METHOD AND FIBRE-OPTIC DEVICE (VERSIONS) FOR MEASURING ELECTRIC CURRENT AND MAGNETIC FIELD Russian patent published in 2013 - IPC G01R15/24 

FIELD: physics.

SUBSTANCE: method of measuring electric current and magnetic field involves generating two orthogonally polarised light waves, passing said waves through magnetically sensitive optical fibre with built-in linear birefringence, placed in the measured magnetic field or magnetic field of the measured electric current, reflecting said waves, transmitting said waves in the reverse direction and determining electric current and magnetic field strength from the intensity of the interfering reflected light waves. Before entering the magnetically sensitive fibre, polarisation of each wave is converted to elliptical polarisation and before reflection, polarisation of each wave is converted to circular polarisation. Azimuths of the orthogonal elliptical polarisation of waves entering the magnetically sensitive fibre before and after reflection either match the azimuths of principal axes of linear birefringence or are orthogonal thereto, and the ellipticity of polarisations matches the natural ellipticity of the fibre. The fibre-optic device for measuring electric current and magnetic field has an optical radiation source connected to the first input of a directional coupler, the second input of which is connected to a photodetector, and one of the outputs is connected to a linear polariser which is connected through a weld joint to series-connected optical modulator, delay line, first retarder, sensitive element made from magnetically sensitive fibre with built-in linear birefringence with a helical structure pitch L_tw and built-in linear birefringence beat length L_b, and a radiation reflector. A second retarder is placed between the radiation reflector and the magnetically sensitive fibre, wherein the fist and second retarders induce phase differences φ₁=arctg(2L_b/L_lw) and φ₂=π/2-arctg(2L_b/L_lw), respectively, between orthogonal linearly polarised components of optical radiation.

EFFECT: wider dynamic range of a fibre-optic sensor.

9 cl, 6 dwg