Multi-Core Fiber Optic Shape Sensing

Higher accuracy: Eliminates the compound errors that are experienced with other measurement methods, even for complex shapes


Greater flexibility: Allows the fiber to twist naturally, eliminating the need to bond the fiber optic in place and minimizing internal stresses on the fiber


Low cost: Uses off-the-shelf mathematics software that can run on standard computing platforms


Robust and reliable: Operates in high-temperature and high-pressure environments

Aerospace: Tracking airframe structural deformation, control surface flutter, hydraulic hose and wire bundle routing, and flexible boom position


Structures: Monitoring the overall health of structures such as bridges and dams that undergo constant stress


Automotive: Studying truck or automobile frames to improve safety and actively control handling


Wind Turbine: Checking blade shapes to improve efficiency and longevity


Medical: Determining shape and pressure in minimally invasive surgical tools such as endoscopes and catheters

This new method determines shape using multi-core optical fiber and greatly advances the processing of information from FBG sensors.

How It Works

FBG sensors, placed at regular intervals along optical fiber, can be used to determine temperature, pressure, and strain measurements. When used in multi-core optical fiber (three or more channels in a single fiber), the strain measurements from each core can indicate the direction and amount of bend in the fiber. The amount of strain in each core is proportional to the bend radius and to the position of each core relative to the center of the bend curve. Using commercially available software to enhance the processing of these directional measurements, this new method gives a highly accurate depiction of how the fiber is positioned.

The new process relies on measurements from a free-sleeved, unbound, multi-core fiber, utilizing the natural elasticity of the fiber as it twists and untwists inside the sleeving to minimize internal stresses while conforming to induced shape changes.

Why It Is Better

Other currently used methods derive shape at each sensor group along the fiber, compounding measurement errors from one sensor group to the next as fiber shape is pieced together. The new method eliminates such error by combining the strain measurements that are taken along the entire fiber into a single shape determination algorithm, giving the true
shape of the fiber.

Other techniques require that the fiber be bonded to a measured surface or in some other way be constrained to prevent additional errors. Using the new method, the optical fiber is only bonded at its origin, otherwise being left free to twist or untwist according to its own elasticity. This arrangement minimizes the internal stresses of the fiber and allows for more accurate shape measurements.

Patent

Langley is seeking patent protection for this technology.

This technology is part of NASA’s Innovative Partnerships Program, which seeks to transfer technology into and out of NASA to benefit the space program and U.S. industry. NASA invites companies to consider licensing this Method for Shape Determination of Multi-Core Optical Fiber (LAR-17629-1) for commercial applications.

If you would like more information or want to pursue transfer of this technology, please contact us by e-mail or phone: or (919) 249-0327.

For more information about other technology licensing and partnering opportunities, please visit:

Innovative Partnerships Program Office (link opens new browser window)
NASA’s Langley Research Center