We report a design and implementation of an Optical Coherence Tomography (OCT) system based on new topology-a probe with partial reflection from a fiber tip, connected with an all-fiber autocorrelator with Faraday mirrors. The system is made of communication fiber SMF-28 and doesn"t need any electronic means (like polarization diversity receiver) to compensate for static and dynamic polarization distortions, associated with birefringence of a flexible fiberoptic probe. Because of the system topology, it no longer requires a full optical length matching arm (reference arm) and is therefore insensitive to the probe length and wave dispersion properties.
The system is implementing time-domain scanning with Doppler detection, with two piezofiber delay elements, one for AC in-depth scanning, and another for DC adjustment of coherence gate scanning range. It uses a 6 mW, 55 nm bandwidth superluminescent diode with 1300 nm central wavelength, and has 15 μm in-depth (free space) and 25 μm lateral resolution, 0.7 frames per second acquisition rate. It has a catheter-based, en face, 8 Fr diameter universal probe, suitable for endoscopic imaging. Simplicity and cost effectiveness of the new topology result in the creation of a commercially available, FDA cleared system for medical OCT imaging.
Theoretical and experimental optimization of the system, including optimization of probe fiber tip "reference" reflection coefficient, has been performed. Special waveform is applied to the AC piezofiber delay line, resulting in good stability of the scanning velocity and instantaneous Doppler frequency over a 70% duty cycle, which enables use of narrow bandpass signal filtering such that signal to noise performance is optimized.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.