Junhui Hu

Guangxi Normal University · College of Physical Science and Technology

In this Letter, a method for measuring large dynamic strain via slope-assisted Brillouin optical time domain reflectometry (SA-BOTDR) is proposed. A linear artificial slope created by a frequency equalizer is used instead of the traditional slope of the Brillouin gain spectrum (BGS) as the linear response region between the Brillouin frequency shif...

A slope-assisted Brillouin optical time domain reflectometry system with large dynamic strain range was proposed and demonstrated using graded-index multi-mode fiber (GI-MMF) as sensing fiber. Analysis of the simulated and experimental results indicated that the Brillouin gain spectrum in GI-MMF could be broadened by controlling the coupling effici...

A microfiber interferometer water hardness sensor is proposed, and its capabilities are demonstrated in an experiment. The sensor is fabricated by using a piece of microfiber with a diameter of 10.4 μm formed via the heating melt stretching technique. At this scale diameter, a strong evanescent field is generated on the surface of the microfiber, w...

To explore a fast, simple, and accurate method to identify adulteration in flaxseed oil, the Raman spectral data of 130 samples containing flaxseed, canola, cottonseed, and adulterated oils were obtained using a portable fiber optic Raman spectrometer. The Raman spectral results showed that the Raman spectra of the flaxseed and canola oils had noti...

Cost-effective and high-responsivity photodetectors at a telecommunication wavelength of 1550 nm are highly desired in optical communication systems. Differing from conventional semiconductor-based photodetectors, several planar hot-electron photodetectors (HE PDs) that operate at 1550 nm have been reported. However, these devices were often compri...

This work proposes a fast and accurate method based on near-infrared (NIR) spectroscopy with partial least-squares discriminant analysis (PLS-DA) and aquaphotomics to identify toxic honeys. PLS-DA was used to construct an optimal model for distinguishing toxic honey from non-toxic honey. The models based on preprocessed NIR spectra have an accuracy...

An in-line reflective dual-parameters fiber-optic sensor is proposed in this work, whereas it is experimentally verified by measuring both the liquid level and the local temperature distribution simultaneously. The proposed sensor configuration comprises a single-mode fiber (SMF), a tapered few-mode fiber (TFMF), as well as a silver-coated capillar...

A highly accuracy optical fiber sensor based on a fiber Bragg grating (FBG) is proposed and demonstrated for surface tension coefficient of liquid (STCL) measurement. In the experiment, pull-off method is applied to measure the STCL, and FBG is used as a high precision tension sensor. The performance is minutely studied in the surface tension coeff...

A fiber in-line Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated for simultaneously measuring transverse loading and temperature. The MZI is fabricated by simply splicing a segment multicore fiber (MCF) with two short sections of multimode fibers (MMFs). The sensing principle is theoretically analyzed and the transverse...

A fibre loop mirror sensor is proposed and demonstrated for strain and temperature measurements in experiment. In these schemes, fibre loop mirrors are constructed with single‐mode‐multimode‐polarization‐maintaining‐multimode‐single‐mode optical fibre (SMPMS) structures. The strain and temperature characteristics of the sensor, depending on the len...

A high sensitivity pressure sensor based on a single mode-polarization-maintaining-single mode fiber (SPS) structure fiber loop mirror is proposed and experimentally demonstrated. The sensing structure is fabricated by simply splicing a section of polarization-maintaining fiber (PMF) between two pieces of single mode fibers. The effect of PMF lengt...

We demonstrate that multiple higher-order topological transitions can be triggered via the continuous change of the geometry in kagome photonic crystals composed of three dielectric rods. By tuning a single geometry parameter, the photonic corner and edge states emerge or disappear with higher-order topological transitions. Two distinct higher-orde...

Water affinity property of the polymer optical fibre (POF) makes it possible for humidity sensing. In this paper, we propose and experimentally demonstrate a high-resolution POF-based humidity sensor that utilizes microwave photonic interrogation technique. A Mach-Zehnder interferometer (MZI) of one arm inserted with the POF is used as the interrog...

We propose and experimentally demonstrate a novel interference fading suppression method for phase-sensitive optical time domain reflectometry (Phi-OTDR) using space-division multiplexed (SDM) pulse probes in few-mode fiber. The SDM probes consist of multiple different modes, and three spatial modes (LP01, LP11a and LP11b) are used in this work for...

A fiber-optics liquid level sensor based on a PM-MD structure fiber loop mirror is proposed and demonstrated experimentally. The PM-MD structure is fabricated by core-to-core splicing a section of polarization-maintaining fiber (PMF) with a segment of multimode D-shaped fiber (MDF). Then the PM-MD structure is built into a Sagnac loop using a 3 dB...

