Umbilical for underwater diving

#This invention is concerned with the illumination of umbilicals, as employed in subsea surface-air diving and subsea saturation diving, for the purpose of improved diver safety and efficiency of working.

#In commercial subsea diving, supply of air to the diver from the surface is the preferred method (as compared to the use of bottled air carried by the diver) since such a supply scheme places less stringent limitations on diver operating time underwater. Surface supplied air requires the diver to be linked to the surface through an umbilical for the supply of the air along with other services.

#In commercial surface air diving umbilical lengths of 75 m with depths down to 50 m combined with an underwater operating radius of up to 25 m typically need to be covered. Alternatively, through the use of saturation diving techniques depths down to 300 m can be reached through the use of a diving bell. In this case an umbilical is required to connect the diver to the bell for the supply of air, with a requirement for the diver being able to operate over a radius of up to 75 m from the bell. In addition umbilicals may be required to connect remote operating vehicles (ROV) or their derivatives to a bell or other installations.

#Various aspects of the invention will now be described by way of example only and with reference to the accompanying drawings, of which:

#FIG. 1 is a schematic representation of a light rope umbilical system;

#FIG. 2 is a view of a fiber-bundle as incorporated within the umbilical;

#FIGS. 1 and 2 show an umbilical in accordance with the invention. This has various conventional umbilical parts 23 that are wound together, such as a gas hose and a power line, as best seen in FIG. 2. In addition, the umbilical of the invention includes a fiber-bundle 2 that has multiple side-emitting optical fibers. The side-emitting optical fibers provide a distributed source of light that allows the umbilical to be lit along its length, thereby providing a guide-path as well as general illumination of the sub sea environment within which the diver or divers are working.

#For the purpose of illuminating the fiber bundle 2 a light emitting diode (LED) 4 is provided powered by a driver 5. The LED 4 is enclosed within a compact watertight enclosure or light-box 6 which is located adjacent to an umbilical interconnect-interface 10. Radiation from the LED passes through an optical coupling arrangement 12 which transforms the spatial characteristics of the primary radiation from the LED to optimize its coupling into the fiber-bundle 2. The radiation then passes through a window 14 which is mounted on a water-tight seal 16 on the side of the watertight compartment 6, before entering the fiber-bundle 2. The prepared ends of the fibers making up the bundle are held in compression by element 18 so as to be in contact with and hence butt-coupled to the outer surface of the window. The optical arrangement described is such that this location of the fiber-end also optimizes the coupling of the radiation into the fiber.

#Whilst any LED may be used, in a preferred example, the LED generates light in the green spectral region. Typically for an electrical input power to the LED of 12 W, the optical output power from the LED in the green spectral region is of the order of 400 mW, and the coupling efficiency for this radiation into the fiber is of the order of 23-28%.