Signal and noise analysis of optical coherence tomography in highly scattering material at 1550nm

The signal and noise properties of standard time domain optical coherence tomography system are analyzed in near-infrared region based on extended Huygens-Fresnel principle. The signal-to-noise ratio and maximum probing depth are estimated for scattering media with discontinuity plane inside. In numerical simulation, the relationship between coherent signal and scattering coefficients, and depth dependence SNR are calculated. The difference between specular and diffuse reflection is given out and analyzed. Numerical result is verified by well established experiment with different concentration mixture solution of IntralipidTM, from 1% to 15%. The OCT system consists of fiber Michelson interferometer and 1550 nm ASE optical source with coherent length of 14μm. Both numerical and experimental results show that multiple scattering events are the main reason for decreasing of signal-to-noise ratio. According to the research, wavelength at 1550 nm is also suitable for imaging of biomedical tissue because of lower scattering coefficients. More than 2 mm penetration depth is obtained in experiment for 10% IntralipidTM which has scattering coefficient similar to skin tissue.