To investigate the feasibility of using spectral feature fusion technology to diagnose Alzheimer’s disease (AD), near-infrared (NIR) and mid-infrared (MIR) spectra were collected on 265 serum samples from healthy individuals and Alzheimer’s disease patients. The optimal number of PCs is used to construct diagnostic models for AD using partial least...

We demonstrate that multiple higher-order topological transitions can be triggered via the continuous change of the geometry in kagome photonic crystals composed of three dielectric rods. By tuning a single geometry parameter, the photonic corner and edge states emerge or disappear with the higher-order topological transitions. Two distinct higher-...

The development of optical fiber technology has facilitated the technological innovation in optical fiber communication and sensing systems over the past decades. Among all the fiber sensing technologies, distributed optical fiber sensing (DOFS) has attracted great research interests and been extensively investigated. In optical fiber communication...

An in-line Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated for simultaneous measurement of temperature and directional torsion. The MZI structure is fabricated by fusion splicing a section of multi-core fiber (MCF) between two segments of multi-mode fibers (MMFs). The temperature and torsion sensing characteristics are...

Early diagnosis is important to reduce the incidence and mortality rate of diabetes. The feasibility of early diagnosis of diabetes was studied via near-infrared spectra (NIRS) combined with a support vector machine (SVM) and aquaphotomics. Firstly, the NIRS of entire blood samples from the population of healthy, pre-diabetic, and diabetic patients...

A highly sensitive temperature sensor based on seven-core multicore fiber-polarization maintaining fiber (MCF-PM) structure fiber loop mirror is proposed and experimentally demonstrated. The effects of lengths of seven-core MCF and PM fiber on the temperature and strain sensitivities were studied. The results show that both the lengths of the MCF a...

A novel Young’s modulus measurement scheme based on fiber Bragg gratings (FBG) is proposed and demonstrated experimentally. In our method, a universal formula relating the Bragg wavelength shift to Young’s modulus is derived and metal wires are loaded strain by using the static stretching method. The Young’s modulus of copper wires, aluminum wires,...

A high-sensitivity all-fiber temperature sensor based on a Sagnac interferometer is demonstrated by splicing a section of polarization maintaining fiber (PMF) between two sections of standard single mode fibers (SMFs). In this sensor, the SMF-PMF-SMF structure in the Sagnac loop is bent into a circle to enhance the sensitivity. The length and curva...

A cost-efficient P-D fiber structure-based Sagnac loop sensor is proposed and experimentally demonstrated for measuring temperature and liquid refractive index (RI). The P-D structure is fabricated by fusion splicing a section of polarization-maintaining fiber (PMF) to a piece of multimode D-shaped optical fiber (MMDF). Then the P-D structure is bu...

We present a method to investigate the influences of the thermal fluctuations on the nanometer-sized particle in pickup manipulation by an atomic force microscope (AFM). We show that thermal fluctuations can play an important and even major role in the interaction between particles at room temperature. Moreover, thermal fluctuations always have an...

Adhesive forces commonly exhibit a monotonic increase or a maximum with increasing relative humidity. However, anomalous behavior has been reported. Here, a numerical model of adhesive forces, comprised mainly of capillary and van der Waals forces, between a tip and a surface is established. It is described by a power law that considers the geometr...

A BOTDA sensing scheme combined frequency sweeping and slope-assisted techniques is proposed and experimentally demonstrated for simultaneously temperature and strain-induced vibration sensing. In this scheme, during sweeping Brillouin gain spectrum (BGS) for temperature measurement, we simultaneously perform FFT to the time-domain traces whose pro...

It is well known that surface effect forces, such as van der Waals force and capillary force, are the major contributions to adhesion when microsized particles are in contact in humid environment. But it is very complex to calculate the adhesion force between two smooth unequal particles. In conventional approaches, the effective particle radius ap...

In classical optical time domain reflectometries (OTDRs), for sensing an 200-km-long fiber, the optical pulses launched are as wide as tens of microseconds to get enough signal-to-noise ratio, while it results in a two-point resolution of kilometers. To both reach long sensing distance and sub-kilometer resolution, we demonstrated a long-haul photo...

We propose a distributed Brillouin temperature fiber sensor using a single-photon detector. In our scheme, the Rayleigh/anti-stokes ratio is used to measure the temperature information along the sensing fiber. A cascading fiber Bragg grating filter is employed to separate Brillouin anti-stokes signals from the backscattering Rayleigh light with a ∼...

