Microsphere Coupled Off-Core Fiber Sensor for Ultrasound Sensing

Area of Science:

• Optoelectronics
• Fiber Optic Sensing
• Acoustic Metrology

Background:

• Fabry-Perot interferometers (FPI) are widely used in optical sensing.
• Enhancing the finesse of FPI sensors is crucial for improving sensitivity and resolution.
• Developing compact, cost-effective ultrasound sensing devices is an ongoing challenge.

Purpose of the Study:

• To propose and demonstrate a compact fiber ultrasound-sensing device.
• To achieve broadband ultrasound sensing in the MHz range.
• To develop a repeatable, cost-effective, and easily fabricated FPI sensor.

Main Methods:

• Coupling a Barium Titanate (BaTiO3) glass microsphere to an open-cavity FPI fiber sensor.
• Fabricating the open cavity via lateral offset splicing of single-mode fiber (SMF-28).
• Tuning the reflection spectrum by adjusting the microsphere's position within the cavity.

Main Results:

• Achieved broadband ultrasound sensing from 0.1-45.6 MHz.
• Demonstrated a 40 dB enhancement of finesse due to multiple passes enabled by the high refractive index microsphere.
• Ultrasound sensing was driven via a piezoelectric transducer (PZT) centered at 3.7 MHz.

Conclusions:

• The proposed device offers a compact and effective solution for ultrasound sensing.
• The design is cost-effective, repeatable, and easy to fabricate.
• The enhanced finesse and broadband capability make it suitable for MHz-range frequency detection.