A fiber Bragg grating (FBG) has been utilized in capacitively coupled plasmas (CCP) for thermometry of neutral gas. We studied the effects of high frequency and low frequency power on radial distribution of neutral gas temperature. The result shows that the neutral gas temperature increases with increasing high frequency power. However, the presence of low frequency power will decrease the neutral gas temperature. Particularly, we eliminated the effect of ion bombardment on temperature measurement by studying axial distribution near plasma–sheath boundary. With features of immune to electromagnetic interference, high precision, and spatial resolving power, the FBG is a commendable candidate for CCP or other radio-frequency plasmas thermometry in both laboratory and industry.

Long period fiber grating is a kind of transmission type optical fiber grating. Due to the advantages such as low insertion loss, wide bandwidth, low-level reflection, high sensitivity, low cost and ease of compactness, LPFGs have been widely applied in optical fiber sensing and optical fiber communication. The Mode coupling of LPFG is the coupling between the fiber core mode and the cladding mode in the same transmission direction. If the ordinary LPFG is combined with bitaper or taper, we can effectively change the original LPFG's transmission spectrum to obtain the composite LPFG, which can stimulate new resonant peaks in the original wavelength-dependent transmission loss of the grating basis, thus applying to the dual-parameter simultaneously measuring field. We report a novel all-fiber narrow-bandwidth intermodal Mach– Zehnder interferometer (MZI) based on a long-period fiber grating (LPFG) combined with a fiber bitaper. The LPFG is written by high-frequency CO₂ laser pulses, and the bitaper is connected in series with the LPFG, forming the Mach– Zehnder interferometer (MZI). Experimental results indicate that the MZI has good temperature sensitivity, The temperature sensitivity of the two loss peaks are 55.35pm/°C and 48.18pm/°C respectively. The strain sensitivity of the two loss peaks are 3.35pm/με and -4.925pm/με respectively. By using the different temperature and strain response characteristics of the loss peaks, the temperature and strain measurement can be realized simultaneously. the proposed device has good repeatability and stability, which would be a promising candidate for precise dual-parameter sensing application.

Optical fiber Bragg grating (FBG) displacement sensors play an important role in various areas due to the high sensitivity to displacement. However, it becomes a serious problem of FBG cross-sensitivity of temperature and displacement in applications with FBG displacement sensing. This paper presents a method of temperature insensitive measurement of displacement via using an appropriate layout of the sensor. A displacement sensor is constructed with two FBGs mounted on the opposite surface of a cantilever beam. The wavelengths of the FBGs shift with a horizontal direction displacement acting on the cantilever beam. Displacement measurement can be achieved by demodulating the wavelengths difference of the two FBGs. In this case, the difference of the two FBGs’ wavelengths can be taken in order to compensate for the temperature effects. Four cantilever beams with different shapes are designed and the FBG strain distribution is quite different from each other. The deformation and strain distribution of cantilever beams are simulated by using finite element analysis, which is used to optimize the layout of the FBG displacement sensor. Experimental results show that an obvious increase in the sensitivity of this change on the displacement is obtained while temperature dependence greatly reduced. A change in the wavelength can be found with the increase of displacement from 0 to 10mm for a cantilever beam. The physical size of the FBG displacement sensor head can be adjusted to meet the need of different applications, such as structure health monitoring, smart material sensing, aerospace, etc.

A smart twisted type carbon fiber reinforced polymer (CFRP) bar was developed with FBG embedment during the manufacturing process. Sensing behaviors of the smart bar under static and fatigue loading were tested. The results show that it retains a good sensing performance after 200 million cycles. Among application, smart steel strand and smart stay cable were designed. And tensile experiments of such smart structures were carried out, showing good performance.

Tilted fiber Bragg gratings (TFBGs) have been demonstrated to be accurate refractometers as they couple light from the fiber core to the cladding. In our experiment, we changed the physical structure of the TFBGs to improve the refractive index sensing ability. One way is to stretch the grating section 5 mm longer. The result showed that not only the number of the cladding mode of the TFBG decreases but also the full width half-maximum (FWHM) of the cladding modes and core mode changes. The FWHM of the cladding mode of the tapered TFBG is more than twice than that of the original. However, the refractive index sensitivity of the tapered TFBG has no obvious improvement. Another way is to etch the grating section with 20% hydrofluoric acid solution. We find that the smaller the clad diameter, the higher the refractive index sensitivity of the TFBG.

Optical whispering gallery modes resonators are characterized by unique properties: ultrahigh quality factor, small amount of the modes and small size. It allows to use them in compact high-precision measuring devices. In particular these resonators can be used in the composition of gyros. For today all researches, devoted to the application of the whispering gallery modes resonators in gyros, deals only with one of induced by the rotation effects (Sagnac effect or the influence of centrifugal forces on the resonator size). In this work we study the interrelation of the effects caused by the rotation of the whispering gallery modes resonator. Also in work we consider the possibility of joint application of both effects (the influence of centrifugal forces and Sagnac effect) for measuring angular velocity.

