Xinyu Meng

Bio: Xinyu Meng is an academic researcher from Shanghai University. The author has contributed to research in topics: Materials science & Computer science. The author has an hindex of 2, co-authored 4 publications receiving 13 citations.

All-fiber mode converter based on fiber grating and multimode interference

Abstract: We propose a novel mode converter (MC) based on multimode interference (MMI). This MC taking advantages of long-period fiber grating and multimode interference, it not only has high conversion efficiency, but also greatly reduces the interference between modes.

Measurement of interfacial characteristics and droplet entrainment in nearly horizontal liquid-liquid flows using PLIF method

Abstract: Liquid-liquid two-phase flows are widely encountered in petroleum, chemical, and other important industrial production fields. The two-phase pipe flow shows obvious multi-scale structure characteristics, including large-scale interface fluctuation and small-scale entrainment of droplets. The study of interfacial characteristics and droplet entrainment is of great significance for uncovering the mechanism of heat and mass transfer between phases and optimizing the industrial production process. In this paper, a planar laser-induced fluorescence (PLIF) system based on a continuous laser was designed, and a liquid-liquid two-phase flow experiment was carried out to obtain PLIF fluid images under different flow patterns. The image processing algorithms were used to accurately detect the liquid-liquid stratified interface and entrained droplets. By extracting the wavelengths and amplitudes of interfacial waves, the relationship between wavelengths and Froude number was studied. The relationship between the amplitude-length ratio of the interfacial wave and Weber number was investigated, and the instability of the interfacial wave and the process of droplet detachment were revealed. The volume entrainment ratios of dispersed droplets in the continuous phases were accurately detected, and the effects of phases velocities and interfacial shear on the entrainment ratio of droplets were studied.

Measurement and Prediction of Droplet Entrainment in Inclined Liquid–Liquid Flow by PLIF Method

Abstract: Inclined liquid–liquid two-phase flows widely exist in petroleum, chemical, and other important industrial processes. The study of droplet entrainment in inclined flow is of great significance for investigating the heat/mass transfer between phases and optimizing the industrial production processes. In this study, a planar laser-induced fluorescence (PLIF) system is designed to visualize the inclined liquid–liquid flows. The silicone oil (organic phase) and water/glycerol mixture (aqueous phase) are used as the experimental media. The length and amplitude of the interfacial waves are derived from the flow visualizations. The relationship between the critical wavelengths and Froude number is explored to indicate the transition from stratified flow (ST) to stratified flow with mixing at the interface (ST&MI). The wave aspect ratio is derived to characterize the instability and breakage of the interfacial wave. Meanwhile, the entrainment ratios of dispersed droplets in the continuous phases are detected, and the effects of the flow rate and the interfacial shear on the droplet entrainment are studied. Finally, a physical model is developed to predict the droplet entrainment ratios based on the force balance analysis of the interfacial wave. In general, the developed model is effective in predicting the droplet entrainment ratio with mean absolute errors of 0.015 and 0.023 for the organic and aqueous droplets, respectively.

All fiber compact bending sensor with high sensitivity based on a multimode fiber embedded chirped long-period grating.

Abstract: We investigated and prepared a chirped long-period grating for high sensitivity bending measurement The novel fiber structure is composed of the multimode fiber (MMF) with fixed length and gradually longer single-mode fiber using the continuous splicing method The powerful ability of refractive index modulation in the MMF renders the miniaturization of the sensor The total length of the sensor is 345 mm Chirped period arrangement is adopted to improve the bending sensitivity Through numerical calculation, the chirp coefficient is determined, and the clear resonance peaks are obtained using the wavelength scanning The experimental results of several samples show that the maximum bending sensitivity is 5368nm/m-1 at 0-1803m-1 With the advantages of small size and high sensitivity, the sensor is especially suitable for bending sensing with a micro-structure

Polarization-Maintaining Fiber Long-Period Grating Based Vector Curvature Sensor

Abstract: We propose and demonstrate an optical fiber vector curvature sensor based on a long-period fiber grating (LPFG) inscribed in Panda type polarization-maintaining fiber (PMF) using CO2-laser heating and tapering system. The uniform heating approach removes the necessity of CO2-laser exposure alignment along the axis of PMFs during grating fabrication. A serial of PMF-LPFGs with grating period from 350 to 490 $\mu \text{m}$ with a step of 20 $\mu \text{m}$ have been fabricated experimentally. The curvature response of the fast and slow axis resonance dips for the LPFG with a period of 450 $\mu \text{m}$ was investigated in the curvature range from 0 to 4.137 m−1 at four bending orientations. The maximum curvature sensitivities were measured to be 9.26 and −6.89 nm/m−1 for the fast and slow axis LP15 modes, respectively. The sensor can achieve 2-dimensional bending direction recognition. The proposed grating has potential application as a vector curvature sensor.

