NxtPhase - Technology - Fiber Optic Current Sensor

This prototype sensor demonstrated accuracy to 0.03%

The Fiber Optic Current Sensor is the core of the NXCT Optical Current Transducer. It consists of a light source, photo detector, optics & electronics coupled to a fiber sensor head wound around a current carrying conductor. The optical phase modulator is the "heart" of the NxtPhase current sensor technology & it, along with the electronics & optics, provide a highly accurate measurement of current. This unique technology is protected by more than 20 international patents.

A light source sends light through a waveguide to a linear polarizer, then to a polarization splitter (creating two linearly polarized light waves) & finally to an optical phase modulator.
This light is then sent from the control room to the sensor head by an optical fiber.
The light passes through a quarter waveplate creating right & left hand circularly polarized light from the two linearly polarized light waves.
The two light waves traverse the fiber sensing loop around the conductor, reflect off a mirror at the end of the fiber loop & return along the same path.
While encircling the conductor, the magnetic field induced by the current flowing in the conductor creates a differential optical phase shift between the two light waves due to the Faraday effect.
The two optical waves travel back through the optical circuit & are finally routed to the optical detector where the electronics de-modulate the light waves to determine the phase shift.
The phase shift between the two light waves is proportional to current & an analog or digital signal representing the current is provided by the electronics to the end user.

Introduction | Current Sensing | Voltage Sensing | Relays & Recorders | Technical Papers