The temperature dependence of a refractive index (RI) sensing probe based on a U-shape tapered plastic optical fiber (POF) was investigated experimentally. The changes in light propagation loss in the probe induced by temperature are of the same order of magnitude as those induced by measured RI changes. The temperature dependence loss and temperature dependence RI deviation of the sensing probe were measured (at the wavelength of 635 nm) in temperature of 10-60 °C. By extracting pure temperature dependence of the sensing probe alone, the influence of temperature to the sensor was characterized.

We compare the temperature sensitivity between the nested fiber ring resonator (NFRR) and the nested fiber ring resonator coupled Mach-Zehnder interferometer (NFRRCMZI). Theoretical results indicate that the temperature sensitivity of the NFRR is almost twelve times higher than that of NFRRCMZI with same parameters, hence complex MZI system can be removed and the whole sensing system will be more compatible without sacrificing the sensitivity. Taking feedback waveguide part as the sensing element in NFRR structure, the limitation of optical quality factor on sensitivity will be broken and arbitrary sensitivity can be acquired by easily setting different feedback waveguide length.

We theoretically investigate the series-coupled fiber double-ring resonator is not exactly the same perimeter, that is, when the double-ring resonator cannot be completely in resonance state, the output characteristics and dispersion characteristics of spectrum and its manifestations. In this paper, we introduce light exhibits different spectral output characteristics through double-ring resonator, when the two rings’ length ratios are δ=1,1.1,1.5, 2. Among them, δ=2 is particularly representative. When the second resonator has the same parameters, the group refractive index of the double-ring resonator whose length ratio is 2 higher than the single ring resonator two or three orders, these results indicate that we could improve the sensitivity of the double-ring resonator because sensitivity is directly related to the group refractive.

We proposed a gain compensation method to overcome the amplitude fading induced by the gain-bandwidth product (GBP) of the detector, which will seriously deteriorate the positioning accuracy of the distributed disturbance sensor at a long sensing range. To guarantee the performance of this method, we used the time-frequency distribution of the interference signal to distinguish the normal signal and the one need to compensate. A positioning measurement experiment using an asymmetric dual Mach-Zehnder interferometer (ADMZI) was carried out to verify the effectiveness of the proposed method. The experiment result showed that the sensing range can reach 121km, which was improved by over 40% compared to the traditional positioning method without gain compensation.

This paper presents a seismic wave detection system based on fully distributed acoustic sensing. Combined with Φ- OTDR and PGC demodulation technology, the system can detect and acquire seismic wave in real time. The system has a frequency response of 3.05 dB from 5 Hz to 1 kHz, whose sampling interval of each channel of 1 meter on total sensing distance up to 10 km. By comparing with the geophone in laboratory, the data show that in the time domain and frequency domain, two waveforms coincide consistently, and the correlation coefficient could be larger than 0.98. Through the analysis of the data of the array experiment and the oil well experiment, DAS system shows a consistent time domain and frequency domain response and a clearer trail of seismic wave signal as well as a higher signal-noise rate which indicate that the system we proposed is expected to become the next generation of seismic exploration equipment.

In digital coherent optical time domain reflectometer (coherent-OTDR) system, a dual-parallel Mach-Zehnder modulator (DP-MZM) is employed to modulate the signal light and to generate frequency-shifted pulse light. However, the environment temperature strongly influent the stability of the DP-MZM. To stabilize the quality of the frequency-shifted pulse light, we proposed a bias control method to keep the modulator at the optimum bias. This bias control method search for the optimum bias by changing three bias voltages at the same time based on chaotic particle swarm optimization algorithm(PSO). The experimental results show obvious effect on locating the optimum bias voltages for the DP-MZM.

A novel method to enhance the positioning resolution of distributed disturbance fiber sensor is proposed in this paper. The proposed scheme combines a high speed data acquisition system and a modified time delay estimate algorithm. The sensor performance is significantly improved by eliminating the impact of fluctuation of the interference signal generated by the environment disturbance. Theoretical analysis shows that with the proposed spatial resolution enhanced method, the disturbance sensing system is more suitable for various environments and provides low uncertainty in long term operation with meter-scale spatial resolution. Compared with the traditional time delay estimate method in distributed disturbance sensing system based on the criterion of spatial resolution, the positioning error of the sensor using our proposed method has been reduced at least an order of magnitude.

The WFE of the optical remote sensor system include the engineering from the fabrication processing, the position from deploying of segmented mirrors in orbit. In the process of feasibility demonstration, the total WFE error budget of large deployable optics plays a vital role in the general design of the remote sensor. According to results of calculation and iteration, in order to ensure the optical performance of the remote sensor in orbit, the WFE of the remote sensor is required to achieve λ/8rms (@ λ=632.8nm), and the WFE of the optical system is required to achieve λ/10rms（@ λ=632.8nm）. In this paper, the error from optical system design, which based the mission realization of optical fabrication and optical alignment.

