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Abstract

An optical fiber loop current sensing controller module, which integrates with the electrical power, and data processing and transmission, back-plane of a digital micro-processor relay for modular integration with the protection, metering, and communication functions of an electrical SCADA system. An optical transmitter is energized from a DC source on the digital relay, and emits unpolarized light of known intensity and wavelength to a linear polarizer, and the Stokes vector polarization parameters are calculated from the Mueller Matrix of the linear polarizer and the known intensity of the unpolarized optical input from the transmitter, which is then launched in alignment with the transmission axes of a polarization maintaining optical fiber link to a remote and passive fiber loop current sensor, where the linearly polarized optical pulse traverses a complete circular path around an energized conductor and experiences polarization state rotation in relation to the magnetic flux density which is proportional to current flow based on Ampere's law. The rotated polarized optical pulse is transmitted back to the optical fiber loop current sensing controller module via a return fiber optic cable, where the Stokes vector polarization parameters for the returned optical pulse having experienced Faraday rotation are calculated by splitting the pulse into four components, passing these components through a linear horizontal polarizer, a linear vertical polarizer, a linear polarizer with transmission axis set at 45 degrees, and a right circular polarizer comprised of a quarter wave plate connected to a linear polarizer with transmission axis set at 45 degrees, respectively, and where the four separate output channels of the four polarizing elements are then connected to be orthogonally incident a quadrature array of four separate photodetectors which transduce the optical intensity to electrical quantities, and the four optical receiver outputs connect to a digital data processing bus, where the Stokes vector parameters for the polarized optical pulse are calculated directly from the array of optical intensity values transduced by the photodetectors, and the change in polarization state is calculated by comparing the initial linear polarization Stokes vector parameters reference state transmitted to the remote fiber loop current sensor with the measured Stokes parameters of the rotated polarized optical pulse received back. This data is then converted to a calibrated current measurement, which is transmitted to a signal and data processing back plane of the digital micro processor relay via digital output ports on the optical current sensing controller module.

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First Claim