Today’s rugged embedded computing industry demands the best of technology and reliability. Driven by requirements for higher performance solutions, platforms continually evolve. Standards organizations, such as the VSO (VMEbus Standards Organization), are diligently working to bring the technology for these solutions to the mainstream. The VSO’s VPX architecture, based on Tyco Electronics’ MULTIGIG RT2 backplane connector as qualified to the VITA 46.0 standard, is the latest technology to be applied to rugged embedded computing. In addition to dealing with escalating processing, power, and cooling requirements of leading edge solutions, the VSO is now addressing the need to realize high bandwidth and high fidelity transmission via alternative media — e.g. fiber optic and coaxial wave guides. This technology is crucial in realizing the full potential of today’s cutting edge C4ISR gear, including RF intensive radar, SIGINT and IED defeat gear, as well as systems benefiting from fiber optics, including secure, long distance and high data rate communications lines.
Unlike prior generations of VME hardware, today’s VPX interconnect is a field of high density, carefully impedance matched contacts. These lines are ideal for high speed differential and single ended signals, and are supplemented with a number of heavier lines dedicated to providing power to the daughter modules. Prior versions of VME had 2nd generation optic and RF contacts. Today’s 3rd generation technology is both higher density and higher performance. Implementation of this technology, while greatly expanding the functionality of the VPX architecture, has brought multiple packaging challenges to the forefront.
As a result, the VSO has formally launched two draft VITA specifications to address the alternate media of optical fiber and coaxial connector/cable managed RF. Drafts of the two new specifications are under way, including
- VITA 66 Fiber Optic Interconnect (previously designated VITA 46.12) as led by The Boeing Company.
- VITA 67 Mixed Signal VPX (previously designated VITA 46.14) as led by DRS Signal Solutions and Pentek Inc. These two draft specifications are now firmly on their feet and accelerating toward implementation as part of the dramatic VPX evolution. Through the development of VITA 66, as initiated in November 2007, the VSO is giving designers a range of fiber optic solutions that will address virtually all applications inside, as well as getting to the outside, of “the box”. Enabled connectivity includes:
- daughter card to daughter card
- daughter card to backplane
- daughter card to chassis input/output (I/O)
- backplane to chassis I/O.
As detailed in the VITA 66 draft specification, fiber optic connectivity is now possible thanks to collection of the new connector modules supplementing the MULTIGIG RT2. The fiber optic connector modules are a standard size and can occupy any position from P2 thru P6 traditionally held by a 16 wafer digital connector module. Early on, a baseline design goal included the common physical envelope and mounting provisions, allowing common printed circuit board designs.
During initial development of the VITA 66 draft specification, three candidate optical termini styles were selected for review by the committee. The termini, including the MT, expanded beam, and 1.25mm ceramic ferrule (ARINC 801), were proposed based on their technical strength, technical maturity, and status in relevant industry standards. Each rugged technology is presently flying, floating, or navigating terrain in demanding mil/aero applications, and each supports multimode and single mode functionality. After review, the committee agreed to pursue all three technologies, enabling the system designer to choose the right tool for the job.
The MT, based on the USConnec MT Ferrule (IEC 61754 with TIA/EIA FOTP-219 as controlling US standard for MT end face geometry inspection), is the king of high density. The VSO has moved forward allowing up to 24 fibers per ferrule, meaning up to 48 fibers can be accommodated in the baseline 2 ferrule modules. This translates to 48 fibers in a 3U VPX module and a staggering 240 fibers in a 6U module.
The expanded beam insert, based on ball lens technology as found in MILDTL- 83526/20 & 21, is the most rugged interface and supports up to 4 fibers per module. The ball lens technology expands the effective diameter of the channeled light and collimates the beam, projecting it across an air gap to the receiving ball lens, which reverses process and reintroduces the light to the awaiting fiber core. Where a speck of debris might completely block a 50 micron or smaller fiber core, the expanded beam minimizes the impact of dirt and debris on insertion loss. It is also the only non-contacting interface, eliminating potential abrasion induced by shock, vibration or repeated mating/ unmating. The fiber ends are basically protected behind safety-glasses, allowing very easy cleaning and inspection, making them suitable for two-level maintenance or applications calling for frequent insertion/extraction.
