It is an ideal test instrument for the fiber testing and troubleshooting. It can test the length of optical fiber and optical fiber cable attenuation coefficient. It can exactly display the loss distribution curve of the optical fiber and cable as well as the loss between two points and the joint loss. It also can test the distance between two points and the position of joint, fault point as well as breaking point. This tester has VFL (Vision Fault Locating) system. So it becomes convenient to test the fault location of jumper wire.