A pulsed coherent vehicle laser radar system basing on the measurement of light flight time and Doppler frequency shift is demonstrated for the first time, which features a simple design that uses one photodiode (PD) as its optical detector. Pseudo random noise (PN) code is used for modulating the amplitude of transmitting light. Correlation function of the received echoes and the local modulating codes is calculated for measuring the light flight time. Due to PN code modulation, beat signal output from PD is piecewise continuous, which causes equidistant sampling of Doppler sine wave not feasible. In order that Doppler frequency be correctly measured by using fast Fourier transform (FFT), a simple signal amplitude modification method is derived from the definition of Fourier transform.

Multi-sensor data fusion and estimation with poor information is a common problem in the field of stress measurement. Small and distribution unknown data sample obtained from multi-sensor makes the data fusion and estimation much difficult. To solve this problem, a novel bootstrap-fuzzy model is developed. This model is different from the statistical methods and only needs a little data. At first, the limited stress multi-sensor measurement data is expanded by the bootstrap sampling. Secondly, the data fusion sequence is constructed by the bootstrap distribution. Finally the true value and the interval of the stress multi-sensor measurement data are estimated by the fuzzy subordinate functions. Experimental results show that the data fusion sequence is in a good agreement with the original measurement data. The accuracy of the estimated interval can reach 85%. Therefore, the effect of the proposed bootstrap-fuzzy model is validated.

Called the 'Reduced Back Projection' technique(or RBP), this new method is an improvement on existing tomographic reconstruction techniques in the field of laser diagnostics on a combustor exhaust. The highlight of this technique is the use of only FOUR views to create a planar reconstruction from path averaged data which is obtained from water absorption spectroscopy in the IR region near 1373nm. Water sensitive wavelengths are generated by using a Tunable Diode laser working in the IR region. For the purpose of this paper, work is done on a plane in the exhaust of a burner perpendicular to the flame direction. The geometry of the burner decides the distribution of water molecules in the interrogation plane. This technique is based on the back projection method but has been extensively modified and improved to work with just four views instead of the hundred or so views used in medical tomography. Simulations have been run to check the working of the new technique and compared with other current methods in tomography (SART, back projection, etc..). Preliminary experimentation over a simple two burner geometry has been performed. In both simulation and experiment, the RBP technique has yielded better results than existing methods by virtue of the new method being able to capture features where the other methods have failed. Thus, RBP can be applied to situations where resources, time and spatial constraints exist.

This article presents the experimental and modeling study of quartz-enhanced photoacoustic detection of nitrogen monoxide (NO) using the off-beam configuration and a distributed-feedback (DFB) quantum cascade laser (QCL) at 5.26 μm as the excitation source. Trace gas monitoring of NO is one of the important subjects for both environmental protection and human health monitoring. Quartz-enhanced photoacoustic spectroscopy (QEPAS) with on-beam configuration is mostly adopted for gas detection. In comparison, the off-beam approach has not only comparative detection sensitivity but also significant advantage of simpler installation and optical alignment. We optimized the sensor performance by adjusting the horizontal and vertical distances between the micro-resonator (mR) and the QTF prongs. Pressure and humidity are two important factors affecting the photoacoustic signal. The effects of both parameters on the NO concentration determination were investigated.

The development of a low complexity fiber optic based protein sensor by functionalizing the surface of silica optical fibers using block copolymers having both hydrophobic poly(methyl methacrylate) (PMMA) and hydrophilic poly[2- (dimethylamino)ethyl methacrylate] (PDMAEMA) blocks is presented here. The amphiphilic thiol-functionalized PMMA₁₁₇-b-P(DMAEMA₁₇-st-TEMA₂) and vinyl-sulfone PMMA₁₁₇-b-P(DMAEMA₁₇-st-VSTEMA₂) block copolymers designed and synthesized in this work contain a cationic hydrophilic PDMAEMA block that can electrostatically bind selected oppositely charged proteins and also appropriate functional groups for reversible or non-reversible protein binding, respectively, leading to a refractive index change of the overlayer and hence, enabling the sensing. The developed PMMA₁₁₇-b-PDMAEMA₁₆-based platform has been evaluated for bovine serum albumin (BSA) sensing, exhibiting linear response to detected BSA concentrations.

Photo-acoustic spectroscopy gas detection technology has the advantages of high sensitivity, good selectivity, small size and real time monitoring and has been widely used in environmental monitoring, industrial production, medical diagnosis, biological technology and monitoring of power facilities. In this paper, a method to improve the sensitivity of photo-acoustic spectroscopy system is presented, which is combined with the technique of Herriott type multiple pass cell. In this experimental apparatus, the design of the experimental device can make the beam pass the cell 18 times. By comparing the signal of one time pass through the photoacoustic cell and the signal of 18 times passes pass through the photoacoustic cell, we can confirm that the signal is increased and this method is feasible.

