Optical Fiber Magnetic Field Sensors Based on 3 × 3 Coupler and Iron-Based Amorphous Nanocrystalline Ribbons

Area of Science:

• Optoelectronics
• Sensor Technology
• Materials Science

Background:

• Optical fiber sensors offer advantages like high sensitivity and environmental adaptability.
• Magnetostrictive effects in materials are key for developing sensitive magnetic field sensors.
• Applications in extreme environments like deep wells and oceans require robust sensing solutions.

Purpose of the Study:

• To propose and experimentally test two optical fiber magnetic field sensors.
• To investigate the performance of sensors based on iron-based amorphous nanocrystalline ribbons.
• To evaluate a passive 3x3 coupler demodulation system for sensor readout.

Main Methods:

• Design of an equal-arm Mach-Zehnder fiber interferometer.
• Integration of iron-based amorphous nanocrystalline ribbons as the sensing element.
• Experimental testing of sensors with different sensing lengths (0.25 m and 1 m).
• Utilizing a passive 3x3 coupler for demodulation.

Main Results:

• Achieved magnetic field resolutions of 15.4 nT/√Hz @ 10 Hz for a 0.25 m sensor.
• Achieved magnetic field resolutions of 4.2 nT/√Hz @ 10 Hz for a 1 m sensor.
• Demonstrated a sensitivity multiplication relationship with increased sensing length.

Conclusions:

• The proposed optical fiber magnetic field sensors exhibit high sensitivity and resolution.
• Increasing the sensing length significantly improves magnetic field resolution.
• The technology holds feasibility for achieving pT-level magnetic field resolution for extreme environment applications.