| 摘要 |
PROBLEM TO BE SOLVED: To make possible use of single-mode optical fibers on transmission paths with a smaller number of components than in the conventional way.SOLUTION: An optical current sensor for alternating currents is equipped with a light source 11, an optical waveguide 20 that propagates the light from the light source, an unpolarizer 31 that unpolarizes the light from the optical waveguide 20, a polarizer 32 that linearly polarizes light from the unpolarizer 31, a polarization plane holding fiber 33 that turns light from the polarizer 32 into two independent linearly polarized light rays, a 1/4 wavelength plate 34 that turns light from the polarizer 32 into clockwise and counterclockwise circularly polarized light rays, a sensor fiber 35 that senses the magnetic field of a measured current SC with light from the 1/4 wavelength plate 34, a mirror 36 that reflects light at the end edge of the fiber 35 and causes it to pass the fiber 35 again, a photo-sensor 13 that detects the light quantities having passed the fiber 35, the polarizer 32, the unpolarizer 31 and the optical waveguide 20, an arithmetic circuit 15 that calculates the magnitude of the measured current SC from the light quantities, and a Faraday rotator (magnet) 37 that gives either of approximately ±π/4 phase differences in relative terms to each of the clockwise and counterclockwise circularly polarized light rays that turn back in the fiber 35.SELECTED DRAWING: Figure 1 |