Combustible or harmful gasses noticeable all around are adequate to decimating a geographical region of bringing about a flame, explosion, and venomous exposure. In this paper, a highly sensitive gas sensor based on slotted-core photonic crystal fiber has been presented which can be used as a gas sensor. The guiding properties of the proposed PCF are numerically investigated by employing finite element method (FEM). The Proposed PCF contains slotted core and a hexagonal cladding where the geometrical parameters are varied to optimized. Simulation result reveals that the proposed PCF shows a high relative sensitivity of 48.26%, the high birefringence of 2.17×10^-2 and a lower confinement loss of 1.26×10 ^-5 dB/m. Effective area, Beat length, Splice loss, V-parameter are also reported in this paper.

Person identification based on biometrics is drawing more and more attentions in identity and information safety. This paper presents a biometric system to identify person using 3D palmprint data, including a non-contact system capturing 3D palmprint quickly and a method identifying 3D palmprint fast. In order to reduce the effect of slight shaking of palm on the data accuracy, a DLP (Digital Light Processing) projector is utilized to trigger a CCD camera based on structured-light and triangulation measurement and 3D palmprint data could be gathered within 1 second. Using the obtained database and the PolyU 3D palmprint database, feature extraction and matching method is presented based on MCI (Mean Curvature Image), Gabor filter and binary code list. Experimental results show that the proposed method can identify a person within 240 ms in the case of 4000 samples. Compared with the traditional 3D palmprint recognition methods, the proposed method has high accuracy, low EER (Equal Error Rate), small storage space, and fast identification speed.

In this paper, we propose and demonstrate a novel self-referencing surface plasmon resonance (SPR) fiber-optic sensor which provides a Fabry-Perot (FP) interference referencing signal for temperature compensating. The sensor is fabricated by splicing a capillary partly coated with gold film between multimode fibers. The multimode fibers act as the lead-in and lead-out fibers while the capillary is used as sensing element. Because the FP interference and SPR effects can occur in the capillary simultaneously, the spectrum of the sensor exhibits SPR absorption and FP interference fringes. Due to the FP interference fringe sensitive to temperature while insensitive to refractive index (RI), it can be used as referencing signal and the SPR absorption was used as measuring signal. Experimental results show that this approach we presented can compensate temperature effect and develop this sensor as a practicable high-sensitivity sensing device. Moreover, as a self-referencing fiber-optic SPR sensor, this simple and low-cost element can be used for highly sensitive biosensing for further investigations.

Breath acetone is a promising biomarker of diabetes mellitus. With an integrated standalone, on-site cavity ringdown breath acetone analyzer, LaserBreath-001, we tested breath samples from 23 type 1 diabetic (T1D) patients, 312 type 2 diabetic (T2D) patients, 52 healthy subjects. In the cross-sectional studies, the obtained breath acetone concentrations were higher in the diabetic subjects compared with those in the control group. No correlation between breath acetone and simultaneous BG was observed in the T1D, T2D, and healthy subjects. A moderate positive correlation between the mean individual breath acetone concentrations and the mean individual BG levels was observed in the 20 T1D patients without ketoacidosis. In a longitudinal study, the breath acetone concentrations in a T1D patient with ketoacidosis decreased significantly and remained stable during the 5-day hospitalization. The results from a relatively large number of subjects tested indicate that an elevated mean breath acetone concentration exists in diabetic patients in general. Although many physiological parameters affect breath acetone concentrations, fast (<1 min) and on site breath acetone measurement can be used for diabetic screening and management under a specifically controlled condition.

In the present paper, we first demonstrate NaLuF₄: Yb³⁺: Tm³⁺/Ho³⁺ rare earth nanocrystals in microstructure hollow fiber. An analysis of the intense blue upconversion emission at 450 and 475 nm in Tm³⁺/Yb³⁺ codoped NaLuF₄ under excitation power 0.65W available from solid laser emitting at 980nm, has been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive blue upconversion emission at 450and 475 nm in this material was recorded in the temperature range from 300 to 345 K. The maximum sensitivity derived from the FIR technique of the blue upconversion emission is approximately 0.005 K−1. The results imply that Tm³⁺/Yb³⁺ codoped NaLuF₄ is a potential candidate for the optical temperature sensor.

Light propagation in strip and slot waveguide arrays for sensing are proposed and analyzed with a new theory of quantum walk. The waveguide arrays are designed on silicon-on-insulator and can be fabricated with mature and cost-efficient complementary metal-oxide semiconductor technology. A new slot waveguide array modified by conventional strip waveguide array with electric field mainly confined in the cladding region is investigated. Quantum walks have an exact mapping to classical phenomena as verified by experiments using bright laser light, so that they are introduced in our work as theoretical foundation. We take the width of waveguide of 450 nm and the coupling distance of 200 nm for strip waveguide array, and 420 nm and 180 nm for slot waveguide array, but with a 100nm slot in the center of waveguide. At last the waveguide array covered by a thin layer of graphene is investigated, which brings higher sensing property as well as a much better biocompatibility. With the monochrome light injection the intensity distribution at the end of the arrays changes with the refractive index of the sensing area (cladding region) and it can be explained by quantum walks theory. The designed waveguide arrays can possess compact footprint and high refractive index resolution, reaching 1E-11 RIU theoretically.

