Catheter-Based Polarization Sensitive Optical Coherence Tomography Using Similar Mueller Matrix Method.

OBJECTIVE: Research of catheter-based polarization sensitive optical coherence tomography (PS-OCT) is a challenging field. In this paper, we present a new polarization determination method, similar Mueller matrix (SMM) method, for a catheter-based PS-OCT system using a standard clinical catheter probe with an outer diameter of 0.9 mm. METHODS: The SMM method can remove the diattenuation and depolarization compositions by polar decomposition. By constructing the similarity between the measured Mueller matrices and sample matrices, the phase retardance of the sample can be determined from the trace of the measured matrices. RESULTS: In the experiments, we find that images processed by the SMM method without any averaging or phase correction have a better polarization contrast of multiple biological tissues than those by the Jones matrix based method. We also preliminarily achieve phase retardance imaging of the ex vivo porcine cardiac blood vessel. CONCLUSION: Compared with the Jones matrix based method, the presented SMM method can provide a more robust birefringence imaging of biological tissues under low signal-to-noise ratio, depolarization, diattenuation, and phase instability. SIGNIFICANCE: The SMM method has a potential to become a widely accepted polarization determination method for catheter-based PS-OCT.

Note: Improving distributed strain sensing sensitivity in OFDR by reduced-cladding single mode fiber.

We present a method to improve distributed strain sensing sensitivity by a reduced-cladding single mode fiber (RC SMF) using a Rayleigh backscattering spectra shift in optical frequency domain reflectometry. Comparing with a standard SMF with 250 µm diameter, a commercial low attenuation RC SMF with 165 µm diameter is shown to enhance the strain sensing sensitivity by about four-fold. Using this property, the system using the RC SMF can achieve smaller minimal measurable strain (MMS) in the same sensing spatial resolution (SSR) or smaller SSR in the same MMS than using the standard SMF. In our experiment, the system using RC SMF can achieve the MMS of 15 µstrain with a SSR of 4.5 cm or the MMS of 3 µstrain with a SSR of 18 cm.