1.

2017-12-11

Distributed gas sensing with optical fibre photothermal interferometry

Lin, Yuechuan; Liu, Fei; He, Xiangge; Jin, Wei; Min Zhang; Yang, Fan; Ho, Hoi Lut; Tan, Yanzhen; Gu, Lijuan

Abstract:

We report the first distributed optical fibre trace-gas detection system based on photothermal interferometry (PTI) in a hollow-core photonic bandgap fibre (HC-PBF). Absorption of a modulated pump propagating in the gas-filled HC-PBF generates distributed phase modulation along the fibre, which is detected by a dual-pulse heterodyne phase-sensitive optical time-domain reflectometry (OTDR) system. Quasi-distributed sensing experiment with two 28-meter-long HC-PBF sensing sections connected by single-mode transmission fibres demonstrated a limit of detection (LOD) of similar to 10 ppb acetylene with a pump power level of 55 mW and an effective noise bandwidth (ENBW) of 0.01 Hz, corresponding to a normalized detection limit of 5.5 ppb.W/Hz-root 5.5ppb.W/Hz. Distributed sensing experiment over a 200-meter-long sensing cable made of serially connected HC-PBFs demonstrated a LOD of similar to 5 ppm with 62.5 mW peak pump power and 11.8 Hz ENBW, or a normalized detection limit of 312 ppb.W/hz-root 312ppb.W/Hz. The spatial resolution of the current distributed detection system is limited to similar to 30 m, but it is possible to reduce down to 1 meter or smaller by optimizing the phase detection system. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Reference：

Lin Y, Liu F, He X, et al. Distributed gas sensing with optical fibre photothermal interferometry[J]. Optics express, 2017, 25(25): 31568-31585.

2.

2017-12

Limit-Cycle-Based Decoupled Design of Circle Formation Control with Collision Avoidance for Anonymous Agents in a Plane

Wang Chen; Guangming Xie

Abstract:

We study the circle formation problem for a group of anonymous mobile agents in a plane, in which the agents are required to converge onto a circle with a preset target as the center, as well as to maintain the desired relative positions when rotating around the target at the same speed. Each agent is modeled as a kinematic point and can merely perceive the relative positions of the target and its limited neighbors. In order to solve the circle formation problem, a limit-cycle-based decoupled-design approach is delivered. We divide the overall control objective into two subobjectives, where the first is target circling that all agents converge onto the circle around the target, and the second is spacing adjustment that each agent maintains the desired distance from its neighbors. Then, we propose to use a controller comprised of converging part and layout part to deal with these two subobjectives, respectively. The former part is based on a limit-cycle oscillator using only the relative position from the target, and the latter is designed by also perceiving the relative position from the agent's neighbors. An important feature of the controller is that it guarantees that no collision between agents ever takes place throughout the system's evolution. Another feature is that some of the parameters in the proposed controller have explicit physical meanings related to the agents' rotating motion around the target, so that they can be set more reasonable and easily in real applications. Numerical simulations are given to show the effectiveness and performance of the proposed circle formation controller.

Reference:

Wang C, Xie G. Limit-Cycle-Based Decoupled Design of Circle Formation Control with Collision Avoidance for Anonymous Agents in a Plane[J]. IEEE Transactions on Automatic Control, 2017, 62(12): 6560-6567.

3.

2017-10-25

Distributed acoustic sensing technique and its field trial in SAGD well

Li Han; Xiangge He; Yong Pan; Fei Liu; Duo Yi; Chengjun Hu; Min Zhang; Lijuan Gu;

Abstract:

Steam assisted gravity drainage (SAGD) is a very promising way for the development of heavy oil, extra heavy oil and tight oil reservoirs. Proper monitoring of the SAGD operations is essential to avoid operational issues and improve efficiency. Among all the monitoring techniques, micro-seismic monitoring and related interpretation method can give useful information about the steam chamber development and has been extensively studied. Distributed acoustic sensor (DAS) based on Rayleigh backscattering is a newly developed technique that can measure acoustic signal at all points along the sensing fiber. In this paper, we demonstrate a DAS system based on dual-pulse heterodyne demodulation technique and did field trial in SAGD well located in Xinjiang Oilfield, China. The field trail results validated the performance of the DAS system and indicated its applicability in steam-chamber monitoring and hydraulic monitoring.

Reference:

Han L, He X, Pan Y, et al. Distributed acoustic sensing technique and its field trial in SAGD well[C]//AOPC 2017: Fiber Optic Sensing and Optical Communications. International Society for Optics and Photonics, 2017, 10464: 104642K.

4.