The van der Waals force (vdW force) between particulate matters at low humid condition and short distance contact is of great scientific importance in surface science. Due to the conventional theory for the van der Waals force between particles in single (vacuum or water) medium can not be directly applied in the humid condition, we present a mathe...

The quantitative description of adhesion force dependence on the probe shape is of importance in many scientific and industrial fields. We performed a theoretical study on the influences of the probe shape (the sphere and parabolic probe) on the adhesion force at different humidity in order to elucidate how the adhesion force varied with the probe...

A hybrid single-end-access BOTDA and COTDR sensing system is proposed and demonstrated experimentally. In our configuration, the heterodyne detection techniques are applied to improve the SNR of the single-end-access BOTDA. Without adding extra instruments, our system could easily switch between BOTDA and COTDR modes by changing the intermediate fr...

A BOTDA with the capacity of break interrogation is proposed and demonstrated experimentally. In our configuration, coherent detection and double sideband probe method are employed to enhance the signal-to-noise ratio (SNR) and to effectively reduce nonlocal effects, respectively. Without amplification, a 72 km sensing range with 5-meter resolution...

Based on the two-dimension cellular automaton traffic flow model (BML model), a mixed traffic flow model for urban traffic considering the transit traffic is established in this paper. Under the don't block the box rules and the opening boundary conditions, the impacts of transit traffic, the central station, traffic lights cycle, the vehicles leng...

Brillouin Optical Time Domain Reflectometry (BOTDR) has the ability to measure strain and temperature continuously in a fiber. It can be applied in the health structural monitoring for large-scale civil project such as bridges, dams and smart grid. Pulse coding/decoding technique can improve Signal to Noise Ratio (SNR) of BOTDR signal. However, at...

A remote fiber Bragg grating (FBG) sensors system based on the self-heterodyne detection and wavelength-sweeping technique is proposed and experimentally demonstrated. In this system, the heterodyne signal produced by the reflected sensing signal and the local reference beam is detected by a balanced photodetector. With frequency-shift and pulse-mo...

Based on the two-dimension cellular automaton traffic flow model (BML model), a mixed traffic flow model for urban traffic considering the transit traffic is established in this paper by using the Don't block the box rules. We have investigated the influences of the transit traffic ratio, and found that, in most cases, the urban traffic flow exhibi...

The prediction and the control of the magnitude of the capillary force are essential for the micromanipulation techniques. It is generally considered that the capillary force is an effective and reliable scheme for micromanipulation. In this paper, a very complicated calculation process for the theoretical capillary force is reviewed, and a practic...

A novel photon-counting optical time-domain reflec-tometry (-OTDR) based on superconducting nanowire single-photon detector (SNSPD) is proposed and demonstrated ex-perimentally. Benefiting from the low noise equivalent power (NEP), high repetition rate and low timing jitter of the SNSPD, our -OTDR system achieves a dynamic range of 22 dB after meas...

Brillouin optical time domain reflectometer (BOTDR) is a distributed optical fiber sensor with broad application prospects. For a given input light wavelength, the Brillouin frequency shift of spontaneous Brillouin scattering light has a linear relationship with both temperature and strain. The distributed temperature or strain can be obtained by m...

A simple approach to generate two bands of tunable microwave signal is proposed and demonstrated. In this scheme, two single-mode fibers with optimized Brillouin frequency shift spacing have been chosen as the scattering medium in two cascaded ring cavities. Two bands of tunable microwave signal from 390 to 453 MHz and 10.863 to 11.076 GHz can be o...

An adaptive step size Gill method is proposed to numerically solve the normal and generalized nonlinear Schrödinger equations. In this method, the Gill algorithm in the interaction picture and the conservation quantity error (CQE) method are used for integration scheme and adaptive step size control, respectively. Nu-merical simulations of the prop...

With the increasing of cars, the influences of bus stops on urban transportation have become increasingly prominent. The researches about the origin-destination of public transportation will help to optimize layout of bus stops, reduce the influences of origin-destination of public transportation on the traffic, and improve the traffic efficiency o...

Using a data sample with a total integrated luminosity of 10.0 pb-1 collected at center-of-mass energies of 2.6, 3.07 and 3.65 GeV with BESII, cross sections for ee annihilation into hadronic final states (R values) are measured with statistical errors that are smaller than 1%, and systematic errors that are about 3.5%. The running strong interacti...

Rare decay modes J/psi -> D(S)(-)pi(+) + c.c., J/psi -> D(-)pi(+) + c.c., and J/psi -> D(0)K(0) + c.c. are searched for using 5.77 x 10(7) J/psi events collected with the BESII detector at the BEPC. No signal above background is observed. We present upper limits on the branching fractions of B(J/psi -> D(S)(-)pi(+)) < 1.3 X 10(-4), B(J/psi -> D(-)p...

