Acta Optica Sinica, Volume. 44, Issue 1, 0106001(2024)
Current Status and Future of Research and Applications for Distributed Fiber Optic Sensing Technology
Figures & Tables(51)
Fig. 6. Typical structure of ROTDR system (FUT: fiber under test; APD: avalanche photo diode; SpRS: spontaneous Raman scattering; WDM: wavelength division multiplexing)
Fig. 10. Schematic diagrams of loop SI and in-line SI. (a) Schematic diagram of loop SI; (b) schematic diagram of in-line SI
Fig. 12. Schematic diagram of distributed fiber optic sensing monitoring technology for coal mine geosafety
Fig. 13. Fiber optic monitoring, sound amplitude logging, and downhole TV results of borehole deformation damage process during grouting
Fig. 14. Schematic diagram of multi-field coupling and monitoring of geologic bodies[203]
Fig. 15. OptoSeisTM subsea permanent reservoir monitoring system layout and operation
Fig. 16. Surface 3D seismic data pre-stack depth migration (PSDM) imaging, underground three-component geophone array Walkaway VSP imaging, Walkaway DAS-VSP imaging, and corresponding amplitude spectra. (a) Surface 3D seismic data PSDM imaging and corresponding amplitude spectrum; (b) underground three-component geophone array Walkaway VSP imaging and corresponding amplitude spectrum; (c) Walkaway DAS-VSP imaging and corresponding amplitude spectrum
Fig. 17. Application diagram of distributed fiber optic sensing technology in transportation field
Fig. 18. Tunnel optical cable laying scheme and two-dimensional visualization data of temperature field[209]
Fig. 19. Train approaching construction personnel warning system schematic (top left image), and recognition results of the 63 km rail section from Mingguang to Chuzhou on the Beijing-Shanghai Line (top right and bottom images)
Fig. 24. Applications of perimeter security monitoring. (a) Cable laying; (b) human intrusion; (c) monitoring interface and results
Fig. 26. Typical setup for OTDR measurement on hollow-core fibers, OTDR measurement curves for anti-resonant hollow-core fibers,and sketch of flying particle distributed fiber sensor in hollow-core fibers. (a) Typical setup for OTDR measurement on hollow-core fibers[308]; (b) OTDR measurement curves for anti-resonant hollow-core fibers[309]; (c) sketch of flying particle distributed fiber sensor in hollow-core fibers
Fig. 27. Typical techniques and applications of machine learning in field of distributed optical fiber sensing
Fig. 28. Correlation analysis of optical fiber sensing signals and feature parameters of monitored structure
Fig. 29. Technical flow of intelligent characterization on physical state of monitored structure
Fig. 30. System configuration of double-digital comb based high spatial resolution Φ-OTDR[407]
Fig. 31. Earthquake detection experimental setup using submarine optical fiber cable[429]
Fig. 34. Integrated sensing and communication system in single optical fiber[445]
Fig. 35. Applications of fiber shape sensors. (a) Flexible wearable instrument based on optical fiber shape sensor; (b) soft robot based on optical fiber shape sensor; (c) fiber shape sensor in flexible instrument for intravascular navigation; (d) optical fiber sensor for wing shape sensing
Table 1. Summary of advanced BOTDR/BOTDA techniques
View tableTable 1. Summary of advanced BOTDR/BOTDA techniques
Type Technical principle Performance Ref. No High spatial resolution Pulse pre-pump 5 cm@0.35 MHz@0.2 km
10 cm@0.35 MHz@1 km
