提出了一种新型的基于菱形空气孔的单一偏振单模太赫兹光子晶体光纤，通过改变光纤中引入缺陷的个数、尺寸以及所处位置，研究其对光纤单一偏振单模特性的影响。全文仿真建模采用全矢量有限元法，结果表明：当光纤中引入两缺陷时，随着缺陷尺寸的增加，单一偏振单模运行区域向高频方向移动，区域宽度稍有增加；当引入四缺陷时，靠近芯区的缺陷对单一偏振单模特性影响占主导；基于此，在芯区四周各引入尺寸相同的缺陷，对比四缺陷和两缺陷时的情况发现，四缺陷时单一偏振单模运行区域（1.07~1.36 THz）向高频方向移动，且区域宽度（为0.29 THz）增加明显，是两缺陷时的1.32倍。此类光纤可应用于某些对偏振态有非常严格要求的系统中，故具有实际意义。

A novel single-polarization single-mode (SPSM) rhombic-hole terahertz (THz) photonic crystal fiber (PCF) is proposed. The influence on the characteristics of SPSM is studied by changing the number, size and location of the defects in fiber. A full-vector finite element method is used for modeling, and the simulation results are as follows. In the case of two defects in PCF, with the increase of defect size, SPSM operation range moves towards high-frequency, and its width is increased slightly. In the case of four defects in PCF, the characteristics of SPSM is affected by the defects near the core region easily. Based on this conclusion, four same defects are introduced around the core region in fiber. Compared with the case of two defects, SPSM operation range (1.07 THz to 1.36 THz) moves towards high-frequency and its width (0.29 THz) increases significantly for four defects case, which is 1.32 times than the case of two defects. So the fibers have wide applications in some systems that have strict requirements about the polarization states, and have practical significance.