Harsh Environment Fiber Optic Connector Selection
Harsh Environment Fiber OpticConnector SelectionIntroductionWhether natural or manmade, cataclysmic or catastrophic, rugged and unforgiving environmentscall for the use of high-performance fiber optic connectors. Appropriate connector selection isessential to assure adequate optical, environmental and mechanical performance. This paperoutlines and describes the attributes, environments, requirements, technologies, and potentialHarsh Environment Fiber Optic (HEFO) connector selection criteria.ScopeExtreme surroundings, severe conditions and misuse describe the applications requiring HEFOconnectors. It is assumed that the reader has a predetermined need for using fiber opticinterconnects and does not need to help in assessing the available alternatives between copperand fiber. Common connector specifications include shock, resistance to vibration, temperature,humidity, submersion, chemical resistance, crush, strength and dirt or dust.It is further assumed the reader has a cursory knowledge of fiber optic connectors andunderstands the principles involved in fiber optic connectivity.Available TechnologiesPhysical contact and expanded beam are the dominant technologies used in harsh environmentfiber optic connectivity. This paper briefly describes each of these two technologies but does notPage 1 of 3212/13/2011
discuss splicing interconnects or other alternative or exotic interconnect technologies. The paperconcludes with a connector suitability trade study performed on a typical harsh environmentfiber optic interconnect application.BackgroundRobust fiber optic interconnects are needed in harsh environments. Military and aerospacesystems must perform in hostile climates, inclement weather and adverse surroundings.Geophysical applications subject interconnects to demanding conditions as well.Relevant Applications/MarketsTactical, shipboard, aerospace, and geophysical applications, among others, present taxingenvironments for interconnects. Because fiber optic connections require alignment accuracy,these applications demand rugged, precise and proven products. Figure 1 shows several harshenvironments where rugged fiber optic connectors may be utilized.Figure 1. Typical harsh environments commonly employing rugged fiber optic interconnectsPage 2 of 3212/13/2011
Mil/AeroArmed forces utilize fiber optics inharsh environments in myriadprograms. Armies employ ruggedfiber optic interconnects in tacticalcommunications, missile systems,and radar installations. The Patriotmissile system shown in Figure 2 isone highly publicized tacticalweapon system using HEFOinterconnects.Figure 2. The Patriot missile systemmakes extensive use of fiber opticsBandwidth, weight andelectromagnetic interferenceconsiderations determine fiber opticinterconnect requirements,particularly in aerospaceapplications. Airborne sensorsrequire enormous bandwidth. Theyalso need to be impervious to and notemit electromagnetic radiation.Fiber optics excel in both militaryand commercial airframeapplications. Fiber optics in space(see Figure 3) has uniquerequirements, including the use oflow outgassing materials, radiationexposure, and component longevity.Figure 3. Space shuttle containing fiber opticsPage 3 of 3212/13/2011
GeophysicalGeophysical fiber optic applications typically require resistance to harsh chemicals, imperviousseals to prevent liquid and/or gas penetration, and salt spray immunity. Mining, oil exploration,drilling rigs, production platforms (Figure 4), submersibles, and undersea systems all utilizefiber optic interconnects. Many of these applications use fiber optic based pressure ortemperature sensors. High pressure, (25,000 psi) and temperatures in the 250 C range can beencountered by HEFO connector products. In addition to connectors in this market space, fiberoptic streamers and feedthrough connections are common.Figure 4. Offshore Production PlatformPage 4 of 3212/13/2011
Oceanographic oil exploration commonly involves using streamer arrays containing fiber opticinterconnects due to the inordinate quantity of captured data. Many such streamers requirehybrid (electrical and fiber optic) connections containing hybrid inserts (see Figure 5).Figure 5. Oil exploration ship with hybrid streamer interconnectFiber optics find their wayinto mining operationsbecause radio links do notwork well underground.Of course, connectors inmines must beconstructed with nonsparking material and beresistant to explosions.Figure 6 shows longwallshearing equipment.Figure 6. Coal miningfiber optic uses includecommunications, roofersand shearing equipmentPage 5 of 3212/13/2011
Disaster Recovery/IndustrialEmergency deployable communication systems (see Figure 7), nuclear power generation,broadcasting, and security applications present unique environments requiring rugged fiber opticconnectors. Bandwidth, channel count, EMI, and extreme weather often determine industrialfiber optic connector requirements.Figure 7. Deployable Telecommunications Disaster SystemRequirementsThe importance of understanding requirements cannot be understated. The ability to choose thebest interconnect system and subsequent connector depends upon knowing and understandingthe optical performance expectations, operating conditions, mechanical and environmentalconstraints, reliability requirements, and maintenance plans.System and interconnect designers must think beyond the environment in establishing andselecting components. HEFO cables and connectors are frequently subject to severe treatmentand