2017-09-10

载波相位偏差对光纤检波器解调的影响

张敏 等

Abstract:

在基于外差方案的干涉型光纤检波器中,正交载波的获取是其中的一个重要环节。谐波失真和相对幅度误差是评价解调信号质量的重要指标,正交载波之间存在的相位偏差会导致解调信号的谐波失真和相对幅度误差增大。分析了正交载波的相位偏差与解调结果的谐波失真、相对幅度误差之间的关系,运用级数分解和贝塞尔函数展开式进行数学推导,并进行了仿真验证。分析结果表明,正交载波的相位偏差与谐波失真/相对幅度误差呈正相关,当要求谐波失真优于-40dB、相对幅度误差小于1%时,需要控制相位偏差在1.6×10-2 rad以下。最后搭建了实验测试系统,实验结果验证了理论的正确性。

Reference:

刘飞, 颜晗, 华波, 等. 载波相位偏差对光纤检波器解调的影响[J]. 光学学报, 2017, 37(9): 0906001.

5.

2017-09-01

Geophysical techniques of reservoir monitoring for marine gas hydrate exploitation

He, Tao; Lu, Hailong; Lin, Jinqing; Dong, Yifei ; He, Jian

Abstract:

Marine gas hydrate is an important resource of clean energy for the future, but its exploitation requires not only the innovation of development techniques but also serious consideration of protection of marine environment. For a timely response to production process, monitoring of the dynamic change of gas hydrate reservoir in real time is a basic requirement for a successful exploitation. However, in previous successful gas hydrate production experiments, either in terrestrial permafrost area (Mallik of Canada and Ignik Sikumi of USA) or on continental slope in deep sea (Nankai Trough of Japan), monitoring was carried out mainly through the instruments installed in the two or three observation wells which were only tens of meters away from the production well, and consequently the monitoring might have covered only a limited area. At the present the monitoring technique for large-scale monitoring of gas hydrate reservoir has not been established worldwide, even systematic discussion and scheme design are absent. Based on the acoustic and electrical responses to the saturation change and granular contact mode of gas hydrate layer, several seismic and electromagnetic exploration methods have been compared to see their feasibility and merits and drawbacks for large-scale monitoring of marine gas hydrate development, and an advanced geophysical monitoring scheme is proposed for the upcoming gas hydrate experimental production in South China Sea and future commercial exploitation. The integrated geophysical monitoring system is comprised of (1) a set of geophysical sensors to be installed in the observation wells, which will continuously collect the key physical parameters as temperature, pressure, electrical resistivity, streaming potential, heat flux, etc.; (2) a high sensitive and endurable full fiber 4-component ocean bottom seismic cable system to record the time lapse variations of reservoir acoustic properties of both compressive and shear waves; (3) a net of multifunctional ocean bottom nodes around the production well to measure the seafloor surface deformation/depression during production, and to directly detect and visually observe possible methane leakage. On a well designed protocol, this monitoring system can quantitatively measure the key geophysical variations associated with gas hydrate dissociation, and the data to be acquired will provide scientific basis for production optimization, environment protection and risk assessment for marine gas hydrate exploitation.

Reference:

He, Tao; Lu, Hailong; Lin, Jinqing; Dong, Yifei ; He, Jian.Geophysical techniques of reservoir monitoring for marine gas hydrate exploitation[J]. Earth Science Frontiers, v 24, n 5, p 368-382, September 1, 2017; Language: Chinese;  ISSN: 10052321;  DOI: 10.13745/j.esf.yx.2016-11-27.

6.

2017-08

Heat flux investigations during flame thermal spray process using the lumped capacitance method

Duo Yi, Min Zhang

Abstract:

The evaluation of heat flux is vital in the field of thermal spray process since it decides the temperature gradient, the formation of the residual stress inside the coating and finally affects the coating properties. Especially for the specific net incident heat flux density launched by the torch during each passage, it affects greatly the interaction between the previous and latter adjacent layers, the temperature gradient formation as well as the residual stress distribution along the vertical direction during the coating deposition process. This work mainly concentrates on the estimation of heat flux density during flame thermal spray process based on a lumped capacitance model. The heat flux evolution during one multi-pass of the torch was analyzed in detail and the average heat flux density impinging the substrate surface was firstly estimated, the root mean square error between the measured temperature and the numerical estimation was selected as the evaluation criteria to compare the calculation accuracy. The dynamic increase of coating mass was then added into consideration and the net incident heat flux density launched by the torch was estimated. The peak power value of the heat flux density was estimated based on an assumed Gaussian form of thermal energy distribution.

