Distributed Temperature Sensing

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Distributed Temperature Sensing (DTS) systems offer precise temperature data for effective thermal monitoring, fire alarm systems, and condition evaluations by employing standard fiber optic cables. These optical fiber systems accurately assess the temperature profile of an asset by analyzing the interaction between light and the glass structure of the fiber. Real-time monitoring of an asset along the fiber optic cable provides essential information needed to initiate or modify preventive or corrective measures for assets like power cables, pipelines, or tunnels.

How DTS Works

Distributed Temperature Sensing (DTS) employs standard optical fibers, which can extend for several kilometers, to function as linear temperature measurement devices. This method offers a detailed spatial temperature profile throughout the full length of the sensor cable, achieving a resolution as fine as one meter.

Light Scattering in Fiber Optics, OTDR

DTS technology operates on the principles of either Raman or Brillouin optical scattering. A laser pulse is intermittently directed into the fiber, resulting in a small percentage of the light being scattered back as it interacts with the glass structure. This returning light is continuously analyzed by the interrogator. The temperature measurement’s location is determined by the time it takes for the light to return, similar to how radar echoes are analyzed. This technique is known as Optical Time Domain Reflectometry (OTDR). Another approach, Optical Frequency Domain Reflectometry (ODFR), is technically different but mathematically similar. When it comes to covering long distances with an optimal signal-to-noise ratio, the time domain (OTDR) method is advantageous due to its lower shot noise.

Temperature Monitoring Based on Raman Reflectometry

In DTS systems that utilize Raman scattering, the Stokes and anti-Stokes bands are analyzed separately. The ratio of the intensity between these two signals is influenced by the local temperature and is utilized to determine the temperature throughout the optical fiber.

Temperature Monitoring Based on Raman Reflectometry

Airway Security employs Raman-OTDR technology, which is significantly enhanced by its unique code correlation (CC) technology. The adoption of CC-OTDR offers multiple benefits: it markedly boosts the signal-to-noise ratio, improving temperature resolution and distance capability, while also allowing for the use of low optical pulse power, thereby alleviating issues related to potential laser degradation. As a result, Airway Security DTS systems are inherently safe for use and suitable for deployment in hazardous areas.

Additionally, a patented design featuring a single receiver ensures enhanced stability of the relative amplitudes of both signals, which consequently affects temperature. A significant benefit of this method is the remarkable reliability of the system that is attained.

The Raman system remains unaffected by strain on the sensor fiber, enabling accurate temperature measurements even when mechanical tension is present. This mechanical stress could otherwise cause misleading temperature readings (such as those from Rayleigh or Brillouin signals) if not managed properly.

How Distributed Temperature Sensing (DTS) works using Raman reflectometry:

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Distributed Temperature Sensing

Temperature Monitoring Based on Brillouin Reflectometry

In DTS systems utilizing Brillouin scattering, the key parameter measured is the frequency shift of the backscattered Brillouin signal. This frequency, referred to as the Brillouin frequency shift, is influenced by temperature changes. Airway Security employs OTDR technology for Brillouin-based DTS. It is essential to prevent strain on fibers, such as through appropriate loose tube designs, since the Brillouin frequency shift is sensitive to strain.

One significant benefit of Brillouin-based DTS over Raman is the enhanced back-scattering signal. This feature allows for greater distance ranges, making it particularly effective for monitoring extensive assets. Furthermore, it provides high spatial resolution across long distances and the ability to concurrently measure temperature and strain.

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Benefits & Advantages of Distributed Temperature Sensing

Continuous Temperature Profile Measurement

DTS systems offer ongoing thermal data, allowing for the accurate identification and localization of thermal irregularities. With extensive coverage spanning several kilometers per measurement unit and real-time data, comprehensive temperature monitoring enables the precise detection of any hot or cold spots. This capability is essential for the early identification of hotspots, fires, or temperature irregularities that may signal faults or other problems.

Furthermore, the DTS system facilitates optimized management of cool-down processes through its continuous thermal data. This feature allows industries to monitor temperature consistently along the fiber, assisting in identifying anomalies, enhancing operational efficiency, and achieving accurate temperature regulation across various industrial applications.

