Distributed fiber optic sensing, selection, purchase, complete guide, DTS/DVS/DAS, advantages

Filo optic e ʻea sensor resistance, Founga vakaiʻi ʻo e ʻatamai poto, Tufaki e filo optic ʻi Siaina

Distributed fiber optic sensing technology includes multiple types, each with its unique advantages and suitable for different application scenarios. The following is a brief introduction and advantages of three distributed fiber optic systems: DTS (mafana ʻo e ʻea), DVD (vibration), and DAS (acoustic):

Type advantages
DTS (Distributed Fiber Optic Temperature Measurement System): Real time, continuous distributed measurement, excellent stability, electromagnetic insulation, intrinsic safety.
DVD (Distributed Fiber Disturbance System): Multi point positioning of vibration positions with an accuracy of about 5 mita ʻe, suitable for security and intrusion prevention applications.
DAS (Distributed Optical Fiber Acoustic Vibration System): With high positioning accuracy, it can simultaneously detect multiple vibration events and is suitable for fields such as secure communication and network physical routing security.

1、 Types of distributed optical fibers

1.1 Classification of refractive index distribution based on fiber profile

Step index optical fiber: The refractive index of its core and cladding changes step by step. In this type of optical fiber, light undergoes total reflection at the interface between the core and cladding, and propagates along the core. For example, in some short distance, high cost fiber optic sensing applications, step index fibers may be used because their manufacturing process is relatively simple and the cost is low.
Gradient optical fiber: The refractive index of the fiber core is gradually decreasing from the center to the edge. This type of fiber can reduce the mode to mode dispersion in multimode fibers, making the transmission of optical signals in the fiber more stable. In some early multi-mode fiber optic communication systems, gradient optical fibers played an important role in improving transmission bandwidth and increasing transmission distance, such as in the early construction of some campus networks.

1.2 Classification by the number of modes of fiber optic transmission

Multimode fiber: a fiber that can transmit hundreds to thousands of modes. The core diameter of multimode optical fibers is relatively large, generally ranging from 50 μ m to 62.5 μ m. Due to its ability to transmit multiple modes, light of different modes travels at different speeds in optical fibers, resulting in inter mode delay differences that limit its transmission bandwidth and distance. Neongo ia, multimode optical fibers have high coupling efficiency and are widely used in short distance transmission, such as local area network wiring inside buildings. For example, in some office buildings, the connection between computers may use multimode fiber optic because it can meet data transmission needs over short distances and the connection equipment is relatively simple.
Single mode fiber: a fiber that can only transmit one mode (fundamental mode), without any inter mode delay difference, and has a much larger bandwidth than multimode fiber. Its mode field diameter is only a few micrometers, suitable for high-capacity, long-distance communication. Single mode optical fiber is the preferred choice for scenarios that require long-distance and high bandwidth transmission, such as long-distance communication trunk lines and submarine cables. For example, submarine communication cables spanning oceans can ensure stable and high-speed transmission of data over thousands of kilometers using single-mode optical fibers.

1.3 Classification according to international standards (classification according to ITU-T recommendations)

G. 651 fiber (50/125 μ m multimode gradient refractive index fiber): This type of fiber is a multimode gradient fiber with a core diameter of 50 μ m and a cladding diameter of 125 μ m. In the early construction of fiber optic communication networks, G.651 fiber optic cables were commonly used for short distance, medium low speed data transmission, such as wiring for some enterprise internal networks or small office area networks.
G. 652 fiber (non dispersive shifted fiber): This is a single-mode fiber with zero dispersion characteristics near the wavelength of 1310nm, and is currently one of the most widely used fibers. It is widely used in the construction of various communication networks such as local networks, metropolitan area networks, and long-distance trunk networks, and can meet the transmission needs of different speeds and distances.
G. 653 fiber (dispersion shifted fiber DSF): Through special design, the zero dispersion point is moved from 1310nm to around 1550nm wavelength. At a wavelength of 1550nm, it has the characteristics of low loss and zero dispersion, making it suitable for high-speed, long-distance single channel transmission systems. Neongo ia, due to the limitations of nonlinear effects such as four wave mixing, its application range is relatively narrow.
G. 654 fiber (cut-off wavelength shifted fiber): Its characteristic is a long cut-off wavelength, with an extremely low attenuation coefficient at 1550nm wavelength. This type of fiber optic cable is mainly used in long-distance, relay free submarine cable communication systems or special communication scenarios with extremely high attenuation requirements.
G. 655 fiber (non-zero dispersion shifted fiber): It has a certain dispersion near the wavelength of 1550nm, which can suppress nonlinear effects such as four wave mixing and utilize the low loss window of 1550nm band for long-distance transmission. Widely used in high-capacity, long-distance fiber optic communication networks such as wavelength division multiplexing (WDM) systems.

