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Proceedings Paper

An etched fiber optic vibration sensor to monitor the simply supported beam
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Paper Abstract

A single mode fiber optic vibration senor is designed and demonstrated to monitor the vibration of a simply supported beam. A rectangular beam (length 30.8 cm, width 2.5cm and thickness 0.5mm) made of spring-steel is arranged as simply supported beam and is made to vibrate periodically. To sense the vibrations a telecommunication fiber is chemically etched such that its diameter reaches 50μm and is glued using an epoxy at the centre of the beam. A broadband light (1550nm) is launched into Fiber Bragg Grating (FBG) through a circulator. The light reflected by the FBG (1540.32nm) is coupled into the centre etched fibre through the circulator and is detected by photodiode connected to a transimpedance amplifier. The electrical signal is logged into the computer through NI-6016 DAQ. The sensor works on transmission power loss due to the mode volume mismatch and flexural strain (field strength) of the fiber due to the bending in the fiber with respect to the bending of the spring-steel beam. The beam is made to vibrate and the corresponding intensity of light is recorded. Fast Fourier transform (FFT) technique is used to measure the frequencies of vibration. The results show that this sensor can sense vibration of low frequency accurately and repeatability is high. The sensor has high linear response to axial displacement of about 0.8 mm with sensitivity of 32mV/10μm strain. This lowcost sensor may find a place in industry to monitor the vibrations of the beam structures and bridges.

Paper Details

Date Published: 9 May 2012
PDF: 7 pages
Proc. SPIE 8439, Optical Sensing and Detection II, 84392F (9 May 2012); doi: 10.1117/12.922176
Show Author Affiliations
Kishore Putha, National Institute of Technology, Warangal (India)
Dantala Dinakar, National Institute of Technology, Warangal (India)
Pachava V. Rao, National Institute of Technology, Warangal (India)
Dipankar Sengupta, National Institute of Technology, Warangal (India)
K. Srimannarayana, National Institute of Technology, Warangal (India)
M. Sai Shankar, National Institute of Technology, Warangal (India)

Published in SPIE Proceedings Vol. 8439:
Optical Sensing and Detection II
Francis Berghmans; Anna Grazia Mignani; Piet De Moor, Editor(s)

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