Reference:

Yi D, Zhang M. Heat flux investigations during flame thermal spray process using the lumped capacitance method[J]. Applied Thermal Engineering, 2017, 123: 554-561.

7.

2017-07-22

Finite element analysis of fiber optic embedded in thermal spray coating

Duo Yi, Min Zhang, Lijuan Gu, Jianming Yang, Wenhui Yu

Abstract:

This study aims to evaluate the thermomechanical behavior of a new composite structure using finite element method. The composite structure consists of the substrate and the thermal spray coating with embedded fiber optic. The temperature evolution of the composite estimated by the finite element model shows good agreement with the experimental recording, which confirms the justifiability of model initialization, and then, the thermal results are applied for the following mechanical analysis. The stress distribution and the variation in refractive index of the embedded fiber are investigated. The results show that the stress level suffered by the embedded fiber is much lower than the yield strength, and the variation in refractive index of the embedded fiber has an insignificant effect on optical transmission, which ensures a good embedding quality of the fiber optic.

Reference:

Yi D, Zhang M, Gu L, et al. Finite element analysis of fiber optic embedded in thermal spray coating[J]. Journal of Intelligent Material Systems and Structures, 2018, 29(5): 896-904.

8.

2017-05-24

Emergence of leadership in a robotic fish group under diverging individual personality traits

Chen Wang, Xiaojie Chen, Guangming Xie, Ming Cao

Abstract:

Variations of individual’s personality traits have been identified before as one of the possible mechanisms for the emergence of leadership in an interactive collective, which may lead to benefits for the group as a whole. Complementing the large number of existing literatures on using simulation models to study leadership, we use biomimetic robotic fish to gain insight into how the fish’s behaviours evolve under the influence of the physical hydrodynamics. In particular, we focus in this paper on understanding how robotic fish’s personality traits affect the emergence of an effective leading fish in repeated robotic foraging tasks when the robotic fish’s strategies, to push or not to push the obstacle in its foraging path, are updated over time following an evolutionary game set-up. We further show that the robotic fish’s personality traits diverge when the group carries out difficult foraging tasks in our experiments, and self-organization takes place to help the group to adapt to the level of difficulties of the tasks without inter-individual communication.

Reference:

Wang C, Chen X, Xie G, et al. Emergence of leadership in a robotic fish group under diverging individual personality traits[J]. Royal Society open science, 2017, 4(5): 161015.

9.

2017-04-27

Real-time phase demodulation and data administration of distributed optical fiber vibration sensing system

Qin, Mengzhe; He, Xiangge; Liu, Fei; Zheng, Xiaoping; Zhang, Min

Abstract:

Distributed optical fiber sensing system (DOFS) has great potential in areas of petroleum exploration and ocean defense. By algorithm optimization in different coding environment, the multi-point and real-time heterodyne demodulation of DOFS is achieved. In experiments, the length of the optical fiber is 500m, the spatial resolution is 5m and the system sampling rate is 200kHz, under which condition the data rate reaches up to 160MB/s and the system can stilled be demodulated timely. Based on this, by plotting the three-dimensional diagram (vibration intensity versus time and space), the whole DOFS can be detected continuously and accurately.

Reference:

Qin, Meng zhe, et al. "Real-time phase demodulation and data administration of distributed optical fiber vibration sensing system." Fiber Optic Sensors and Applications XIV. Vol. 10208. International Society for Optics and Photonics, 2017.

10.

2017-04-24

A new fiber optic accelerometer with push-pull structure using 3x3 coupler

Xiaokang Qiu; Fei Liu; Bin Xie; Hongpu Zhou; Duo Yi; Xiangge He; Xiaoping Zheng; Min Zhang

Abstract:

In this paper, we propose a new type of push-pull structure fiber optic accelerometer based on 3×3 coupler for the first time and carried out measurements of its responsivity and cross-axis sensitivity. With specific algorithm, the phase signal of the sensor can be extracted without complicated modulation and demodulation. Experiments show that the responsivity of the accelerometer is larger than 40dB (0dB ref 1rad/g) within the frequency band from 10Hz to 800Hz, which agrees well with the theoretical analysis. In addition, the cross-axis sensitivity can be optimized as low as about -30dB due to the push-pull structure. The results reported here indicate that this type of fiber optic accelerometer can be applied in vibration sensing such as micro seismic monitoring.

Reference:

Qiu X, Liu F, Xie B, et al. A new fiber optic accelerometer with push-pull structure using 3×3 coupler[C]//Optical Fiber Sensors Conference (OFS), 2017 25th. IEEE, 2017: 1-4.

