Distributed Fiber Optic Twist Measurement in Shape Sensing Tethers

Existing methods to provide cable orientation and array element localization in the Navy’s fixed and towed array systems and tethered unmanned vehicles rely on devices embedded in the cable itself, such as hydrophones, magnetic heading and orientation sensors, and accelerometers. These traditional sensors have power, weight, space, and EMI budgets within the cable that require design compromises to be made and further increase the design complexity of the system. Luna has recently made advances in a break-through fiber optic shape sensing technology that is based on Optical Frequency Domain Reflectometry, enabling accurate positional information at all points along a tether in an extremely small, lightweight, EMI-immune fiber optic package. In the proposed research effort we will conduct a concept study designed to add another degree of freedom to the measurement system, which will significantly increase the accuracy of the shape measurement and is essential for applications where external twist may be imposed on the fiber. Luna will work with a leading University to develop analytical and FEA models of new fiber geometries and to determine a baseline for comparison to experiments designed to be completed during the Phase I Base period of performance. In the Option period, designs will be refined based on experimental results and concepts down selected in advance of the Phase II.