Orthogonality breaking through few-mode optical fiber.

Area of Science:

• Optics and Photonics
• Biomedical Engineering
• Materials Science

Background:

• Polarization sensing and imaging via optical fibers present challenges for in vivo and in situ biomedical diagnosis.
• The depolarization/dichroism sensing by polarization orthogonality breaking (DSOB) technique enables remote depolarization/diattenuation measurements in single-mode fibers.

Purpose of the Study:

• To investigate the applicability of the DSOB technique in slightly multimode waveguides.
• To determine the conditions necessary for preserving polarization orthogonality in few-mode fibers for DSOB measurements.
• To analyze the influence of experimental parameters on DSOB technique performance in multimode waveguides.

Main Methods:

• Theoretical modeling and numerical simulations to understand polarization behavior in few-mode fibers.
• Experimental validation using transmission and reflection configurations in few-mode fibers.
• Analysis of detection geometry, sample tilt, and fiber length effects on orthogonality preservation.

Main Results:

• Identified conditions for preserving polarization orthogonality after propagation in few-mode fibers, particularly concerning spatial mode detection geometry.
• Experimental results in few-mode fibers confirmed theoretical predictions for both transmission and reflection setups.
• Quantified the impact of experimental parameters on orthogonality preservation and DSOB measurement dynamics.

Conclusions:

• The DSOB technique is applicable to slightly multimode waveguides, extending its utility beyond single-mode fibers.
• Preservation of polarization orthogonality in few-mode fibers is achievable under specific conditions related to mode detection.
• This research provides a foundation for developing advanced polarimetric endoscopic tools for biomedical applications.