Magneto-Optical Probe With Integrated Optical Elements for Measuring Environmental Magnetic Fields in the Low- and Intermediate-Frequency Bands

In recent years, the development of devices using magnetic fields in the low-frequency bands (dc–100 kHz) and intermediate-frequency bands (300 Hz–10 MHz) is progressing. The influence of magnetic fields generated from such devices on human body is drawing attention. Responding to the requirement to construct the measurement system with the ability to measure wideband frequency range for evaluating such magnetic fields, the authors have developed a prototype of the new measurement system, measuring environmental magnetic fields from dc to 20 kHz, and confirmed its performance. It is confirmed that the output signal from the conventional magneto-optical probe (MO probe) fluctuates when the optical fiber cable is bent between the polarizer, probe, and analyzer. Therefore, it is proposed that the polarizer and analyzer are miniaturized and integrated into the body of MO probe, and optical fiber cables inside the housing are fixed. The output signal from the new MO probe does not fluctuate when optical fiber cables outside the housing are bent. Furthermore, the measurement system using this MO probe is examined under applied magnetic fields from dc to 20 kHz. Similar signals are observed both in voltage signals obtained by the new measurement system and in magnetic field signals measured by the Hall element-type magnetic field probe. In addition, a comparison with existing sensors and an example of the application of this measurement system to the measurement of magnetic fields generated by power equipment are shown.