Phase-Shifted Fiber Bragg Grating by Selective Pitch Slicing

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Materials Science

Background:

• Standard Fiber Bragg Gratings (FBGs) are widely used but can be modified for enhanced functionality.
• Phase-shifted FBGs offer unique optical properties for sensing applications.
• Controlling phase shifts in gratings is crucial for advanced optical device design.

Purpose of the Study:

• To introduce and characterize a novel phase-shifted Fiber Bragg Grating (FBG) called the sliced-FBG (SFBG).
• To investigate the SFBG's performance as a vibration sensor.
• To demonstrate the tunability of the phase shift by altering the grating's final pitch.

Main Methods:

• Fabrication of SFBG by cutting a standard FBG within its grating region.
• Characterization of the SFBG's optical output signal, resulting from the overlap of FBG reflection and fiber-cleaved tip reflection.
• Testing the SFBG as a vibration sensor within the frequency range of 150 Hz to 70 kHz.

Main Results:

• Successful fabrication of the SFBG with a shorter last grating pitch.
• Demonstration of the SFBG's capability to sense vibrations from 150 Hz to 70 kHz.
• Confirmation that the phase shift in the SFBG can be controlled by adjusting the length of the last pitch.

Conclusions:

• The sliced-FBG (SFBG) is a viable new fiber optic device with dual functionality as a filter and a sensing element.
• The SFBG demonstrates significant potential as a vibration sensor for monitoring mechanical structures.
• The ability to control phase shifts offers flexibility for various optical sensing and filtering applications.