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In this study, the silver mirror reaction was used to coat the silver film on the surface of self-made microstructured fiber (MSF) to stimulate the surface plasmon resonance effect, and Polydimethylsiloxane (PDMS) with a high thermal-optical coefficient was coated on the silver film as temperature-sensitive material. The MSF with silver and PDMS films was coupled with multi-mode fiber on both sides to form the temperature sensor. In this sensor system, the energy is coupled into the cladding of the microstructure fiber by multi-mode fiber, and the surface plasmon resonance can be further excitated in the MSF. When the temperature of the external environment changes, the refractive index of PDMS will also change. At this time, combined with the surface plasmon resonance effect, a resonant absorption peak corresponding to the temperature appears in the transmission spectrum so that the temperature can be measured quickly and accurately. We found that, in the temperature range of 35 °C to 95 °C, the average temperature sensitivity of the sensor during heating and cooling was −0.83 nm/°C and −0.84 nm/°C, respectively. The advantages of this sensor are the simple structure, convenient operation and good reversibility. The relative sensitivity deviation value (RSD = 0.0059) showed that the sensor has high stability. The temperature sensor based on MSF has favorable prospects for use in fields such as medical treatment, biochemical detection and intelligent monitoring. [ABSTRACT FROM AUTHOR]

Arterial stenosis will reduce the blood flow to various organs or tissues, causing cardiovascular diseases. Although there are mature diagnostic techniques in clinical practice, they are not suitable for early cardiovascular disease prediction and monitoring due to their high cost and complex operation. In this paper, we studied the electromagnetic effect of arterial blood flow and proposed a method based on the deep neural network for arterial blood flow profile reconstruction. The potential difference and weight matrix are used as inputs to the method, and its output is an estimate of the internal blood flow velocity distribution for arterial blood flow profile reconstruction. Firstly, the weight matrix is input into the convolutional auto-encode (CAE) network to extract its features. Then, the weight matrix features and potential difference are combined to obtain the features of the blood velocity distribution. Finally, the velocity features are reconstructed into blood flow velocity distribution by a convolution neural network (CNN). All data sets are obtained from a model of the carotid artery with different rates of stenosis in a uniform magnetic field by COMSOL. The results show that the average root mean square error of the reconstruction results obtained by the proposed method is 0.0333, and the average correlation coefficient is 0.9721, which is better than the corresponding indicators of the Tikhonov, back propagation (BP) and CNN methods. The simulation results show that the proposed method can achieve high accuracy in blood flow profile reconstruction and is of great significance for the early diagnosis of arterial stenosis and other vessel diseases. [ABSTRACT FROM AUTHOR]

In this work, a surface plasmon resonance (SPR) temperature sensor based on a con-joined-tubular anti-resonance optical fiber (CTF) was theoretically designed and analyzed using the finite element method. The CTF cladding was composed of eight pairs of conjoined tubes, and one or two holes of the tubes were selectively coated with gold to generate the SPR effect. Alcohol was injected into the core of the CTF to work as the sensing medium using vapor deposition. The proposed sensing structure exhibited excellent birefringence and produced more than six resonant peaks in different wavebands of the X and Y polarization. The positions of those resonant peaks were sensitive to temperature change, and the simulated sensitivity was about 3.2–3.6 nm/°C. The multiple working wavebands of the proposed sensing structure could be used for self-verification. Moreover, the influence of structural parameters on sensing performance was analyzed in detail. Possessing features of high sensitivity, good birefringence, multiple measuring wavebands, and self-verification, the proposed CTF-based SPR sensor has great potential in practical applications such as biological research and chemical sensing. [ABSTRACT FROM AUTHOR]

This paper proposes a highly sensitive surface plasmon resonance (SPR) refractive index sensor based on the photonic crystal fiber (PCF). The optical properties of the PCF are investigated by modulating the refractive index of a liquid analyte. The finite element method (FEM) is used to calculate and analyze the PCF structure. After optimization, the fiber can achieve high linearity of 0.9931 and an average refractive index sensitivity of up to 14,771.4 nm/RIU over a refractive index range from 1.47 to 1.52, with the maximum wavelength sensitivity of 18,000.5 nm/RIU. The proposed structure can be used in various sensing applications, including biological monitoring, environmental monitoring, and chemical production with the modification and analysis of the proposed structure. [ABSTRACT FROM AUTHOR]

This paper proposes a Photonic Crystal Fiber (PCF) refractive index sensor model based on the surface plasmon resonance effect. The proposed PCF model also uses the full vector finite element method to transfer the structure under the anisotropic Perfect Matching Layer (PML) boundary condition. Numerical calculations were carried out on the sensor characteristics. The calculation results show that the elliptical air hole on the left side of the PCF core is coated with a gold-nano film which serves as a Surface Plasmon Resonance (SPR) sensing channel to detect the refractive index of liquid materials. Compared with other structures, the resonant peak generated by the excited SPR effect from the elliptical sensing channel has a high sensitivity to the change of the refractive index of the liquid to be measured. With the help of this attribute, it is relatively easy to adjust the sensitivity. The refractive index range of this structure is within 1.43–1.49 and the sensitivity is up to 12,719.97 nm·RIU−1. The linearity is good; R2 = 0.99927, which is very suitable for liquid sensing. [ABSTRACT FROM AUTHOR]

