Measuring Bragg gratings in multimode optical fibers.

Area of Science:

• Optics and Photonics
• Fiber Optic Sensing
• Materials Science

Background:

• Fiber Bragg gratings (FBG) are crucial for cost-effective optical sensor systems.
• Parasitic mode effects in multimode optical fibers complicate spectral analysis.
• Understanding mode coupling is essential for optimizing sensor performance.

Purpose of the Study:

• To develop a theoretical framework for analyzing mode coupling in multimode fiber optic systems.
• To explain the influence of parasitic modes on multi-resonance reflection spectra.
• To provide a method for optimizing mode effects in FBG-based sensors.

Main Methods:

• Utilized a mode transfer matrix formalism to model complex mode coupling.
• Investigated parasitic mode effects in optical components.
• Conducted two experiments to validate the theoretical model.

Main Results:

• The mode transfer matrix formalism accurately describes mode coupling effects.
• Experimental results demonstrate the theory's accordance.
• The formalism provides detailed insights into spectral variations caused by parasitic modes.

Conclusions:

• The developed formalism enables a deeper understanding of mode effects in multimode fiber optics.
• This approach facilitates the optimization of multimode fiber optic sensor systems.
• It contributes to the design of more robust and reliable optical sensing devices.