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Navigating the diverse factors in deploying a subsea fibre optic maintenance vessel

Wednesday 1st May 2024



In this most recent article, Global Marine’s Head of Maintenance, Steve Holden, explores the variables that distinguish each repair operation. He highlights the importance of meticulous planning, coordination, and strict adherence to safety protocols essential for successfully repairing faults in subsea fibre optic cables

The decision to deploy a cable ship depends on various factors such as the severity of the fault e.g. full break vs shunt, and the impact of the fault on applicable stakeholders services; also the availability of vessel or equipment resources, logistical and regulatory considerations etc.

In some cases, temporary solutions or alternative communication methods and paths may be implemented while arrangements are made to mobilize a cable ship for repair.

Additionally, weather conditions and other operational constraints such as client permissions, permitting and availability of repair materials may also affect the timing of a deployment.

Ultimately, the decision to deploy a cable ship is made based on a careful assessment of the situation and the best course of action to restore the functionality of the subsea fibre optic cable.

Deploying a cable ship to repair a subsea fibre optic cable fault typically involves several steps:

Identification of Fault: The first step is to identify the location and nature of the fault in the subsea fibre optic cable. This may involve using DC or Optical sensing equipment and tests, or once on site trailed electrodes or remotely operated vehicles (ROVs), to survey the seabed and locate the fault position.

Client and Stakeholder Agreement: The logistical requirements and speed of deployment can also be dependent on the nature of the terms of a specific maintenance agreement, or the consortium/stakeholders involved. In cases where multiple customers are impacted by a fault, obtaining all the required permissions from each stakeholder for deployment becomes imperative.

Qualifications, Equipment, Toolkit and Spares:  It is essential to ensure that the faulty cable is UJ/UQJ qualified (or applicable equivalent) and the vessel is equipped with all the necessary equipment, parts, spares, and specialized toolkits onboard to address the specific requirements of each repair operation. 

Permitting: Where relevant, engagement with local authorities and stakeholders to identify any required permitting aspects of a maintenance project should be conducted prior to and throughout the lifecycle of the project. All consents, licences, permits or other permissions are subject to an array of legislative requirements, particular to each country, which can be complicated by international, national and local legislation.

Mobilization of Cable Ship: Once the fault is identified and the necessary agreements are in place to deploy, a cable ship (equipped with all the necessary repair equipment and personnel) is mobilized and sets off to the location of the fault.

Preparation for Repair: Upon arrival at the fault location, the cable ship crew prepares for the repair operation. This may involve deploying ROVs to inspect the cable and seabed to assess the extent of the damage, as well as setting up equipment for cable splicing or other repair techniques.

Cable Repair: Depending on the depth and nature of the fault, the repair process may involve various recovery, testing, and jointing techniques i.e. ROV or grapnel recovery. This may involve the creation of mini blocks or line sections connecting spare and recovered cable sections to reinstate the cable system to full operational capability.   Highly skilled technicians and engineers typically carry out these repair tasks.

Testing and Verification: Once the repair is completed, the repaired section of the cable is tested and if applicable powered to ensure it is functioning correctly and transmitting data effectively. This may involve conducting optical time-domain reflectometer (OTDR) tests or other diagnostic procedures e.g. COTDR for repeatered systems, to verify the integrity of the repaired cable and plant.

Recovery and Redeployment: After successful testing, the repaired cable is deployed back as close as possible to its original position on the seabed and if applicable buried. The cable ship then returns to port, and the repaired cable has traffic re-applied and resumes normal operations.

Because of the complexities and variables mentioned above, every repair operation is unique and differs from the next. Throughout the entire process, careful planning, coordination, and adherence to safety protocols are essential to ensure a successful repair of the subsea fibre optic cable fault.