Defective Section Detection of Optical Transmission Line Utilizing Degree of Polarization of Backscattered Light

Abstract

Novel technique for measuring a position of a fiber with a high birefringence is proposed using polarization optical time domain reflectometer (P-OTDR) for the purpose of detecting the defective section in the optical transmission line. Our technique is based on the fact that the degree of polarization (DOP) of backscattered light from the position with high birefringence becomes large when the polarization state of the input pulse coincides with either fiber axes and it becomes small in other cases. Taking the above relation into account, the fiber position with the high birefringence can be detected in our technique, as the position with lower DOP which is obtained from the average backscattered light measured for the various polarization states of input light. Moreover, it is confirmed experimentally that the position of fiber coil with a diameter of 6 cm, which is inserted into the transmission line, can be detected by our present technique. It is also confirmed that our technique can be successfully applied to the optical cables installed outside.