［ 45 -46 ］Differential pulse-width pair 5 cm@50 m ［ 47 ］Long sensing distance Distributed Raman/Brillouin amplifier 8 m@2.06 MHz@175 km ［ 48 -51 ］Optical pulse coding 1 m@2.2 MHz@100.28 km ［ 52 -55 ］High measurement accuracy — 2.5 m@0.55 MHz@62.3 km ［ 56 -58 ］Dynamic measurement Fast Fourier transform/short-time Fourier transform 2 m@10 km ［ 59 -60 ］Slope-assisted techniques 2.5 m@2 km ［ 61 -63 ］Frequency-agility modulation 1 m@30 m ［ 64 -65 ］Optical frequency comb 12.5 m@10 km ［ 66 -68 ］Multi-parameter measurement Specialty optical fiber 2 m@0.2 °C/9.7 µε@19.38 km ［ 69 -72 ］
Table 2. Summary of ROTDR manufacturers and their performance
View tableTable 2. Summary of ROTDR manufacturers and their performance
Company Sensing range /
km
Spatial resolution /m Temperature resolution /℃ Time /s Link AP Sensing 8 ≥1 0.5 — https://www.apsensing.com/ SensorTran/Halliburton 5-15 1-2 0.1-1.8 100 https://www.halliburton.com/ IFOS 5 1（3 km） 1 ≥120 https://www.ifos.com/ LUNA/ LIOS 10 — 1 — https://lios.lunainc.com/ Schlumberger 4 <1.2 0.1 30 https://www.slb.com/ Sensornet/Nova Metrix 15-45 1-5 2.25-2.75 10 https://www.novavg.com/platforms/nova metrix/ Silixa 10-35 — 0.01-0.1 ≥1 https://silixa.com/ Weatherford 5-20 1.2 2.3（9760 m） 40 https://www.weatherford.com/ Yokogawa Electric 6-50 ≤1 0.02-2.6 — https://www.yokogawa.com/ Optromix 16 0.5-4 — ≥10 https://optromix.com/ Hangzhou Sensys Photonics 4-16 0.5-3 0.2 1-10 http://www.hzsensys.com/ Zhejiang ZhenDong 2.5-16 0.5 0.2 <2 https://www.zdong.net/ Bandweaver 2-40 1-5 0.1-1 240-600 http://www.bandweaver.cn/index.php AGIOE 2-30 1-5 — 1-30 http://www.agioe.com/ Brillouin ε 10 0.5-2 0.1 2.5 http://www.buliyuan.com/ WUTOS 10 1 2 1 http://www.wutos.com/
Table 3. Summary of OFDR sensing performance improvement methods
View tableTable 3. Summary of OFDR sensing performance improvement methods
Methods Performance Nonlinear phase noise compensation methods Hardware compensation［ 105 ］Sensing distance：35 m；spatial resolution：22 μm Resampling method［ 107 ］Sensing distance：300 m；spatial resolution：0.3 mm Concatenately generated phase method［ 112 ］Sensing distance：40 km；spatial resolution：5 cm Deskew filter method［ 109 ］Sensing distance：80 km；spatial resolution：1.6 m Increasing sensing distance methods Highly linear swept fiber laser source［ 128 ］Sensing distance：200 km Phase noise term detection［ 129 ］Sensing distance：170 km Optical fiber delay loop compensation［ 130 ］Sensing distance：30 km Improving strain/temperature range methods Local spectral matching method［ 119 ］Maximum strain：3000 με Machine learning prediction［ 117 ］Maximum strain：2900 με Wavelet transform and Gaussian filtering［ 144 ］Maximum strain：7000 µε Differential phase phase accumulation［ 132 ］Maximum strain：3700 µε Femtosecond optical fiber grating［ 145 ］Maximum temperature：1000 ℃ Annealed zirconia doped fiber［ 146 ］Maximum temperature：800 ℃ Improving sensing resolution methods Complex domain denoising［ 121 ］Sensing resolution：0.89 mm Position offset compensation algorithm［ 103 ］Sensing resolution：0.5 mm Total variational method and two-dimensional Gaussian filtering［ 136 ］Sensing resolution：0.4 mm Improving dynamic measurement range methods Time-frequency-multiplexing［ 141 ］Maximum vibration frequency：33 kHz Phase demodulation algorithm［ 116 ］Maximum vibration frequency：100 Hz Compressed sensing［ 145 ］Maximum vibration frequency：40 Hz Time-gated digital OFDR［ 143 ］Maximum vibration frequency：600 Hz
Table 4. Overview of pipeline monitoring based on DOFS and its applications