Integrated Mach-Zehnder interferometers (MZIs) based on flexible polymer materials have been demonstrated as evanescent field sensors for the detection of refractive indices and molecule concentrations. The used application of a measurement window in classical MZIs is difficult in a roll-to-roll fabrication process. We have previously demonstrated foil-based asymmetric MZIs with different widths in sensing and reference arm which do not need a measurement window. Here we present the use of a multimode interference structure (MMI) inserted into the sensing arm of the interferometer to increase the sensitivity. We consider the expected interference signal from numerical simulations and optimize the system in terms of sensitivity, dimensions and absorption losses. The fabricated MMI-MZI foils are tested experimentally to demonstrate the function of the MMI-MZI system by applying water/glucose solutions with different refractive indices.

The reflected intensity change of the Bloch-surface-wave (BSW) resonance influenced by the loss of a truncated onedimensional photonic crystal structure is numerically analyzed and studied in order to enhance the sensitivity of the Bloch-surface-wave-based sensors. The finite truncated one-dimensional photonic crystal structure is designed to be able to excite BSW mode for water (n=1.33) as the external medium and for p-polarized plane wave incident light. The intensity interrogation scheme which can be operated on a typical Kretschmann prism-coupling configuration by measuring the reflected intensity change of the resonance dip is investigated to optimize the sensitivity. A figure of merit (FOM) is introduced to measure the performance of the one-dimensional photonic crystal multilayer structure under the scheme. The detection sensitivities are calculated under different device parameters with a refractive index change corresponding to different solutions of glycerol in de-ionized (DI)-water. The results show that the intensity sensitivity curve varies similarly with the FOM curve and the sensitivity of the Bloch-surface-wave sensor is greatly affected by the device loss, where an optimized loss value can be got. For the low-loss BSW devices, the intensity interrogation sensing sensitivity may drop sharply from the optimal value. On the other hand, the performance of the detection scheme is less affected by the higher device loss. This observation is in accordance with BSW experimental sensing demonstrations as well. The results obtained could be useful for improving the performance of the Bloch-surface-wave sensors for the investigated sensing scheme.

Realizing that current microfluidic chip fabrication techniques are time consuming and labor intensive as well as always have material leftover after chip fabrication, this research work proposes an innovative approach for rapid microfluidic chip production. The key idea relies on a combination of a widely-used inkjet printing method and a heat-based polymer curing technique with an electronic-mechanical control, thus eliminating the need of masking and molds compared to typical microfluidic fabrication processes. In addition, as the appropriate amount of polymer is utilized during printing, there is much less amount of material wasted. Our inkjet-based microfluidic printer can print out the desired microfluidic chip pattern directly onto a heated glass surface, where the printed polymer is suddenly cured. Our proof-of-concept demonstration for widely-used single-flow channel, Y-junction, and T-junction microfluidic chips shows that the whole microfluidic chip fabrication process requires only 3 steps with a fabrication time of ~6 minutes.

Magnetooptic sensor based on electrogyration compensation is proposed and experimentally demonstrated by using single quartz crystal. The sensing unit is composed of single quartz crystal and two polarizers. Quartz crystal exhibits magneto-optic, electro-optic and electrogyration effects, thus magneto-optic Faraday rotation angle can be compensated by the electrogyration angle induced by the compensating voltage applied to the crystal. The compensating voltage is sensitive to both the deviation angle between light beam and principal crystalline axis, and the azimuth angle of polarizer. The 50Hz ac magnetic flux density within 267Gs has been measured, the compensating voltage is 0.72V/Gs for a single quartz crystal with a length of 23mm. The proposed sensor has potential application to closed-loop measurement of magnetic field.

Due to the overwhelming advantages compared with traditional electronicsensors, fiber-optic acoustic sensors have arisen enormous interest in multiple disciplines. In this paper we present the recent research achievements of our group on fiber-optic acoustic sensors. The main point of our research is high sensitivity interferometric acoustic sensors, including Michelson, Sagnac, and Fabry-Pérot interferometers. In addition, some advanced technologies have been proposed for acoustic or acoustic pressure sensing such as single-mode/multimode fiber coupler, dual FBGs and multi-longitudinal mode fiber laser based acoustic sensors. Moreover, our attention we have also been paid on signal demodulation schemes. The intensity-based quadrature point (Q-point) demodulation, two-wavelength quadrature demodulation and symmetric 3×3 coupler methodare discussed and compared in this paper.

In this paper, a novel quarter wave plate which is composed of two segments of high birefringence fibers which are orthogonally welded is proposed and demonstrated. The orthogonally welded fibers are used to construct a high birefringence fiber loop mirror (Hi-Bi-FLM). Based on the transfer function of the Hi-Bi-FLP the length difference of the two segments can be calculated and by tuning one of them an equivalent quarter wave plate can be got. The tuning method is analyzed and discussed in detail.

