DTS Fiber dts fiber optic

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Discussion on DTS Fiber Distributed Fiber

 

1、 Principle of Distributed Fiber Optic Temperature Sensing System DTS

The basic principles of distributed fiber optic temperature sensing systems (DTS) are based on the optical time domain reflectometry (OTDR) principle of optical fibers and the Raman scattering effect of optical fibers.

When laser pulses interact with fiber molecules, various scattering phenomena occur, such as Rayleigh scattering, Brillouin scattering, and Raman scattering. In theory, all three types of scattering could have been used as reference signals for temperature measurement. بهرحال, long-term research has found that the intensity of Rayleigh scattering is extremely unstable to the loss sensitivity of optical fibers. If Rayleigh scattering light is used as a reference signal for temperature measurement systems for a long time, it will cause uncertainty in the loss characteristics of optical fibers, leading to decreased system stability and even eventual inability to operate. تنهن ڪري, the system selects Raman scattering that is sensitive to temperature changes as the reference signal.

Raman scattering is generated by the thermal vibration of fiber molecules, which produces a Stokes light longer than the wavelength of the light source and an Anti Stokes light shorter than the wavelength of the light source. The modulation of optical fiber by external temperature will cause changes in the anti Stokes intensity in the fiber. The ratio of anti Stokes to Stokes can provide an absolute indication of temperature. Combined with high-quality pulse light sources and high-speed signal acquisition and processing technology, accurate temperature values can be obtained at all points along the fiber.

The DTS system includes a pulsed laser that sends approximately 1m pulses (equivalent to 10ns of time) to the fiber optic cable. When the pulse propagates along the optical fiber and interacts with the glass, a small amount of the original laser pulse is reflected back to the DTS sensing system due to small defects in the glass. By analyzing the reflected light, DTS can calculate the temperature of the event (based on the power of the reflected light) and the location of the event (based on measuring the time it takes for the backscattered light to return).

This technology has some characteristics, such as real-time monitoring. The system can monitor the temperature of the tested area in real-time for 7 × 24 hours, detect and locate temperature anomalies in a timely manner, and provide early warning; Its continuous distributed measurement capability can achieve simultaneous monitoring of multiple points and events without affecting each other, and the part before the fiber break can still work normally, with strong resistance to destruction; ان کان علاوه, it has ultra-high precision and high sensitivity. The system parameters can be configured according to the environment, and standard communication optical cables can be directly used. The monitoring area is divided according to on-site requirements; The response is very rapid, with a scanning cycle as low as 1 second. Overall, DTS utilizes the Raman scattering effect of light in optical fibers and the propagation characteristics of light to achieve effective measurement of temperature distribution along the fiber.

2、 DTS Fiber Distributed Fiber Types

Classify according to the different optical fibers used
Multimode fiber optic sensor: Fiber optic cables that can transmit multiple transmission modes are called multimode fibers. In multimode fiber optic sensors, the transmission type fiber optic sensor uses multimode optical fibers to transmit optical signals and measures them based on different light reception intensities. This type of sensor is commonly used for industrial detection, such as detecting liquid level, pressure, deformation, temperature, flow rate, موجوده, magnetic field, وغيره. It has the advantages of stable and reliable performance, simple structure, and low cost, but its sensitivity is relatively low. The transmission bandwidth of multimode fiber can reach 30 megahertz to several hundred megahertz, making it suitable for sensing and measurement over shorter distances (up to 40km). مثال طور, in some temperature and physical quantity sensing and monitoring scenarios where distance requirements are not particularly long and cost needs to be controlled, multimode fiber type distributed fiber sensors will be used.
Single mode fiber optic sensor: A type of optical fiber with a very thin core and cladding (with a small refractive index difference between the core and cladding) that can only transmit one transmission mode, called a single-mode fiber. This single-mode fiber optic sensor can be constructed using single-mode optical fibers to form interferometers. External factors can cause changes in the optical path in the optical fiber, resulting in variations in interference fringes, which can be used for measuring various physical quantities. Single mode fiber optic transmission has a bandwidth of up to 10 gigahertz, suitable for long-distance (40-100km) measurements. In scenarios that require long-distance distributed fiber optic sensing, such as temperature and strain monitoring of oil and gas pipelines, single-mode fiber optic sensors can play a role by stably transmitting optical signals over long distances to achieve sensing functions.
Classified by sensing function
Raman Thermometry (DTS): This type is based on the Raman scattering effect to measure temperature. It is a standalone temperature measurement system that measures the temperature distribution along the fiber by utilizing the temperature dependent relationship between the Stokes and anti Stokes intensity ratio generated by Raman scattering in the fiber. Its price is relatively cheaper than the Brillouin type, usually in the tens of thousands of yuan. Raman type DTS is widely used in many scenarios that require temperature monitoring, such as temperature monitoring and warning systems in buildings, industrial equipment, power cable trenches, وغيره. By distributing sensors in these places, real-time temperature changes can be monitored to avoid safety hazards caused by abnormal temperatures. مثال طور, in power cable trenches, temperature increases caused by overload or local faults can be detected in a timely manner to prevent accidents such as cable fires.
Brillouin type (such as BOTDR): This type of distributed fiber optic sensor can simultaneously measure temperature and stress, based on the Brillouin scattering effect. Two optical fibers are required on site, one for temperature measurement and one for stress measurement, but the cost is very high, with prices reaching millions. Although Brillouin type distributed fiber optic sensors are expensive, they have important applications in some special engineering and scientific research scenarios that require simultaneous measurement of temperature and stress. مثال طور, in the structural health monitoring of large bridges, Brillouin type distributed fiber optic sensors can be used to obtain the temperature distribution and stress distribution of the bridge under different working conditions, which is of great significance for the safety assessment and life prediction of the bridge. بهرحال, due to their high cost, they are rarely used in ordinary civilian scenarios.