DTS systems demonstrate exceptional reliability even in challenging industrial environments characterized by heat, dirt, dust, and corrosion. Utilizing optical fibers for sensing, DTS systems are resistant to corrosion and are inherently safe to use in explosive settings.

Based on the construction of the cable and the type of fiber coating used, DTS applications can measure temperatures spanning a broad range, from as low as -185 °C (-300 °F) to over +750 °C (+1400 °F). Discover more about fiber optic sensor cables here.

The utilization of optical fiber, which is inherently non-conductive, provides the sensor with immunity against electromagnetic interference (EMI or RFI). This resistance is due to the fact that light in glass is employed for sensing and transmitting signals, rather than relying on electrical voltage and current, which can be affected by electromagnetic fields or radio frequency interference. Consequently, this guarantees accurate temperature measurements even in environments characterized by high electromagnetic noise.

DTS systems deliver precise and dependable temperature measurements for thorough analysis. They possess a high sensitivity to identify even slight temperature fluctuations, making them advantageous for predictive maintenance. Consequently, they are well-suited for applications where small temperature changes are crucial, such as in industrial processes, research, or monitoring variations in the burial depth of submarine power cables.

A DTS system operates in a truly distributed manner, effectively detecting heat at any location along the cable uniformly. This results in a continuous temperature profile throughout the entire length of the fiber optic cable, offering a distinct advantage over traditional sensors for various applications. By using a single passive fiber optic cable over extensive distances, significant cost savings can be achieved in both equipment and installation, as opposed to the need for multiple conventional sensors. Furthermore, minimal maintenance requirements enhance operational efficiency and contribute to long-term cost savings.

Use Cases of DTS Systems

Distributed Temperature Sensing Systems are essential for highly demanding applications. They improve safety, operational efficiency, and temperature monitoring in difficult environments. Consequently, DTS systems are utilized in various applications such as temperature monitoring for power utilities, pipelines, and geothermal monitoring in wells and reservoirs. One significant advantage is their low maintenance requirement and seamless integration into current operational systems.

Some of the key applications of Distributed Temperature Sensing Systems include:

Power Cable Monitoring
Pipeline Leak Detection
LNG Facility Monitoring
Well and Reservoir Monitoring
CCS Monitoring
Geothermal Monitoring

Airway Security’s DTS Systems

DTS N45-Series

Airway Security addresses all market needs with its systems. Our DTS N45-Series is built to function in any environment, from deserts to polar regions. Boasting the most comprehensive range of certifications and rigorous type testing in the industry, we ensure top product quality and extended product longevity.

Discover Our Raman-based DTS System

DTS N62-Series

The state-of-the-art DTS N62-Series exemplifies advanced engineering. Utilizing the sophisticated features of B-OTDR technology, this DTS system guarantees outstanding measurement accuracy for overseeing extended assets.

Explore Our Brillouin-based DTS Solution

Enhanced DTS (eDTS)

Comprehensive Monitoring Solution in Combination with Distributed Acoustic Sensing

The integration of Distributed Temperature Sensing (DTS) and Distributed Acoustic Sensing (DAS) into the enhanced Distributed Temperature Sensing (eDTS) solution creates a powerful and comprehensive monitoring system. This combination effectively addresses temperature fluctuations and acoustic disturbances, improving the assessment, protection, and optimization of infrastructure. Raman-based DTS delivers consistent absolute temperature readings, while DAS, featuring Distributed Temperature Gradient Sensing (DTGS), enables ultra-rapid and accurate detection of minute temperature variations. Merging these technologies enhances response time and temperature resolution, providing exceptional long-distance measurement capabilities compared to standalone DTS. eDTS is particularly advantageous for accurately monitoring temperature profiles over extensive distances, such as over 50 km, making it ideal for applications like power cable surveillance and oil & gas pipeline leak detection systems.

Read More About Our eDTS Solution
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Airway Security, known for its reliable performance and ongoing innovation, provides a fully integrated, comprehensive solution crafted in Germany. Our team collaborates with you to choose the ideal combination of technologies that meet your needs.

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