This PDF file contains the front matter associated with SPIE Proceedings Volume 11554, including the Title Page, Copyright information, and Table of Contents

Lanthanide-based nanocomplexes stand out among optical sensors since for them one can implement an up-conversion luminescence (UCL) mode. The property eliminates the problem of extraction of nanoprobe luminescent signal against the background of the biological system autoluminescence. However, the surrounding molecules in natural biological systems crucially affect the luminescent properties of upconversion nanoparticles (UCNP). The study focuses on the effect of salts, acids and biomacromolecules on luminescent properties of UCNP in aqueous suspensions. UCL spectra of the NaYF4:Yb/Tm nanocomplexes in the presence of various molecules excited by 980 nm laser radiation were analyzed. The mechanisms of interaction of the nanocomplexes with surrounding molecules in aqueous suspensions, as well as the nature of the influence of various chemical groups on the UCNPs luminescent properties are discussed. This study was supported by Russian Foundation for Basic Research (Project №18-02-01023).

This study is devoted to a new approach to solve the problem of pH (in range of pH from 5 to 8) and temperature (in range of 30-45°C) measurements at nanoscale level, by using carbon dots (CDs), prepared from citric acid. These 10 nm sized nanoparticles with luminescence quantum yield ~10% have broad unstructured luminescence spectrum in the range from 420 to 750 nm, which is sensitive to the change of the environmental parameters. Different influence of pH and temperature values on luminescence spectra of CDs in aqueous suspensions was observed. The CD-based nanosensor was developed for simultaneous determination of pH and temperature using artificial neural networks.

This study is devoted to the study of the effect of different cations (Na+, Cs+, NH4+) and anions (F-, Cl-) on colloidal and photoluminescent properties of CDs, obtained from citric acid. The obtained results are explained using the theory of ions hydration.

Perfluoroisobutyronitrile (C₄F₇N) has the potential to replace SF₆ due to its excellent environmentally friendly dielectric properties, and has received extensive attention at home and abroad. C₄F⁷N has a low liquefaction temperature, so it is necessary to mix it with low-boiling gas during application. Among them, the C⁴F7_N/CO₂ mixed gas has excellent performance, but the insulation capacity is closely related to the C₄F₇N content. Therefore, the preparation of high-precision C₄F₇N/CO₂ mixed gas is conducive to scientific demonstration of C₄F⁷N and minimizes the hidden dangers of industrial applications. Through the Fourier infrared detection platform, the infrared absorption information of C4F7N gas in the 500~4500cm^-1 band was obtained, and the 1200~1300cm-1 band was determined as the key research object. A portable detection system for C₄F₇N/CO₂ mixed gas is designed based on NDIR technology. As for the C₄F₇N gas sensor module, the low-power EMIRS50-AT06V standard blackbody light source with rugged MEMS design and the dual-channel detector with InfraTec LRM-202 narrow bandpass filter, combined with the gold-plated gas chamber structure of the reentrant light path, can effectively improve the detection accuracy of the system.Determine the inversion algorithm of the difference principle, and finally realize the fast detection of the C4F7N gas content. The experimental results show that the non-linear correlation between SB/SA (the ratio of the amplitude of the reference signal and the signal amplitude of the measurement channel) and the volume concentration fitting nonlinearity R² is 0.99797. Within the range of the sensor, the maximum indication error is 1.05%, and the RSD of the sensor repeatability experiment is 0.47%, 0.36%, 0.31%, 0.34%, all of which do not exceed 0.5%, indicating that the sensor has good accuracy and consistency.The high integration and portability of the system can provide a novel method for the rapid online detection of the C₄F₇N/CO₂ mixed gas mixture ratio of high-voltage electrical equipment.

Electrostatics plays a critical function in most biomolecules, therefore monitoring subtle biomolecular bindings and dynamics via the electrostatic changes of biomolecules at biointerfaces has been an attractive topic recently and has provided the basis in diagnosis and biomedical science. Here we present a bioelectrostatic responsive microlaser based on liquid crystal (LC) droplet and explored its application for ultrasensitive detection of negatively charged biomolecules. Whispering gallery mode (WGM) lasing from positively charged LC microdroplets was applied as the optical resonator, where the lasing wavelength shift was employed as a sensing parameter. With the dual impacts from whispering-gallery mode and liquid crystal, molecular binding signals will be amplified in such LC droplet sensors. It is found that molecular electrostatic changes at the biointerface of droplet triggered wavelength shift in lasing spectra. The total wavelength shift increased proportionally with the adhering target concentrations. Compared to a conventional polarized optical microscope, significant improvements in sensitivity and dynamic range by four orders of magnitude were achieved. Our work indicated that the surface-to-volume ratio plays a critical role in the detection sensitivity in WGM laser-based microsensors. Finally, bovine serum albumin and specific biosensing using streptavidin and biotin were exploited to demonstrate the potential applications of microlasers with a detection limit on the order of 1 pM. We anticipate this approach will open new possibilities for the ultrasensitive label-free detection of charged biomolecules and molecular interactions by providing a lower detection limit than conventional methods.