misuse. A warfighter may use cable to rappel down or climb atop a shelter. An oilfieldexplorer technician may pull a cable reel using the cable. Oftentimes, cables are tied to an objectand placed under unintentional stress. Connectors/cables are placed in puddles, pulled danglingbehind vehicles, and used haphazardly. Installation is another area fraught with potential forconnector/cable damage. Accidentally, or out of necessity, fiber optic cables and connectors areastonishingly abused.Applications in contaminated environments frequently require fiber optics. Connectortechnology, sealing, and cleanliness all play a major role in connector selection and interconnectperformance in these environments. Dust, moisture, chemical exposure, oily films, andmaintenance planning must be considered for any application. Figure 8 shows a particular dustyenvironment common to rugged fiber optic interconnects.Page 6 of 3212/13/2011
Figure 8. Many HEFO applications are extraordinarily contaminatedSystem level design dictates the type of fiber employed (typically multimode or single mode),the number of channels, and packaging density. Trade studies during system design influencecost, performance, and nearly each attribute of the interconnect system. For example, by usingwavelength division multiplexing (WDM) or dense wavelength division multiplexing (DWDM)technologies, fewer actual fiber connections are required since each fiber carries multiple signals.However, while this drives down system weight, it also introduces a single point of failureshould the cable be accidentally cut or destroyed.Why Use Fiber Optic InterconnectsThe choice to use fiber optics is typically determined by bandwidth, cost, weight, size, datasecurity, and signal distance. Table 1 displays a comparison between fiber connection attributesand coaxial cable. Fiber holds significant advantages over copper interconnect systems, asshown in the table.Page 7 of 3212/13/2011
Coaxial CableFiber OpticCable (MM)Fiber Optic Cable(SM)100 MHz km500 MHz km100,000 MHz km 45 dB1 dB0.2 dB 11/81/84501515711Data SecurityLowGoodExcellentEMI ImmunityOKExcellentExcellentRepresentative Distance-Bandwidth ProductsAttenuation/km @ 1 GHzCable Cost ( /m)Cable Diameter (in.)Cable Weight (lbs/km)Minimum Bend Radius (in.)Table 1. Comparison of coaxial cable and fiber attributesOne significant fiberoptic attribute isimmunity toElectromagneticInterference (EMI),emissions, andsusceptibility, whichmakes them ideal for usein areas prone to highEMI environments andRF over fiberapplications. Figure 9shows the newElectromagnetic AircraftLaunch System(EMALS) planned forthe next generation ofshipboard fixed-wingaircraft launchingplatforms.Figure 9. A portion of the fiber optic based EMALS systemPage 8 of 3212/13/2011
Requirements DriversAs previously noted, environment and performance determine requirements, as do system levelchoices. Power budgets, source and detector selection, and redundancy requirements alsoinfluence connector selection. By properly identifying and understanding requirements,expensive redesigns or changes can be avoided. Over-specifying can increase cost. SettingHEFO interconnect system requirements to clearly defined optical performance, environmentalconditions, and mechanical parameters ensures optimal system level performance.Multiple connector technologies are available for HEFO applications. Physical contact,expanded beam, and MT are commonly available technologies. Exotic interconnects such asplanar wave and silicon v-groove are suitable for select and specific applications. For acomparison of physical contact and expanded beam technologies, please see the AFSI ExpandedBeam vs. Physical Contact white paper.Fiber and cable type is determined by system design, which in turn can determine cable assemblyand connector selection and the design thereof. Is single mode or multimode fiber desired? Howmany channels? Does the system require glass or plastic fiber? Is ribbon cable necessary, orwill circular cable suffice? If circular, is “D” mount or flanged mounting preferred? What typeof strain relief is necessary? These are just a few of the initial connector selection questions toaddress when defining the interconnect system.Design choices also influence connector selection. Additional questions regarding in connectorselection may be: Does the customer need a commercial or a mil qualified connector? Is APC required to meet return loss requirements? Is an electrical and optical hybrid connector desired? What material and plating requirements are required to meet theenvironments? Does the application require cable segregation which necessitates multiplekeying configurations? How important is mass/weight? Is standardization/intermateability a requirement?Operational and test requirements definition are just as important as the physical characteristicsof the interconnect system. These factors determine terminus polishing requirements, equipmentrequirements, and inspection parameters. Tests and test methodology must be adequatelydefined to ensure performance measurements. Multiple standards bodies (SAE, EN, IPC, TIA,DOD ) have many specifications, standards and recommendations covering terminus end faces,polishing, inspection, cleanliness and test practices.Page 9 of 3212/13/2011
