In order to measure a voltage, an electro-optic element is placed in an electrical field generated by the voltage, and light is passed from a light source through a Faraday rotator and the electro-optic element onto a reflector and from there back through the electro-optic element and the Faraday rotator, thereby generating a voltage-dependent phase shift between two polarizations of the light. The interference contrast as well as a principal value of the total phase shift between said polarizations are measured and converted to a complex value having an absolute value equal to the contrast and a phase equal to the principal value. This complex value is offset and scaled using calibration values in order to calculate a compensated complex value. The voltage is derived from the compensated complex value.

An optically isolated lightwave current sensor including a control circuit, including: a light source configured to generate an input light beam; and a bias signal generator configured to generate an optical bias signal; a sensor head, including: an optical-to-electrical signal converter configured to convert the optical bias signal into a first electrical bias signal; a phase polarization modulator configured to phase modulate a linear polarization of at least one second light beam based on the first electrical bias signal, wherein the at least one second light beam is based on the input light beam; and an optical fiber coil optically coupled to the phase polarization modulator; and at least one optical fiber configured to route the input light beam and the optical bias signal from the control circuit to the sensor head.

In this electric field vector detection method, an electro-optic crystal, where a (111) surface of an optical isotropic medium is cut out, is used as a terahertz wave detection element. The method includes: causing polarization of probe light of ultrashort pulsed light to be circular polarization; allowing the probe light having circular polarization to enter the terahertz wave detection element and probing the terahertz wave; modulating the probe light, having probed the terahertz wave, by a rotating analyzer and detecting the modulated probe light by a photodetector; performing lock-in detection of a detection signal from the photodetector by a lock-in detector using a frequency based on a rotational frequency of the rotating analyzer as a reference signal; and detecting an electric field vector of the terahertz wave based on a detection signal from the lock-in detector.

The present application discloses electric field measurement device for measuring electric field of a target. Electric field measurement device includes optical waveguide which transmits transmission light, electrode portion, which gives optical characteristics of optical waveguide periodic variation, antenna for setting first state, in which electric field is coupled to optical waveguide, and second state, in which electric field is disconnected from optical waveguide, detector which detects light intensity of emission light emitted from optical waveguide, and applicator which applies voltage to electrode portion to give periodic variation. Applicator includes setting portion, which sets reference voltage in correspondence to light intensity under the second state, and output portion, which outputs voltage in correspondence to difference between reference voltage and induced voltage happening to electrode portion under first state.

An optical modulator configured to modulate an intensity of an incident light depending on a voltage between first and second electrode pads; first and second contact terminals that are configured to be in contact with the measurement point; a first electric line connecting the first contact terminal with the first electrode pad; and a second electric line connecting the second contact terminal with the second electrode pad are provided, the first and second contact terminals or the first and second electric lines are crossed with each other at least one time in a non-contact manner, and electromotive forces in opposite directions are induced between the first and second contact terminals or between the first and second electric lines at portions before and after a crossing portion when a magnetic field penetrating between the first and second contact terminals or between the first and second electric lines varies.

An optical voltage sensor system for measuring a high-voltage (HV) signal includes a voltage divider configured to generate a low-voltage (LV) signal representative of the HV signal, an electro-optic crystal, and electrodes arranged on the electro-optic crystal and connected to receive the LV signal from the voltage divider. The electrodes are configured, upon an unpolarized light beam being launched through the electro-optic crystal, to apply a voltage of the LV signal to the electro-optic crystal to alter a spatial distribution of a portion of the light beam exiting the electro-optic crystal in response to the LV signal. The optical voltage sensor system further includes a light collector configured to collect light having an intensity which varies based on the applied voltage, and a light converter configured to convert the collected light into an electronic signal representative of the HV signal.