We propose and demonstrate single optical fiber tweezers based on graded-index multimode fiber (MMF) which can adjust captured microparticles position in pendulum-style. The optical fiber tweezers can capture the yeast cell stably in three dimensions and swing the yeast cell 57.5 degrees around the fiber tip like a pendulum. The optical fiber tweezers are fabricated by asymmetrical fiber heating fused and tapered method. The capture and swing functions of the proposed optical fiber tweezers provide a new manipulation method for biomedical field.

In recent years, there has been a growing demand for hand held and miniaturized spectroscopic Raman systems that can be employed in the field to distinguish and quantify different analytes. In this paper, a novel and integrable system to detect a Raman spectrum is presented. We present the system principle, sensor design, experimental set-up and primary measurement results. In a conventional Raman setup, the four important components are: a light source, sensor, spectrometer and detector. We utilize a tunable laser as light source in the new Raman detecting system to replace the spectrometer by scanning the pump wavelength. A Raman sensor based on silicon nitride platform which has small size and high signal-background ratio is demonstrated in this paper to enable the excitation and the collection of the Raman signal using a plasmonic slot waveguide structure. Besides the tunable laser and the Raman sensor, there are two basic devices in our system, a narrow band-pass filter and a power detector. In this work, the Raman signal of the measured molecule 4-nitrothiophenol (NTP) is obtained by scanning the pump wavelength from 735 nm to 786 nm. The light source and detector in our experiment are implemented by discrete components. Silicon photonics promises the integration of a complete on-chip Raman spectroscope where the tunable laser, detector, sensor and filter can be integrated in a millimeter sized chip. We analyze the primary results measured by the discrete devices and discuss the feasibility of the on-chip integration in the end.

We studied the energy distribution and leakage in a single curved polymer nanowire .Through theoretical simulation , we found that the energy distribution in the curved nanowire is related to it’s the radius of curvature、wavelength and the refractive index of the environment.When the radius of curvature is 1 micron, the bending loss of the polymer nanowire placed on the substrate in the air is greater than its transmission loss, and the degree of energy leakage at the bend is affected by the refractive index of the environment. The results of this study provide strong theoretical and support for the design and application of micro-nano sensors based on curved micron waveguide.

The strong photon limiting ability of the resonant cavity makes it a critical general-purpose device. The silicon-based photonic resonant cavity is the most potential high-efficiency, low-cost on-chip solution. The organic combination of mature microelectronic technology and broadband optoelectronic technology in the micro-nano category makes this arrangement a bright future. Fano resonance with the sharp symmetry-broken line shapes occurs when a discrete quantum state interferes with a continuum band of states. Here, we analyze two directly coupled microresonators (a low- Q passive resonator and a high-Q active resonator) using the temporal coupled-mode theory (CMT). High-sensitivity refractometric sensing based on Fano resonance with directly coupled active and passive optical microresonators is investigated theoretically. It is shown that the line shape and amplitude of power transmission spectra is determined by the judgment coefficient and the pump gain of high-Q microresonator. Through modulating the loss rate, pump gain, and the detuning frequency of both cavities, the refractive index sensitivity can be enhanced six order than two directly coupled loss-loss microresonators. As the system response to the slight change of external parameter benefits from the critical behavior, ultrahigh-sensitivity refractometric sensing could be realizable due to the mechanism achieving a large slope with a relatively high extinction ratio. Our scheme is valuable for various applications of refractometric sensing in the future.

An optical fiber refractive index (RI) sensor based on open microcavity Mach-Zehnder interferometer (OMZI) and fiber ring laser (FRL) is proposed and demonstrated experimentally. The OMZI is manufactured by splicing a tiny single mode fiber (SMF) segment with multi-mode fiber (MMF) joints laterally. The large offset structure forms an open microcavity which can be filled with the liquid under test. Through inserting the OMZI into an erbium-doped FRL, the RI measurement can be achieved by discriminating the lasing wavelength, and the detection limit (DL) can be effectively improved owing to the laser sensing spectrum with narrower 3-dB bandwidth and higher optical signal-to-noise ratio (OSNR). Experimental results show that the output laser wavelength has a linear response to the RI change with a sensitivity of −2947.818 nm/RIU during the range of 1.33302~1.33402, and the DL is as low as 5.89×10−6 RIU. Compared with other optical fiber RI sensors, the proposed fiber laser RI sensor with an open microcavity has the advantages of small size, high sensitivity and low DL, making itself a competitive candidate for the microfluidic RI measurement in biochemistry.

