Lifetime Test Results and Polarization Performance Verification in Fiber Wrap for Free-Space Optical Communications Gimbals

The continuing need to miniaturize mechanisms with wide range of motion for use in free-space optical communications has motivated the design of a low size, weight, and power (SWaP), two-axis gimbal with an optical fiber wrap as the key enabling feature. Our efforts to design a small gimbal with 100 micro-radian pointing accuracy for free-space optical communications have resulted in an unconventional optical fiber wrap design in order to achieve the low optical noise needed to meet system performance goals. Traditionally, fiber optic leads are installed in a stationary configuration to ensure maximum life and performance for the component. The fiber wrap design employed by Applied Technology Associates utilizes a combination of supplier design specifications and "mechanical spring" design techniques to construct a dynamic, innovative fiber mechanism, with life expectancy scaled to expected on-orbit operations and with negligible performance degradation. An engineering mockup was created to test both life expectancy and polarization performance at accelerated lifetime rates to verify the design. Presented in this paper is the design approach, test configuration approach, resulting lifetime testing (from cyclical stress testing), and polarization performance test outcomes. The polarization performance test outcomes show that the design results exceed planned lifetime goals, and maintain optical performance throughout the testing process. These test results confirm that fiber wrapping is a viable and available tool for miniature mechanisms in compact optical communications gimbals.