The potential applications of old or obsolete jointing techniques.
Submarine Cable Jointing is a core part of the whole undersea communications network. It has often been called a Black Art, and whole careers have been built around some apparently miniscule aspect of jointing. In recent years, a large amount of time and effort has been spent understanding the processes involved and introducing tight process control to reduce the dependence of jointing on the supernatural. Marine cable jointing is not a variant of the civil engineering activity which involves the roads being dug up in busy cities at the busiest times of the year. Both types of joint involve splicing fibre, but there the similarity ends. The demands of a submarine cable joint are more extreme. First there is the sea bed pressure to contend with – joint cavities must not implode when installed in the deepest oceans. The tension and torsion that a joint undergoes during deployment and recovery require a jointed length of cable to have similar mechanical properties to the parent cable. Long haul submarine cables require DC power feed to the repeaters or regenerators. The insulating material or dielectric must form an effective waterproof seal of the joint (at sea bed pressures) as well as bonding to the cable to form an effective
IN CABLE JOINTING By Jim Bishop electrical insulation capable of withstanding voltages of up to 12 kV for the duration of the system life. Marine cable jointing is not exclusively a cable ship activity. Manufacture of a submarine cable involves a significant number of consecutive processes. An ‘event’ in any one manufacturing process can cause unplanned system joints. Planned joints are also employed during system assembly or as a transition from one armour type to another. In the ideal world, jointing at sea and in a factory should employ the same equipment and processes, although a number of factory specific techniques have been introduced to increase the throughput of joints, in an environment where ease of equipment manoeuvrability is not a prime consideration. Having established that jointing is an essential part of both system assembly and marine operations, whether installation or maintenance, the technologies
involved are often traceable back to analogue cable system joints. Moulding and X-ray techniques have changed little in principle from the analogue systems from which they are descended. Some of the tolerances and measurements quoted in specifications are often a direct conversion into millimetres of a round number in inches or thousandths of an inch. A jointer, who spliced the earliest optical submarine cables, would not have difficulty recognising the mechanical construction of a modern joint (splicing equipment excepted - which has improved unrecognisably). The jointing technologies in use at sea today are few, and closely protected by the owners and users of the technologies. On cable ships and at dockside depots around the world, large sums of money have been invested in supporting these technologies in the form of large stocks of equipment and jointing kits. Developing a new joint design as an alternative to established products would be an expensive project, involving the same extensive range of mechanical, environmental optical and electrical tests to meet the requirements mentioned earlier (and more). If a new joint is developed in parallel with a new cable design and qualified simultaneously, the cost can be shared 33