Ultrafast Time-Stretch Optical Coherence Tomography Using Reservoir Computing for Fourier-Free Signal Processing.

Area of Science:

• Biomedical Optics
• Optical Imaging
• Signal Processing

Background:

• Swept-source optical coherence tomography (SS-OCT) provides high-resolution cross-sectional images for medical diagnostics.
• Nonlinear wavelength sweeping in SS-OCT degrades depth resolution, necessitating complex correction methods.
• Fourier transform-based analysis is susceptible to chirp-induced spectral broadening.

Purpose of the Study:

• To introduce the first ultrafast time-stretch optical coherence tomography (TS-OCT) system.
• To utilize reservoir computing (RC) for direct temporal signal analysis, bypassing Fourier transform limitations.
• To address nonlinear wavelength sweeping issues in SS-OCT without complex re-sampling or chirp compensation.

Main Methods:

• Developed an ultrafast TS-OCT system incorporating reservoir computing (RC).
• Focused on direct temporal signal analysis of interference signals, independent of frequency chirp.
• Employed an RC-based model for classifying interference signals based on temporal patterns.

Main Results:

• Achieved precise depth resolution unaffected by system chirp.
• Demonstrated 100% classification accuracy with a root mean square error (RMSE) of 0.2416 at a 50 MHz A-scan rate.
• Successfully bypassed challenges associated with Fourier analysis and chirp-induced spectral broadening.

Conclusions:

• The proposed TS-OCT system with RC offers an efficient solution for nonlinear wavelength sweeping.
• This classification-based temporal analysis provides a robust alternative to Fourier-based methods in SS-OCT.
• The system maintains high-resolution depth measurement, proving effective in chirp-prone imaging scenarios.