In this paper, we propose a back propagation neural network (BPNN) for temperature forecasting by helical microfiber sensors. The structural parameters, such as the microfiber diameter, the tapered angle, the input and output offset angle, the waist length and the helical angle, are considered as the input parameters of the network for sensing the temperature (T). 758 transmitted intensity (I)-T data pairs obtained from over 38 helical microfiber sensors are used for the network training. The prediction ability of the model is evaluated by root-mean-square error (RMSE). Compared with the fitting curve based on the measured I-T data, the neural network can directly predict the temperature according to the training model with RMSE of 0.6033.In addition, the major structural parameters are determined by comparing the prediction performances of the networks with different inputs.

We propose a novel method to extract Brillouin frequency shift (BFS) from Brillouin Gain Spectrum (BGS) in Brillouin distributed fiber sensors. The method is based on machine learning of nearest neighbors. In order to find the BFS from the BGS, we design two datasets, one for storing all possible BGS, and the other for storing the corresponding BFS. By comparing the given BGS with the dataset of BGS, we get the minimal kth BFS. The BFS of the given BGS is determined by voting of the kth BFS. By simulations, we compare the performance of both neighbor-based machine learning and curve-fitting. The results show that the method of neighbor-based machine learning is more robust under a wide range of signal-to-noise ratios, pump pulse widths, and frequency scanning steps. The extracting method of neighbor-based machine learning is highly competitive for future Brillouin distributed fiber sensors.

To date, many works devoted to the influence of grazing angle on the spectral properties of nanostructured metasurfaces have been published. In this case, the dependence of the spectrum on grazing angle was previously considered within the framework of solving filtering problems, for example: constructing tunable optical filters based on metasurfaces; development of a bandpass filter with characteristics that are minimally dependent on the angle of incidence of light (angular tolerant color filter), etc. We propose to use the described property of nanostructured metasurfaces for solution of an inverse problem – determination of light incidence angle from the change in the metasurface spectral response. It will provide no-contact determination of an inclination angle of an object, on which the metasurface is installed; it is a step towards creating a miniature and accurate angle sensor. We consider the idea of using metasurfaces to measure inclination angles of objects on the basis of dielectric subwavelength gratings using computer simulation. We also analyze the possibility of simultaneous measurement of rotations (inclination angles) along two orthogonal axes using the same nanostructured metasurface.

In this paper, a corrugated surface tilted long period grating (LPG) is proposed for liquid-level sensing. The tilted LPGs are fabricated on commercial plastic optical fiber (POF) by a simple mechanical die-press-print method. The liquid-level sensing performances of the so-obtained non-tilted LPGs (with the tilted angle of 0°) and the tilted LPGs (with the tilted angle of 10-30°) are investigated, respectively. The results show that the tilted LPG exhibits a better sensing performance than that of the non-tilted LPG. When the LPG period is 300μm, the groove depth is 155μm, and the tilted angle is 20°, the highest sensitivity of 0.417dB/mm is obtained by measuring the liquid-level with the refractive index (RI) of 1.33. In addition, the influence of RI on the liquid-level sensing performance of the sensor is also studied. The results show that the sensitivity of sensor is increased as the RI of liquid increased from 1.33-1.43, and the highest sensitivity can reach to 0.454dB/mm when the RI of liquid is 1.43. The proposed sensor is a low-cost solution for liquid-level measurement and with the features of easy fabrication, high sensitivity, and continuous measurement.

In this paper, we propose and demonstrate a high-integration intracavity displacement-sensor through inserting U-shape single-mode fiber interferometer (U-SMFI) into an Er-doped fiber ring laser. Considering that the U-SMFI can be realized only through bending a SMF, its characteristic of easy fabrication can reduce the cost of manufacturing process in contrast with those wavelength-modulated displacement sensors based on fiber Bragg grating, long-period grating and surface plasmon resonance. When the U-SMFI is inserted into the laser cavity, the variation of the bending radii can modulate the cavity loss so as to have an effect on the spectrum of the output laser. The proposed sensor has a higher signal to noise ratio and a narrower full width at half maximum. Through measuring the change of the spectrum, a high-resolution displacement sensor can be realized. The experimental results indicate that the sensitivities are 39 pm/μm when the bending radius is 6.5 mm.

Superconducting nanowire single photon detector response to X-ray photon was demonstrated using a laser-plasma subps X-ray radiation, to the best of our knowledge. The time jitter was measured to be 248.2 ps, which is larger than ordinary visible or NIR SNSPDs and its efficiency is relatively lower, but the results pave the way for a new competitive X-ray detector with ultrahigh count rates, ultralow timing jitter, ultrahigh sensitivity and negligible dark counts.

The principle of operation of all resonator micro-optical gyroscope prototypes developed to date involves frequency scanning of the ring resonator. In previous works on this topic, we proposed and considered an optical resonator gyroscope scheme that does not require frequency scanning of the ring resonator. There two counterpropagating waves pass along the same optical path. It reduces the parasitic nonreciprocity, which leads to additional errors in measuring the angular velocity in most of the known schemes. In addition, this scheme allows further reduction of gyro prototypes dimensions. In this work, we simulate a resonator gyroscope made according to the described scheme. In this case, we simulate both the optical path of the proposed resonator gyroscope and the system for generating the output signal. Using the model, we evaluate its characteristics, including limiting sensitivity, operating range, etc.

