In the previous article "Development Route of Fiber Optic Sensing Technology in China: Current Status of Key Technology Development", we introduced the development paths of several key technologies in fiber optic sensing, including special optical fibersFBG, fiber optic gyroscope, fiber optic hydrophone, distributed Brillouin fiber Ф-OTDR、OFDRElaborate on the current development status and problems faced by these types of technologies. Today, let's take a look at the application of fiber optic sensing technology in product applications such as gas sensing, three-dimensional shape sensing, coal mine safety monitoring, oil and gas underground measurement, and ocean development applications. Application of Fiber Optic Sensing Technology in Several Typical Fields 1Fiber optic gas sensing technology The development of aerospace, navigation, energy, food hygiene, environmental protection, medicine and other fields has put forward increasingly high requirements for gas detection capabilities. The commonly used gas detection technologies currently include gas chromatography/Mass spectrometry analysis, electrochemistry, photoionization detection, etc. are difficult to meet the growing demand in terms of measurement accuracy, dynamic range, gas type, cost, volume, online or remote measurement, etc. The traditional spectroscopy gas sensor is composed of discrete optical elements, and uses the space gas chamber as the sensing unit, which has a large volume and is difficult to align. Laser spectroscopy technology has the advantages of good selectivity and no need for labeling. In particular, micro/nano structured fiber has good flexibility, which can realize long-distance interaction between light and gas in the fiber and maintain a compact gas chamber structure. Micro/nano structured fiber has strong binding to the light field, small mode field size, high energy density, and high overlap with the sample, which can enhance the nonlinear interaction between light and gas and improve the detection sensitivity. The use of micro/nano optical fiber itself as the gas chamber sensing unit simplifies the alignment and link between optical paths, helps to promote the development of spectroscopy measurement technology to the practical direction, and facilitates the realization of remote detection. By utilizing the optical mode, acoustic mode, and thermal conductivity characteristics of micro/nano fibers themselves, a new type of highly sensitive gas sensor can be achieved. The sensing fiber can be a hollow photon belt gap fiber, a hollow anti resonance fiber or a micro nano core fiber. According to measurement needs, the working wavelength can be selected from ultraviolet, visible light, or infrared bands. The report of the first application of micro/nano structured optical fiber for gas measurement can be traced back to2001Year. The first research used solid core micro structure fiber, followed by hollow core fiber. Over the past two decades, researchers have made remarkable progress in the design and fabrication of fiber optic gas chambers, improved response speed, new detection methods, noise suppression, improved sensitivity, increased dynamic range, improved system stability, and practicality, as shown in the table below1。 surface1 Development of micro/nano structure optical fiber gas sensing technology
At present, under the laboratory conditions, micro/nano structure optical fiber gas sensors have realized the(Such as methane, ethane, acetylene, ammonia, carbon monoxide, carbon dioxide, etc)The measurement has reached sensitivity10-6to 10-12magnitude. The following main issues still need to be addressed for practical applications in different fields:
2Fiber optic 3D shape sensing technology If you want to track a dynamic object, shape perception becomes particularly crucial in the absence of visual contact. In recent years, sensing methods based on fiber shape have received widespread attention from both academia and industry. Fiber optic shape sensors provide a very effective alternative to traditional shape perception, allowing for continuous, dynamic, and direct tracking of shapes without the need for visual contact. Fiber optic sensors have the characteristics of compact structure, small size, strong flexibility, and strong embedding ability, which can be well attached to the monitored object, while ensuring the convenience of installation and the effectiveness of shape tracking. These advantages make it widely applicable in fields such as healthcare, energy, national defense, aerospace, structural safety monitoring, and other intelligent structures. chart1It is a key component of a domestically produced four core fiber optic 3D shape sensing system.