View tableTable 4. Overview of pipeline monitoring based on DOFS and its applications
Parameter Techniques Applications Acoustic signal Φ-OTDR［ 214 -217 ］Threat detection and identification，micro-flow，flow Vibration Sagnac interferometer［ 218 ］，Mach-Zehnder interferometer［219 ］Leak detection，pipeline pre-warning，intrusion detection Temperature ROTDR［ 220 ］，BOTDR［221 ］，BOTDA［222 ］Leakage location，micro-leakages，leak flow rate Strain BOTDR［ 223 ］，BOTDA［222 ］，OFDR［223 ］Buckling of pipeline，leakage of pipelines，pipeline corrosion and leakage
Table 5. Typical application scenarios and key indicators of distributed optical fiber sensing in aeronautic and aerospace fields
View tableTable 5. Typical application scenarios and key indicators of distributed optical fiber sensing in aeronautic and aerospace fields
Applications Specific scenarios Measured & derived parameters Types of DOFS and their indicators Resources Ground test and flight demonstration verification of civil aircraft Flight verification of MU-300（climb，descend，and turn） Measured：temperature and strain BOCDA；indicators：spatial resolution of 30 mm and dynamic strain sampling rate of 27.8 Hz Mitsubishi Heavy Industries，Ltd.（2014）［ 225 ］Composite head and wing box of airplane（landing，pressuring，and maneuvering） Measured：temperature and strain；
derived：disbond and impact
R-OFDR；indicators：spatial resolution of 5 mm/10 m Airbus Defense and Space
National Aerospace Laboratory of India［
229 ］Manufacturing of composite structures Measured：temperature and strain；
derived：pressure
R-OFDR；indicators：spatial resolution of 2.6 mm，600 points，and sampling rate of 10 Hz Imperial College London（2022） BOTDR and OTDR；optical fiber sensor embedded inside the composite laminate The University of Tokyo（2012） Rocket component test Cryogenic pressurization test of rocket fuel tanks Measured：temperature and strain OTDR；indicators：spatial resolution of 10 mm and strain sampling rate of 20 Hz Xiamen University（2022）［ 234 ］Liquid rocket engines Measured：temperature and strain；
derived：heat flux and pressure
3D printed integrated distributed sensors with OFDR；indicators：temperature range of -191-70 ℃，measurement accuracy of 3.6%-7.1%，and pressure range of 0-20.7 MPa NASA and Luna（2020）［ 224 ］Smart sensing of spacecraft Inflatable space habitats Measured：strain OTDR NASA and Luna（2020）［ 230 ］Deformation reconstruction and shape sensing Measured：strain；
derived：displacement and distortion
OTDR Italy and NASA，Dalian University of Technology
（2021）［
235 ］
Table 6. Recent advances of hybrid distributed optical fiber sensing systems
View tableTable 6. Recent advances of hybrid distributed optical fiber sensing systems
Classification Sub-system combination Method for scattering light seperation Method for performance enhancement Fiber end access Year Combining Rayleigh and Brillouin scattering POTDR/BOTDR［ 244 ］Polarization switch - Single 2013 Φ-OTDR/BOTDR［ 245 ］Optical switch Pulse modulation Single 2016 FS-Φ-OTDR/BOTDA［ 247 ］FBG Frequency-agile pulses Double 2020 Φ-OTDR/BOTDA［ 249 ］Space division multiplexing - Double 2017 Φ-OTDR/BOTDA［ 250 ］Wavelength division multiplexing Distributed amplification technique Double 2018 Φ-OTDR/BOTDR［ 251 ］Frequency division multiplexing Double heterodyne detection Single 2022 TW-COTDR/BOTDA［ 253 ］Not mentioned Improved data processing Double 2014 COTDR/BOTDR［ 254 ］Frequency division multiplexing Coherent fading reduction Single 2021 FS-OTDR/BOTDA［ 