Dynamic Fiber-Optic Shape Sensing Using Fiber Segment Interferometry

Abstract

Dynamic fiber-optic shape sensing, often also referred to as curvature or bend sensing, is demonstrated using fiber segment interferometry, where chains of fiber segments, separated by broadband Bragg grating reflectors, are interrogated using rangeresolved interferometry. In this paper, the theory of interferometric curvature sensing using fiber segments is developed in detail, including techniques to infer lateral displacements from the measured differential strain data and methods for directional calibration of the sensor. A proof-of-concept experiment is performed, where four fiber strings, each containing four fiber segments of gauge length 20 cm each, are attached to the opposing sides of a flexible support structure and the resulting differential strain measurements are used to determine the lateral displacements of a 0.8 m cantilever test object in two dimensions. Dynamic tip displacement measurements at 40 nm • Hz −0 .5 noise levels over a 21 kHz bandwidth demonstrate the suitability of this approach for highly sensitive and cost-effective fiber-optic lateral displacement or vibration measurements.

Flexible High Aspect Ratio Wing: Low Cost Experimental Model and Computational Framework

“…In Section III the low cost accelerometer and gyroscope system is discussed, but the BeaR D S programme also allows for high speed camera image tracking and strain measurement based on Fibre Bragg Grating (FBG). 24 Testing is conducted in the Cranfield University closed section 8'x6' and Weybridge open section wind tunnels. Steady state response is obtained by defining angle of attack and airspeed.…”

Bend-Direction and Rotation Plastic Optical Fiber Sensor

“…The interference between two supermodes excited in the MCF has been used to obtain an interferometric strain sensor. Multi-parameter sensors for rotation and bending are reported in the literature as well [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

1.5 Dynamic Measurement of Strain and Shape on a Rotating Helicopter Rotor Blade Using Optical Fibre Sensors

“…FBGs represent a relatively mature technology, and their use in the ground vibration testing of rotor blades was described in [3], where their sensitivity to the flapping and lagging vibration modes of the blade was a result of the local curvature induced strain and was shown to be dependent on the location of the optical fibre relative to the structure's neutral axis, requiring an appropriate distribution of the sensor elements over the surface of the rotor blade. Direct fibre optic shape sensing (DFOSS) [4], based on the fibre segment interferometry approach [5] deployed in the form of three optical fibres arranged around a thin, flexible plastic former and attached to the surface using adhesive tape, was shown to allow the full characterization of the rotor blade's structural dynamics using a single sensor rod aligned along the axis of the blade [3]. Successful characterization of vibration mode shapes has also recently been achieved.…”