N121-026 TITLE: Fiber Optic End Face Termination and Processing

TECHNOLOGY AREAS: Information Systems, Materials/Processes, Sensors

OBJECTIVE: Develop fiber optic end face termination or processing method that minimizes insertion loss and return loss at the connector interface for use in aerospace platforms.

DESCRIPTION: Optical waveguide theory and application performance have revealed that power budgets and system operational integrity are sensitive and inhibited by poor termination and signal coupling attenuation. Great emphasis has been put on the component interface loss mechanisms to reduce these network impediments. Fiber end face polishing, coating and lens technologies have been developed to minimize end face degradation from contamination, signal reflections and coupling power loss. System data has shown the combination of these effects over time debilitate the overall throughput of the network. Back reflections not only represent power that is not reaching its intended destination, but can introduce potential complications to the optical system. Reflected light propagates in the opposite direction of the source signal, causing interference, fluctuations in source wavelength and power, and can permanently damage the transmitter. With multiple interfaces and components throughout the cable plant, a given path can easily exceed the 3.0 dB link budget margin designed into most optical links. Power loss can raise the bit error rate (BER) in digital systems and lower the signal-to-noise ratio (SNR) in analog systems, both causing a loss of information. Changes to source wavelength can be very detrimental to information accuracy, especially when implementing wavelength division multiplexing (WDM).

As existing fiber optic networks look to exercise unused bandwidth and evaluate co-deployment of digital and analog Millimeter Radio Frequency (RF) applications, loss budgets and component operational integrity becomes critical in maintain continuous spatial and temporal reliability of information exchanges. Future digital based fiber optic network designers looking to integrate analog signaling schemes have now realized focus on reducing connector end face effects for calculating link loss budgets and system reliability over the lifetime of the infra-structure.

Fiber termination processes employed by commercial harness and interconnect manufactures provide them with automated and manual capabilities that typical produce connector insertion losses range between 0.2 and 1.0 dB with a maximum allowable end-of-life loss of 1.5dB. In order to remove any obstacles to utilizing fiber networks for RF applications, target insertion loss will have to be 0.05 - 0.10 dB, while target return loss is less than � 60 dB. In addition, mechanical end face performance should also be durable enough to withstand 500 mate/de-mate operations, while keeping end-of-life insertion loss below 0.50 dB. It is envisioned that Electro-Optic (EO) based systems components, modules, backplanes and weapon replaceable assemblies would utilize this technology.

Design should work with multiple termini (MIL-PRF-29504) connectors (MIL-DTL 38999, MIL-PRF-64266, and Glenair NGCON).

PHASE I: Design, model, simulate and demonstrate intended termination/processing methods ability to meet design targets. Demonstrate feasibility of the design.

PHASE II: Design, construct and demonstrate the termination/processing method from Phase I in a laboratory environment and ensure results are repeatable and manufacturable to the design targets. Meet entry criteria for Technology Readiness Level (TRL) 6 accreditation. Construct plan for cost effective mass production of qualified fiber segments.

PHASE III: Transition technology for mass production of cable segments.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Durable, low loss fiber optic endfaces can be used in the medical, automobile and telecommunication industries to provide reliable human to machine interfaces. These requirements can be found in surgical apparatus, test equipment, probe interfaces, etc. in all of the mentioned industries.

REFERENCES:
1. Audet, F. (2004). Optical Return Loss Testing�Ensuring High-Quality Transmission. EXFO Application Note 044. http://documents.exfo.com/appnotes/anote044-ang.pdf

2. MIL-STD-220B. (2004) METHOD OF INSERTION LOSS MEASUREMENT. http://www.everyspec.com/MIL-STD/MIL-STD+(0100+-+0299)/MIL-STD-220B_CHANGE-1_21983/

3. MIL-PRF-29504/18 - Termini, Fiber Optic Connector, Removable. http://www.dscc.dla.mil/Downloads/MilSpec/Docs/MIL-PRF-29504/prf29504ss18.pdf

4. MIL-PRF-64266 - CONNECTORS, FIBER OPTIC, CIRCULAR, PLUG AND RECEPTACLE. http://www.dscc.dla.mil/Downloads/MilSpec/Docs/MIL-PRF-64266/idprf64266ss21.pdf

KEYWORDS: Fiber Optic Interface; End Face Performance; low optical loss; Low Return Loss; MIL-PRF-29504; MIL-STD-220B

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