268 ］Wavelength division multiplexing Enhanced slope-assisted method Double 2023 Φ-OTDR/single-end BOTDA［ 246 ］Rayleigh backscattering as probe of BOTDA Average Single 2023 Combining Rayleigh and Raman scattering Φ-OTDR/ROTDR［ 256 ］Raman filter Cyclic Simplex coding Single 2016 Φ-OTDR/ROTDR［ 257 ］Wavelength division multiplexing Heterodyne detection Single 2018 Φ-OTDR/ROTDR［ 258 ］Space division multiplexing Wavelet transform denoising method Single 2018 Combining Brillouin and Raman scattering BOTDR/ROTDR［ 269 ］Wavelength division multiplexing - Single 2004 BOTDA/ROTDR［ 260 ］Raman filter Cyclic Simplex coding Double 2013 BOTDR/ROTDR［ 261 ］Space division multiplexing - Single 2016 Combining Rayleigh Brillouin and Raman scattering Φ-OTDR/single-end BOTDA/ROTDR［ 262 ］Raman filter Simplex coding Single 2023
Table 7. Enhancement factor G, fiber loss α, and application systems of different optical fiber types of continuous scattering enhancement
View tableTable 7. Enhancement factor G, fiber loss α, and application systems of different optical fiber types of continuous scattering enhancement
Fiber type G /dB α /（dB/km） Application system Ref. No Continous FBG 14 0.4 DAS ［ 270 ］Ge/B-doped fiber 10 >20000 OFDR ［ 272 ］Er-doped fiber - - DAS ［ 272 ］High-NA photonic crystal fiber 12 3 DTS/DAS ［ 273 ］
Table 8. Several typical structures of temperature sensing optical cables
View tableTable 8. Several typical structures of temperature sensing optical cables
Sensing cables Technical characteristics Ref. No Highly thermal conductivity temperature sensing optical cables Coated with a highly thermal conductivity composite material，i.e.，graphene for fast temperature sensing ［ 322 ］Highly thermal conductivity temperature sensing optical cable Equipped with a highly thermal conductivity composite material jacket and tight cladding ［ 323 ］High temperature resistant measuring optical cable Polyimide high temperature optical fiber is used，the middle is reinforced by Kevlar，and the outer sheath is protected by a layer of polytetrafluoroethylene ［ 324 ］Multi-core armored high-temperature resistant optical cable Adopting a spiral armored tube and aramid braided structure，the working temperature range is -55-150 ℃. Preparation using high-temperature resistant engineering materials such as fluoroplastics ［ 325 ］High strength steel wire armored temperature sensing optical cable Outer double steel wire twisted，sealed design，resistant to electrochemical corrosion，water and oil resistance，working temperature is -40-85 ℃ ［ 326 ］
Table 9. Typical strain sensing optical cables
View tableTable 9. Typical strain sensing optical cables
Sensing cables Technical characteristics Ref. No Sensing fiber optic cable for distributed fiber optic strain measurement Strengthen the protection of optical fibers through the design of equalizing fillers，and use equalizing fillers to evenly distribute the pressure at points ［ 327 ］Metal based cable Metal based cable structure，optical fiber wrapped with metal reinforcement，thread structure based sensor surface ［ 194 ］Tightly sheathed sensing optical cable Elastic modulus is small and should not be excessively stretched during the laying process ［ 194 ］Fiber reinforced multi-core strain sensing optical cable Using glass fiber reinforced plastic（GFRP）reinforcement for protection，the overall elastic modulus is equivalent to that of concrete，and the strain transmission is good ［ 194 ］
Table 10. Typical vibration sensing optical cables