3、 DTS Fiber Distributed Fiber Application

Fire alarm field
In fire alarm systems in large spaces such as subways, highway tunnels, warehouses, etc., distributed fiber optic temperature measurement systems play a good role in temperature monitoring and fire monitoring. In highway tunnels, the detection fiber optic cable is installed at the top middle position of the tunnel. If it is a closed tunnel, the fiber optic cable can also be placed on the side or top middle position of the tunnel (and 1m away from the wall) for easy monitoring. The detection optical cable needs to be fixed at regular intervals. The fiber optic host is placed in a monitoring room with good environmental conditions, and its display can show the main interface of the monitoring system. The working mode can be selected according to the usage requirements, and it can be used for real-time temperature monitoring, real-time monitoring of spatial temperature field distribution, alarm and other operations. And the fiber optic host can be connected to the fire alarm controller, setting partition parameters according to the actual spatial distribution, such as alarm temperature, partition range, وغيره. The number of partitions can reach hundreds, and each partition can independently sound an alarm.
For some special places where flammable materials or high fire risks are stored, such as crude oil storage tanks, when installing fire automatic detection devices on oil tanks, distributed fiber optic temperature sensors can be installed on the secondary sealing ring of the oil tank float. Distributed fiber optic temperature sensors can be regarded as continuous distributed temperature fire detectors here, which can measure the temperature at any point along the fiber optic cable without blind spots. They can quickly respond to temperature changes, timely warn of fire hazards, ensure the safety of oil tanks, and prevent serious consequences such as oil and gas explosions caused by abnormal temperature increases.
Monitoring of power facilities
For temperature monitoring of power devices such as high-voltage transmission and distribution cables, power cables, cable trenches, and power equipment, the temperature distribution and temperature change trend of the high-voltage cables covered by the detection optical cables can be monitored in real time by laying detection optical cables on the high-voltage cables to be tested. High voltage cables can also be divided into several areas and monitored separately according to requirements, with segmented functions such as warning temperature, alarm temperature, heating rate, and temperature difference alarm. The distributed fiber optic monitoring and alarm system provides an effective way for temperature monitoring, alarm, analysis, and management of high-voltage cables and other power devices, which helps to timely detect faults such as cable overheating and ensure the stability and safety of power supply. Due to its use of optical fiber as a medium, it is not affected by electromagnetic interference like some traditional electrical sensors, and linear distribution detection can fully cover the cable without any monitoring blank areas.
It is also applied in temperature monitoring of power equipment such as switchgear and transformers. It can achieve distributed temperature measurement of these devices, timely grasp the temperature situation during device operation, prevent equipment damage caused by high temperature, and improve the reliability and safety of power equipment operation. In substations or distribution rooms, distributed fiber optic temperature sensors can be arranged along key parts of switchgear and transformers, such as around the windings of transformers, which can sensitively capture small temperature changes in equipment and help power workers take maintenance measures in advance.
Monitoring of oil and gas storage tanks
The temperature rise of oil and gas storage tanks can lead to an increase in pressure inside the tanks, which may cause serious consequences. By using distributed fiber optic temperature sensors and laying detection cables on the outer surface and top of oil and gas storage tanks, the temperature distribution and trend of the entire tank can be monitored. When the alarm condition is reached, the system outputs an alarm signal. This monitoring method has many advantages, such as real-time monitoring of the entire oil and gas tank to provide comprehensive temperature analysis; Flexible setting of constant temperature alarm, differential temperature alarm, and temperature rate alarm; The detection cable is non electrified, corrosion-resistant, and can work safely in hazardous environments; Easy to install, one optical cable can simultaneously measure dozens of oil and gas tanks; Through proper installation, it is also possible to measure whether there are leaks in oil and gas tanks. The DTS system has the characteristics of strong environmental adaptability and high long-term stability, making it suitable for long-term temperature monitoring of oil and gas storage tanks.
Pipeline monitoring
In terms of pipeline monitoring, whether it is liquid or gas transportation pipelines, especially in the important pipeline parts of underground transportation in the energy industry, distributed fiber optic temperature sensor technology can be used for pipeline monitoring, leakage detection, and data measurement during pipeline transportation, including detection of pipelines and leaks, location of leaks, and provision of auxiliary equipment for existing pipelines. مثال طور, in oil and gas transportation pipelines, by laying optical fibers along the pipeline, it is possible to monitor the temperature changes of the surrounding environment or the pipeline itself in real time. If there is leakage or other situations, the temperature around the leakage point may change. The DTS system can detect this temperature anomaly and accurately locate the leakage location, which is of great significance for preventing economic losses (such as material losses caused by oil and gas leaks) and environmental pollution.
Applications related to water conservancy building structures
In the inspection and measurement of the safety status of water conservancy structures such as dams, distributed fiber optic temperature sensors can not only measure the temperature distribution field of dams and other buildings, but also play a role in temperature measurement during concrete pouring. They can also detect dam leakage and locate leakage points. Distributed fiber optic deformation measurement technology also allows for static measurement and dynamic deformation measurement of hydraulic building structures. In reservoirs, temperature monitoring, concrete dam monitoring, leakage detection and positioning, water leakage path positioning, measurement of subsidence process, deformation measurement, rock layer research and other work can be carried out; In terms of dams and embankments, temperature monitoring, dam and embankment monitoring, leakage detection and positioning, positioning of groundwater leakage paths, leakage detection of sealing bodies and joints, and other monitoring work can be carried out, providing comprehensive data monitoring methods for the safety guarantee of water conservancy buildings.

