Grating sensor array demodulation by use of a passively mode-locked fiber laser

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Strain Measurement

Background:

• Fiber Bragg gratings (FBGs) are widely used for sensing applications.
• Interrogation of FBG sensor arrays typically requires a broadband light source and a wavelength-demodulation technique.
• Existing methods can face limitations in terms of speed, strain range, or multiplexing capability.

Purpose of the Study:

• To demonstrate a novel demodulation scheme for interrogating fiber Bragg grating sensor arrays.
• To utilize a passively mode-locked fiber laser source for high-bandwidth interrogation.
• To enable fast sensing of large strains using a dispersive fiber-based temporal conversion method.

Main Methods:

• A passively mode-locked fiber laser with a broad source bandwidth (>85 nm) was employed.
• A novel demodulation scheme was developed using highly dispersive fiber.
• The scheme converts wavelength shifts of FBGs into temporal shifts in reflected pulse arrival times.

Main Results:

• The proposed demodulation technique successfully converted wavelength shifts to temporal shifts.
• The broad source bandwidth facilitated the interrogation of multiple gratings within an array.
• The system demonstrated the capability for fast sensing of large strain values.

Conclusions:

• The demonstrated technique offers a promising approach for high-speed, large-strain FBG sensing.
• The use of a dispersive fiber for wavelength-to-time conversion simplifies the demodulation process.
• This method enhances the performance of fiber optic sensor arrays for various applications.