The principle and application of distributed fiber optic sensors-INNO

בשנים האחרונות, fiber optic sensing technology has developed rapidly and received increasing attention, gradually becoming another major fiber optic application technology industry after the development of fiber optic communication industry. ביניהם, distributed fiber optic sensing is currently one of the hot research topics both domestically and internationally.

Distributed fiber optic sensing measurement is a technology that utilizes the one-dimensional spatial continuity characteristics of optical fibers for measurement. Fiber optic serves as both a sensing element and a transmission element, allowing for continuous measurement of environmental parameters distributed along the entire length of the fiber, while obtaining the spatial distribution status and temporal information of the measured data. סיבים אופטיים מבוזרים sensing technology mainly includes optical time-domain reflection and frequency-domain reflection technology based on fiber Raman scattering or Brillouin scattering (R/B-OTDR/OFDR), polarized optical time-domain reflection technology based on fiber Rayleigh scattering (P-OTDR), long-distance optical interference technology, and quasi distributed fiber Bragg grating multiplexing technology.

Principles of חישת סיבים אופטיים מבוזרת טֶכנוֹלוֹגִיָה

Distributed Fiber Optic Sensing Technology Based on Backscattering

When light waves propagate in optical fibers, they generate backscattered light, including Rayleigh scattering, פיזור ראמאן, and Brillouin scattering. By detecting the backscattering generated by various points along the fiber optic cable, the relationship between the backscattered light and the measured (כגון טמפרטורה, לְהַדגִישׁ, רֶטֶט, וכו') can be used to achieve distributed fiber optic temperature sensing based on Raman scattering.

Measuring the anti Stokes Raman reflection signal in optical fibers can achieve distributed חישת טמפרטורה. Since the 1980s, מחקר מקיף נערך על טכנולוגיית מדידת תחום הזמן האופטית של אותות פיזור אנטי סטוקס ראמאן הן מקומיות והן בינלאומיות.

על ידי ניצול השפעת הטמפרטורה של פיזור לאחור של סיבים אופטיים, שדה הטמפרטורה בכל נקודה בחלל שבו נמצא הסיב מווסת את עוצמת האור נגד פיזור לאחור של סטוקס בסיב. השתקפות תחום הזמן האופטית (OTDR) הטכנולוגיה של הסיבים האופטיים משמשת לזיהוי ואיתור נקודות הטמפרטורה הנמדדות. לטכנולוגיה זו עקרון מדידה פשוט ועלות נמוכה יחסית. כַּיוֹם, זה יכול להשיג מרחק מדידה של מעל 10 ק"מ והוחל במידה מסוימת. אוּלָם, זה דורש עוצמה גבוהה, מקורות אור דופק קצר ומכשירי הגברה ורכישה של אותות במהירות גבוהה, and its temperature measurement accuracy and spatial resolution are limited by device performance and cost.

בשנים האחרונות, optical frequency domain reflection technology (OFDR) has also experienced rapid development. OFDR technology uses a power modulated continuous laser as the light source, so the backward Raman scattering power is nearly 2000 times higher than that of OTDR technology under the same incident conditions. Although the signal is modulated at high speed, the frequency band is narrow and easy to remove noise through filtering, which can greatly improve the signal-to-noise ratio of the sensing signal. It has greater advantages in spatial resolution, detection accuracy, and real-time performance.

Distributed fiber optic temperature/stress sensing based on Brillouin scattering

When using narrow linewidth continuous laser to pump single-mode fibers, Brillouin scattering is a major nonlinear effect. The scattering performance of Brillouin scattering can be described by the magnitude of the Brillouin scattering frequency shift, which is related to the phonon rate of the medium, and this rate depends on temperature and strain. Distributed fiber optic temperature and stress sensing can be achieved by obtaining temperature or stress information through spectral analysis and locating the parameter field distribution using pulsed light.

The distributed fiber optic sensing technology based on stimulated Brillouin scattering has high accuracy and spatial resolution for measuring single distributed parameters such as temperature and stress, and is the most promising and breakthrough technology developed in recent years. It generally adopts a Pump Probe structure, known as Brillouin optical time-domain analysis (BOTDA). כַּיוֹם, distributed fiber optic sensing technologies based on stimulated Brillouin scattering mainly include BOTDA based on pulse laser pumping, BOTDA based on correlated continuous waves, and BOTDA based on dark pulse laser pumping.

Distributed sensing based on polarized light time-domain reflection

Polarized time-domain reflection (POTDR) sensing is a novel sensing technology that achieves distributed fiber sensing by detecting changes in polarization state in optical fibers. POTDR technology is developed on the basis of OTDR technology, and its working principle is that the backward Rayleigh scattering light in the tested single-mode fiber contains additional information about the polarization state changing along the fiber. By coupling linearly polarized light into a fiber optic, Rayleigh scattering occurs when light pulses are transmitted in the fiber. During the scattering process, the polarization state of the light changes with the action of external parameters on the fiber, and the polarization of the light is a function of position. לָכֵן, by detecting the polarization characteristics of backscattered light, the temporal and spatial distribution of polarization characteristics in the fiber optic can be obtained, thereby obtaining the measured field distribution. Distributed fiber optic sensing technology has excellent measurement accuracy, אֲמִינוּת, and dynamic measurement characteristics, and is inherently safe and easy to lay in engineering. לָכֵן, it is widely used in civil engineering, תְעוּפָה, כּוֹחַ, פטרוכימי, medical and other fields.

