Optical-guided ablation system for use with pulsed fields or other energy sources

Described herein is a system including a catheter, an optical circuit, a pulsed field ablation energy source, and a processing device. The catheter includes a proximal section, a distal section, and a shaft coupled between the proximal section and the distal section. The optical circuit is configured to transport light at least partially from the proximal section to the distal section and back. The pulsed field ablation energy source is coupled to the catheter and configured to transmit pulsed electrical signals to a tissue sample. The processing device is configured to analyze one or more optical signals received from the optical circuit to determine changes in polarization or phase retardation of light reflected or scattered by the tissue sample, and determine changes in a birefringence of the tissue sample based on the changes in polarization or phase retardation.