1.4 Classification according to IEC standards

A-class multimode fiber
A1a multimode fiber (50/125 μ m multimode fiber): Similar to ITU-T’s G.651 fiber, it is a commonly used multimode fiber that is widely used in short distance, low to medium speed data transmission scenarios, such as indoor wiring in some campus networks.
A1b multimode fiber (62.5/125 μ m multimode fiber): It is also a multimode fiber, which was widely used in early network cabling. Neongo ia, with the development of technology, it has gradually been partially replaced by 50/125 μ m multimode fiber.
A1d multimode fiber (100/140 μ m multimode fiber): This type of multimode fiber is relatively thick and may be used in some special short distance transmission scenarios with low coupling requirements.
Class B single-mode fiber
B1.1 corresponds to G652 fiber optic: inheriting the characteristics of G.652 fiber optic, it is widely used in communication networks and can meet the transmission requirements of various speeds and distances.
B1.2 corresponds to G654 fiber: similar in characteristics to G.654 fiber, suitable for long-distance, low attenuation communication scenarios.
B2 fiber corresponds to G.653 fiber: it has the characteristics of G.653 fiber and is suitable for specific single channel high-speed, long-distance transmission systems.
B4 fiber corresponds to G.655 fiber: It has the characteristics of G.655 fiber and is widely used in high-capacity, long-distance communication networks such as wavelength division multiplexing systems.
Classified by material of optical fiber
Quartz fiber: generally refers to a fiber composed of a doped quartz core and a doped quartz cladding. Quartz optical fiber has the advantages of low loss, high strength, and good chemical stability, and is currently the most widely used type of optical fiber in the field of communication. Quartz fiber dominates applications such as long-distance communication, local networks, and fiber optic sensing.
All plastic optical fiber: The core and cladding of all plastic optical fiber are both made of plastic materials. This type of fiber optic cable has good flexibility and low cost, but relatively high loss and short transmission distance. Mainly used in some short distance communication scenarios that do not require high transmission distance and are sensitive to cost, such as communication lines inside automobiles and short distance control signal transmission in industrial automation.

1.5 Classification by working wavelength

UV fiber: a fiber with a working wavelength in the ultraviolet band. UV fiber has applications in some special scientific research, medical equipment (such as UV phototherapy equipment), photolithography technology, and other fields. Due to the high energy of ultraviolet light, ultraviolet optical fibers require special materials and manufacturing processes to ensure their transmission performance and stability towards ultraviolet light.
Observable fiber (possibly due to an error in the description of visible light fiber): If referring to visible light fiber, its operating wavelength is in the visible light band. This type of fiber optic cable can be used in some special lighting systems, fiber optic sensors (such as visible light intensity sensors), and art exhibitions.
Near infrared fiber: a fiber with a working wavelength in the near-infrared band. The near-infrared band is of great significance in fiber optic communication. Many fiber optic communication systems operate in the near-infrared band (such as 1310nm and 1550nm) because the fiber loss is low in this band and long-distance transmission can be achieved.
Infrared fiber optic: Fiber optic that operates in the infrared band. Infrared fiber has applications in some fields such as infrared spectroscopy analysis and infrared thermal imaging. For example, infrared night vision equipment in military and infrared temperature detection equipment in industry may use infrared optical fibers to transmit infrared signals.