1. Application in Civil Engineering Structures

Distributed fiber optic sensing technology is widely used in safety detection of civil engineering structures such as bridges, rock deformation measurement, road and site measurement, and perimeter security monitoring. It can provide important data for monitoring the speed, load capacity, and type of transportation vehicles. The measurement accuracy of this type of sensor can reach several microstrain levels, with good reliability, and can achieve dynamic measurement. By using distributed embedding, it can also monitor the health status of the entire building, thereby preventing the occurrence of engineering and traffic accidents.

2. Applications in the aerospace field

In the field of aerospace, flight safety is a highly concerned aspect. Fiber optic sensors have the advantages of small size, משקל קל, and high sensitivity. Distributed fiber optic sensing technology was successfully used for non-destructive testing in the aerospace field as early as 1988. Embedding fiber optic sensors into aircraft or launch tower structures to form a distributed intelligent sensing network can enable real-time monitoring of the internal mechanical performance and external environment of the aircraft and launch tower. Boeing has conducted a lot of research in this area. כַּיוֹם, distributed fiber optic sensing technology can be used to achieve strain and displacement monitoring at aircraft wings, wings, stabilizer shafts, support rods, and other locations, כמו גם מדידה מקוונת בזמן אמת של טמפרטורות הפעלה בנקודות חיבור כגון מנועים ומעגלים.

3. יישומים בענף בניית ספינות

טכנולוגיית חישה סיבים אופטיים נמצאת בשימוש נרחב גם בתעשיית בניית הספינות, כגון ניטור מתח בעמדות קריטיות של הספינה, הערכת נזקים, והתרעה מוקדמת בתנאי עומס יתר. פגמים מבניים באוניות משפיעים לרוב על ביצועי הבטיחות שלהן. מערכת ניטור בריאות מבנית בקנה מידה גדול המבוססת על טכנולוגיית חישת סיבים אופטיים מבוזרת יכולה לנטר את מצב הבריאות של הספינה בזמן אמת, ובכך למנוע התרחשות תאונות. יישום בקנה מידה גדול של טכנולוגיית חישה סיבים אופטיים לזיהוי בזמן אמת של נזק בספינות ובצוללות.

4. יישומים בתעשיית החשמל

The rapid expansion of the power grid and the continuous improvement of voltage levels have put forward higher requirements for the reliability and safe operation of power equipment. אוּלָם, high-voltage detection technology cannot keep up with the development of the situation, and conventional detection equipment can no longer meet the current needs. כַּיוֹם, distributed fiber optic sensors are an ideal detection technology and have important applications in the safety monitoring of high-voltage power systems. לְדוּגמָה, it can be used for monitoring cable temperature and cable conductor current carrying capacity. חיישני טמפרטורה בסיבים אופטיים can be used to monitor the surface temperature of long-distance transmission lines in real time, calculate the allowable load and current carrying capacity of conductor temperature, and provide comprehensive and effective solutions for fault monitoring and load management of transmission lines, ensuring the safety of transmission lines, improving asset utilization, discovering potential faults, and achieving preventive maintenance.

5. Applications in the petrochemical industry

Leakage is the main fault in the operation of oil pipelines, often resulting in huge losses. לָכֵן, oil pipeline leakage detection is an important issue that urgently needs to be solved in the petroleum industry. By using sensors installed near pipelines, pressure and vibration signals generated by incidents such as leaks, nearby mechanical construction, and human damage can be picked up. יֶתֶר עַל כֵּן, pipeline leaks can be detected and located through sensing related technologies. Distributed fiber optic sensing technology is very suitable for long-distance pipeline leakage detection due to its ability to obtain continuous spatial and temporal distribution information of the measured physical field. בנוסף, חישה מבוזרת של סיבים אופטיים technology can also be used to monitor the strain and bending status of high-pressure pipelines in real time.

6. Applications in Medicine

Fiber optic sensors are soft, קוֹמפָּקטִי, with high degrees of freedom, בִּדוּד, and are not affected by radio frequency and microwave interference, with high measurement accuracy. They have obvious advantages in medical applications, such as detecting human blood vessels, human surgical correction, and ultrasonic field measurement. Fiber optic endoscopy makes it feasible to examine almost all parts of the human body, and the operation does not cause pain or discomfort to patients. ביניהם, fiber optic vascular endoscopy has been applied in human cardiac catheterization. Fiber optic endoscopy is not only used for diagnosis, but is also currently entering the field of treatment, such as polypectomy surgery. Microwave heating treatment technology is currently an effective way of treatment, but the temperature of microwave heating treatment technology is difficult to grasp, ו חיישני טמפרטורה בסיבים אופטיים can precisely monitor the effective temperature of microwave heating treatment technology. The research and application of fiber optic temperature sensors in cancer treatment are increasingly emerging.