The connections of the telecommunications tract elements have a significant influence on the quality of the information transmission. In the essay reasons and an analysis of the losses in fiber optic connectors are introduced. The case of fiber optic connectors: PC type and with a surface enlargement are emphasized. Different types of fiber sleeve connectors are discussed. These optical connectors can be divided according to following criteria: structure (ST, FC, Sc, E-2000, F-3000, LC, MT-RJ, MU, etc.) types of applied ferrules (monolithic, with multiple elements) technology of production (standard, Light Crimp - AMP, Hot Melt - 3MCrimp Lok - 3M, Universal Com Lite - Siecor) and tuning. Moreover the quality of DWDM fiber optic connectors, which have high functional density and an impact on the light polarization is touched on. The results of measurements of transmission parameters and of mechanical resistance on vibration, folding of the cable in the fiber, strikes on hard surfaces, multiple connection and disconnecting, pulling out of a cable from the connectors and climate conditions are discussed. The results of the measurements listed above with additional interferometric tests of ferrule head constitute the main factor of the fiber connectors quality analysis. Furthermore, the up to date results of the compatibility analysis of the connectors manufactured by different producers are mentioned and a future development in the field is forecasted.