2、 Advantages of DTS Temperature

2.1 Measurement Range and Spatial Positioning

Large scale spatial measurement: DTS (Tufaki ʻo e filo Optic e mafana ʻo e ʻea) can achieve distributed real-time measurement of temperature in a large range of space, with long measurement distance and no measurement blind spots. For example, in temperature monitoring of large infrastructure such as tunnels and subways, the entire area can be monitored along fiber optic lines, without the need to install a sensor at each monitoring point like traditional point sensors, greatly reducing the number of sensors and installation costs.
Accurate spatial positioning: capable of simultaneously achieving temperature measurement and spatial positioning functions. It utilizes optical time domain reflectometry (OTDR) technology to accurately determine the location of temperature anomalies. In the power system, if a cable experiences local overheating, DTS can accurately locate the location of the overheating point to the meter level or even higher, which is crucial for timely detection of potential faults and ensuring the safe operation of the power system.

2.2 Stability and Durability

The stability of the fiber itself: When the sensing fiber strength of the DTS temperature measurement system is sufficient, it is not easily damaged. Compared with traditional point sensors, it has better stability. For example, in some harsh industrial environments such as petrochemical plants, coal mines, mo e ala meʻa pehē., traditional point temperature sensors may be easily damaged due to corrosion, vibration, collision, mo e ala meʻa pehē., while DTS fiber optic sensors can work stably in these environments for a long time.
Long term reliability: Due to the chemical stability and physical properties of optical fibers, DTS systems have high long-term reliability. In projects that require long-term stable monitoring such as dam temperature monitoring, DTS system can accurately measure temperature changes for many years, providing reliable data support for dam safety assessment.

2.3 Functional Diversity and Adaptability

Adapt to various environments: By using different fiber optic outer protective layers, it can adapt to various extreme temperature measurement environments. DTS can effectively monitor temperature in environments such as high-temperature oil wells, low-temperature polar facilities, and high humidity underground pipe galleries.
Multi functional alarm settings: Different temperature sensing point alarms can be set, and different alarm temperatures can be set according to user needs. The alarm system can also arrange different area divisions based on the actual situation of the surrounding environment. In terms of fire warning, different areas can set different alarm thresholds according to the degree of fire risk, such as setting different alarm temperatures in the flammable storage area and passage area of the warehouse to improve the accuracy and effectiveness of the warning.
<4>2.4 Integration with other systems

: The DTS system can be combined with advanced fire intelligent alarm judgment algorithms to achieve real-time online monitoring of the entire sensing fiber, and can seamlessly connect with other fire protection systems (such as standard equipment such as fire alarms and relays). In the building fire protection system, DTS can serve as an important temperature monitoring subsystem, working in conjunction with fire alarm systems, fire extinguishing systems, mo e ala meʻa pehē., to improve the efficiency of the entire fire protection system.

3、 Advantages of DVS vibratio

3.1 Measurement performance aspect

Rich vibration information acquisition: DVD (Distributed Fiber Optic Vibration Monitoring System) can provide rich vibration information, including the position, magnitude, frequency, direction, mo e alā meʻa pe. of vibration. This is because it uses a single optical fiber to simultaneously monitor vibration and transmit signals, and can distribute fiber Bragg grating sensors around the structure that needs to be monitored to achieve multi-point, distributed monitoring. For example, in the health monitoring of bridges, the DVS system can obtain real-time vibration information of various parts of the bridge. By analyzing this information, the structural health status of the bridge can be determined, such as whether there are structural damage, fatigue, and other problems.

High precision positioning capability: It has the advantage of precise positioning. Its positioning accuracy can reach a certain level (such as a positioning accuracy of up to 5 meters in some systems), and it can accurately determine the location where vibration occurs. In the monitoring of long-distance natural gas pipelines, if abnormal conditions such as drilling and oil theft, geological disasters, mo e alā meʻa pe. occur along the pipeline, causing vibration, the DVS system can accurately determine the location of the abnormal point, making it convenient for staff to take timely measures for repair and prevention.
In terms of safety and reliability

3.2 Intrinsic Safety Characteristics

Fiber optic sensing technology uses light waves as carriers and optical fibers as media. Compared with traditional electrical sensors, DVS has intrinsic safety characteristics. In some flammable and explosive environments (such as around production facilities in the petroleum and petrochemical industry), using DVS for vibration monitoring will not generate safety hazards such as electric sparks, ensuring the safe operation of production facilities.

