The coating also must show no hysteresis in multiple temperature cycles. The modulus of the selected coating must remain low enough (<3000 MPa) at ?54!C that attenuation would meet the project?s power budget requirements. Honeywell directed Spectran to evaluate and determine the correct coating based on material size and dimensional tolerances. There are many design considerations for the finished gyroscope, however, that depend on the fiber draw process, in particular the physical properties and dimensions of the coating. In the fiber draw process, the main cost-saving parameter is cycle time, including both setup time and line speed. Improving dimensional symmetry was essential to minimize polarization effects in the fiber due to coiling. An additional goal in core and clad processing is to improve the dimensional symmetry of the fiber to maintain a consistent profile and achieve the required optical parameters?mode field diameter, cutoff wavelength, and core/clad concentricity?with minimal processing. Improving these processes increases the batch size and reduces the overall fabrication time per preform. In the preform fabrication process, the goals were to reduce the cycle time (the time it takes to manufacture the preform) and to increase the overall preform size. The manufacture of this type of specialty fiber was divided into two processes?glass preform fabrication and optical fiber draw?and both were analyzed for their cost-cutting potential. These steps included preform manufacturing, fiber drawing, coating selection, and the process/product flow. SpecTran Specialty Optics reviewed all of the steps involved in the fiber manufacturing process, looking for opportunities to cut costs while still satisfy the system requirements. To be cost-effective, the cost of the fiber had to be reduced from more than $1.00 per meter to less than $0.20 per meter (if manufacturing 10,000 km per year). Finally, a balance is needed between bending and coupling losses to achieve the optical system budget requirements. The overall coil size and weight requirements dictate an extremely small (80 ?m) cladding diameter fiber. The single-mode fiber must have very low bending loss atġ560 nm. The coil must demonstrate stable, consistent, and predictable optical and mechanical performance through a temperature range of ?54!C to +92!C. in diameter and conforms to many performance requirements (see table on p. Three coils are used to complete the full gyroscope, one for each axis. The fiberoptic gyroscope design requirements include a precision-wound coil of approximately one kilometer of single-mode optical fiber. As part of the two-year program, Honeywell formed a consortium of companies to contribute to the redesign effort and selected SpecTran Specialty Optics Company (Avon, CT) to design and manufacture the new single-mode optical fiber, GyroSil. In addition, nonpolarized single-mode fiber is more closely related to the industry-standard telecommunications single-mode fiber, which increases the potential for cost reduction. The nonpolarized single-mode fiber is significantly less expensive, thereby reducing the overall system component cost. Honeywell adopted a depolarized gyroscope design using a nonpolarized single-mode fiber as opposed to previous fiberoptic gyroscope designs that used a polarization-maintaining single-mode fiber. To this end, Honeywell Industries (Phoenix, AZ) was awarded a contract to develop a pilot production line and demonstrate the ability to manufacture a navigational-grade gyroscope scalable to a 10,000-axes-per-year production rate at a cost of $1500 per axis. Development of high-performance, low-cost fiberoptic gyroscopes was unlikely without ManTech support. The philosophy behind the ManTech program is to encourage companies to optimize military technology within acceptable cost parameters for high-volume production. To address this challenge, the US Defense Advanced Research Projects Agency (DARPA), as part of its ManTech (manufacturing technology) program, established a program to create an advanced-design, navigation-grade, fiberoptic gyroscope system that could be manufactured at reduced cost.įiberoptic gyroscopes were originally designed and manufactured for US military applications, and present costs are not competitive with other technologies. The design and production of a high-performance, low-cost, single-mode fiber for gyroscope coils is a critical aspect of developing interferometric fiberoptic gyroscopes (IFOGs) for military and commercial aviation applications. Improved manufacturing lowers cost of single-mode fiberĬonsortium develops a high-performance, low-cost optical fiber for demanding applications.
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