Rare decay modes J/ψ→Ds-π+c.c., J/ψ→Dπ+c.c., and J/ψ→DK+c.c. are searched for using 5.77×10J/ψ events collected with the BESII detector at the BEPC. No signal above background is observed. We present upper limits on the branching fractions of B(J/ψ→Ds-π)<1.3×10, B(J/ψ→Dπ)<7.5×10, and B(J/ψ→DK)<1.7×10 at the 90% confidence level.

R values measured with the BESII detector at center-of-mass energies between 3.7 and 5.0 GeV are fitted to determine resonance parameters (mass, total width, electron width) of the high mass charmonium states, ψ(3770), ψ(4040), ψ(4160) and ψ(4415). Various effects, including the interferences and relative phases between the resonances, the energy-d...

R values measured with the BESII detector at center-of-mass energies between 3.7 and 5.0 GeV are fitted to determine resonance parameters (mass, total width, electron width) of the high mass charmonium states, psi (3770), psi (4040), psi (4160) and psi (4415). Various effects, including the interferences and relative phases between the resonances,...

With singly-tagged (D) over bar samples selected from the data collected at and around 3.773 GeV with the BESII detector at the BEPC collider, we have measured the branching fractions for the inclusive K-+/- decays of D+ and D-0 mesons, which are BF(D+ -> K- X) = (24.7 +/- 1.3 +/- 1.2)%, BF(D+ -> K+ X) = (6.1 +/- 0.9 +/- 0.4)%, BF(D-0 -> K- X) = (5...

Using 14.0×106ψ(2S) events collected with the BES-II detector, the C-parity violating process J/ψ→γγ via ψ(2S)→π+π-J/ψ is studied. We determine a new upper limit for the J/ψ→γγ branching ratio of B(J/ψ→γγ)<2.2×10-5 at the 90% C.L., which is about 20 times lower than the previous measurement.

We report measurements of the observed cross sections for e+e-→ωπ+π-, ωK+K-, ωpp̄, K+K-ρ0π0, K+K-ρ+π-+c.c., K*0K-π+π0+c.c., K*+K-π+π-+c.c., φπ+π-π0 and ΛΛ̄π0 at Ös = 3.773\sqrt{s}= 3.773 and 3.650GeV. Upper limits (90% C.L.) are given for observed cross sections and for ψ(3770) decay branching fractions for production of these final states. These m...

Using 58×106 J/ψ and 14×106 ψ(2S) events collected by the BESII detector at the BEPC, branching fractions or upper limits for the decays J/ψ and ψ(2S)→ΛΛ̅ π0 and ΛΛ̅ η are measured. For the isospin violating decays, the upper limits are determined to be B(J/ψ→ΛΛ̅ π0)<6.4×10-5 and B[ψ(2S)→ΛΛ̅ π0]<4.9×10-5 at the 90% confidence level. The isospin con...

By analyzing the data sets of 17.3 pb−1 taken at and 6.5 pb−1 taken at with the BESII detector at the BEPC collider, we have measured the observed cross sections for 12 exclusive light hadron final states produced in e+e− annihilation at the two energy points. We have also set the upper limits on the observed cross sections and the branching fracti...

Hadronic event selection and hadronic detection efficiency are two main sources of systematic error for the R measurement at BES/BEPC. If only the hadronic events with 2-prong and higher prong are selected as done in the previous measurements, the lost events with 0-prong and 1-prong will cause the systematic error for both of the number of hadroni...

We report the statistical properties of three bus-transport networks (BTN) in three different cities of China. These networks are composed of a set of bus lines and stations serviced by these. Network properties, including the degree distribution, clustering and average path length are studied in different definitions of network topology. We explor...

The uncertainty of the treatment for the beam associated backgrounds is one of the dominant errors in the previous R measurement at BES/BEPC. A new method is developed to separate the beam associated sample from the raw data, and this sample is used in tuning the parameters of the hadronic generator LUARLW. This improvement can decrease the systema...

Using 14 x 10(6) psi(2S) events accumulated at the BESII detector, we report first measurements of branching fractions or upper limits for psi(2S) decays into gammapp, gamma2(pi+pi-), gammaKS0K+pi-+c.c., gammaK+K-pi+pi-, gammaK*0K-pi++c.c., gammaK*0K*0, gammapi+pi-pp, gamma2(K+K-), gamma3(pi+pi-), and gamma2(pi+pi-)K+K- with the invariant mass of h...