In short, clearly defined, well understood and agreed upon requirements set the stage for meetingexpectations. Adequate requirements definition reduces performance risk and is a necessary stepin meeting system level performance. First pass success is reasonably attainable with adequateperformance and requirements definition.MaterialsEach application and/or environment usually has specific requirements that are best addressed bycertain materials. The ability of materials and protective coatings to withstand the corrosivenature of the ocean’s salt spray is paramount in naval shipboard applications. Aerospaceplatform performance is determined by weight; accordingly, composite connectors are common.In addition to weight constraints, airframe engine connectors must withstand relatively hightemperatures, and, titanium connectors may be required. This paper does not provide a detailedanalysis of the various materials used in connector construction and manufacture, but theseconnector factors should be considered during the specification and selection process. Forfurther information on connector metallic material and plating information, see the AFSI HarshEnvironment Connector Material Guide.Unique Application/Market RequirementsEach harsh environment fiber optic market segment typically has associated requirements. Ageneralized list of these common HEFO requirements by market is captured in Table 2.ShipboardCorrosionHumiditySalt gWeightNuclearOil & GasSingle Mode APCHybridsCorrosionSealingTemperaturePressureTable 2. Common HEFO Application/Market Product RequirementsAs an example, shipboard applications have multiple critical requirements including shock,humidity, and typically a corrosive environment. Shipboard connectors must endure rigidqualification testing. The AEGIS program makes extensive use of fiber optic interconnects.Aegis is the Navy's most modern surface combat system and was designed and developed asintegrated state-of-the-art radar and missile systems. See Figure 10.Page 10 of 3212/13/2011
Figure 10. Naval systems employing HEFO connections include weapon systems such as AEGISPotential SpecificationsOne must take caution in over-specifying requirements as this can adversely affect cost. Risk,cost and likelihood of failure should be evaluated to determine which requirements are specifiedand need test verification. Likewise, under-specifying requirements may result in a system thatdoes not meet performance expectations.Each application and/or platform has a unique set of requirements as does each fiber opticconnector. To provide a complete and comprehensive list of all the potential environments andspecifications is not this paper’s purpose. Table 3 contains some of the more commonly usedfiber optic connector (and cable assembly) specifications.Page 11 of 3212/13/2011
Table 3. Potential fiber optic connector and cable specifications AltitudeCable FlexCable Pull Test/Cable RetentionCable Seal FlexingChemical ResistanceCoupling Engagement/Disengagement Force/TorqueCrosstalkCrush ResistanceDust Cap RetentionExternal Bending MomentFiber Pull Out ForceFlex LifeFluid ImmersionFreezing WaterHumidityIce CrushImpactInsert Retention Axial StrengthInsert Retention Radial StrengthInsertion LossInterchangeabilityIntermateabilityMaintenance AgingMating DurabilityMTBFMud/Mud CleaningNon-Operating TemperatureOperating TemperatureOptical DiscontinuitiesOptical PowerOptical SkewPage 12 of 3212/13/2011 OutgassingPolarization (PMD, PDL, Extinction Ratio)PressureRadiationReturn LossRF/EMI Susceptibility, Emissions, RadiatedSalt Fog/Salt SprayScoop ProofSealing; Optical Junction Sealing; CableSealingSelf Extinguishing (Flame)Shell-to-Shell ConductivityShockSizeSkewSolar RadiationStorage TemperatureSubmersionTemperature CyclingTemperature Humidity CyclingTemperature LifeTensile LoadingTermini Pull TestTermini Spring ForceTerminus Insertion and Removal ForceThermal ShockTwistUniformityVibration (various)Water PressureWeight and Size
Specifying Test RequirementsWhen specifying the connector (or cable), testing requirements should be kept in mind. Requirements such asinsertion loss, temperature and vibration are typically tested and verified either formerly or informally. Budgetconstraints, performance risk and schedule help decide which connector parameters and attributes should betested. Qualification by design or similarity can also be an acceptable means for verification, depending uponthe requirement. It is unusual to have testing or verification requirements for outgassing, RoHS (Restriction ofHazardous Substances) compliance, or flammability for a multitude of applications, particularly when thedesign components are manufactured with material previously tested or known to conform to specifications.Adherence to requirements related to mission success, demanding environments, safety, and opticalperformance are usually tested.When comparing products, one should review in detail the testing requirements and testing performed. Manytests have extensive variations and testing specifications. Test callouts may seem similar but vary greatly induration or severity. Temperature testing is fairly straight forward when specified. Shock and vibrationrequirements can require a deeper understanding of specifications to determine if an apples-to-applescomparison between two products’ test requirements is comparable.Optical measurement methods, processes, and procedures should be adequately defined to attain like andrepeatable results. The use of single channel test cables or probes versus a multi-channel test connector canyield different test results. Launch conditions, referencing, and test set-up should likewise be adequatelydefined. The use of industry standards or recommended practices can be valuable in determining which productis