View tableTable 10. Typical vibration sensing optical cables
Sensing cables Technical characteristics Ref. No Variable winding pitch sensing optical cable Fiber optic unit is wound around the center reinforcement to change the winding pitch and continuously spiral wound for placement ［ 328 ］Flexible sensing cables Cables are designed and made with different reinforcement materials and structures. They have shown advantages such as small diameter，light weight，and flexibility while sensitivity being enhanced ［ 329 ］Vibration sensing cables Inner wall of the outer sheath is fixedly connected with a wrapping tape，a reinforcing layer，a central bundle tube，and a colored optical fiber. The outer part of the colored optical fiber and the inner part of the central bundle tube are filled with ointment ［ 330 ］YOFC vibration sensing cables Good flexibility，convenient construction of S-shaped laying，and good vibration sensitivity ［ 331 ］AP SENSING vibration sensing cables Including metal tubes，non-metallic，sleeved or armored stainless steel ［ 332 ］
Table 11. Intelligent signal processing methods and technical status at home and abroad of dynamic measurement DOFS
View tableTable 11. Intelligent signal processing methods and technical status at home and abroad of dynamic measurement DOFS
Signal
type
Processing
type
Institution Multi-dimentional
input
Model/method Accuracy/
SNR enhancement
Application
scenario
Publication date Single
-source
signal
Traditional
machine
learning
University of Electronic Science
and Technology of China
Time ANN 94.4% Pipeline 2017［ 343 ］Shanghai Maritime University T-F PNN 96.67% Cable 2018［ 344 ］Beijing Jiaotong University Time F-ELM 95% Perimeter 2020［ 345 ］University of Alcala，Spain Time GMMs 81.1% Pipeline 2016［ 346 ］University of Alcala，Spain Time（long-short-term） GMMs+HMM 89.1% Pipeline 2019［ 347 ］University of Electronic Science
and Technology of China
Time（long-short-term） HMM 98.2% Pipeline 2019［ 348 ］Deep
learning
University of Electronic Science
and Technology of China
Time 1-D CNN 98.19% Pipeline 2019［ 349 ］Huazhong University of
Science and Technology
Time 1-D CNN +
DenseNet
98.4% Cable 2021［ 350 ］Beijing Jiaotong University Time DBN-GRU 96.72% Cable 2023［ 351 ］UGES of Türkiye T-F 2-D CNN 93% Cable 2017［ 352 ］Beijing Institute of Technology T-F 2-D CNN 98.02% Cable 2018［ 353 ］Zhejiang University T-F 2-D CNN+SVM 93.3% Cable 2018［ 354 ］University of Electronic Science
and Technology of China
T-F Unsupervised SNN 96.52% Cable 2021［ 355 ］Tongji University T-S 2-D CNN 98% Pipeline 2020［ 356 ］Shantou University T-S Transfer learning 96.16% Cable 2021［ 357 ］Tsinghua University T-S Semi-supervised learning（SSA） 97.9% Pipeline 2021［ 358 ］Shanghai Institute of Optics and Fine Mechanics S-F DPN 97% Railway 2019［ 359 ］Multi-source
aliasing
signals
Enhancement
/ separation
University of Electronic Science
and Technology of China
— Multi-scale wavelet
decomposition
28.42 dB Perimeter
security
2015［ 360 ］Anhui University and
Nanjing University
— Time delay
estimation
— Acoustic detection 2017［ 361 ］Shanghai Institute of Optics and Fine Mechanics — Beamforming 21 dB Acoustic detection 2020［ 362 ］University of Electronic Science
and Technology of China
— FastICA — Cable 2022［ 363 ］Tianjin University — Deep learning
（TFA-DRNN）
— Perimeter 2022［ 364 ］
Table 12. Representative applications of frequency-division multiplexing techniques in Φ-OTDR system
