Dual excitation scheme for direct suppression of residual signal in fibre-optic magnetometers

A novel dual-excitation scheme capable of suppressing the residual signal responsible for up-converting low-frequency noise in a fibre-optic magnetometer is reported. This scheme provides a magnetic carrier with spatially varying strength and can reduce both the up-converted interferometer noise and the up-converted transducer noise. With a 5 cm long amorphous wire transducer, 30 dB of residual signal suppression resulting in a signal-to-noise ratio improvement of 25 dB has been obtained for a magnetic signal at 1 Hz when the response using dual excitation is compared with that using single excitation.