Glass yarn is a tensile resistance component material between optical cable sheath and cable core and is used in communication optical fiber cable. A layer of soft PU coating attached to the glass fiber surface to increase horizontal and vertical force strength of glass fiber during mechanical bending. The quality-improved glass fiber yarn used in cables is not easy to break, can ensure the tensile strength performance of cable materials, don't prick the hand and no harm to human body in the continuous construction of the optical fiber cable. There are two types: ordinary glass yarn and water-blocking glass yarn.