Influence of the centrifugal forces on angular velocity sensors that measure a spectral shift of whispering gallery modes is investigated. Spherical whispering gallery mode resonators of different materials are considered as sensing elements. The study is based on the results of the simulation in OOFELIE::Multiphysics software.

The object of this study is the bionic quadruped mobile robot. The study has proposed a system design plan for mobile robot obstacle avoidance with the binocular stereo visual sensor and the self-control 3D Lidar integrated with modified ant colony optimization path planning to realize the reconstruction of the environmental map. Because the working condition of a mobile robot is complex, the result of the 3D reconstruction with a single binocular sensor is undesirable when feature points are few and the light condition is poor. Therefore, this system integrates the stereo vision sensor blumblebee2 and the Lidar sensor together to detect the cloud information of 3D points of environmental obstacles. This paper proposes the sensor information fusion technology to rebuild the environment map. Firstly, according to the Lidar data and visual data on obstacle detection respectively, and then consider two methods respectively to detect the distribution of obstacles. Finally fusing the data to get the more complete, more accurate distribution of obstacles in the scene. Then the thesis introduces ant colony algorithm. It has analyzed advantages and disadvantages of the ant colony optimization and its formation cause deeply, and then improved the system with the help of the ant colony optimization to increase the rate of convergence and precision of the algorithm in robot path planning. Such improvements and integrations overcome the shortcomings of the ant colony optimization like involving into the local optimal solution easily, slow search speed and poor search results. This experiment deals with images and programs the motor drive under the compiling environment of Matlab and Visual Studio and establishes the visual 2.5D grid map. Finally it plans a global path for the mobile robot according to the ant colony algorithm. The feasibility and effectiveness of the system are confirmed by ROS and simulation platform of Linux.

Compared with the infrared focal plane array (IRFPA) based on amorphous silicon (α-si), IRFPA based on vanadium oxide (VO_x) has the advantages of big temperature coefficient of resistance, low noise and so on. In this paper, the design of the micro uncooled infrared imaging system based on VO_x IRFPA is introduced. Firstly, the hardware design of the proposed system is discussed, which includes the system structure, VO_x IRFPA module, driving module and the signal processing module based on FPGA. Secondly, the designs of the system configuration program as well as the consistency correction of the proposed system are discussed. Finally, some experiments were carried out to verify the validity of the models and the whole infrared imaging system, which indicated that our work will lay a foundation for the implement of micro and low-cost infrared imaging system.

In this work, a medical respiratory monitoring sensor based on the microbend effect of optical fiber on light transmission is proposed. The microbend effect of multimode optical fiber is analyzed theoretically using optical theory. A respiratory signal modulator with a “sandwich” microbender structure is designed enabling the noninvasive real-time monitoring. In vitro testing showed that the proposed sensor has excellent following characteristics and can automatically discern respiratory condition, the signal-to-noise ratio can be better than 28dB.

This paper puts forward a kind of optical fiber temperature sensor based on fluorescence lifetime, which can be applied to measurement in strong electromagnetic, strong corrosion and other harsh environment. A small volume, long service life, strong anti-jamming capability of fluorescence temperature sensor was designed by matching rare earth fluorescent material with longer fluorescent lifetime with tee optical coupler. The experimental results show that this method has a high measuring precision within the scope of 0-90℃.

Application of high temperature fiber sensing system is very extensive. It can be mainly used in high temperature test aerospace, such as, materials, chemicals, and energy. In recent years, various on-line optical fiber interferometric sensors based on modular interference of single-mode-multimode-single-mode(SMS) fiber have been largely explored in high temperature fiber sensor. In this paper we use the special fiber of a polyimide coating, its sensor head is composed of a section of multimode fiber spliced in the middle of Single-mode fiber. When the light is launched into the multimode fiber(MMF) through the lead-in single-mode fiber(SMF), the core mode and cladding modes are excited and propagate in the MMF respectively. Then, at the MMF-SMF spliced point, the excited cladding modes coupled back into the core of lead-out SMF interfere with SMF core mode. And the wavelength of the interference dip would shift differently with the variation of the temperature. By this mean, we can achieve the measurement of temperature. The experimental results also show that the fiber sensor based on SMS structure has a highly temperature sensitivity. From 30℃ to 300℃, with the temperature increasing, the interference dip slightly shifts toward longer wavelength and the temperature sensitivity coefficient is 0.0115nm/℃. With high sensitivity, simple structure, immunity to electromagnetic interferences and a good linearity of the experimental results, the structure has an excellent application prospect in engineering field.

In this experiment, the optical parameters of optical fiber sensing measurements with the wavelength division multiplexer (WDM) and Fiber Bragg grating have obtained in temperature-controlled cabinet. The wavelength division multiplexer device not only make different wavelength illuminant input at the same time be possible, but also can achieve multi-channel output based on the feature of WDM. We design and put forward a new method which can realize various parameters measured at the same time, such as temperature and the refractive index or stress measurement. In addition, it can measure the same parameters with different wavelengths of laser at the same time. The contrast analysis results of different wavelengths of illuminant on the same parameter sensitivity and reliability of the measurement will use to provide reference to design the same illuminant with different parameter measurements.

