Dynamic strain measurement with a fibre Bragg grating sensor system

In this paper a fibre Bragg grating measuring system is presented to detect dynamic seismic signals in underground structures, rock mass and bridges, etc. To improve the sensitivity of dynamic strain measurement the wavelength of the used DFB-laser is automatically optimised by the actual dc photovoltage measurement. A strain calculation method is given. An adaptive filtering algorithm is proposed and applied to the noise reduction and the delectability of seismic signals. Results from laboratory and field experiments are given. This technique can be applied to the detection of dynamic strain variations down to 10(-9) at 1.7 kHz in underground rock mass excavations and to the monitoring of bridge structures, etc. (C) 2002 Published by Elsevier Science Ltd.