光采样耦合技术是全光多输入多输出(MIMO)信号处理中的关键技术。模式相关损耗(MDL)和插入损耗(IL)是影响器件性能的关键因素，矩阵条件数可以用于衡量光采样耦合器的性能。对支持3个线偏振模式(LP01, LP11a, LP11b)全光MIMO信号处理的光采样耦合器进行了理论分析。在3个采样点的情况下，对采样光斑的大小和位置进行优化，将矩阵条件数作为优化条件，并将MDL和IL分别降低至0.03 dB和1.90 dB。研究发现，通过增加采样点的数目可以降低器件的IL，优化后得到的MDL和IL分别为0.04 dB和1.56 dB。尽管增加采样点的数目可以降低IL，在少模光纤及采样点的几何限制下，仍存在最优采样点数目。

Optical sampling coupling technique is one of key techniques in all-optical multiple-input multiple-output (MIMO) signal processing. Both the mode dependent loss (MDL) and the insertion loss (IL) are key parameters which effect the device performance. The condition number of matrix can characterize the performance of optical sampling coupler. The optical sampling coupler which supports all-optical MIMO signal with three linear polarization modes (LP01, LP11a, LP11b) is numerically investigated. Under the condition of three sampling points, the condition number of matrix is used as the optimization condition to optimize the size and the position of sampling spots. MDL can be reduced to 0.03 dB and IL can be reduced to 1.90 dB. In order to further reduce the IL, the number of sampling points is increased. MDL is 0.04 dB and IL is 1.56 dB after the optimization for the size and the position of sampling spots. Although IL can be reduced when we increase the number of sampling points, an optimal number of sampling points exists under the geometric constraints of few mode fibers and sampling points.