Reducing Multipath Artifacts in Double-Clad Fiber for Multimodal Endoscopic Optical Coherence Tomography

Double-clad fiber (DCF) is used in multimodal endoscopic optical coherence tomography (OCT) systems to facilitate the simultaneous collection of OCT and secondary modality signals through a single-mode core and a multimode cladding, respectively. However, DCF can induce ghost-like multipath artifacts that degrade the quality of OCT images. This study presents a multipath artifact-reduction (MAR) collimator with index-matched cladding to expand the cladding area. This design can be integrated into the rotary joint (RJ) of a multimodal endoscopic OCT system to mitigate multipath artifacts by reducing the cladding-to-core coupling between the DCF and the single-mode fiber of the OCT system. Experimental results demonstrated that the MAR collimator achieved an improvement of up to 8.9 dB in terms of the signal-to-noise ratio when imaging a rabbit aorta using a DCF-based catheter. This innovative collimator is expected to enhance the quality of OCT images in various clinical settings, thus enhancing diagnostic accuracy in multimodal endoscopic OCT systems.