A fiber-optic refractive index sensor assisted surface Plasmon resonance of metal dielectric layer around a longperiod fiber-optic grating with hollow fiber core has been proposed and comprehensively analyzed. Its operation principle is based on the efficient energy transfer between the fiber waveguide mode and the co-directional surface Plasmon waves excited with a long-period fiber-optic grating properly designed by the light refracted through the interface between the waveguide area and the metal dielectric film. The long-period fiber-optic grating is fabricated on a waveguide area of a specially designed fiber-optic with hollow fiber core. Simulations have been carried out in coupled mode theory of fiber-optic gratings in the wavelength ranges from 1500 to 1600nm, and for sensing characteristics of refractive index. Unlike a previous proposed fiber Bragg grating fabricated on this kind of fiber, t the sensitivity of the long-period fiber-optic grating SPR refractive index sensor is much higher than that of a FBG in the same structure. The proposed long-period fiber-optic refractive index sensor assisted surface Plasmon resonance is compact, light weight, and highly sensitive with a large sensing range

Various porous silicon-based photonic device structures has attracted more attention for use as biochemical optical sensors. In this study, we have designed and characterized porous silicon-based two-dimensional photonic crystal waveguide structure as an optical biosensor. Field intensity distribution of two-dimensional photonic crystal waveguide was simulated using COMSOL Multiphysics. When the refractive index changes, the field strength changes greatly. This study lays the theoretical foundation for further work.

Polarization crosstalk is a phenomenon that the powers of two orthogonal polarization modes propagating in a polarization maintaining (PM) fiber couple into each other. Because there is certain mathematical relationship between the polarization crosstalk signals and external perturbations such as stress and temperature variations, stress and temperature sensing in PM fiber can be simultaneously achieved by measuring the strengths and locations of polarization crosstalk signals. In this paper, we report what we believe the first distributed temperature sensing demonstration using polarization crosstalk analysis in PM fibers. Firstly, by measuring the spacing changes between two crosstalk peaks at different fiber length locations, we obtained the temperature sensing coefficient (TSC) of approximately −0.73 μm/(°C•m), which means that the spacing between two crosstalk peaks induced at two locations changes by 0.73 μm when the temperature changes by 1 °C over a fiber length of 1 meter. Secondly, in order to bring different temperature values at different axial locations along a PM fiber to verify the distributed temperature sensing, four heating-strips are used to heat different fiber sections of the PM fiber under test, and the temperatures measured by the proposed fiber sensing method according to the obtained TSC are almost consistent with those of heating-strips measured by a thermoelectric thermometer. As a new type of distributed fiber temperature sensing technique, we believe that our method will find broad applications in the near future.

In this letter, surface plasmon resonance sensors based on grapefruit-type photonic crystal fiber with different silver nano-film structure have been analyzed and compared though the finite element method (FEM). Numerical results show that excellent sensor resolution of 7.143×10^-5RIU can be achieved as the thickness of the filling silver film is 30nm by spectrum detection method.

We report an new approach of integrating photonic crystal fiber (PCF) SERS sensors to a Raman spectrometer for high sensitivity to the explosive 2,4,6-trinitrotoluene (TNT). The PCF SERS probe can be fabricated by using gold nanoparticles immobilized on the inner surface of air channels in a PCF through polymer-mediated self-assembly. To study the response of above fabricated substrates to the TNT vapor, the PCF SERS probe integrated with a Raman spectrometer was proposed and demonstrated in this study. The TNT-induced SERS signals are measured and the sensing capability of the proposed sensors is investigated experimentally.

In order to obtain the accurate torque measurements in harsh condition, such as marine environment, a torque transducer based on fiber Bragg grating is proposed in this paper. According to its optimized elastomer design and fiber Bragg grati ng patching tactics, the new proposed torque transducer realizes automatic compensations of temperature and bending moment which avoids influences from environment. The accuracy and stability of the torquetransducer, as well as its under water performance are tested by loading tests both in air and in underwater environment, which indicate the designed tor que transducer is not only able to realize highaccurate and robust measurements, but also can be applied in torque sensing in harsh environment. We believe the proposed design detailed illustrated in this paper provides important reference for studies and applications on torque measurements in marine environment.

