable to connector transition.

But the most important design consideration behind the use of such specialized backshells is the ability to provide some level of repairability to the assembly. Unlike overmolded solutions, the reinforced extruded cable/backshell package allows maintenance technicians to open the cable for field service. Backshells are selected for functionality (strain-relief, shield termination, and so on) and for compatibility with the chosen connector.

Glenair is able to provide turnkey assemblies of this type as well as all the discrete components- from the extruded cable to the backshells, connectors, termini, dust-caps and other fiber optic interconnect accessories.


Packaging Solutions for Field Termination


Figure 9

Click here for more information


So far we have covered packaging solutions for inside-the-box applications and rugged, environmental applications. The third major packaging category for fiber optic interconnect applications covers those situations in which a pre-assembled cable or harness cannot be used due to the difficulty of cable installation and routing. A classic example is found in shipboard installation, where long cable runs, unpredictable bulkheads, kick-pipes and other barriers make a factory-terminated harness an impossibility.

The basic problem in many shipboard applications is that the fiber optic trunk cable often has to travel a great distance between the various equipment components in the system. A below-deck control room, for example, may rely on sensors or communications equipment located on the mast of the ship. Between these two elements lies a complicated maze of deck-plating, impenetrable bulkheads and kick-pipes.

Obviously, it would be impossible to install a factory-terminated assembly into this maze of holes and walls. So, long (trunk) cable runs are completed from point "A" to point "B" and the termination of the fiber optic connector is completed on site at each end of the cable. The challenge is to provide technicians with (a) the ability to strip back an adequate length of the cable to complete the individual fiber line terminations, (b) some subsequent way to protect the stripped back cable from environmental damage, and (c) a means of exposing the terminations at a later date for maintenance and repair. Glenair has perfected two different solutions for applications of this type employing junction boxes and unique conduit and backshell assemblies.


Junction Boxes

One obvious solution to the problem is to mount a cable junction box at each end of the system and bring the trunk cable into the box with a cablesealing gland or environmental feed through fitting. A long length of stripped cable can be sealed away in the box for subsequent repair and maintenance. Alternatively, a short run receptacle connector assembly may be used to complete the interconnection between the cable and the electronic device. Such boxes may of course be positioned in a centralized location to provide service to multiple pieces of electronic equipment. Any number of design configurations featuring feed throughs, box-mounted connectors and junction boxes may be employed to provide the necessary flexibility for the field termination, routing, and storage of the fiber leads.

Glenair is uniquely positioned to provide integrated fiber optic cable junction boxes of this type. Our line of CostSaver Composite Junction Boxes are specifically designed for harsh environments such as shipboard weather decks. The boxes may be outfitted with any number of customer specified components such as indicator lights and switches. The boxes are lightweight, completely corrosion-free and rated to IP67 for water and particle protection.

Specialized Conduit/Backshell Assemblies

Glenair's extensive background in providing fiber optic interconnect solutions for the navy has led to the development of some completely unique solutions to the field termination of fiber. Again, the challenge is to allow the trunk cable to be stripped back an adequate length to enable the termination work to occur, and then to protect the cable to connector transition from environmental and mechanical damage. Glenair offers a unique backshell and conduit assembly that perfectly suits this requirement (See Figures 3, 4, and 5).


Packaging is Just Half of the Story
Glenair has said for years that the fiber optic technology itself is only half of the story. The rest has to do with our commitment to providing a complete, full-spectrum fiber optic solution, or "one-stopshopping;" with our commitment to shrinking the lead times on both components and assemblies; with our willingness to act as more than just a supplier when it comes to the business of engineering the right solution for every application-and that means free samples, free application engineering and a liberal attitude when it comes to tooling expenses and other one-time charges. Across the board, Glenair is committed to becoming not only the technology leader, but the service leader, when it comes to meeting the fiber optic requirements of our customers. That's the other half of the story.
Figure 3.
Figure 3: The difficulty of terminating individual fibers in a large cable bundle has led to the development of unique conduit/backshell assemblies.
Figure 4.
Figure 4: Long lengths of fiber are much easier to terminate, but harder to protect with standard backshell accessories. Glenair has developed two unique packaging solutions.
Figure 5.
Figure 5: This unique Glenair assembly solves the problem of terminating fiber media in the field. It allows technicians ample working room and uses a backshell and conduit accessory to fully protect the terminations and facilitate future maintenance.

  Glenair QwikConnect Navigator  
Previous
Next

Home Same-Day RFQ Product Sales and Services QuikConnect: What's New at Glenair Feedback