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Proceedings Paper

Development of multipoint strain measurement systems using small-diameter fiber Bragg gratings
Author(s): Seiji Kojima; Kouji Satori; Keisuke Fukuchi; Akihito Hongo; Nobuo Takeda
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Paper Abstract

We have been studying optical sensing technologies using fiber Bragg gratings (FBGs) for health-monitoring systems in the fields of constructions, civil engineering, aerospace and so on. In these fields, various kinds of sensing techniques such as strain, temperature, vibration and crack detection are required. To meet these needs, we have fabricated the FBGs by precisely controlling photo-induced refractive index modulation or the grating period along a fiber. Also, as embedded sensors, we developed small-diameter FBGs which are embedded in fiber reinforced plastics (FRP) composite materials without inducing any mechanical deterioration. In this paper, we present the progress of our small-diameter FBGs and propose a new wavelength detection technique for FBG sensors using a wavelength division multiplexing (WDM) coupler. The reflected light is divided at the ratio depending wavelength through the WDM coupler. Especially, we adopted a PLC-type WDM coupler which has the advantage in low polarization sensitivity and integration compared with a fused-optical fiber-type WDM coupler. This technique is useful in high-speed detection for vibration or impact damage. Another application is a multipoint measurement system by using together with optical time domain reflectometry (OTDR) method. In this system, pulses of light incident into an optical fiber return from the FBGs to a detector with different arrival time. As a result, we can use FBGs with the same Bragg wavelength, because measuring delay time of the pulses enables to distinguish each FBG location. In addition, using together with wavelength division multiplexing within wavelength region for optical communications can increase the number of FBG sensors. The results of the basic performance in this system showed that it is very promising for the multipoint measuring system. These wavelength detection techniques will expand sensing applications using small-diameter FBGs.

Paper Details

Date Published: 27 June 2002
PDF: 8 pages
Proc. SPIE 4694, Smart Structures and Materials 2002: Smart Sensor Technology and Measurement Systems, (27 June 2002); doi: 10.1117/12.472619
Show Author Affiliations
Seiji Kojima, Hitachi Cable, Ltd. (Japan)
Kouji Satori, Hitachi Cable, Ltd. (Japan)
Keisuke Fukuchi, Hitachi Cable, Ltd. (Japan)
Akihito Hongo, Hitachi Cable, Ltd. (Japan)
Nobuo Takeda, Univ. of Tokyo (Japan)

Published in SPIE Proceedings Vol. 4694:
Smart Structures and Materials 2002: Smart Sensor Technology and Measurement Systems
Daniele Inaudi; Eric Udd, Editor(s)

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