The paper continues [12] the Finite-Difference Time-Domain (FDTD) mathematical modeling method application of electric field distortion near the surface of spherical gold nanoparticles functionalized by two shells: water shell as a model substance for a drug and S_iO₂ as a capsuling silicon polymer. During the simulation, parameters such as particle size, the thickness of surface layers, the wavelength of exciting radiation, and the dependence of the effective amplification of the E component of electromagnetic field on the thickness of the polymer and water layers were investigated. The prospects of the theoretical approach of core-shell complexes for theranostics tasks are shown. The data presented can be used as a basis for controlled chemical synthesis of spherical nanoparticles.

Optical fiber pressure gradient sensors possess the merits of no suspension and easy installation compared to the co-vibration vector sensors. Recent studies are focused on the discrete structure made by individual pressure sensing units. Because the sensor is extremely sensitive to the difference between the units, improvements should be made in many areas, such as the manufacturing process, calibration method, and error correction. Benefited by the mature manufacturing process, a vector sensor with directivity larger than 40 dB is obtained. Considering that the measurement uncertainty is up to 0.7 dB in standing wave tube, an optimized calibration method is developed, which can eliminate the relative measurement error. Besides, an enhanced demodulation method is carried out to decrease the fluctuation of phase shift to within ±0.5 dB. 2-D and 3-D sensors are fabricated and tested on the lake and on the sea. Results show that the sensors have achieved good acoustic measurements.

Optical fiber-based smart sensing is a key technology for ultrasound sensing and monitoring applications. It plays a vital role in areas from laboratorial scientific research to the field non-destructive testing. However, the sensitivity of the current optical fiber acoustic sensor is limited. Hence, it is necessary to develop highly sensitive fiber-based sensors for ultrasonic/acoustic sensing. Here, we present a photonic crystal fiber-based Bragg grating sensor, which offers significant advantages and has higher performance for ultrasonic/acoustic sensing applications. In this research, the theoretical investigations of the proposed sensor are presented. The polymer material is utilized for filling into the fiber air hole structure to enhance the sensitivity. The design of the proposed device has been optimized to provide high optical quality factor to ensure high detection sensitivity, which can be used for high sensitive ultrasonic/acoustic sensing applications.

Due to the factors such as environment, material aging, and fatigue loads, structural members are prone to crack damage during the service, which could lead to the risk of collapse as the crack-induced strain accumulates. This paper proposes a method for structural crack identification and location based on a distributed optical fiber dynamic strain monitoring method. The Savitzky-Golay smooth filtering method was used to extract the crack information from the obtained dynamic strain signal. Based on the local strain anomaly of the structure and the nonlinear vibration characteristics of the "breathing" crack model, the cracks distributed along the structure can be located. According to the change of harmonic component, the crack development process can be identified, and early identification and localization of structural cracks during operation can be realized, which provides a practical approach of the damage monitoring for the cracked structures.

This study mainly compares two optimized interrogation techniques for an interferometric fiber-optic surface plasmon resonance (SPR) sensor. For this sensor, both SPR and interference effects are excited in a single fiber structure and they can be applied for dual-parameter measurement. On the other hand, the interference fringe patterns are mixed into the SPR transmission spectra, and the novel interrogation technique should be evaluated. In this study, two optimized interrogation techniques are proposed and their performances are compared. For the first one, the non-linear least square method is used to filter out the interference components and only retain the SPR signal. For the second one, the wavelength-distributed spectra are converted into the spatial frequency-distributed spectra, hence SPR components and the interference components can be discussed individually. The advantages and disadvantages of the two interrogation techniques are discussed thoroughly.

Transition edge sensors (TES) are highly sensitive detectors and have been widely used at different wavelengths from millimeter to X-ray astronomy. Especially at optical/near infrared wavelengths TES exhibits photon-number resolving capability because of its high energy resolution, which also makes it attractive in quantum information. In order to verify the possibility of space applications, we study the effect of ion irradiation on the performance of titanium-based optical TESs including normal-state resistance (RN), critical temperature (TC), thermal conductance (G), effective response time, detection efficiency, and energy resolution by measuring the DC and optical characteristics. The optical TESs survive in the ion irradiation and their parameters keep almost the same as before ion irradiation, which makes it possible for future space applications.

An economical and reliable fiber-optic vibration sensing system is proposed in this paper, which can eventually cooperate with distributed fiber sensing systems for long-span structural inspection. The system is designed to monitor the vibration state of the position to be measured, based on the principle of a Sagnac fiber-optic sensor. A novel algorithm of analyzing the strength ratio between a certain frequency band and the background frequency band of the signal is employed in this sensing system. Two sets of experiments were implemented to validate the reliability of the algorithm. In the first experiment, we tested whether the algorithm can recognize the sensing fiber was trampled. Application of the sensing system on a cast-iron pipeline detection was performed in the second experiment. Experimental results showed that the forced vibration frequency of the pipeline is between 170~230 Hz, and the sensing system is reliable for rapid recognizing the vibration state of the sensing fiber, which indicated that this system has a potential in application of field measuring as a part of traditional distributed optical fiber sensing system.