In practical applications, such as large-scale three-dimensional shape sensing scenarios such as oil pipelines and bridge structures, it is suitable to combine multiple single core optical fibers with the object to be measured, and use Brillouin optical time-domain reflection technology to monitor its shape changes; For medium or small-scale application scenarios, such as robots, flexible medical devices, etc., multi-core fiber optic arrays are suitable for useFBGDemodulation technology or distributedOFDRThe method of curvature integration and shape reconstruction is used to achieve high-precision 3D shape sensing. Among them, this technology has the most potential for development in the medical field. There are two development ideas for fiber optic 3D shape sensing technology: firstly, using multi-core optical fibers; The second is to achieve three-dimensional shape sensing by combining multiple single core optical fibers with cylindrical structures. The discussion here is mainly based on the first approach. surface2Outline the development of three-dimensional shape sensing technology based on multi-core optical fibers. surface2 Summary of the Development of Multi core Fiber Optic 3D Shape Sensing Technology
After nearly two decades of rapid development, the fiber optic three-dimensional shape sensing technology has enabled all key components involved in this technology to be domestically produced, approaching the level of practical application. Several domestic units have successively conducted relevant research. The multi core fiber grating based 3D shape sensing system developed by Guilin University of Electronic Science and Technology has dynamic 3D shape sensing capabilities, providing various key technologies for engineering applications. In recent years, it has gradually been applied in several fields, and the main problems it faces are:
3Coal Mine Fiber Optic Sensing Technology Fiber optic sensors do not require power supply and have unique advantages for monitoring flammable and explosive gases underground in coal mines, as well as online monitoring of deformation and rock stress in long-distance multi-point tunnels. In the past two decades, semiconductor laser methane sensors (as shown in the figure)2）There has been a lot of research and development on engineering technology for coal mine applications, ranging from laboratory principle verification to engineering prototypes, and then to recent developments10The large-scale application of ten thousand fiber optic sensors in over a thousand coal mines. Laser methane sensors have unique advantages such as full range, calibration free, high selectivity, and long-term stability and reliability, and have been widely recognized in the coal mining industry, gradually replacing traditional catalytic combustion methane sensors.2016year12At the end of the month, the former State Administration of Coal Mine Safety Supervision clearly stated in the "Technical Plan for Upgrading the Coal Mine Safety Monitoring System" that it is recommended to use advanced sensors, including laser methane sensors with full range, low power consumption, and self diagnosis functions. This marks the official commercialization of laser methane sensors.
In addition, the fiber optic distributed temperature sensor based on Raman scattering principle and multimode optical fiber has demonstrated a unique role in online monitoring and early warning positioning of spontaneous combustion hazards in coal mine goaf, solving the problem of blind spots in detection of electronic sensors for goaf fire hazards. This type of sensor has undergone an upgrade process from explosion-proof and intrinsic safety to low-power intrinsic safety mining instruments, It has been applied in monitoring and warning of fire hazards in goafs and belt transportation systems in hundreds of coal mines across the country. Based on laser/Methane in optical fibersCOVarious gas sensors, such as temperature, displacement, strain, pressure, wind speed sensors based on fiber Bragg gratings, and fiber optic distributed temperature, strain, vibration, and gas sensors, will have a very broad development space in the increasingly emerging intelligent mining construction. With the development of mid infrared semiconductor laser technology, coal mine fire monitoring and warning technology is expected to achieve breakthroughs during the 14th Five Year Plan period. The next research and breakthrough focuses on the adaptability of optical fiber distributed vibration, optical fiber wind speed, optical fiber dust sensors, optical fiber current and voltage sensors under the conditions of high humidity, dust and strong mechanical shock in the coal mine. 4Oil and Gas Fiber Optic Sensing Technology Fiber optic sensing technology has been widely applied in foreign oil companies and is a relatively mature technology. With the rapid development in recent years, domestic oil field companies have increased their efforts to promote the marketization of this technology, and currently the technology has achieved industrial development scale. At present, fiber optic sensing technology has been widely applied in various fields of oilfield logging, used to monitor downhole temperature, pressure, sound waves, flow rate, etc., which can effectively analyze the utilization of oilfield reservoirs and guide the design and adjustment of oil and gas development plans. Fiber optic distributed temperature sensing based on Raman scattering(DTS)Technology:DTSIt was first applied to monitor wellbore temperature in heavy oil thermal recovery wells, and rich temperature data can help oilfield operators have a clearer understanding of reservoir blocks to achieve effective development. Traditional temperature sensors can only detect the temperature at the discontinuity point within a certain period of time; And the fiber optic distributed temperature sensing technology can achieve continuous and long-term temperature monitoring throughout the entire well, thus better tracking the situation of underground temperature profiles, as shown in the figure3。 However, the downhole temperature of typical heavy oil wells is as high as260℃~300℃ and the presence of hydrogen containing layers greatly shortens the service life of optical fibers in this environment, making it impossible to achieve full lifecycle monitoring of the target well. Therefore, increasing the research and testing efforts of high-temperature hydrogen resistant optical fibers and striving for breakthroughs in key technologies is an urgent issue.
Fiber Fabry-Perot cavity pressure measurement technology(PT)According to fiber optic Fabry-The principle that the length of the Perot cavity changes with the change of external pressure is used to monitor the pressure in oil wells. This method has the advantages of strong anti-interference ability, high safety, and long-term stability, and is widely used in underground monitoring. Its application scenarios are shown in the figure below4As shown in. However, the processing technology of underground pressure sensors requires high requirements and low reliability. In high-temperature and hydrogen containing environments underground, the sensor life is short; And there are mode jumps caused by inaccurate models in the demodulation algorithm.
