Stable multi-megahertz circular-ranging optical coherence tomography at 1.3 µm.

Area of Science:

• Biomedical Engineering
• Optical Physics
• Medical Imaging

Background:

• Fourier-domain optical coherence tomography (OCT) systems face depth and speed limitations due to finite electronic bandwidth.
• Existing circular-ranging OCT (CR-OCT) methods offer improved range but suffer from instability and operate at suboptimal wavelengths (1.55 µm).

Purpose of the Study:

• To develop a novel CR-OCT architecture that enhances stability, simplifies design, and shifts the operating wavelength for improved biological tissue penetration.
• To overcome the limitations of previous CR-OCT systems, enabling wider applicability.

Main Methods:

• Replaced temperature-sensitive optical modules and eliminated long fiber spools in favor of a 10-meter chirped fiber Bragg grating (CFBG).
• Implemented an active quadrature demodulation circuit using a lithium niobate phase modulator.
• Shifted the operating wavelength to 1.29 µm using CFBG-based dispersive fibers for enhanced tissue imaging.

Main Results:

• Achieved a stable CR-OCT system with a simplified design.
• Demonstrated operation at 1.29 µm, improving imaging penetration.
• Maintained a broad 100 nm optical bandwidth, a 4 cm imaging range, and a high 7.6 MHz A-line rate.

Conclusions:

• The novel CR-OCT architecture significantly enhances stability and simplifies system design compared to previous methods.
• Operating at 1.29 µm allows for deeper imaging in biological tissues.
• This improved CR-OCT system is poised for broader exploration in medical and non-medical fields.