The off-line sampling destructive test is often used in the seal integrity test of vials, which has the disadvantages of long time consuming, low accuracy and high missing rate. In order to solve the above problems, the tunable diode laser absorption spectroscopy technology and wavelength modulation spectroscopy technology are used to measure the oxygen concentration in the vials. The ratio method of second harmonic and first harmonic is used to eliminate the influence of the rapid change of light intensity. The experimental results show that the system can complete the seal integrity detection of 300 vials per minute. This method belongs to the non-destructive online detection mode, which can realize the fast detection of vials without interference.

Sensor system optimization is an important issue in the development of new systems. In order to improve the resolution of the imaging system and reach the theoretical limit, from the perspective of theory and engineering, an adaptive equivalent focal length optimization algorithm is proposed. With a complete 4π stereo angle wide field of view, this kind of imaging distortion correction simulation system is established, and the multi-level effectiveness strategy is developed. And the simulation results based on this algorithm are given in many environments..

We demonstrate a polarization maintaining fiber (PMF) sensing tape capable of measuring transverse-force (TF) and temperature simultaneously, based on the distributed polarization crosstalk analysis (DPXA) technique. Using a self developed automatic birefringence axis alignment equipment, a PMF is fixed on a transparent PET strip with the highest sensitivity to TF and high polarization crosstalk consistency along the axial direction. 6 preset crosstalk points with an adjacent spatial distance of 2 m along the PMF are produced through fusion splicing, and the temperature spatial resolution of 2 m is determined. The distributed TF and temperature sensing can be achieved by independently monitoring the intensities of TF-induced polarization crosstalk peaks and the distance-resolved delay spacing of adjacent preset crosstalk peaks, respectively. The maximum temperature measurement error is measured to be 6.84 ℃, which can be seen as the temperature resolution of sensing. The experimental results indicate that our sensing tape can be practical after several improvements.

A compact all-photonic-crystal-fiber (all-PCF) polarizer based on fused-type mode-selective fiber coupler is proposed theoretically. Around the wavelength of 1550 nm, the injected unpolarized fundamental mode in the solid-core PCF was selectively coupled into one polarization-mode of polarization-maintained photonic crystal fiber (PMPCF) by welldefined fiber cladding reduction, pretapering and fusion. Numerical simulations indicate the polarization direction of the excited polarization-mode depends on the tapered diameters of solid-core PCF and PMPCF. Moreover, the operation bandwidth of the proposed polarizer is more than 400 nm, which can completely cover the bandwidth of the erbiumdoped solid-core PCF amplified spontaneous emission (ASE) light source. The all-PCF polarizer is anticipated to serve as the key element in the PCF optic gyroscope.

A cascading core-offset in-line fiber Mach-Zehnder interferometer (MZI) was proposed to improve the RI sensitivity and eliminate the cross sensitivity between RI and temperature. The sensor was fabricated by cascading a small core-offset inline fiber MZI (the offset displacement is 6μm and interference arm length is 30mm) with a large core-offset in-line fiber MZI (the offset displacement is 40μm and interference arm length is 30mm). By enlarging the offset displacement, the RI sensitivity was improved from -9.177 to 108.326nm/RIU. And the MZIs with two offset displacement offer interference dips with different RI response, by utilizing the interference dips, the simultaneously measurement can be realized to eliminate the cross sensitivity.

Although the cascaded double ring sensor can improve the sensitivity due to the difference between the radii of the reference ring and the sensing ring to produce Vernier effect, a large bandwidth spectrometer or a large tunable range laser is required for the wavelength interrogation. In this paper, the cascaded double ring senor based on silicon on insulator (SOI) with thermo-optical tuning for refractive index sensing is investigated. The peak wavelength shift of the transmission envelope can be converted into the electric power change of the micro-heater. The sensitivity reaches 33.703×10³ mW/RIU by fitting Gaussian function to the spectral envelope for the wavelength interrogation with 7.9 nm wavelength measurement range.

Fiber optic distributed acoustic sensing (DAS) based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) technology has been widely used in safety monitoring areas including monitoring of oil/gas pipes, communication or power cable, perimeters and so on, however it suffers from the high nuisance alarm rate (NAR) due to the non stationarity characteristics of signal and the interference of external environment. In this paper, GMMs-HMMs is utilized to reduce nuisance alarm rate, we prove that short time signal unit of appropriate length can contain the main frequency domain characteristics of signal, GMMs-HMMs is efficient recognition method for frequency domain sequence of signal. the experience results show the average recognition accuracy rate is 88.89% for seven events.