View tableTable 12. Representative applications of frequency-division multiplexing techniques in Φ-OTDR system
Sensing solution Improvement Sensing range Dynamic range Spatial resolution Ref. No Multi-frequency probe pulse Interference fading suppression 10 km - 5 m ［ 400 ］Temporally sequenced multi-frequency probes Extend the frequency measurement range 9.6 km 0.5 MHz - ［ 405 ］Interrogating weak reflector array by using OFDM probes Frequency response enhancement 51 km 25 kHz 20.4 m ［ 406 ］Dual-comb spectrometry Detection bandwidth reduction and spatial resolution improvement 200 m 20 Hz 2 cm ［ 407 ］
Table 13. Some important investigations of frequency-division multiplexed fast BOTDA
View tableTable 13. Some important investigations of frequency-division multiplexed fast BOTDA
Sensing solution Improvements Sensing range Spatial resolution Frequency resolution Measurement speed Ref. No Pump-probe pair Scanning free 2 km 5 m 3 MHz 5.5 kHz ［ 401 ］Digital optical frequency comb Dynamic range expansion 10 km 51.2 m 1.95 MHz 100 Hz ［ 67 ］Polarization-diversity frequency comb pump Single-shot measurement 10 km 51.2 m 1.95 MHz 10 kHz ［ 408 ］Frequency comb and multiple pump pulses Spatial resolution improvement 10 km 12.5 m 2 MHz 10 kHz ［ 409 ］Frequency comb and pump pulse array coding Spatial resolution improvement 9.5 km 10.24 m 2 MHz 4.77 kHz ［ 410 ］Frequency-agility digital optical frequency comb Spatial resolution improvement 10 km 5 m 2 MHz 40 Hz ［ 411 ］
Table 14. Configurations of communication and sensing hybrid systems
View tableTable 14. Configurations of communication and sensing hybrid systems
Implementation scheme Feature Ref. No Wavelength-division multiplexing Flexible，with little cross-talk；but the sensing probe will occupy spectrum resources ［ 435 -438 ］Frequency-division multiplexing Flexible；but the sensing probe occupies spectrum resources and has cross-talk ［ 439 -441 ］Mode-division multiplexing Share the same wavelength，but might suffer from strong cross-talk ［ 442 ］Sensing using the received optical phase of communication signals No additional sensing probe required，supporting long sensing range；but the positioning accuracy is bad ［ 434 ］Sensing using the backscattered light of communication signals No additional sensing probe required；but special design on the communication signal and system is generally required ［ 443 -445 ］
Table 15. Summary of distributed optical fiber shape sensing methods
View tableTable 15. Summary of distributed optical fiber shape sensing methods
Method Sensor fiber Sensing spatial resolution /mm Error % PPP-BOTDA［ 447 ］SMF 100 1.17 DPP-BOTDA［ 449 ］MCF 100 1 OFDR［ 454 ］Fiber bundle 1.907 0.58（2D）
3.45（3D）
OFDR［ 455 ］MCF+FBG array 10 0.6（2D）
0.1（3D）
OFDR［ 299 ］Helical MCF 1.5 0.4 Φ-OFDR［ 464 ］MCF+PS array 0.2 2.21（2D）
1.45（3D）
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Xuping Zhang, Yixin Zhang, Liang Wang, Kuanglu Yu, Bo Liu, Guolu Yin, Kun Liu, Xuan Li, Shinian Li, Chuanqi Ding, Yuquan Tang, Ying Shang, Yishou Wang, Chen Wang, Feng Wang, Xinyu Fan, Qizhen Sun, Shangran Xie, Huijuan Wu, Hao Wu, Huaping Wang, Zhiyong Zhao. Current Status and Future of Research and Applications for Distributed Fiber Optic Sensing Technology[J]. Acta Optica Sinica, 2024, 44(1): 0106001
Paper Information
Category: Fiber Optics and Optical Communications
Received: Aug. 25, 2023
Accepted: Dec. 1, 2023
Published Online: Jan. 11, 2024
The Author Email: Zhang Xuping (xpzhang@nju.edu.cn)
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