needed, how the product should be tested, and the comparison of seemingly similar products.Real vs. Perceived RequirementsAlthough requirements definition is important, there are some common misconceptions and misleadinginformation within our industry. Carefully crafted data sheets or demonstrations could lead one to believe aproduct meets requirements or is qualified when in fact it is not. Unless a product has been rigorously andactually tested, there is no basis for a product to be qualified or to have demonstrated adherence to specification.Common misleading statements such as “designed in accordance with,” or “designed to,” or “equivalent”should each be met with skepticism, if neither test data/report nor an acknowledgement by a qualifyingauthority is available. The Department of Defense publishes a Qualified Parts List (QPL) of products that meetmilitary specifications.Many specifications and datasheets contain words like “typical.” Useable specifications contain maximum andminimum parameters or values. If an average value is specified in product literature, sampling size andstandard deviation requirements should be defined along with measurement methods and processes. Allparameters should be calculable or measurable. Typical values are only meaningful if quantified or defined.Connection insertion loss versus connector insertion loss is another common area of misunderstanding.Connections are what is measured, not connectors. A great example of marketing hype as opposed to actualconnector performance involves the use of video transmission. In this demonstration, a fiber optic link carriesvideo between a source (camera, video player, etc ) and a display (television, monitor, LCD screen ). Thevideo on the display appears acceptable or even bright, detailed and with apparently good resolution. This is aqualitative display and does not show the inherent insertion loss in the fiber optic link that may be critical inanother application. This demonstration does not show suitability for use in data transmission.Page 13 of 3212/13/2011
Preferred Fiber Optic Connector Design CharacteristicsIn addition to application, environmental, and mechanical attributes, fiber optic connectors should be designedwith inherent best practices or preferred connector characteristics, such as: Low insertion lossMinimal back reflectionSmall profile backshellsNon-rotating elementsMinimized contamination/sealingTiered alignmentMany mate/de-mates“Free floating”, self-aligning terminiTermination (initial and repair) easeLow cable & termination stressesMaintainable/cleanable/repairableHigh densitySingle mode specific fiber optic connectors have additional preferred design features including: Ceramic ferrulesSplit ceramic sleevesLow back reflectionTight ferrule concentricity and diameter dimensionsPre-radius ferrule designRemovable captive alignment sleevesPrecision alignment systemAPC capabilityFiber Optic Connectors and TechnologiesHEFO connectors can generally be organized into two major categories: physical contact and expanded beam.Each of these two differing and readily a
Harsh Environment Fiber Optic Connector Selection Introduction Whether natural or manmade, cataclysmic or catastrophic, rugged and unforgiving environments call for the use of high-performance fiber optic connectors. Appropriate connector selection is . Environment Connector Material Guide. Unique Application/Market Requirements
Fiber optic termination - ModLink plug and play fiber optic solution 42 Fiber optic termination - direct field termination 42 Fiber optic termination - direct field termination: Xpress G2 OM3-LC connector example 43 Cleaning a fiber optic 45 Field testers and testing - fiber optic 48 TSB-4979 / Encircled Flux (EF) conditions for multimode fiber .
Nowadays fiber optic is one of the technologies used for structural and geotechnical monitoring projects. Fiber optic sensors are normally classified as point, multiplexed, long-base or distributed sensors. . D., "Fiber Optic Methods for Structural Health Monitoring", John Wiley & Sons, Ltd, 2007. 2. Inaudi, D., "Distributed Fiber Optic .
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Figure 12: Construction of a Single Fiber Cable Figure 13: Example of the Construction of a Multi- Fiber Cable II.3 Connectivity Fiber optic links require a method to connect the transmitter to the fiber optic cable and the fiber optic cable to the receiver. In general, there are two methods to link optical fibers together. II.3.1 Fusion Splice
Fiber Optic Infrastructure Application Guide ENET-TD003C-EN-P Deploying a Fiber Optic Physical Infrastructure within a Converged Plantwide Ethernet Architecture Fiber Optic Cabling Systems Overview Figure 3 Permanent Link Diagram The typical channel is composed of multiple assemblies connected by a combination of the optical fiber
The Condux Fiber Optic Cable Blower operates efficiently with most common combinations of cable and innerduct sizes. The Fiber Optic Cable Blower is designed for the installation of fiber optic cables with diameters from 0.23" (5.8 mm) to 1.13" (28.7 mm) into
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The American Petroleum Institute Manual of Petroleum Measurement Standards (API MPMS) Chapter 19 details equations for estimating the average annual evaporation loss from storage tanks. These equations are based on test tank and field tank data and have been revised since initial publication for more accurate estimations. WHAT IS EVAPORATION? Evaporation is when a substance changes from the .
