Fiber motion-insensitive fiber-based polarization-sensitive optical coherence tomography for optic axis determination

Abstract

Polarization-sensitive optical coherence tomography (PS-OCT) is widely used to image fibrous biological tissues, providing additional image contrast compared to intensity-based OCT, including birefringence and optic axis orientation information. Here a theoretical and experimental analysis of the effect of the system fiber on determination of sample optic axis orientation using a previously reported algorithm based on the angle between Stokes vectors on the Poincaré sphere in fiber-based PS-OCT experimentally confirms that the algorithm only works correctly when the parameters of the system fiber are kept constant during the imaging acquisition of each frame. To extend the use of the algorithm to situations in which the parameters of the system fiber are varied among A-scans or image frames, which is true when the OCT probe scanning does move the sample arm fiber, we propose the use of polarization maintaining fiber (PMF) with a special polarization axis orientation as the sample arm fiber for extracting sample optic axis orientation using fiber-based PS-OCT systems. The use of the PMF makes the system insensitive to variations of the sample fiber birefringence for determining optic axis orientation by automatically removing the offset ambiguity from each A-scan. We demonstrated by using a computer evaluation model that the proposed method is capable of extracting the relative optic axis orientation correctly when the PMF birefringence is varied among A-scans due to external disturbances to the system fiber, provided that the polarization axis orientation (slow or fast) of the PMF is kept constant during the measurement.