Abstract

A fibre-coupled Michelson interferometer has been developed for vibration measurement in seismic sensors for deep boreholes at temperatures up to 300°C. Results of long-term thermal stability tests of components and construction techniques have been used to develop a sensor device showing constant interference visibility at temperatures between 20 and 300°C. For application of high-resolution optical phase shift detection to a three-component seismic measuring system, three measuring interferometers and a fourth thermally stabilized all-fibre referencing interferometer with equalized unbalances are externally modulated by sinusoidal current modulation of a tunable 1.3 μm DFB diode laser source.

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