MEMS accelerometer is one of the most popular sensors which is widely used in resource explorations, seismic measurements, structural monitoring, and consumer electronics as its good performance and low cost. However, the stiffness of the conventional accelerometers is fixed, which limits the bandwidth of the sensor, so that they are just used in specific applications. In this paper, a stiffness adjustable optical MEMS accelerometer based on electro-thermal actuator is proposed, whose stiffness can be adjusted over a large range by the electro-thermal actuator. The stiffness adjustment is just depending on the voltage applied on the electrodes, which changes the geometrical characteristic of the spring beams by exerting an axial compression displacement on them, enabling the device to neutralize its intrinsic positive stiffness, thus a neutrally stable quasi-zero stiffness region is obtained. The test results show that the first order resonant frequency of the accelerometer can be tuned to below 19 Hz from the unloaded state value of 500 Hz, which greatly changes the working bandwidth of the accelerometer. Combined with the high-resolution optical read-out scheme, the theoretically achievable system resolution can be μg levels. Therefore, the designed stiffness adjustable accelerometer can be used in different bandwidths application fields.

High resolution submarine seismic survey techniques have become necessary in many actual geological and geophysical investigations. A new type of mini- distributed acoustic sensing (DAS) module is developed for working at the bottom of the sea with several kilometers long single-mode fiber cable for tens of thousands channels at the same time. Integrated designs of optics and electrics help to significantly reduce volume and power consumption. Compared with common Land-based DAS system, the size and power consumption of the mini-DAS module are significantly optimized. The size is 150mm x 300mm x 110mm (Width x Length x Height), and the power consumption is down to 25W. The spatial sampling resolution of ~0.8m is retained for high resolution seismic profile in the deep sea survey. The upper limit of response frequency is set by 500Hz for the channel sample rate of 1000S/s to realize the long term data storage. It presents a powerful signal acquisition ability with the average system noise of 4.79×10^-4 rad/√Hz and the minimum detectable strain is 10.4pε/√Hz. The novel mini-DAS module has high enough capabilities for real-time seismic wave signal detection in deep sea.

A non-invasive optical fiber pulse sensor is proposed and experimentally demonstrated. It comprises a simple structure in which a section of thin-core fiber is spliced into another single-mode fiber. And a silicone rubber device is designed to ensure that weak pulse signals are detected. To assess the availability of the optical fiber pulse sensor, a commercial photoplethysmograph is used to measure the pulse of the same subject as a control. The measurement results of the two methods are consistent. The fiber pulse sensor can show a segmented signal in individual pulses, which provides more physiological information. It also possesses the advantages of high sensitivity, simple signal acquisition and processing, easy fabrication, and thus is an ideal candidate for replacing traditional electrical sensor.

Fiber-optic hydrophone can be used to monitor and detect the weak acoustic signal in the marine environment. It has the characteristics of high sensitivity, good frequency response and wide dynamic range. In order to detect the acoustic signal in the open sea, the repeated fiber-optic hydrophone transmission system is necessary to realize the long-distance transmission. Due to the unidirectional optical isolation of the repeater in the optical transmission path, the Rayleigh back-scattered light of the optical cable after the repeater cannot be returned to be detected, so there is no means to monitor the status of the optical cable after the repeater. In order to realize the monitoring of the vibration state of the submarine cable after the repeated fiber-optic hydrophone transmission systems, a vibration measurement technique based on the combination of distributed acoustic sensing(DAS) technology and the optical cross coupling technology between each amplifier pair of the repeater is proposed. In order to reduce the influence of optical surge caused by the returned optical pulse amplification, the multi-wavelength pulse of optical fiber hydrophone is used as the filling light pulse of distributed vibration detection. The Rayleigh back-scattered light with vibration information is amplified by the repeater through the cross-coupling path, then detected and demodulated by Heterodyne detection technology, and the vibration information is acquired. A distributed fiber-optic vibration sensing system for repeated fiber-optic hydrophone transmission system is established in the laboratory. The system can not only use the multi-wavelength light of fiberoptic hydrophone as the filling light of distributed vibration detection, but also filter the Rayleigh back-scattered light induced by the multi-wavelength light , so as to improve the signal-to-noise ratio of detection. The system can accurately locate the vibration of optical cable within 5km after the repeater in real time, and the maximum measured vibration frequency is 2kHz. The power spectrum density fluctuation at 1kHz is less than 2dB. The experimental results show that the coupling optical path does not affect the demodulation of the fiber-optic hydrophone array signal by the fiber- optic hydrophone demodulation system.

We develop an on-line monitoring method for partial discharge of high-voltage electrical cable. The optical fiber current sensor construction that combines the magneto-optic material with the ferromagnetic ring concentrator. We carry on the simulation and analysis to air gap magnetic field of the ferromagnetic ring concentrator using the COMSOL Multiphysics finite element analysis software, find the method to solve the air gap size of ferromagnetic ring concentrator and the placement of the magnetic field crystal according to the magnetic field distribution rule. We have studied distinctive features of the response of a fibre-optic current sensor with a magneto-optic crystal sensing to short current pulses. The response of the current sensor to the pin-to-plate discharge model of electrical cable at different voltage levels has a linear relationship and its duration is determined by the relationship between the current pulse duration.

