Fibre sensing for critical infrastructure  

Fibre optic sensing systems assist critical infrastructure ranging from telecommunication services, oil, gas and water pipelines to mining, marine applications, electrical power transmission and data centre interconnects in optimising efficiency and implementing preventive protection and security. Fibre sensing technology involves the integration of optical fibres within the infrastructure to monitor various physical parameters in real time that can prevent outages, avoid costly repairs to critical infrastructure and help in faster restoration.

Fibre optic sensing

Fibre optic sensing uses the physical properties of light as it travels along a fibre to detect changes in temperature, strain, vibration (acoustics) and other parameters. Fibre optic sensing utilises fibre as the sensor to create thousands of continuous sensing points along the fibre. The technique is called ‘distributed fibre optic sensing,’ where a standard single optical fibre can act as an extended sensor over long distances and with high spatial resolution, covering vast areas of critical infrastructure.

Changes in the surrounding physical parameters, such as strain or temperature, cause minute variations in the light’s characteristics, which can be detected and analysed. Advanced signal processing techniques allow engineers to convert these variations into valuable data. Traditional fault detection methods can be slow and costly, often requiring extensive manual inspection. Fibre optic sensing can quickly identify and locate faults caused by physical damage, environmental factors or operational anomalies.

Applications of fibre optic sensing

Distributed fibre sensing offers a versatile range of capabilities, enabling monitoring of various physical parameters critical to infrastructure health. The three primary types of fibre sensing utilised in infrastructure monitoring are for temperature, strain, and acoustics. Their key features include:

• Temperature sensing-Temperature anomalies and overheating can significantly impact the structural integrity of infrastructures like pipelines, electrical power cables, and electrical equipments. Distributed temperature sensing (DTS) utilises the principle of measuring the change in back-scattered light frequency or power as a function of temperature. This method allows for continuous monitoring of temperature profiles along the entire length of the optical fibre, providing valuable data on potential hotspots or temperature variations that might affect the infrastructure’s performance.
• Strain sensing-Monitoring strain due to mechanical loads is crucial in assessing the health of civil engineering assets. Distributed strain sensing (DSS) relies on the principle of measuring minute variations in light frequency caused by mechanical strain applied to the optical fibre. This technique allows engineers to detect deformations, cracks, or excessive loads, helping prevent catastrophic failures and extending the lifespan of critical structures.
• Acoustic sensing-Distributed acoustic sensing (DAS) is a cutting-edge technology that enables the detection and localisation of acoustic disturbances and vibrations. By analysing changes in light scattering caused by mechanical pressure waves, DAS turns an optical fibre into an array of thousands of virtual microphones distributed over a vast area. This capability is particularly beneficial for monitoring large infrastructure networks, such as pipelines or railroads, as it can detect potential leaks, third-party intrusions, and interference, or even ground movements caused by seismic events.

The combination of these different types of fibre sensing not only provides a comprehensive solution for infrastructure monitoring but also opens up new possibilities for integrated and intelligent systems that can adapt to the evolving needs of complex and interconnected modern world. By harnessing the power of fibre sensing technology, organisations can enhance the safety, efficiency and reliability of critical infrastructure, ensuring a sustainable and resilient future.

Advantages of fibre optic sensing

• Cost effectiveness- Traditional monitoring systems often require multiple sensors at various points, leading to higher installation and maintenance costs. Distributed fibre sensing, on the other hand, uses a single optical fibre to cover large areas, significantly reducing cost of deployment and operation.
• Proactive maintenance- Distributed fibre sensing provides timely information on any changes or abnormalities, allowing for early responses to potential issues or threats.
• Longevity and durability- Optical fibres and cables used in sensing are highly robust and can withstand harsh environmental conditions, making them ideal for long-term infrastructure monitoring.
• Remote sensing- Fibre sensing allows for remote monitoring, reducing the need for physical inspections and minimising human exposure to hazardous locations.
• Scalability- The technology is scalable and can be adapted to monitor various parameters simultaneously, providing a comprehensive monitoring solution for complex infrastructure systems.

NITRO fibre sensing

NITRO fibre sensing is an integrated real-time asset monitoring and analytics solution for critical infrastructure. Comprising DTS, distributed temperature and strain sensing (DTSS) and DAS, NITRO fibre sensing provides the critical intelligence needed to swiftly identify and locate threats.

Using remote fibre test heads, commonly known as interrogators to monitor fibre optic cables or fibre-enabled infrastructure, NITRO fibre sensing measures temperature and strain along a fibre or detect acoustic vibrations close to a fibre in real time. NITRO fibre sensing offers solutions for industries like:

• Power transmission- Real-time thermal rating (RTTR) and cable temperature, cable exposure and depth of burial and third-party interference.
• Pipeline infrastructure- Real-time asset monitoring, leak detection and localisation, and third-party interference detection.
• Telecoms infrastructure- Cable health monitoring, smart cities and environment, plus detection of third-party interference with data centre interconnect (DCI).
• Protection and security- Real-time perimeter monitoring, people and vehicle, tunnelling and excavation detection.

Ensuring safety and integrity of critical infrastructure

The continuous development and integration of fibre sensing technology into infrastructure monitoring practices will undoubtedly play a pivotal role in safeguarding critical infrastructure, providing engineers with the necessary tools to address challenges proactively and make informed decisions. As society becomes more connected, the demand for monitoring, security, and minimised reaction times will continue to grow. Creative utilisation of fibre optic sensing will help make this possible.