Passive Network Infrastructure

Passive Network Infrastructure

“Programme, having worked with us to develop our baseline programme in the first place and through their hard work and flexibility once the works were on site we completed the project with weeks to spare …no mean feat in the nuclear sector!” – Nuclear Sector, Project Manager


Our Customer is a world-leading nuclear fuel fabrication plant, supplying more than 50 utilities in 19 countries around the world that has been in operation for more than 40 years.

They make a substantial contribution to the total global supply of nuclear energy, they have a considerable responsibility to nmaintain a level of production which will continue to service the industry.

Nuclear fuel production is a highly technical, scientific industry that uses world-leading technology but, like all manufacturing businesses with such a long, successful history, elements of their infrastructure need to be replaced and updated to keep operations running smoothly.


“The preparation of the documentation and their systematic approach to the job in hand made the network migration run very smoothly” – Projects Testing and Handover Engineer

The problem, outlined by the site Engineering team was that the network infrastructure that supports their manufacturing process was starting to have reliability issues. With failures on the increase, it was clear that the obsolete network now had to be brought up to date.

This paper considers the challenges associated with the passive infrastructure element and its readiness to support a major active network upgrade. The active network challenges are discussed in a second paper “Active network design and live migration case study”.

An initial ‘restricted access’ survey identified some physical issues that would challenge the new network installation, these included:

  • Space and restricted access around the operational plant
  • Cable routing, labelling and certification records
  • Operational status of backup paths


Equipment Location

Major decisions on physical infrastructure and equipment location were necessary before the active network topology could evolve. Whilst increasing scope, IT4A felt strongly that missing this opportunity would be a mistake. A meeting of minds between IT4A’s consultant and the site project team produced a solution that would simplify the entire installation, providing a robust and scalable installation for the future. A disused storage area, no more than 20m from the existing plant cabinets, would become the new network hub. Plant fibre-optic cables would be extended from legacy panels to three new purpose-built, environmentally managed, racks. Once migration was complete and active equipment removed, the legacy racks would become passive fibre patch panels.

Infrastructure Validation

With the structural elements of the design in place, additional surveys were performed first to identify then validate the plant-wide fibre cabling. The identification process required all existing cables to be manually traced through the plant where they were clearly tagged, documented and numbered. Knowing where the ends were presented made the re-certification to a reference standard (EN-50173) far easier.

Re-certification was necessary as, while primary and backup paths were both physically connected, there was no evidence that a backup path worked. With live migration planned there was no space for error – all paths had to be proven and this proof was gathered through a formal fibre certification process.

IT4A’s fibre clean and certification service identified the cores that simply needed a clean to achieve certification and the ones that required repair and re-testing. This process identified multiple backup paths where the fibre’s poor condition gave them operations team a false sense of security and would have impacted the live migration process. All fibres are now certified and, during the migration, carried live data.

Operational Status

While the network core was to be upgraded the decision was made not to change the transceiver equipment at the network’s perimeter. The approach was reasonable; spares of the legacy Ethernet Attachment User Interface (AUI) to Dual Fibre Transceiver, albeit dated and end of life, had proven to be reliable over the years and spares were still available. With the controllers AUI port providing power to the transceiver, beyond testing, no perimeter work was necessary.

This approach made one major assumption that needed testing – would the legacy device interoperate seamlessly with the new network hardware? A thorough IT4A proof of concept and report determined the functional compatibility of the legacy interconnection but also identified a deficiency relating to limited link status information. This was seen as an acceptable compromise as plans were afoot to upgrade PLCs within the foreseeable future; any limitations would be overcome then.


This phase of works resulted in a fully EN-50173 certified, labelled and documented fibre installation. Legacy plant-wide fibre has been extended to a new communications room that has become the network hub for the respective process areas, ready for the active Ethernet network replacement. The works were completed without introducing any risk to production. Higher risk activities that were carried out in the proximity of live plant were passive only – no disruption, planned or otherwise, was seen by the plant.

“I cannot recommend them highly enough, they have been a pleasure to work with and will be the first people I turn to for advice and help in the future!” – Nuclear Sector, Project Manager


IT4A are passionate about ‘critical network infrastructure’ and the protection of automation and site-wide security systems that rely upon it.

IT4A create bespoke Network Solutions that are secure by design we take proven, CPNI (www.cpni. recommended methodologies and apply them to critical automation systems and projects. Our 24/7 monitoring service can detect abnormal events and our expertise will help defend your business from misuse or attack.

Our Security ‘SC’ Cleared support and maintenance services have been delivering reliable and secure critical network infrastructures for over 18 years. IT4A is unique in its ability to combine proven ISO accredited service with leading brand product supply; IT4A’s main distributor status ensures best value is achieved every time.

Customers that need advice on challenges relating to critical network design, security, cyber-security, management and system monitoring, have come to trust in and rely upon IT4A. It is the combination of technology partnership and solutions provision that sets IT4A apart, it is why the nuclear sector selected IT4A.



  • Refurbish passive network infrastructure for critical control and monitoring networks
  • Review physical network topology and re-validate legacy fibre infrastructure
  • Prepare infrastructure for live network integration and migration


  • High-security nuclear facility
  • Limited evidence of backup system readiness
  • Large industrial plant with strict permit-to-work system

IT4A Solution

  • topology for the new plant layout
  • Clean, re-certify, re-work and protect process-wide fibre infrastructure
  • Deliver a ‘fit for nuclear’ approach consistent with project needs and site sensitivity
  • Prepare a robust infrastructure platform for the active network deployment