Optical sensor

An optical sensor for measuring a magnetic field intensity and current intensity in a magnetic field ranging from a low-magnetic field to a high-magnetic field, the optical sensor comprising:

• a light irradiation means for irradiating a linearly polarized light having a wavelength of 740 to 890 nm;
• a first magneto-optical element for low-magnetic field use which has a composition of Y.sub.3-x Tb.sub.x Fe.sub.5 O.sub.12 (0.3.ltoreq..times..ltoreq.0.8) for Faraday rotating the linearly polarized light to output a first rotated polarized light;
• a second magneto-optical element for high-magnetic field use which has a higher magnetic field for saturation than that of the first magneto-optical element for Faraday rotating the linearly polarized light to output a second rotated polarized light, which is arranged in parallel to the first magneto-optical element;
• and
• detecting means for modulating in intensities of the first and second rotated polarized lights which have been respectively Faraday rotated by the first and second magneto-optical elements and for detecting each of the light outputs of the rotated polarized lights from the first and second magneto-optical elements.