Digital calibration method to enable depth-resolved all-fiber polarization sensitive optical coherence tomography with an arbitrary input polarization state

We present a fully integrated depth-resolved all fiber-based polarization sensitive optical coherence tomography (PSOCT). In contrast to conventional fiber-based PSOCT systems, which require additional modules to generate two or more input polarization states, or a pre-adjustment procedure to generate a circularly polarized light, the proposed all-fiber PSOCT system can provide depth-resolved birefringent imaging using an arbitrary single input polarization state. Utilizing the discrete differential geometry (DDG)-based polarization state tracing (PST) method, combined with several geometric rotations and transformations in the Stokes space, two problems induced by the optical fibers can be mitigated: 1) The change in the polarization state introduced by the optical fibers can be effectively compensated using a calibration target at the distal end of the probe, and the computations of the local axis orientation and local phase retardation can be achieved with a single arbitrary input polarization state, eliminating the need for a pre-defined input polarization state, allowing a flexible system design and user-friendly experimental procedure; 2) The polarization mode dispersion (PMD) induced by the optical fibers can be compensated digitally without the requirement of additional input polarization states, providing an accurate PSOCT imaging result. To demonstrate the performance of the proposed method, the depth resolved PSOCT results of a plastic phantom and in vivo skin imaging are obtained using the proposed all-fiber PSOCT system.