Before the submerged plant is loaded onto the main laying vessels it undergoes a number of optical and electrical tests to ensure that the overall system performance will be achieved. Repeaters have started to arrive in the cable factory in Hitachi in preparation for them being coupled into the already manufactured cable.
Each repeater is tested prior to shipment for overall optical performance and fitted with an impacto-graph. This device records shock and vibration that the repeater experiences during the shipment from the USA to Japan. Upon arrival, a goods inwards optical test is conducted prior to the unit being coupled into the cable and the impacto-graph is checked for any out of tolerance shocks.
If any non conformance is detected then this is assessed by engineering staff and rework may be required or the unit may be passed as fit for use.
The cable is tested for optical loss, chromatic dispersion, PMD and electrically for: insulation resistance, capacitance and linear resistance of the power conductor . The LW cable for example, is covered with an approximately 4mm thick layer of medium density polyethylene. This forms an insulating barrier between the central power conductor and the seawater and must be completely free of voids/inclusions or any other form of damage that would reduce the design thickness of polyethylene remaining in situ. This is critical to ensure the cable can withstand the HV DC powering voltages during the design life of the system.
We will discuss more on the testing procedures as we progress during the next few weeks.