Two-core optical fiber magnetic field sensor

A two-core optical fiber magnetic field sensor at least comprising:

• a light incidence/emission unit;
• a lens;
• a magnetic garnet;
• a reflector;
• a λ/4 wavelength plate (λ:
• a wavelength of a light beam which is incident on the two-core optical fiber magnetic field sensor),
• wherein the lens, the magnetic garnet, and the λ/4 wavelength plate are arranged between the light incidence/emission end portion of the light incidence/emission unit and the reflector,
• the light incidence/emission unit is configured to include two polarization plane preserving optical fibers, and the two polarization plane preserving optical fibers are arranged so that directions of slow axes of the two polarization plane preserving optical fibers are different by 90 degrees from each other,
• the λ/4 wavelength plate is arranged so that a direction of a crystal axis of the λ/4 wavelength plate is different by 45 degrees from the direction of the slow axis of any one of polarization plane preserving optical fibers,
• a light beam which is emitted from the one polarization plane preserving optical fiber transmits through the λ/4 wavelength plate, the lens, and the magnetic garnet and is reflected by the reflector, and after the reflection, the light beam transmits through the magnetic garnet, the lens, and the λ/4 wavelength plate again and is incident on the other polarization plane preserving optical fiber, and
• the light beam which is emitted from the other polarization plane preserving optical fiber transmits through the λ/4 wavelength plate, the lens, and the magnetic garnet and is reflected by the reflector again, and after the reflection, the light beam transmits through the magnetic garnet, the lens, and the λ/4 wavelength plate again and is incident on the one polarization plane preserving optical fiber again.