OPTICAL CURRENT AND MAGNETIC FIELD MEASURING DEVICE

PURPOSE:To obtain the same effect as in case a rotational angle by an optical Faraday effect becomes twice as large, and a Verdet constant becomes twice as large, by constituting so that light goes and returns in an optical Faraday element. CONSTITUTION:A wavelength plate 10 rotates an incident linear polarized wave by 22.5 deg., and accordingly, rotates it by 45 deg. by going and returning. Also, a polarizing prism 9 operates as a polarizer against light from an optical tansmitter 1, as an analyzer against light emitted to an optical receiver 8. When a magnetic field is not applied, an incident wave is rotated by the wavelength plate 10, therefore, the polarizer and the analyzer are equivalent to arrangement rotated by 45 deg. relatively, that is to say, the wavelength plate 10 provides optical bias. A linear polarized wave which is Faraday-rotated by a magnetic field to be measured is converted to optical intensity by an analyzer function of the polarizing prism, is optical/electric-converted by the optical receiver 8 through an optical fiber 2', and from its output signal, a magnetic field H can be measured. Also, when an optical Faraday element 11 whose Verdet constant is large is used, a measuring device having high sensitivity is obtained.