Strong anti-interference ability: The DVS system has strong anti-interference ability against electromagnetic interference. In the vicinity of power facilities or industrial environments with strong electromagnetic interference, traditional vibration sensors may be affected by electromagnetic interference and affect measurement results, while DVS systems can work stably and accurately monitor vibration information.

3.3 Installation and application aspects

Easy and convenient installation: Monitoring can be achieved by laying the detection optical cable in the same trench or parallel along the pipeline, and the installation process is relatively simple. In the monitoring and investigation of communication resources, simply lay the optical fiber along the communication line and use the DVS system to monitor the vibration of the communication line, without the need for complex installation equipment and processes.
Suitable for various fields of application: It can be widely used in important places to prevent intrusion, important engineering to prevent damage, important resources to prevent theft, early warning of dangerous events, monitoring and troubleshooting of communication resources, and other fields. In dam safety monitoring, the DVS system can monitor the vibration of the dam under water flow impact, earthquakes, mo e ngaahi tūkunga kehé, and timely detect potential safety hazards; DVS can be used to prevent security threats such as illegal intrusion around important military facilities.

4、 The advantages of DAS sound waves

4.1 Measurement Characteristics

Broadband Dense Sampling: DAS (Distributed Acoustic Sensing) can densely sample seismic wavefield over a wide frequency band. For example, in geophysical exploration, DAS can obtain rich seismic wave information for the detection of underground structures. By analyzing this information, the geological structure and stratigraphic distribution of the underground can be more accurately inferred.
Can detect multiple sound wave signals: can detect real-time sound wave signals around the fiber optic cable at any position (up to 40kHz). In the monitoring of the acoustic vibration process of oil and shale gas fracturing, the acoustic signals generated during the fracturing process can be monitored in real time, thereby improving the effectiveness of fracturing and the response of the formation; In coal mines, one can hear sounds such as falling rocks, hitting walls, people walking, and speaking loudly, providing important sound information for emergency rescue.

4.2 Environmental adaptability and anti-interference aspects

Resistant to harsh environments such as high temperature and high pressure: In some special industrial environments or underground detection scenarios, such as oil wells, the underground is extremely quiet under normal conditions, but the environment is harsh. DAS systems can work normally under harsh conditions such as high temperature and high pressure, and monitor real-time acoustic vibrations at any position underground to monitor whether the casing leaks, oil-water stratification, and other geological structural changes occur underground.
Strong anti-interference ability: Due to its sensing principle based on the optical characteristics of optical fibers, there is no electrical signal, so it has strong anti-interference ability. In industrial environments near power facilities or with strong electromagnetic interference, DAS systems can stably perform acoustic monitoring without being affected by electromagnetic interference.

4.3 Multi functionality aspects

Simultaneous measurement of multiple physical quantities: DAS systems can not only measure acoustic signals, but also simultaneously measure physical quantities such as acoustics, mafana ʻo e ʻea, pressure, strain, and pore noise. In the field of pipeline transportation of resources such as water, oil, and natural gas, DAS systems can more accurately determine whether a pipeline leak has occurred, as well as the location and degree of the leak, by monitoring changes in various physical quantities such as sound waves, mafana ʻo e ʻea, and strain.
Equipment status monitoring and fault diagnosis: It can directly analyze the wear and tear, vibration frequency, operating speed, and lubrication of the equipment, further predict possible situations, and make decisions. In unmanned factories, power plants, nuclear power plants, ships, submarines, and other places, DAS systems can simultaneously monitor the sound of hundreds of motors, pumps, gearboxes, and bearing housings. Through artificial intelligence analysis, the operating performance, speed, oil shortage, wear and tear of each equipment can be determined, and potential faults of the equipment can be detected in a timely manner to ensure the safe operation of the equipment.