11.

2017-04-23

Phase-sensitive optical time-domain reflectometry with heterodyne demodulation

Xiangge He; Fei Liu; Mengzhe Qin; Shan Cao; Lijuan Gu; Xiaoping Zheng; Min Zhang

Abstract:

A phase-sensitive optical time-domain reflectometry (Φ-OTDR) system using dual heterodyne pulses combined with heterodyne demodulation is proposed. The theory of this system is analyzed. The experimental results show that this system can achieve a very large dynamic range with a frequency range of 50 Hz to 25 kHz and an amplitude range of 0.9 rad to 73 rad. At the same time, multi vibrations at different locations can also be well detected.

Reference:

He X, Liu F, Qin M, et al. Phase-sensitive optical time-domain reflectometry with heterodyne demodulation[C]//25th International Conference on Optical Fiber Sensors. International Society for Optics and Photonics, 2017, 10323: 103235Q.

12.

2017-04-23

A new measurement scheme for delay parameters in TDM fiber optic interferometric sensor network

Fei Liu; Xiaokang Qiu; Bin Xie; Lijuan Gu; Xiaoping Zheng; Min Zhang

Abstract:

In this paper, a new scheme for delay parameters measurement in time division multiplexing (TDM) fiber optic interferometric sensor (FOIS) network is proposed. This scheme provides a solution of delay parameters measurement through the variance vector of the reshaped original data. By calculating the correlation between the variance vector and the system's pulse template vector, the scheme is capable to resist much more noise in the original data. Even when the SNR of the original data decreases to 7 dB, the scheme can still work with a correct rate higher than 98%. What's more, the scheme is feasible to be carried out, and it is able to work real-time.

Reference:

Liu F, Qiu X, Xie B, et al. A new measurement scheme for delay parameters in TDM fiber optic interferometric sensor network[C]//25th International Conference on Optical Fiber Sensors. International Society for Optics and Photonics, 2017, 10323: 103231N.

13.

2017-04-15

Numerical and experimental analysis of polarization dependent gain vector in Brillouin amplification system

Min Zhang, et al.

Abstract:

The polarization dependent gain (PDG) of Brillouin amplification systems is numerically investigated in detail by solving a new model describing the evolution of PDG vector along the fiber with random birefringence. In this model both the modulus and orientation of the PDG vector are considered. By including the temporal distribution of fiber birefringence, the statistical properties of the PDG vector, including its mean value and standard deviation, are presented as function of fiber beat length, input pump power and fiber length, which can be directly applied in practice to estimate the performance of Brillouin amplification systems in term of its polarization dependence. Experimental results on a Brillouin amplification system are also reported to support the validity of our model. The analysis presented here helps to gain insight for the properties of PDG vector in any SBS systems.

Reference:

Cao S, Xie S, Liu F, et al. Numerical and experimental analysis of polarization dependent gain vector in Brillouin amplification system[J]. Optics Communications, 2017, 389: 23-28.

14.

2017-04-11

Numerical analysis of a new sensing composite structure embedding optical fiber

Yi, Duo; Zhang, Min; Yang, Jianming ; Yu, Wenhui

Abstract:

In this study, a numerical model based on finite element method was proposed to evaluate the thermo-mechanical behavior of a composite structure material. The composite structure consisted of substrate, thermal spray coating, and an embedded optical fiber. The stress level of the composite structure especially the embedded fiber at the end of elaboration process was analyzed. The variations of refractive index of the embedded fiber due to the thermo-optic effect and the elasto-optic effect were investigated. The results showed that the the variation of stress and refractive index during the elaboration process had an insignificant effect on the embedding quality of the optical fiber under the presented optimized experimental conditions.

Reference:

Yi, Duo, et al. "Numerical analysis of a new sensing composite structure embedding optical fiber." Fiber Optic Sensors and Applications XIV. Vol. 10208. International Society for Optics and Photonics, 2017.

15.

2017-04-11

Research on an optimized optical fiber accelerometer for well logging

Yi, Duo; Qiu, Xiaokang; Gu, Lijuan; Zhang, Min

Abstract:

The optical fiber accelerometer owns exceptional advantages in various industrial applications due to its high sensitivity, immunity to electromagnetic interference, small size, low cost and easy to form sensor network etc. This study aims to evaluate an optimized interferometric optical fiber accelerometer based on Michelson structure. An integral parameter S was firstly proposed to assess the general performance of the accelerometer including both the sensitivity and resonance frequency, the compliant cylinder of the accelerometer proposed in this study was optimized as the composite structure materials, two typical sensitivity enhanced elastic materials of polycarbonate and silicone rubber were selected. This new type accelerometer was capable to provide higher phase sensitivity and wider flat bandwidth with optimized proportional mixing between two materials. The comparison analysis of Young's modulus and Poisson ratio on the promotion of integral parameter S was finally discussed.