In the era of the Internet of everything, 5G is on the way out, and the demand of various terminal devices for sensors is increasing, but at present, the commercial sensors on the market are mainly made of rigid materials.Therefore, flexible and transparent sensors are rare in certain situations (such as human wearable devices).Therefore, it is an ideal choice for wearable electronic products to develop a flexible and transparent pressure sensor with high sensitivity, quick response, wide range of production and simple process.Based on the photolithography process, we successfully manufactured a flexible transparent capacitance sensor with a pyramid structure based on nickel electrode /PDMS sandwich structure.Although the biomimetic structure reported in other literature or the folded microstructure generated by tensile PDMS can also be used to improve sensitivity, it does not have graphic controllability and affects mass production. Compared with this, the lithography process has incomparable benefits.The production process is standardized, and the graphic control can be controlled, and the unified and standardized production can be carried out in large area and large quantity.And as far as we know, the nickel electrode capacitive pressure sensor was reported for the first time.Its flexibility and transparency are better than ITO electrodes currently on the market.Simple process, low price and easy to manufacture in large format.Compared with the pure PDMS dielectric layer with planar structure, the pyramid microstructure sensor has higher sensitivity, lower detection limit, good stability and durability.The mechanism of enhanced sensing for pyramid microstructure is also discussed.Therefore, the developed pressure sensor has a great application prospect in the field of electronic skin.

Based on the theoretical model and simulation, this paper presents the acoustic detective sensitivity of three types of optical fiber acoustic sensors – RIM-FODS (reflective intensity modulated fiber optic displacement sensor), extrinsic F-P (Fabry-Perot) interferometer and all-fiber photoelastic interference sensor. Three designed optical fiber acoustic sensor systems are implemented to analyze the performance of each type and tested to investigate the detective sensitivity at 1kHz 94dB SPL (sound pressure level). The experimental results are in good agreement with those obtained by theoretical analysis and simulation.

Non-enzymatic glucose sensor has the characteristics of simple operation and low production cost compared with the strict operating condition of enzyme-based glucose sensor, and various nanostructured Cu have been investigated extensively for non-enzymatic glucose sensor due to their high electrocatalytic performance, low-cost and abundance. In addition, most of the current glucose sensors have poor adhesion due to their rigid structures, or increased discomfort in the wearable devices due to poor breathability. In this paper, a flexible, transparent, breathable, and attachable nonenzymatic glucose sensors was fabricated via in situ growth of Cu nanoparticle on transparent nickel-mesh electrodes. The prepared Cu-Ni non-enzymatic glucose sensors have the advantages of ultrathin (~10 μm), high transparency (~ 80% transmittance), and high breathability (duty cycle ~ 90%). In addition, the non-enzymatic glucose sensors we prepared exhibited an extraordinary limit of detection as low as 2 μM and free from chloride poisoning. Furthermore, the interference from urea, fructose, lactose, sucrose, uric acid at the level of their physiological concentration were insignificant, indicating excellent selectivity. Therefore, the prepared Cu-Ni non-enzymatic glucose sensors may become a promising nonenzymatic glucose sensor and the work also provides a strategy for the design of wearable glucose sensors.

The laser has good coherence and its polarization is easy to modulate. It is an important light source. The surfaces of common objects can be regarded as random rough surfaces at the laser wavelength scale. Random rough surface modulates incident polarized light, and the scattered light contains the information of geometric profile and physical properties of the target surface. For the laser detection system, it is important to perceive the high dimensional information which was contained in the target echo signal. In this paper, the Stokes vector was used to describe the scattered light. The virtual instrument technology was adopted to develop a laser scattering measurement system. The Labview software that running on the computer issued control commands to microcontroller unit (MCU) by serial port communication. We made a high precision digital light detector. The MCU obtained the scattered light intensity from the photoelectric sensor via I²C bus. The incident light was modulated to two typical linearly polarized light using a polaroid and a half wave plate. The Stokes vector could describe the state of the scattered light completely, and which was measured by the polarization detection system. The Stokes vector of all angular hemispheric space backscattering light was measured. The results showed that the scattered light on the surface of metal object appeared circularly polarized component. However, the circular polarized component of the scattered light on the dielectric target surface was almost zero. The above conclusions could provide theoretical basis for the laser detection system to identify metal targets.

