Passive cable laying system for subsea cabled observatory

For the developing research and exploring of deep-sea mineral and biological resources, subsea observatory is quite an effective method for long-time automatic data or image collection of subsea environment and creatures. But building an observatory network underwater is complicated and the power/optical signal transmission between subsea nodes requires extension cables. In this paper, a new kind of passive cable laying system which is attached to 4500m Deep-Sea ROV (Remotely Operated Vehicle) is proposed for optical fiber laying operations for subsea cabled observatory. With full-mechanic cable tension management device, the tension of optical fiber could remain constant during laying operation, and the system requires no close-loop control for cable releasing speed. And because of long-distance operation, flotation adjustment is also an important issue for consideration. A buoyancy variation control system solves the problem by non-continuously adjustment for the weight of cable released from the bobbin.