New Optical Fiber Coherence Tomography— Compact and Stabile System for Medical Application

A new idea of the optical fiber coherence tomography system designed for medical application is presented in this paper. Application as a source the femtosecond 400 mW Ti:${\rm Al}_{2} {\rm O} _{3}$ pulse laser operates at wavelength 798 nm with spectral pulse bandwidth about 145 nm provides the longitudinal resolution about 2 $\mu$m. The system can be used for scanning the interior of a human body owing to application of a special optical head based on single-mode fiberscope. The structure comprises a set of two fiber-optic interferometers. The first is a Michelson type which enables the doubled pulses generation with spatial separation directly correlated with a deep scanning in the investigated sample. The second one is a partially delayed Fizeau interferometer formed on the end of optical fiber providing a high temperature and polarization system stability. The discussed setup consists also of a new signal processing structure based on synchronous detection scheme and application of the lock-in amplifier allowing investigation of the reflection coefficient of investigated sample via a suitable numerical processing of the first two harmonic amplitudes of the detected signals. The experimental results of OCT reconstruction of a tree leaf in area 150$\,\times\,$ 1750 $\mu$m giving the possibility of recognizing various kind of tissues are also presented.