4、 InnoTech is the best company in the DTS field

Fuzhou Yingnuo Electronic Technology Co., لميٽيڊ. is a high-tech enterprise engaged in scientific research and development, production, sales, and service. The company has a range of products and achievements in DTS.

Technical research and product characteristics
Yingnuo Technology’s distributed fiber optic temperature measurement system product technology is based on the basic principles of DTS, such as using fiber optic spontaneous Raman scattering effect to achieve temperature measurement and optical time-domain reflection for spatial positioning function. Its products, such as the IF-DTS measurement host, can use high-speed narrow pulse semiconductor laser pulses coupled into the sensing fiber, and further filter, detect, and collect high-speed data through the weak backscattering signal of the fiber to obtain temperature sensitive anti Stokes signals and temperature insensitive Stokes signals, thereby obtaining accurate temperature information distributed along the fiber. And combined with advanced fire intelligent alarm judgment algorithms, achieve real-time online monitoring of the entire sensing fiber optic process.

The product has some outstanding features, such as a measurement range of -30.0 ℃~240.0 ℃, distributed real-time measurement function, which can cover the detection area and accurately locate the location of the fire; Long measurement distance and rich measurement information; High measurement accuracy and fast response speed; High reliability and low false alarm rate; The alarm method is flexible and can achieve multi-level differential temperature alarm, ensuring reliable alarm in the early stage of a fire. ان کان علاوه, the detection optical cable serves as both a signal transmission carrier and a temperature sensing element, with advantages such as easy installation, long lifespan, and low maintenance costs in the later stages.

Yingnuo Technology’s products have a wide range of applications, such as tunnels, subways, electricity, petrochemicals, dams, oil wells, and other fields. Compared with other traditional methods in tunnel fire monitoring, the advantages of high precision and accurate positioning through distributed fiber optic temperature measurement can more timely detect fire hazards. Real time monitoring of various key equipment temperatures can be achieved in power equipment monitoring, reducing equipment operation risks. ان کان علاوه, the product has a certain cost advantage and can provide products and services at relatively reasonable prices in the market (such as the IF-DTS distributed fiber optic temperature measurement system with different price options), which is very attractive for large-scale projects that require the deployment of a large number of sensors.