Table of Content

30 September 2021, Volume 39 Issue 5

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Optical Fiber Sensors Technology

Research Progress of Reconstructive Spectrum Analyzer

WAN Yangyang, FAN Xinyu, HE Zuyuan

2021, 39(5):  695-712.  doi:10.3969/j.issn.0255-8297.2021.05.001

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Spectrum measurement is widely used in the fields of scientific research and industrial production. Conventional spectrometers cannot meet the requirements of many applications due to their large volume. In recent years, reconstructive spectrum analyzer has become a research hot topic due to its compactness, high-resolution and wide-bandwidth. Owing to the one-to-one mapping relationship between the wavelength and the speckle generated from reconstructive spectrum analyzer, the unknown spectrum can be reconstructed from the generated speckle via appropriate demodulation algorithms. Spectral resolution in am-level and broad bandwidth of hundreds of nm can be achieved in reconstructive spectrum analyzers. This review introduces the recent development of reconstructive spectrum analyzers. The performances of various types of implementations are compared and analyzed, their applications are presented and future prospects are discussed.

Research Progress of Raman Distributed Optical Fiber Temperature Sensor

XU Yang, LI Jian, ZHANG Mingjiang

2021, 39(5):  713-732.  doi:10.3969/j.issn.0255-8297.2021.05.002

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Raman distributed optical fiber sensing technology can realize large-scale and high-precision temperature detection, and has a wide range of social needs and application prospects in the field of large-scale infrastructure structure health monitoring such as bridges, tunnels, oil and gas pipelines, and smart grids. This paper introduces the basic working principle of the Raman distributed optical fiber temperature sensor, reviews the current main researches in the performance improvement of distributed optical Raman sensors, including temperature measurement accuracy and spatial resolution. We also summarize the general applications of Raman distributed optical fiber sensors, furthermore, make a list of the representative application cases of the sensors in tunnel fire detection, pipeline leakage detection and solar panel temperature monitoring.

Review of Sensing Technology Research Based on Side Polished Fiber

ZHUO Linqing, TANG Jieyuan, ZHU Wenguo, ZHENG Huadan, LU Huihui, GUAN Heyuan, LUO Yunhan, ZHONG Yongchun, YU Jianhui, ZHANG Jun, CHEN Zhe

2021, 39(5):  733-746.  doi:10.3969/j.issn.0255-8297.2021.05.003

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With the development of optical fiber microfabrication technology, side polished fiber (SPF) has opened up a new era in fiber optic sensors. On the basis of ordinary communication fiber, the "leakage window" of the transmission light field is formed by completely or partially removing a length of fiber cladding. The light-matter interaction is used to excite, control, and detect the transmission light field in the fiber core to fabricate various sensors based on evanescent field. Optimizing the polishing parameters and guiding characteristics of the optical fiber is the key to realizing high-performance fiber optic sensors. The SPF has reliable mechanical properties, minimal insertion loss and polarization-dependent loss, making it a high-quality platform for research on the "lab on fiber". This article reviews the principle, classification, research progress, and application prospects of the SPF-based fiber optic sensors.

Review of Distributed Optical Fiber Sensing Technology and Application Based on Large-Scale Grating Array Fiber

GUI Xin, LI Zhengying, WANG Honghai, WANG Lixin, GUO Huiyong

2021, 39(5):  747-776.  doi:10.3969/j.issn.0255-8297.2021.05.004

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Fiber Bragg grating (FBG) sensing technology is widely used in the detection of temperature, strain and vibration in harsh environment, owing to its high sensitivity, anti-electromagnetic interference, small size and easy reuse. The realization of large-scale grating array fiber preparation method based on on-line fiber drawing tower breaks through the limitations of traditional distributed sensing technology of fiber grating due to mechanical strength and complex preparation process, which greatly expands its application in the field of distributed sensing. In this paper, the fabrication, distributed demodulation method and application progress of large-scale grating array fiber are systematically introduced. Firstly, the on-line fabrication technology and process of large-scale grating array fiber are introduced. Secondly, the distributed sensing demodulation technology including quasi-static wavelength demodulation technology, high-speed wavelength demodulation technology and enhanced dynamic phase demodulation technology are introduced, where some key technologies such as demodulation speed, spatial resolution, multiplexing capacity and sensing performance are especially focused on. At the same time, the applications based on large-scale grating array fiber are also introduced, including quasi-static applications of temperature and strain distribution and phase dynamic applications of vibration distribution, which can be widely applied in safety monitoring and fault diagnosis in large-scale construction, machinery, aerospace, petrochemical, and other engineering fields.

Detection Technology of Atomic Spin Precession

CHEN Dongying, YANG Yuanhong

2021, 39(5):  777-792.  doi:10.3969/j.issn.0255-8297.2021.05.005

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Spin is the intrinsic characteristic of atoms, which is sensitive to magnetic field or inertial rotation. Magnetic field or inertial rotation can be measured by detecting the spin precession of atoms, accordingly, atomic magnetometer, atomic gyro, and other atomic sensors are formed. Atomic sensing technology based on atomic spin-exchange relaxation free (SERF) states includes the preparation of atomic SERF states and the detection of atomic spin precession. The preparation of atomic SERF states is the premise to achieve high sensitivity, low noise, and high stability sensing, and the detection of atomic spin precession is the key to achieve high-performance measurement. In this paper, the principle of atomic precession and its detection method is briefly described first. For the spin precession detection of high-performance SERF atomic spin gyroscope and magnetometer, three types of atomic spin precession detection techniques and their characteristics are introduced, compared, and analyzed.