A kind of fiber optic particle velocity sensor based on planar cantilever beam is studied. The fiber laser is attached to the surface of a cantilever. The cantilever beam is deformed by the acoustic field in the vertical direction of the surface, and the frequency of the output of the fiber laser is modulated, so as to realize the acoustic vector sensor. In particular, in viscous fluids, the cantilever is driven by an additional force proportional to the velocity of fluid particle. By selecting the appropriate liquid, the fluid viscous force will become the main driving force of the cantilever beam, making the sensor respond directly to the velocity of water particle, thus having a flat sound pressure sensitivity response curve. According to the cantilever beam equation in fluid, the theoretical simulation of the frequency response of the sensor shows that the acoustic pressure sensitivity is 10⁴Hz/Pa and the acceleration sensitivity is 10⁸Hz/g from 10Hz to 60Hz. The acoustic pressure sensitivity and acceleration sensitivity of the sensor in air and water are studied by experiment, and the results are consistent with the theoretical simulation. Compared with the traditional fiber optic accelerometer, the sensor of this structure has the advantages of small size, simple structure and high sensitivity, which is of great significance for application of vector hydrophone in low frequencies and is beneficial to constitute large scale hydrophone array.

The phase noise induced by the intensity noise fluctuates in some sensing systems, which could affect the assessment of system performance. In this paper, the phase noise induced by the intensity noise in the phase generated carrier (PGC) detection system is modeled. It manifests that the phase noise level has a trigonometric relation with the initial phase of the interference fringes, namely workpoint-related fluctuation. Besides, the shape of the fluctuation to the workpoint is also a function of the modulation depth. As a result, the measurement for phase noise should iterate over many workpoint sets at a special modulation depth. Whereas the workpoint iteration is not always actually viable, a modified PGC detection scheme that combined the 3×3 coupler multi-phase method is proposed. To average out the three demodulated outputs, the phase noise is theoretically independent of the workpoint, which is also smaller than the traditional value. The tested results show good accordance with the theory. The theoretical model and method in this paper can be used as a guidance of the noise assessment in large-scale multiplexed sensing networks.

The photoelectric detecting technology bas-ed on the 3×3 coupler is widely used in interferometric fiber optic hydrophone systems. Parameters such as DC and AC amplitude and phase difference of the couplers have a crucial influence on the accuracy and stability of demodulation. In this paper, an ellipse fitting algorithm based on light source modulation is used to achieve real-time, accurate measurement and correction of the detection parameters, eliminating the impact of the 3×3 coupler asymmetry on the system. The signal detecting accuracy is improved with the effectively suppressed system noise, realizing the stable signal detecting for the fiber optic hydrophone. Compared with the traditional ellipse fitting algorithm based on external large signal modulation, the proposed algorithm presents higher reliability and practicability. Furthermore, in view of the characteristics of large-scale array data processing and high real-time requirements, this paper adopts a heterogeneous design of ARM+FPGA, using the SDSoc platform to carry out software and hardware collaborative development of the 3×3 coupling demodulation algorithm based on light source modulation. ARM implements task allocation and scheduling functions, and FPGA implements specific function calculation modules. this design greatly reduces the pressure of computer data processing, and ensures that the optical fiber hydrophone system can complete automatic parameter calibration while real-time demodulation. The demodulation efficiency of the 3×3 algorithm is improved, coupled with the high integration and easy expansion of the system itself, provides the possibility for future large-scale arrays of 3×3 detection schemes in fiber optic hydrophone systems.

The paper performs Finite-Difference Time-Domain (FDTD) mathematical modeling method application of electric field distortion near the surface of rough gold surfaces. During the simulation, parameters such as particle size, nanoparticles height, the effective amplification of the E component of electromagnetic field on the surface morphology were investigated. The prospects of the theoretical approach of rough surface modeling for sensory purposes tasks are shown. The data presented can be used as a basis for controlled nanolithography fabrication of gold rough surfaces.

This paper reports a resonant type optical fiber vector hydrophone (OFVH) for deep-sea applications, which is composed of a three-component optical fiber accelerometer and an optical fiber pressure hydrophone. To meet the acoustic requirements in the deep-sea, the orthogonal and unitized structure of the three-component accelerometer is adopted to increase the sensitivity and the operating frequency band of the accelerometer. The results show that the acceleration sensitivity is about 40dB re rad/g and the pressure sensitivity is nearly -147 dB re rad/μPa. The fluctuations of the acceleration and pressure sensitivity are less than 1.5dB over the 10-2000Hz frequency range. The deep-sea trial verified its excellent acoustic detection performance. Both the direction-of-arrival (DOA) and range for distant ship is estimated. The DOA estimation error is no higher than 10° and the range estimation error is less than 10%. This OFVH has a wide application prospect in the deep-sea.

A surface-enhanced Raman scattering (SERS) based microRNA (miRNA) probe was designed using molecular beacon (MB). In such a probe, silver nanoparticles were employed as the SERS substrate while 6-FAM was selected as a Raman reporter, which were connected by a hairpin shaped DNA. In the presence of target miRNA, the hairpin opened, making 6-FAM far away from the substrate with a decreased SERS intensity. As the concentration of the targets increased, the SERS intensity of Raman reporters decreased. Thus, according to the intensity-concentration calibration curve, the detection of miRNA-21 could be realized. The convenient, stable and sensitive detection method holds potential in the application of diagnosis.