Depolarization characteristics of spatial modes in imaging probe using short multimode fiber

Area of Science:

• Biomedical optics
• Medical imaging technologies

Background:

• Optical coherence tomography (OCT) provides high-resolution 3D imaging but is limited to depths within 3mm.
• Minimally invasive imaging techniques are crucial for deeper tissue visualization.

Purpose of the Study:

• To evaluate the effectiveness of short multimode fibers (SMMF) for minimally invasive imaging at depths up to 6-8mm.
• To investigate the image depolarization characteristics within SMMF.

Main Methods:

• Utilized a short multimode fiber (125μm diameter, 6-8mm length) with graded index optical fibers.
• Measured reflected images at the SMMF facet using an LED light source and varying polarizer angles.
• Investigated image depolarization and polarization characteristics.

Main Results:

• SMMF allows for imaging depths of 6-8mm, exceeding standard OCT capabilities.
• Image depolarization occurs within the SMMF core due to scattering and multirefraction.
• The depolarization ratio was estimated at 0.7, with measured degrees of polarization ranging from 0.15 (center) to 0.90 (periphery).

Conclusions:

• Short multimode fibers are a promising tool for extending the depth range of minimally invasive medical imaging.
• Understanding and characterizing depolarization is key to optimizing SMMF for deeper OCT applications.