Research Progress on Demodulation Methods of Optical Fiber Fabry-Perot Sensor

DUAN Yanan, WANG Shuang, JIANG Junfeng, TAN Ke, LIU Tiegen

2021, 39(5):  793-808.  doi:10.3969/j.issn.0255-8297.2021.05.006

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Optical fiber Fabry-Perot sensor is a type of optical fiber sensors with the longest development history, the widest range of applications, and the most mature technology, and it has been widely used in many extremely complex environments. In Fabry-Perot sensors, accurate demodulation of sensing information of is the key to gain high-precision measurement. In this paper, first of all, the development history of optical fiber FabryPerot sensors is reviewed and commented. Then, the types and basic sensing principles of optical fiber Fabry-Perot sensors are introduced and the research progress of demodulation methods for optical fiber Fabry-Perot sensors is described. Also, intensity demodulation method, spectrum demodulation method and low-coherence interferometric demodulation method are introduced from two aspects of intensity demodulation and phase demodulation respectively. At last, the application characteristics of these demodulation methods are summarized, which could provide a reference for the future research and application of high-precision and fast demodulation of optical fiber Fabry-Perot sensors.

Review of Optofluidic Laser Based Biochemical Sensing

WANG Chaoqin, SONG Haoyue, YANG Xi, WANG Yanqiong, GONG Yuan

2021, 39(5):  809-820.  doi:10.3969/j.issn.0255-8297.2021.05.007

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Optofluidic laser has shown great potential in biochemical sensing. Here in this review, we systematically introduced the sensing mechanism and research progress of optofluidic laser based biochemical sensors. The gain medium regulated optofluidic laser sensing mainly depends on the quantity and state of gain molecules. When the biochemical reaction or molecules change the characteristics of microcavity, the resonance condition changes accordingly, and the change can be reflected and read out in the modes, wavelength and emission direction of lasing light. Furthermore, the biochemical molecules can introduce absorption loss and scattering loss in the laser cavity, causing measurable deterioration in laser intensity. Thanks to the amplification of lasing process and optical microcavity, and the narrow linewidth of laser, the laser output characteristics are ultrasensitive to the subtle changes of biochemical process to achieve high sensitivity and high-throughput biochemical sensing.

Research Progress of Optical Fiber Seismograph

ZHANG Wentao, LI Huicong, HUANG Wenzhu, LI Zhengbin, LI Li, LIU Ruifeng

2021, 39(5):  821-842.  doi:10.3969/j.issn.0255-8297.2021.05.008

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The optical fiber seismographs, whose sensing terminal and signal transmission link are free of electronic devices, have advantages of strong environmental adaptability and distributed networking observation, etc., and they are expected to provide new technical methods for seismic observation in deep wells, seafloor, volcanoes and other extreme environments with high density. However, there are still challenges in the design of vibration picking structure, the study of system transfer function, the suppression of noise level and the broadening of frequency band. This paper summarizes the basic principles, problems and typical cases of four types of optical fiber seismographs, including acceleration type, displacement type, strain type and rotation type. The advantages and disadvantages of the optical fiber seismographs are analyzed and discussed. And on this basis, the development prospect of optical fiber seismographs is discussed.

Review of Distributed Optical Fiber Sensing Technology

SHANG Ying, WANG Chang

2021, 39(5):  843-857.  doi:10.3969/j.issn.0255-8297.2021.05.009

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Distributed optical fiber sensing technology is an important part in the field of optical fiber sensing. Sensing fibers which integrate sensing and transmission functions enable long-distance and large-scale sensing and networking. Distributed optical fiber sensing technology can continuously sense the spatial distribution and change information of physical parameters such as temperature, strain, and vibration along the optical fiber. Sensing information of up to tens of thousands of points along the fiber can be obtained. This article reviews the current domestic and foreign developments of distributed optical fiber sensing technologies, especially focusing on the advantages and disadvantages of distributed sensing technologies based on Rayleigh backscattering and interference.

Fiber Devices Based on Eccentric Hole-Assisted Dual-Core Fiber and Applications

YANG Jing, JIN Yuan, YE Peng, GUAN Chunying

2021, 39(5):  858-880.  doi:10.3969/j.issn.0255-8297.2021.05.010

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As optical fiber sensors are keeping extending its application in new fields, they are facing with many new challenges at the same time. Currently, optical fiber sensors based on special optical fibers which enable outstanding performance have become a research hotspot. In this paper, the design of an eccentric hole-assisted dual-core fiber (EHADCF) is introduced, and on this basis, the working principles, fabrication methods and sensing characteristics of a variety of sensors based on hole-assisted dual-core fibers are discussed. In addition, a fiber mode convertor based on EHADCF is also introduced.