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What is FOCS?
(Fiber-Optic Current Sensing)
Fiber-Optic Current Sensing (FOCS) is an optical sensing technology that measures electrical current by detecting the magnetic field generated around a conductor. It uses a sensing fiber wound around the conductor and exploits the magneto-optic Faraday effect to convert current into a measurable optical phase shift.
FOCS provides a non-contact method for current measurement and can offer high accuracy, electrical isolation, and immunity to electromagnetic interference, making it suitable for demanding electrical and power-system applications.
HOW Fiber-Optic Current Sensing Works
The principle can be understood through three main steps:
Light propagation
Two circularly polarized optical signals are launched into a sensing fiber coil surrounding the electrical conductor.
Faraday effect
The magnetic field produced by the current causes the polarization states of the light to experience a different phase shift as they propagate through the fiber.
Current measurement
The resulting phase difference is measured and directly related to the current flowing through the conductor.
