An Extrinsic Fabry Perot Fiber Optic Current Transformer Based on PZT Coupling

Area of Science:

• Optoelectronics
• Sensor Technology
• Materials Science

Background:

• Conventional fiber-optic current transformers face challenges in low-current detection due to structural complexity, sensitivity limitations, and operating point instability.
• Environmental factors can also affect the stable operating point, hindering accurate measurements.

Purpose of the Study:

• To develop a novel fiber-optic current transformer (FOCT) that overcomes the limitations of conventional designs for enhanced low-current detection.
• To improve the structural simplicity, detection sensitivity, and operating point stability of FOCTs.

Main Methods:

• A hybrid sensor design coupling an extrinsic Fabry-Perot interferometer (EFPI) with a lead zirconate titanate piezoelectric ceramic (PZT) was proposed.
• A toroidal magnetic core and induction winding convert alternating current to an induced voltage, driving the PZT for axial displacement and modulating the EFPI cavity length.
• A DC-component-feedback control method was implemented to stabilize the operating point during intensity demodulation by tracking the optimal interference spectrum wavelength.

Main Results:

• The fabricated EFPI-PZT FOCT demonstrated a stable reflected interference spectrum and a flat frequency response from 0 to 7 kHz.
• The sensor successfully detected low currents, producing a distinguishable signal at 0.13 mA.
• Good linearity was observed between the output peak-to-peak value and the measured current within the linear operating region, though nonlinear distortion appeared near 75 mA.

Conclusions:

• The proposed EFPI-PZT fiber-optic current transformer offers a simpler structure, effective low-current response, and adjustable parameters.
• This design provides a valuable reference for the miniaturization and advancement of new fiber-optic current sensors.