On-line monitoring system of 110 kV submarine cable based on BOTDR

• An effective on-line monitoring system of 110 kV submarine cable is realized.
• The system is based on the BOTDR, which can get temperature/strain information.
• The temperature/strain coefficient of G.652 optical fiber is calibrated.
• The cable laying topography has a very close relationship with the strain.
• Influence of sea wave scouring and sediment migration is slight at a flat area.

The submarine cable is large-scale and high cost, and at the same time, it locates at the bottom of the ocean, which leads to difficulties in its daily inspection and fault detection. At present, there is no effective real-time on-line monitoring system for it. To solve the problem, an on-line monitoring method based on the Brillouin optical time domain reflectometer (BOTDR) is proposed. The BOTDR technology can measure the temperature/strain distribution along the submarine cable with high accuracy, and the temperature and strain coefficients of the G.652 optical fiber are calibrated. On the basis of systematic investigations, the real-time on-line monitoring system based on BOTDR has been realized. A 110 kV optical fiber composite submarine cable can be monitored by the established BOTDR system with a spatial resolution of 1 m. The system is put into service in China, and runs well. The large amounts of data are acquired and analyzed, and the results reveal that currently, the three phases’ submarine cables function well. At the same time, the influence of the sea wave scouring and sediment migration is slight at the relatively flat area. However, the cable laying topography has a very close relationship with the measured data, that is, the steeper the topography, the larger the measured Brillouin frequency shift value. The monitoring system proposed in the paper provides a feasible scheme for the on-line monitoring of the submarine cable, which can ensure the safe operation of the submarine cable.