In this paper, we describe our study on a novel high-frequency magnetic field probe based both on the BiRIG rotation magnetization (RM) phenomenon and the third-generation optical probing scheme. First, we explain our experimental investigation on RF sensitivity and frequency response of the RM-based Faraday effect in a commercially available Bi-substituted rare-earth iron garnet plate. Second, we report on the implementation of fiber-optic magneto-optic (MO) probe heads with bandwidths of 10 GHz or broader, which have been brought about by careful arrangement of the magnetization axis of a single-domain crystal and the highly sensitive fiber-edge optical probing scheme. Third, we describe a few RF magnetic field distribution measurements carried out successfully over GHz-band microstrip line circuits. The results of the study imply the substantial potential of the present MO probe head for the RF current visualization.

In this paper, design and experimental results are described about a newly developed highly flexible fiber Faraday effect current sensor using the flint glass fiber as the sensor element. In the new type, a mirror is coated at an end of the flint glass fiber, and light takes round trip transmission in it. By the round trip transmission, the effect of rotation of polarization plane due to the torsion of the fiber is automatically canceled. Because of the low photo-elastic constant of the flint glass fiber, and the automatic canceling of the rotation, the polarization state of light passed through the fiber is stable. Therefore, in the new reflection type, it is not necessary to support the flint glass fiber with a durable circular frame to maintain accuracy. And so, the sensor head is small, light, and can be easily installed to existing power apparatus by winding the flint glass fiber around the current conductor without pulling out or cutting it. Experiments were done to verify the stable characteristics using the developed sensor model. In the experiments, relation between the final output signal of the sensor and shape of the curve of the flint glass fiber were examined. From the experiments, it became clear that the final output is almost perfectly independent on shape of the curve of the fiber. It was also confirmed that accuracy of the sensor conform to the standard of conventional current transducers for protection of power systems in Japan.