Reference:

Yi, Duo, et al. "Research on an optimized optical fiber accelerometer for well logging." Fiber Optic Sensors and Applications XIV. Vol. 10208. International Society for Optics and Photonics, 2017.

16.

2017-04-01

Long-term glacier melt fluctuations over the past 2500 yr in monsoonal High Asia revealed by radiocarbon-dated lacustrine pollen concentrates

Liping Zhou, et al.

Abstract:

Long-term records of glacier mass changes are important for improving our understanding of glacier dynamics and for predicting the response of glaciers to future climate change. In contrast to moraine sequences that only record isolated stages of glacier status, proglacial lake sediments may record long-term continuous glacier activities. The melt of old glacier ice releases old pollen that may affect the radiocarbon ages of pollen in proglacial lake sediments. We define the offset between the calibrated pollen 14C ages and the sediment depositional age as the“old pollen effect”(OPE). In small catchments dominated by glaciers, the OPE may record variations in glacier melt intensity and extent, even though complex processes (e.g., modern pollen flux to a glacier or a proglacial lake, glacier flow velocities) may also impact the OPE. Using the sediments of a small proglacial lake on the southern Tibetan Plateau, we found that over the past 2.5 k.y., a weakened OPE occurred during three historical cool periods that coincided with regional glacier advances defined by moraine ages. Thus, we interpret the OPE as a new indicator of glacier melt intensity and its fluctuations. Our reconstructed glacier variability agrees well with glacier fluctuations in the European Alps and the global average temperature record, suggesting that hemispheric-scale temperature variations and/or mid-latitude Westerlies may have controlled the late Holocene glacier variability in monsoonal High Asia. We also show that the 20th century glacier melt intensity has exceeded that of two historical warm periods and is unprecedented over the past 2.5 k.y. This implies that current anthropogenic warming poses a serious threat to the survival of glaciers in monsoonal High Asia.

Reference:

Zhang J F, Xu B, Turner F, et al. Long-term glacier melt fluctuations over the past 2500 yr in monsoonal High Asia revealed by radiocarbon-dated lacustrine pollen concentrates[J]. Geology, 2017, 45(4): 359-362.

17.

2017-02-01

Multi-event waveform-retrieved distributed optical fiber acoustic sensor using dual-pulse heterodyne phase-sensitive OTDR

Min Zhang, et al.

Abstract:

We demonstrate a novel type of distributed optical fiber acoustic sensor, with the ability to detect and retrieve actual temporal waveforms of multiple vibration events that occur simultaneously at different positions along the fiber. The system is realized via a dual-pulse phase-sensitive optical time-domain reflectometry, and the actual waveform is retrieved by heterodyne phase demodulation. Experimental results show that the system has a background noise level as low as 8.91010310-4090009090009rad/090806Hz with a demodulation signal-to-noise ratio of 49.17 dB at 1 kHz, and can achieve a dynamic range of 09080460090009090009dB at 1 kHz (0.1 to 104 rad) for phase demodulation, as well as a detection frequency range from 20 Hz to 25 kHz.

Reference:

He X, Xie S, Liu F, et al. Multi-event waveform-retrieved distributed optical fiber acoustic sensor using dual-pulse heterodyne phase-sensitive OTDR[J]. Optics letters, 2017, 42(3): 442-445.

18.

2017-02

Polarized and birefringence-dependent stimulated Brillouin scattering in single mode fiber

Cao Shan; Min Zhang

Abstract:

The vector model on the polarization properties of stimulated Brillouin scattering is analyzed theoretically with the Stratonovich generator. The quantitative characteristics of average Brillouin gain and alignment of pump and signal waves are numerically investigated. Simulation results show a more general conclusion about the state of polarization that corresponding to the maximum Brillouin gain, when a wider range of birefringence value is considered. In addition, the fluctuation range of signal output is presented. Finally, the statistics of signal output is studied and found to be Gaussian distributed in log-scale. The detailed quantitative study contributes to further understanding of the effect of polarization and birefringence on stimulated Brillouin scattering and statistics of Brillouin gain.

Reference:

Cao S, Zhang M. Polarized and birefringence-dependent stimulated Brillouin scattering in single mode fiber[J]. Optik-International Journal for Light and Electron Optics, 2017, 131: 374-382.