DASTechnology: Based on Φ-OTDRThe principle of measuring vibration in spatial distributionDASTechnology is the most cutting-edge technology in the field of fiber optic logging in recent years. To achieve the best monitoring effect, it is necessary to lay the optical fiber outside the casing of the oil and gas well and directly contact the formation, but the construction is difficult. In addition, it is necessary to further improve the performance of low-frequency or even ultra-low frequency signal acquisition, and face the problems of large data volume and complex algorithms in data preprocessing, noise reduction, and artificial intelligence feature extraction; And the problem of weak acoustic signals and low signal-to-noise ratio in the production process of oil and gas wells. 5Fiber optic multi parameter sensing technology for marine exploration and monitoring In recent years, the optical fiber sensing technology for ocean exploration and monitoring has received widespread attention from academia and industry, and has received in-depth research from many scholars both domestically and internationally, achieving fruitful research results. The developed sensors, such as ocean optical fiber temperature sensor, salinity sensor, depth sensor, ocean optical fiber oil pollution sensor, optical fiber hydrophone, ocean optical fiber velocity and direction sensor, ocean wind power optical fiber magnetic field sensor and optical fiber seismic sensor, provide technical and equipment support for understanding, understanding and managing the ocean. The ocean optical fiber sensing technology for various parameters has undergone rapid development in the past decade, and its sensing structure and key components have been able to achieve full localization, approaching the level of practical application. In recent years, it has gradually entered several application fields, and the main problems it faces are:
Vision for the Development of Fiber Optic Sensing Technology in China With the development of fiber optic sensing technology in China, the mode of talent cultivation in various universities is also slowly changing. This is because demand drives academic technology, while the market drives technological engineering. In this era of rapid changes in information technology, there are few opportunities to have more time to allow talent to slowly develop and follow the pace of rapid changes in information technology. How to meet the diverse needs of the talent market? How to respond to rapidly developing and changing related industries? These issues pose new challenges to the talent cultivation methods of various universities. Starting from the logic of the market, demand drives market expansion, and the market drives technological progress. In terms of fiber optic sensing technology, if a particular sensing technology is useful, it can receive more in-depth research and market investment, and the technology itself can achieve faster development and progress. The maturity of fiber optic sensing technology is accompanied by the maturity of fiber optic communication technology, but it is opposite to the market situation of fiber optic communication. The fiber optic sensing market is not only segmented by various demands and diverse application scenarios, but also by supporting technologies that can meet various applications. This reality hinders the scale of capital investment and objectively restricts the development of fiber optic sensing technology. Until today, China's fiber optic sensing technology is in a period of rapid development and coincides with the active period of China's financial market. On the one hand, segmented markets promote the rise of industrial level backbone enterprises, in order to achieve the integration of segmented markets and complete the supply of key materials and devices with high reliability, low cost, and scale in the basic layer. These supplies include three aspects: 1) Provide special sensing optical fibers and cables suitable for specific application scenarios; 2) Provide special optical fiber devices that are compatible with special sensing optical fibers; 3) Provide industrial grade high reliability, low-cost specialized optoelectronic signal integrated processing chips or processing modules. On the other hand, the diversity of the market has also promoted the development of various industry enterprises that can meet the segmented market demands of the application end. They are active engineering application oriented enterprises in various application terminals and can deeply and closely integrate with various traditional application fields. The demand for industrial level backbone enterprises in the basic device layer is small but precise, while the demand for application end engineering technology enterprises is large but strong. Through the division of labor and cooperation between these two types of enterprises, as well as the continuous increase in investment in venture capital in the technology market, the high-speed development of various links in China's fiber optic sensing industry chain has come for a long time. The author of this article Yuan Libo1,Tong Weijun2,Jiangshan3,Yang Yuanhong4,Mengzhou5,Dong Yongkang6,Raoyunjiang7, He Zuyuan8,Jin Wei9,Liu Tongyu10,Zou Qilin11,Bi Weihong12 1Photonics Research Center, College of Electronic Engineering and Automation, Guilin University of Electronic Science and Technology 2State Key Laboratory of Optical Fiber and Cable Preparation Technology of Changfei Optical Fiber and Cable Co., Ltd 3Wuhan Science and Technology Optoelectronics Co., Ltd 4School of Instrument Science and Optoelectronic Engineering, Beijing University of Aeronautics and Astronautics 5School of Meteorology and Oceanography, National University of Defense Technology 6State Key Laboratory of tunable laser Technology, Harbin Institute of Technology 7Fiber Optics Research Center, Key Laboratory of Fiber Sensing and Communication, Ministry of Education, School of Information and Communication Engineering, University of Electronic Science and Technology 8State Key Laboratory of Regional Optical Fiber Communication Network and New Optical Communication System of Shanghai Jiaotong University 9Department of Electrical Engineering, Hong Kong Polytechnic University 10Shandong Key Laboratory of Fiber Optic Sensing Technology,Qilu University of Technology(Shandong Academy of Sciences)Laser Research Institute of Shandong Academy of Sciences 11Beijing Perception Technology Co., Ltd 12School of Information Science and Engineering, Yanshan University,Key Laboratory of Special Fiber Optic and Fiber Optic Sensing in Hebei Province This article is adapted from the article "Roadmap for the Development of Fiber Optic Sensing Technology in China" published in the Journal of Optics. We would like to express our special gratitude to Professor Yang Yuanhong for his guidance on this article |
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