Multiplexing fiber-optic ultrasound sensors using laser intensity modulation

Area of Science:

• Photonics
• Optical Sensing
• Acoustic Metrology

Background:

• Fiber Bragg grating (FBG) sensors are widely used for ultrasound detection.
• Multiplexing multiple FBG sensors in a single optical fiber presents challenges for signal isolation and crosstalk.
• Existing multiplexing techniques can be complex and may require multiple photodetectors.

Purpose of the Study:

• To propose and demonstrate a novel laser intensity modulation technique for multiplexing and demultiplexing FBG-based ultrasound sensors.
• To enable crosstalk-free detection of ultrasound signals from multiple sensors using a common photodetector.
• To provide theoretical analysis and experimental validation of the proposed method.

Main Methods:

• Utilizing laser intensity modulation at a frequency significantly higher than the ultrasound frequencies.
• Employing the high-frequency modulated optical signal as a carrier for ultrasound information.
• Demultiplexing signals in the frequency domain by isolating carrier and sideband frequencies corresponding to each sensor.
• Using electronic bandpass filters to separate individual sensor signals and eliminate crosstalk.

Main Results:

• Demonstrated successful multiplexing and demultiplexing of FBG-based ultrasound sensors using laser intensity modulation.
• Achieved crosstalk-free ultrasound detection by isolating modulated signals in the frequency domain.
• Verified the theoretical model through experimental measurements, confirming the efficacy of the technique.

Conclusions:

• Laser intensity modulation offers an effective and simple approach for multiplexing FBG ultrasound sensors.
• The proposed method allows for the use of a single photodetector for multiple channels, simplifying the sensor system.
• This technique enhances the efficiency and practicality of distributed fiber optic sensing for ultrasound applications.