Principles and Applications of Distributed Fiber Optical Temperature Sensing-INNO

Détection de température distribuée par fibre optique (ETD) is an advanced temperature monitoring technology that utilizes optical fibers as temperature sensitive components and signal transmission media to achieve continuous and real-time monitoring of temperature distribution over long distances and large ranges. DTS systems are typically based on the principle of optical time domain reflectometry (OTDR) and the Raman scattering effect of optical fibers, and obtain temperature distribution information along the fiber by analyzing the intensity changes of backward Raman scattering light in the fiber.

1、The main components of DTS system

source de lumière
Laser: High power pulsed lasers such as Nd: YAG lasers or Erbium doped fiber amplifier (EDFA) lasers are commonly used. The pulse light signal emitted by the laser is transmitted to the measured area through optical fiber.
Fibre optique
Sensing fiber: used for transmitting optical signals and serving as a temperature sensitive component. Common sensing fibers include single-mode fibers and multi-mode fibers. Single mode fiber is widely used due to its low loss and high resolution.
détecteur
Photodetector: used to detect backscattered Raman light returning from optical fibers. The commonly used photodetectors include photomultiplier tubes (PMT) and avalanche photodiodes (APD).
signal processing unit
Data acquisition card: used to collect electrical signals output by photodetectors and convert them into digital signals.
Signal processor: processes the collected digital signals and extracts temperature information. Common signal processing algorithms include Fourier transform, wavelet transform, etc..
software system
Data analysis software: used to display and analyze temperature distribution data, generate temperature curves and temperature distribution graphs. Software systems typically have data storage, alarm functions, et capacités de surveillance à distance.
The working principle of DTS system
Principle of Optical Time Domain Reflectometry (OTDR)
The pulse light signal emitted by the laser propagates along the optical fiber, and when it encounters uneven points or end faces in the fiber, it will produce backscattered light. By measuring the return time and intensity of backscattered light, the propagation distance and position of the optical signal in the fiber can be determined.
diffusion Raman
When optical signals propagate in optical fibers, various types of scattering occur, including Rayleigh scattering, Diffusion Brillouin, et diffusion Raman. L'intensité de la lumière diffusée Raman dépend de la température. Raman scattering is divided into Stokes scattering and Anti Stokes scattering. The intensity of anti Stokes scattering light increases with temperature, while the intensity of Stokes scattering light does not change significantly with temperature. By measuring the intensity ratio of anti Stokes scattering light to Stokes scattering light, the temperature at each point along the fiber can be calculated.

2、Application scenarios of DTS system

Système d'alimentation
Cable temperature monitoring: In high-voltage cables and cable trenches, DTS system can monitor the temperature distribution of cables in real time, detect overheating problems in a timely manner, and prevent cable damage and fire accidents.
Substation temperature monitoring: In the substation, the DTS system can monitor the temperature of equipment such as transformers and switchgear to ensure the safe operation of the equipment.
Oil and gas industry
Oil pipeline monitoring: In long-distance oil pipelines, the DTS system can monitor the temperature distribution of the pipeline in real time, detect leakage points and temperature anomalies in a timely manner, and prevent environmental pollution and economic losses.
Oil well temperature monitoring: Dans les puits de pétrole, DTS systems can monitor the temperature distribution underground, providing data support for oil extraction.
Architecture and Infrastructure
Bridge temperature monitoring: In large bridges, DTS systems can monitor the temperature distribution of the bridge body, evaluate the health status of the bridge, and promptly detect potential safety hazards.
Tunnel temperature monitoring: In tunnels, DTS systems can monitor the temperature distribution inside the tunnel to ensure its safe operation.
protection de l'environnement
Surveillance de la température du sol: Dans la recherche agricole et écologique, DTS systems can monitor soil temperature distribution, provide guidance for agricultural production, and study soil microbial activity and nutrient transformation.
Water temperature monitoring: In rivers, lakes, and oceans, DTS systems can monitor the temperature distribution of water bodies and study the impacts of water ecosystems and climate change.
sécurité incendie
Warehouse temperature monitoring: In large warehouses, DTS systems can monitor the temperature distribution inside the warehouse, detect fire hazards in a timely manner, and prevent fire accidents.
Tunnel fire monitoring: In tunnels, DTS systems can monitor the temperature distribution inside the tunnel in real time, detect fires in a timely manner, and activate the fire protection system.

3、Advantages of DTS system

Surveillance longue distance: The DTS system can achieve temperature monitoring for up to tens of kilometers, suitable for large-scale, long-distance temperature monitoring scenarios.
High resolution: DTS systems can provide temperature distribution data with high spatial resolution, typically up to several meters or even shorter.
Surveillance en temps réel: The DTS system can achieve real-time and continuous temperature monitoring, and detect temperature anomalies in a timely manner.
Anti-interférence électromagnétique: Optical fibers have good anti electromagnetic interference capabilities and are suitable for temperature monitoring in strong electromagnetic environments.
Installation facile: The installation and maintenance of DTS system are relatively simple and cost-effective.

4、Limitations of DTS system

Coût: Although the unit cost of DTS system decreases with the increase of monitoring distance, the initial investment cost is still relatively high.
Accuracy limitation: The temperature measurement accuracy of DTS system is affected by various factors, such as fiber quality, environmental temperature changes, external interference, etc..
Complex data processing: DTS systems require complex signal processing algorithms and high-performance computer systems to process large amounts of data.
summary
Le Détection de température distribuée par fibre optique (ETD) system is an advanced temperature monitoring technology that utilizes the Raman scattering effect and optical time domain reflection principle of optical fibers to achieve continuous and real-time monitoring of temperature distribution over long distances and large ranges. DTS system has a wide range of applications in the fields of power system, industrie pétrolière et gazière, construction and infrastructure, protection de l'environnement, sécurité incendie, etc.. It has advantages such as long-distance monitoring, haute résolution, surveillance en temps réel, anti-interférence électromagnétique, and easy installation. Cependant, DTS systems also have limitations such as high cost, limites de précision, and complex data processing.