A novel fiber sensor for simultaneous measurement of ammonia gas concentration and temperature is proposed. The sensor is fabricated from two sections of single-mode fiber which are cleaved and then a fusion splicer and which is then used to fabricate spherically shaped structures at the end facets. The fusion arc is used to soften the glass which naturally assumes a spherical shape due to surface tension. A short section of multimode fiber is then fusion spliced with the two spherical-shaped ends of the single mode fibers so both the core modes and the cladding modes of the multimode fiber are excited to create two kinds of interference dips: One is created by core modes only which is not sensitive to ammonia gas since the core is isolated by the cladding so the effective refractive index of the core does not change when the refractive index of the environment changes, The other dip is created by the coupling of the core mode and cladding mod, which with a suitable coating is sensitive to ammonia gas. Silica sol-gel was prepared and coated on the fiber surface as a sensing layer for detecting ammonia gas concentration. The experimental results show that the two dips have linear wavelength shift responses but with different sensitivities to ammonia gas concentration (5.03×10-4nm/ppm for dip1 and -2.5×10- 5nm/ppm for dip2) and temperature (0.0067 nm/ºC for dip1 and 0.0149 nm/ºC for dip2. By constructing a wavelength shifts matrix for the two dips vs. ammonia gas concentration and temperature, both the ammonia gas concentration and temperature can be measured simultaneously.

A refractive index sensor based on taper Michelson interferometer in multimode fiber is proposed. The Hydrofluoric acid corrosion processing is studied in the preparation of single cone multimode optical fiber sensor. The taper Michelson interferometer is fabricated by changing corrosion time. The relationship between fiber sensor feature and corrosion time is analyzed. The experimental results show that the interference spectrum shift in the direction of short wave with the increase of the refractive index. The refractive index sensitivity can reach 115.8008 nm/RIU. Thereby, it can be used in detecting the refractive index in different areas including the environmental protection, health care and food production.

A scanning imaging system based on 6144×96 multi-band five-color TDI-CCD was built, which is featuring Real-time imaging capability with high sensitivity and high dynamic range in multi-spectral bands for the same target. In this paper, the respective pixel topology for five TDI-CCD was obtained on the basis of their spatial relationship in five bands. Finally, high resolution gray-scale image and color image reconstruction for the scenic target were achieved by multi-Spectral fusion algorithm.

In the paper, an accurate and sensitive system was used to monitor the ambient atmospheric NO₂ concentrations. This system utilizes cavity attenuated phase shift spectroscopy(CAPS), a technology related to cavity ring down spectroscopy(CRDS). Advantages of the CAPS system include such as: (1) cheap and easy to control the light source, (2) high accuracy, and (3) low detection limit. The performance of the CAPS system was evaluated by measuring of the stability and response of the system. The minima (~0.08 ppb NO₂) in the Allan plots show the optimum average time(~100s) for optimum detection performance of the CAPS system. Over a 20-day-long period of the ambient atmospheric NO₂ concentrations monitoring, a comparison of the CAPS system with an extremely accurate and precise chemiluminescence-based NOx analyzer showed that the CAPS system was able to reliably and quantitatively measure both large and small fluctuations in the ambient nitrogen dioxide concentration. The experimental results show that the measuring instrument results correlation is 0.95.

Canopies are major part of plant photosynthesis and have distinct architectural elements such as tree crowns, whorls, branches, shoots, etc. By measuring canopy structural parameters, the solar radiation interception, photosynthesis effects and the spatio-temporal distribution of solar radiation under the canopy can be evaluated. Among canopy structure parameters, Leaf Area Index (LAI) is the key one. Leaf area index is a crucial variable in agronomic and environmental studies, because of its importance for estimating the amount of radiation intercepted by the canopy and the crop water requirements. The LAI can be achieved by hemispheric images which are obtained below the canopy with high accuracy and effectiveness. But existing hemispheric images canopy-LAI measurement technique is based on digital SLR camera with a fisheye lens. Users need to collect hemispheric image manually. The SLR camera with fisheye lens is not suit for long-term canopy-LAI outdoor measurement too. And the high cost of SLR limits its capacity. In recent years, with the development of embedded system and image processing technology, low cost remote canopy hemispheric image acquisition technology is becoming possible.

In this paper, we present a remote hemispheric canopy image acquisition system with in-field/host configuration. In-field node based on imbed platform, low cost image sensor and fisheye lens is designed to achieve hemispherical image of plant canopy at distance with low cost. Solar radiation and temperature/humidity data, which are important for evaluating image data validation, are obtained for invalid hemispherical image elimination and node maintenance too. Host computer interacts with in-field node by 3G network. The hemispherical image calibration and super resolution are used to improve image quality in host computer. Results show that the remote canopy image collection system can make low cost remote canopy image acquisition for LAI effectively. It will be a potential technology candidate for low-cost remote canopy hemispherical image collection to measure canopy LAI.

Mid-infrared (IR) spectroscopy, typically 3 to 5 µm, is often the technology of choice to monitor the interaction between and concentration of molecules during photochemical reactions. However, classical mid-IR spectrometers are bulky, complex and expensive, making them unsuitable for use in the miniaturized microreactors increasingly being employed for chemical synthesis. We present here the concept for an ultra-miniaturized mid-IR spectrometer directly integrated onto a chemical microreactor to monitor the chemical reaction. The spectrometer is based on micro-machined Fabry-Perot resonator filters realized using pairs of Bragg mirrors to achieve a high spectral resolution. The fabrication of the optical filters is outlined and the measurement of transmittance spectra in the mid-IR range show a good agreement with theory and are thus promising candidates for a fully integrated system.