Optical transmission line monitoring device and optical transmission line monitoring method

An optical transmission line monitoring system that monitors an optical transmission line in an optical transmission system that bidirectionally transmits a frame in a specified frame cycle between a first terminal node and a second terminal node via the optical transmission line, the optical transmission line monitoring system comprising:

• an optical transmission line monitoring device provided at the first terminal node;
• and
• a correspondent node device provided at the second terminal node, wherein
• the optical transmission line monitoring device includes:
• a polarization state monitor that monitors state of polarization of the optical transmission line;
• a first storage unit that stores first polarization state data representing a state of polarization detected by the polarization state monitor;
• a second storage unit that stores second polarization state data representing a state of polarization of the optical transmission line, the second polarization state data being detected by the correspondent node device;
• a processor configured to
• detect a first time representing a time at which a polarization fluctuation component caused by polarization fluctuation generated in the optical transmission line arrives at the optical transmission line monitoring device by comparing a polarization fluctuation value representing a fluctuation speed of polarization detected by the polarization state monitor with a specified threshold level,
• generate reference data by extracting the first polarization state data near the first time from the first storage unit,
• detect a second time representing a time at which a polarization fluctuation component caused by the polarization fluctuation arrives at the correspondent node device by searching for a section having a polarization state similar to the polarization state represented by the reference data in the second polarization state data, and
• determine a polarization fluctuation position representing a position where the polarization fluctuation occurs based on the first time and the second time, and
• the correspondent node device includes:
• a second polarization state monitor that monitors a state of polarization of the optical transmission line;
• a frame generation unit that generates a transmission frame including a polarization fluctuation value detected by the second polarization state monitor in the specified frame cycle;
• and
• a transmission unit that transmits the transmission frame to the optical transmission line monitoring device in the specified frame cycle.

An optical transmission line monitoring method for monitoring an optical transmission line in an optical transmission system that bidirectionally transmits a frame between one set of terminal nodes via the optical transmission line, the method comprising:

• monitoring a state of polarization of the optical transmission line in a first terminal node of the one set of terminal nodes;
• storing first polarization state data representing a state of polarization detected at the first terminal node;
• storing second polarization state data representing a state of polarization of the optical transmission line, the second polarization state data being detected at a second terminal node of the one set of terminal nodes;
• detecting a first time representing a time at which a polarization fluctuation component caused by a polarization fluctuation generated in the optical transmission line arrives at the first terminal node by comparing a polarization fluctuation value representing a fluctuation speed of the polarization detected in the first terminal node with a specified threshold level;
• generating reference data by extracting the first polarization state data near the first time;
• detecting a second time representing a time at which a polarization fluctuation component caused by the polarization fluctuation arrives at the second terminal node by searching for a section having a polarization state similar to the polarization state represented by the reference data in the second polarization state data;
• and
• determining a polarization fluctuation position representing a position where the polarization fluctuation occurs based on the first time and the second time.