Last, but certainly not least, the 1.25mm ceramic ferrule (ARINC 801), brings all the advantages of discrete ceramic ferrule connectivity. This module will carry up to 6 fibers, will be very high performance in both single-mode and multimode, and allow individual fiber installation/reparability. The ceramic ferrules offer the performance features to which users of positive contact technology have grown accustomed, including angled polishes and keyed orientation for optimal single mode performance. In an age when fiber optics is utilized in everything from automobiles to combat aircraft, applications for the rugged VITA 66 fiber optic modules are everywhere. The modules can be used to route fiber inside the box, or be routed to I/O connectors on virtually any side of the box — front, back, or side.
By way of example, let’s say fiber optic connectivity is required for an extremely fast, low weight, EMI immune switch card. This is not a problem — implement the 48 fiber MT module. How about having an ISR platform networked to another series of platforms along a sensitive multi-kilometer border? Simple — equip your chassis’ media converter with a module having single mode capabilities, as enabled by the 1.25mm ceramic ferrule. Or perhaps you have a secure storage device that needs to be routinely removed and replaced between flight operations in adverse conditions? The expanded beam is just what flight ops ordered. Ease of cleaning, a non-contacting interface, and flight pedigree are all attributes of the expanded beam. Fiber optic technology has been a mainsteam solution for decades in the commercial world. It is now accelerating into applications within the mil/aero networking world.
Shortly after the VITA 66 (formerly VITA 46.12) initiative was on its feet, the VITA 67 (formerly VITA 46.14) working group was kicked off. Work began in the first half of 2008, targeted at enabling the VPX architecture for mixed signal applications. As with the VITA 66 modules, the goal was to adopt proven termini for minimal risk and to expedite implementation. The committee set a very high bar for performance, including frequency up to 26 GHz, isolation >100dB and VSWR of 1.5:1. Tyco Electronics’ blindmate SMPM RF contact was chosen due to its multiple qualities, including high- performance, highdensity and robustness. In cabled configuration, the SMPM is capable of up to 40 GHz using semirigid or conformable (0.047" or 0.086" diameter) coaxial cable. Two basic configurations, including a 4 position and an 8 position, were selected to move forward. The 4 position occupies 1⁄2 of a 16 column P2 module and is envisioned primarily for 3U applications. The 8 position is primarily targeted at P2 and P6 of a 6U card. Both are standard form factors, offering scalability and the prospect of mounting multiple modules on a card edge. The present module configuration is cable-tocable, which happens to be the highest performance and most application neutral permutation. As with VITA 66, this feeds the waveguides through the backplane, from where they can be routed to front or back panel I/O connectors, or to another daughtercard. Exit from the backplane can be specified in SMPM push/pull for optimal ergonomics, or OSMM threaded connectors for optimal performance.
As the VITA 67 draft standard matures, early adopters are already implementing the capability. The modules offer the ease of installation, upgrade and reparability, as well as backplane and front panel connectivity, never before realized as a mainstream rugged embedded computing solution. The VITA 66 and VITA 67 modules can even reside on the same card edge — anyone for RF over fiber?
ANSI-ratified VITA 47, the environmental specification applying to VPX, will likewise be the environmental benchmark for VITA 66 and 67. Each committee will develop and conduct testing of these technologies within the scope of VPX, including VITA 46, 47 and 48, thereby demonstrating and qualifying the solutions for the marketplace.
While existing VME hardware has a variety of RF and fiber optic solutions, none carry the density, performance, or options in user configurability offered by VITA 66 and 67.
Where does the technology go from here? The future is very bright for VITA 46 VPX and the emerging VITA 66 and 67 standards. VITA 46 has proven to be overwhelmingly successful, with the same anticipated for the fiber optic and RF derivatives. The modules will move into qualification in coming months and rugged embedded computer designers are awaiting the rollout. Prototypes are already being supplied to integrators for evaluation and chassis development. A wide variety of backplane slot configurations utilizing the two new modules have been planned by the OpenVPX and VITA 65 committees. The VITA 66 and 67 technologies will harness fiber optic and RF bandwidth, effectively interfacing the world with the computer.