FIBRE LASER SENSOR FOR MEASURING DIFFERENTIAL PRESSURES AND FLOW VELOCITIES

摘要

The invention relates to a fibre laser pressure sensor (1) which is suitable in particular for the measurement of differential pressures and flow velocities v1 in oil boreholes. The fibre laser (2) provided for in the invention comprises two sensor fibre segments (5a, 5b) subjected to different pressures in which a double refraction proportional to the differential pressure DELTA p=p1-p2, and thus a beat frequency, are induced between the polarization modes or spatial modes in the fibre laser (2). Embodiments of the invention comprising polarimetric monomode fibres (5a, 5b) and/or elliptical dual-mode fibres (5a, 5b) are given as examples. The invention also relates to pressure-resistant multi-chamber sensor housings (25) and wavelength multiplex configurations for the fibre laser pressure sensor (1). An advantage of such a sensor is that the pressure signal is wavelength coded and thus highly insensitive to interference. Readings can be obtained directly by optic fibres over great distances separating the passive optical sensor head (1) and optoelectronic measurement device (12, 17). An application of the invention concerns the measurement of a flow velocity v1 using a Venturi tube (23).