Fibre Optic Remote Displacement Sensor for Seismic Events at High Temperature
Recent geophysical research includes measurement of seismic events in non-trivial surroundings. Seismic sensors have to be installed in very deep boreholes as well as in volcanic regions at measuring sites with temperatures above 250°C and with several km of transmission lines between sensor and signal processing. The application in a three-dimensional seismic network requires detection of vibration amplitudes Δs=0.1nm. 100μm at frequencies 0.1Hz..30Hz. Under these conditions, interferometric detection and signal transmission using optoelectronic and fibre-optic components of photonic technology seems to be the only possibility to perform long-term measurement of seismic waves. In this paper, results are presented concerning high-temperature parameters of fibre-optic key components and interferometer construction, signal processing for evaluation of optical phase, and first results of the sensor test.
KeywordsSignal Scheme Wavelength Modulation Michelson Interferometer Optical Phase Deep Borehole
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- 1.K.-H. Jäckel, E. Unterreitmeier, and R. Stecher, Ein Bohrlochseismometer für den Einsatz unter extremen Bedingungen, in: Jahresbericht 1994/95, GeoForschungsZentrum Potsdam (1995)Google Scholar
- 4.W. Ecke, R. Landrock, V. Tschernjawski, and R. Willsch, A novel phase shift demodulation technique for optical interferometers using interference pattern generation, Int. J. of Optoelectronics 8:635 (1993)Google Scholar
- 5.R. Emmermann, Abenteuer Tiefbohrung, Geowissenschaften 13:114 (1995)Google Scholar