Reference Power Optimization for Common-Path Probes in Optical Coherence Tomography.

Common-path optical coherence tomography (CP-OCT) has garnered significant interest for use in biomedical imaging due to its compact configuration, enhanced phase stability, and reduced sensitivity to environmental disturbances. The imaging performance of a common-path probe is significantly influenced by the reference power generated within the probe, which determines the interference modulation, signal-to-noise ratio (SNR), phase stability, and ultimately, the image quality. This study presents a systematic optimization of reference power in a fiber-based common-path OCT probe through numerical simulation and experimental validation. The optical coupling efficiency was evaluated using the Fiber Coupling analysis implemented in Zemax OpticStudio and validated experimentally using a fabricated probe incorporating an index-matching UV-curable adhesive as a partial Fresnel reflector. The influence of fiber-to-reflector separation on the coupled reference power was investigated and correlated with SNR, phase stability, and OCT image quality. The results demonstrate that increasing the reference power improves SNR and phase stability up to an optimum range of 20-60 µw, beyond which a gradual performance reduction is observed. In contrast, phase stability shows minimal additional improvement. The optimized reference power also enhances image contrast and structural visibility. These findings establish practical design guidelines for selecting the fiber-to-reflector spacing to achieve balanced reference power and improved imaging performance in compact common-path OCT probes for biomedical imaging applications.