将光学相干层析成像系统采样臂的光纤与聚焦系统和被测样品作为一个整体来模拟光学相干层析成像信号的形成机理.通过追迹采样光束中每一光子在聚焦系统和被测样品中的随机传输轨迹,来决定该光子对光学相干层析成像信号是否有贡献及贡献大小.对样品IntralipidTM的模拟结果与实验结果表明：1）高散射系数和弱前向散射是引起光学相干层析成像信号随测量深度增加迅速减弱的主要原因;2）对于确定的聚焦系统,光纤的数值孔径有一最佳取值范围.数值孔径太小,则光学相干层析成像信号很弱；数值孔径超出这一范围继续增大,光学相干层析成像信号变化很小.3）当光纤的光轴偏离聚焦系统的光轴h距离时,光学相干层析成像信号随h的增加而减弱.

The optical fiber & focusing system in the sampling arm of OCT system and the measured sample were taken as a whole to simulate the formation mechanism of OCT signal.Whether a photon within sampling beam would contribute to OCT signal and how much contribution it would do were determined by tracing its stochastic propagating trajectory through the focusing system and within the sample.OCT signal was composed of the contributions of all photons in sampling beam.The simulated results and the experimental results on IntralipidTMshow: 1) High scattering coefficient and weakly forward scattering are the prime causes of OCT signal attenuation as measurement depth increase.2) For a given focusing system,there exits a best numerical range for the numerical aperture (NA) of the fiber.OCT signal is very weak when NA is small,and OCT signal profile only changes a bit when NA exceeds the best numerical range and increases continuously.3) When the optical axis of the fiber is offset a distance h from the axis of focusing system,OCT signal decreases with the increase of h.