Arbitrary TE $_0$ /TE $_1$ /TE $_2$ /TE $_3$ Mode Converter Using 1 × 4 Y-Junction and 4 × 4 MMI Couplers

Abstract: We propose a compact silicon-on-insulator based device which is capable of arbitrarily converting optical modes TE $_\text{i}$ to TE $_\text{j}$ (i, j = 0, 1, 2, 3). The device consists of two symmetric 1 × 4 Y-junction couplers connected back-to-back with a 4 × 4 multimode interference coupler (MMI). While the two 1 × 4 Y-junction couplers are designed to divide and combine modes at the input and output of the device, the 4 × 4 MMI coupler is used to direct signals from its inputs to suitable outputs. The conversion of a pair of modes is decided by four phase shifters located at the input and output of the MMI coupler. Through beam propagation method (BPM) with effective index method (EIM) simulations, we show that by setting the phase shifters to 0° or 180°, 16 different conversion pairs of input-output modes (TE $_\text{i}$ –TE $_\text{j}$ ) are successfully realized with a mode conversion efficiency larger than 98% and a crosstalk smaller than −30 dB within a wide wavelength range from 1530 nm to 1565 nm.

Bend-Insensitive Simultaneous Measurement of Strain and Temperature based on Cascaded Long-Period Fiber Gratings Inscribed on a Polarization-Maintaining Photonic Crystal Fiber

Abstract: We report an optical fiber sensor capable of bend-insensitive simultaneous measurements of strain and temperature by using cascaded long-period fiber gratings (LPFGs) inscribed on a polarizationmaintaining photonic crystal fiber (PMPCF). The cascaded LPFGs written on the PMPCF have two different interference spectra for orthogonal input polarization states exciting the principal axes of the PMPCF. Each fringe spectrum is created by the interference between the uncoupled core mode and the cladding mode recoupled to the core mode at the second LPFG. Due to the birefringence of the PMPCF, the order of this cladding mode can be different depending on the input polarization. The lowest dip in each interference spectrum is designated as a sensor indicator dip (SID) A or B. These SIDs originating from cladding modes with dissimilar orders can have different strain or temperature sensitivities. The strain and the temperature responses of these SIDs were investigated in an applied strain range of 0 −2244 μe and an ambient temperature range of 25 −95 °C, respectively. The strain sensitivities of the SIDs A and B were measured as approximately −0.93 and −1.41 pm/μe (R2 values: ~0.9984 and ~0.9949), and their temperature sensitivities as ~11.48 and ~15.14 pm/°C (R2 values: ~0.9974 and ~0.9905), respectively. In particular, their bending responses were also explored over a wide curvature range of 0 − 7.984 m−1. Themaximum bend-induced wavelength shift was ~0.06 nm. Owing to their linear and independent responses to strain and temperature and their insensitivity to bending, our LPFG device can be a strong candidate for a practical sensor head for simultaneous measurements of strain and temperature.

Temperature-Insensitive Strain Sensor Based on Microsphere-Embedded Core-Offset Fiber With High Sensitivity

Abstract: Strain sensor with low temperature crosstalk over large strain range is essential for field monitoring of structural safety. We develop a tension-compression strain sensor with high strain sensitivity, large strain range, low temperature, and polarization crosstalk due to many high-order modes interferences from asymmetric off-core microsphere-waveguide. It is based on BaTiO3 (BTO) microsphere embedded on the surface of the silica core-offset fiber via negative thermal coefficient UV glue. Multi-beam reflection and whispering-gallery modes (WGMs) in the microsphere enhance the multi-mode interference, and then improve the strain sensitivity to 17.29 pm/μϵ, which is three times higher than that without microsphere, along with the temperature sensitivity of −0.87 pm/°C, and the strain accuracy of 0.5 μϵ. Thanks to the reduced effective Young's modulus by microsphere and UV glue on an asymmetric core-offset structure, strain range of tension and compression is increased to 153.2 mϵ.