Deals with the configuration of autonomous underwater vehicle (AUV) for inspection of underwater cables considering low hydrodynamic drag, sensor alignment, collision avoidance manoeuvre, turning manoeuvre and rolling motion. The AUV consists of a fuselage of body of revolution with low hydrodynamic drag, fore and aft horizontal wings, upper and lower vertical tails and a pair of horizontal thrusters at both sides of the aft horizontal wings. The shape of the forward horizontal wing and that of the rear horizontal wing can be determined by use of a nonlinear optimization method under the constraints of magnetic sensor alignment for cable tracking, dynamic stability in the vertical plane and the performance of the collision avoidance manoeuvre. The performance of the turning manoeuvre and rolling motion are attributed to thrust force difference between a pair of thrusters at both sides of the rear horizontal wing, because the shapes of the upper and lower vertical tails can be designed from the viewpoint of the dynamic stability in horizontal plane.

A new type of tether cable with high quality signal transmission characteristics was developed by adopting optical fibers. As the tether cable is subject to frequent and various mechanical and thermal loads under the severe operating conditions in the offshore environment, the greatest care should be paid to the design of its structure to preserve the optical fibers from those loads. This paper describes the design requirements and the characteristics of the optical fiber/power line composite tether cable under the loads such as tensile loading, bending, twisting, water pressure, and cable heating. The termination of the tether cable is also discussed. This tether cable has been in practical use for remotely operated submersible MARCAS whose mission is inspection and location of the submarine telecommunication cables.