Patent ID: 7046867

Claim:
A fiberoptic sensor for measuring at least one electric current or magnetic field, having a light source, N sensor heads that can be arranged in the shape of a coil around current conductors or along the magnetic field, N being a whole number with N≧2; exactly one phase modulation unit, having at least one phase modulator; at least one detector; a control and evaluation unit that is connected via at least one detector signal line to the at least one detector, and via at least one modulator signal line to the at least one phase modulator; first means being provided for guiding light from the light source into an end, on the detector side, of the phase modulation unit; second means being available for guiding light from the end, on the detector side, of the phase modulation unit to the detector; wherein the phase modulation unit has a further end, on the sensor head side, that is optically connected to at least one of the N sensor heads, and N reflection interferometers are provided, each of the N reflection interferometers includes exactly one of the N sensor heads, and the N sensor heads in each case having a mirrored end, and wherein by means of the phase modulation unit linearly polarized lightwaves can be phase-modulated differentially in a non-reciprocal fashion, wherein N modulation amplitudes φ 0,n and N modulation frequencies v n are provided for the non-reciprocal differential phase modulations, the modulation frequencies v n and two prescribable positive whole numbers p, q with p≠q being selected in such a way that the following equation is fulfilled for all positive whole numbers z and for all whole numbers n, m with n≠m and 1≦n,m≦N that: p×v n ≠z×v m and q×v n ≠z×v m and the modulation amplitudes φ 0,n and the modulation frequencies v n being selected as a function of modulation-relevant optical path lengths l n .