Micromachined low-finesse Fabry-Perot interferometer for the measurement of DC and AC electrical currents

A micromachined low finesse Fabry-Perot interferometer for measuring DC and AC electrical current is presented. Interrogation of the microcavity is achieved by a dual-wavelength fiber Bragg grating technique working in quadrature. A linear relation between the DC electrical current and the optical phase defined by the microcavity was detected. Large enhancement of the sensitivity of the microcavities is presented with the use of a planar coil instead of a power line. The sensitivity of the sensor with the planar coil configuration is 7.9 rad/A and resolution of ∼0.18 mA/√Hz is achieved when the distance between the planar coil and the transducer head is 2 mm. The response of the sensor for AC measurements is 0.14 V/A with a resolution of 6 mA/√Hz when the distance between the power line and the transducer head is 5.5 cm.