Real-time mode-modulation enhanced stable imaging through flexible multimode fiber

Area of Science:

• Biomedical Optics
• Fiber Optics
• Medical Imaging Technology

Background:

• Multimode fibers (MMFs) offer potential for ultra-thin, high-resolution endoscopes but suffer from dynamic instability and limited transmission.
• Clinical application of MMFs is hindered by their susceptibility to bending-induced distortions and performance degradation.

Purpose of the Study:

• To develop a method for stable, high-fidelity, real-time imaging through flexible, ultra-thin MMFs.
• To overcome dynamic instability and performance limitations of MMFs for minimally invasive endoscopy.

Main Methods:

• A rapid calibration routine (approx. 75 ms) identifies the MMF's bending state using focusing wavefront probes.
• A pre-calculated database provides a corresponding singular vector for mode modulation.
• Synchronous retrieval and projection of the singular vector excite intrinsic fiber modes for enhanced transmission.

Main Results:

• Substantial improvements in image fidelity were achieved in dynamically flexing 40-µm and 105-µm-core MMFs.
• Peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) improved by up to 7.75 dB and 0.069 for digits.
• Edge preservation index increased by 12.10% for biological specimen imaging.

Conclusions:

• The proposed method effectively stabilizes MMFs, overcoming the trade-off between miniaturization and image quality.
• This technique provides a robust, fast solution, removing a critical barrier for MMF-based imaging.
• Enables a practical pathway for deploying high-resolution, hair-thin fiber endoscopes in clinical settings.