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Ultra Low-Profile Hermetic Fiber Optic Interconnect


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Hypersonics; Microelectronics; Nuclear The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Reduce the size of state-of-the-art optical fiber hermetic interconnects so that they can be packaged into small form factor fiber optic gyroscopes. DESCRIPTION: Delivering optical fibers into and out of hermetically sealed systems is a common problem in optical experiments and applications. While there are numerous commercially available options and even MIL-Spec options such as MIL-DTL-38999 hermetic fiber interconnects [Ref 1], these solutions are often bulky and limited to specific fiber types. While much work has been done to improve the fiber feedthrough seals, which can now achieve helium diffusion rates of < 10-12 mbarr/sec, shrinking the footprint of fiber optic interconnects has not been effectively achieved. The smallest custom hermetic fiber optic interconnect solutions are on the order of 40mm in length and ¼” in diameter [Ref 2]. In order to continue to miniaturize optical sensors it is necessary to greatly reduce the size of the currently available hermetic fiber optic interconnections. This SBIR topic proposes to design, prototype, and test an 80µm fiber hermetic interconnect that is 3.155mm in length with a stretch goal of achieving 0.1mm in length. PHASE I: Perform a design and materials study aimed at reducing the length of currently available hermetic optical fiber interconnects. The technique should be compatible with 80 micron polarization maintaining (PM) fiber. The study must assess performance criteria and consider all aspects of device fabrication. The study shall include a preliminary assessment of long-term environmental stability assuming a design life of 30 years at 50°C based on a materials physics analysis, including Mean Time Between Failure (MTBF), Mean Time to Failure (MTTF) and Failure In Time (FIT) values, along with identification of the assumptions, methods, activation energy, and confidence levels associated with these values. The study shall justify the feasibility/practicality of the approach for achieving reduced hermetic optical fiber interconnect with negligible impact on PM fiber performance including, overall optical loss, polarization extinction ratio, and polarization cross-talk. For the performance impact to be deemed negligible, the impact must be consistent with that of a fiber splice, index matching joint, or other high-performance interconnect. The Phase I Option if exercised, will include the initial design specifications and capabilities description to build prototype solutions in Phase II, as well as a test plan for an accelerated aging study (minimum 5 year real-time equivalent) to be conducted in Phase II. PHASE II: Based on the Phase I results, design, fabricate, and characterize six (6) prototype ultra low-profile optical fiber hermetic interconnects, that can be flush-mounted onto stainless steel cover suitable for incorporation into test beds for interferometric inertial sensors. Characterization must comprise evaluation of hermeticity over temperature with minimal-to-no impact on PM fiber performance. An accelerated aging study elevated temperatures must be performed to develop a predictive model of long-term environmental stability. The prototypes should be delivered by the end of Phase II. PHASE III DUAL USE APPLICATIONS: Based on the prototypes developed in Phase II, continuing development must lead to productization of ultra low-profile hermetic optical fiber interconnects suitable for interferometric inertial sensors. While this technology is aimed at military/strategic applications, optical fiber interconnects are heavily used in many optical circuit applications, including in telecom industry hardware. An optical interconnect with significantly reduced size could be employed to deliver light from a single light source into multiple fiber optic Sagnac interferometers and is likely to bring value to many existing commercial applications. Also, technology meeting the needs of this topic could be leveraged to bring IFOG technology toward a price point that could make it more attractive to the commercial markets. REFERENCES: 1. MIL-DTL-38999M, Connectors, Electrical, Circular, Miniature, High Density, Quick Disconnect (Bayonet, Threaded, or Breech Coupling), Environment Resistant with Crimp Removable Contacts or Hermetically Sealed with Fixed, Solderable Contacts, General Specification for. 08-SEP-2017. 2. “KTRAV-M10: Hermetic Fiber Optic Feedthroughs for Vacuum and Pressure up to 600 bars.” Laser Components. September 2020. KEYWORDS: Ultra low-profile, hermetic, optical fiber, interconnect, optical fiber feedthrough, polarization maintaining fiber
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