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Stress test verification of optical fiber wrap design for compact free space optical communications gimbals

Given the rapid demand for higher and higher bandwidth and the contention for radio frequency (RF) spectrum allocations, the need for space-based Free Space Optical Communications (FSOC) systems is ever increasing. We have previously presented design concepts for a lightweight, small, and high performance two-axis gimbal focusing on the use of commercial off-the-shelf (COTS) subsystems. Our efforts to design a small gimbal with 100 micro-radian pointing accuracy for FSOC have resulted in an unconventional optical fiber wrap design in order to achieve the low optical noise needed to meet the design goals. However, the design raised concerns about stress induced in the optical fibers. To verify our design assumptions and the actual gimbal performance, a mockup of the fiber wrap configuration was subjected to a Cyclical Stress Test conceived to mimic the desired on-orbit lifetime. At regular intervals throughout the test duration, optical power measurements were collected to characterize the degradation of the fiber wrap fiber. The results of the Cyclic Stress Test validated assumptions regarding the design performance, and provided insights used to modify the design prior to hardware implementation into compact free space optical communications gimbals.