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International Society for Industrial Process Tomography

6th World Congress on Industrial Process Tomography

Grooved Sensors for Photonic Guided Path Tomography

Nurgiyatna Nurgiyatna1, Patricia Scully2, Krikor B. Ozanyan1,2

1School of Electrical and Electronic Engineering,

2Photon Science Institute

The University of Manchester, Manchester M13 9PL, United Kingdom


ABSTRACT


In this work we report on the detailed study of the measured signal attenuation along Plastic Optical Fibre (POF) sensor elements, sensitised to bending by cutting a number of transversal grooves to modulate the overall integrated transmission. We present the results from systematic measurements in the case of a single groove, as well as multiple grooves, for positive or negative curvature of bend. The results reveal substantial contributions from the un­grooved POF (u­POF) which is superimposed on the much stronger effect from the grooves. We show that the dependence of power loss vs positive bending is close to linear when this contribution is eliminated (e.g. by sensor calibration). We further show that the u­POF contribution for negative bending causes a maximum in the sensitivity followed by close to zero response, depending on the groove depth. This is discussed in terms of Photonic Guided Path Tomography (PGPT) system design and the strategies for groove deployment – single angle (in the fibre cross­sectional plane) vs multiple angle grooving, as well as measures to secure control over the groove angle relative to the local imaged surface normal.

Further we show and discuss results from multiple groove experiments revealing the effect on the path integral values from the length of bent sections (positive and negative). We focus on the potential deterioration of sensitivity because of cancelling contributions from opposite sign sections, as well as the saturation of sensitivity caused by the compliance of the fibre sensor to the 2­D shape of the deforming object, especially for very soft underlying materials.


Keywords Guided Path Tomography, path integrals, plastic optical fibre, grooved sensor


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