According to the beam propagation method, a fiber refractive index-sensitive multimode interference (MMI) structure fabricated by splicing a self-made silica glass rod between two single mode fibers (SMF–NCF (no core fiber)–SMF structure) is proposed for liquid level monitoring. Theoretical and experimental investigation was carried out meticulously using a 4.5 cm and a 9.5 cm long silica glass rod. It is proved that the simple and economical sensor with the shorter length has high sensitivity, satisfactory repeatability, and favorable stability. The sensitivity climbs with the increase in refractive index of the measured liquid, which is 204 pm/mm for pure water, 265.8 pm/mm for 10% glycerin solution, and 352.5 pm/mm for 25% glycerin solution. The proposed sensor can be standardized in certain application circumstances to achieve accurate liquid level monitoring. [ABSTRACT FROM AUTHOR]

For this study, a temperature sensor utilizing a novel tellurite photonic crystal fiber (PCF) is designed. In order to improve the sensor sensitivity, alcohol is filled in the air holes of the tellurite PCF. Based on the degenerate four-wave mixing theory, temperature sensing in the mid-infrared region (MIR) can be achieved by detecting the wavelength shift of signal waves and idler waves during variations in temperature. Simulation results show that at a pump wavelength of 3550 nm, the temperature sensitivity of this proposed sensor can be as high as 0.70 nm/°C. To the best of our knowledge, this is the first study to propose temperature sensing in the MIR by drawing on four-wave mixing (FWM) in a non-silica PCF. [ABSTRACT FROM AUTHOR]

Ultrafast all-optical signal modulation induced by optical Kerr effect (OKE) was demonstrated in an all-solid tellurite photonic bandgap fiber (PBGF) which was designed and fabricated based on TeO2-Li2O-WO3-MoO3-Nb2O5 (TLWMN, high-index rods), TeO2-ZnO-Na2O-La2O3 (TZNL, background), and TeO2-ZnO-Li2O-K2O-Al2O3-P2O5 (TZLKAP, cladding) glasses. At the input of a control pulse with high intensity, OKE occurred in the tellurite PBGF and the transmission bands of the tellurite PBGF shifted. The signal at 1.57 μm transmitting in the fiber core can be ultrafast all-optically modulated by the ultrafast single pulse (200 kW, 200 fs) under OKE, where the modulation speed can reach 50 GHz, faster than some commercial LiNbO3 modulators. The results in this paper can be applied to multi-monitors, local area network, detectors, multi-sources, etc. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance (SPR) liquid refractive index sensor based on photonic crystal fiber (PCF) is proposed. The PCF is made of the exposed core structure, and the gold film is formed by electron beam evaporation within its defects. The sensitivity of the sensor is improved by coating graphene on the surface of the gold film. The experimental results show that the sensitivity of the sensor is increased by 390 nm/RIU after the introduction of graphene, and finally to 2290 nm/RIU. The experiment and simulation have a good consistency. Significantly, the sensor can be reused, and the measurement accuracy can be maintained. [ABSTRACT FROM AUTHOR]

In this paper we propose a gold-plated photonic crystal fiber (PCF) refractive index sensor based on surface plasmon resonance (SPR), in which gold is coated on the external surface of PCF for easy fabrication and practical detection. The finite element method (FEM) is used for the performance analysis, and the numerical results show that the thickness of the gold film, the refractive index of the analyte, the radius of the air hole in the first layer, the second layer, and the central air hole can affect the sensing properties of the sensor. By optimizing the sensor structure, the maximum wavelength sensitivity can reach 11000 nm/RIU and the maximum amplitude sensitivity can reach 641 RIU−1. Due to its high sensitivity, the proposed sensor can be used for practical biological and chemical sensing. [ABSTRACT FROM AUTHOR]

A photonic crystal fiber (PCF) sensor based on gold nanowires able to detect changes in surface plasmon resonance (SPR) was proposed and numerically investigated through the finite element method. To facilitate real-time detection, the analyte in this sensor was located outside the optical fiber. The effects of diameters of both air hole and gold wires on the sensing characteristics of the sensor were discussed. The sensor was designed to detect liquids with refractive indexes ranging between 1.33 and 1.36. The numerical simulations indicated that sensor structure improved its functionality. The maximum spectral sensitivity reached 9200 nm/RIU over the entire refractive index range. The average spectral sensitivity was estimated to be 5933 nm/RIU, and corresponded to a sensor resolution of 2.81 × 10 -6 RIU. These findings look very promising for future use in detection of liquid.