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A new method to modify excessively titled fiber gratings (Ex-TFGs) with 20 nm gold nanoparticles (GNPs) through 3-mercapt-otrimethoxysilane(MPTMS) was proposed. By monitoring the wavelength shift of Ex-TFGs for every modified step and using the scanning electron microscope (SEM), it proves that GN Ps are firmly combined on the surface of Ex-TFGs. Finally, by using different concentration of NaCl solutions...
An in-line Mach-Zehnder interferometric refractive index (RI) sensor is demonstrated by concatenating two single-mode fiber (SMF) half-tapers separated by one section of SMF. The cladding modes excited at the first half-taper interferes with the core mode at the second half-taper to generate the interference fringe. Theoretical and experimental results consistently show that the interference fringe...
A sensitivity-enhanced temperature sensor for marine monitoring based on fiber Bragg grating (FBG) has been proposed and experimentally investigated. The temperature sensor has been realized by electroplating a copper coating on a metalized FBG. Then, the coated FBG is packaged by a carbon film, which protects the copper coating from being corroded when the sensor is used in the ocean. The carbon...
A design of mine wind velocity sensor is reported, which is based on differential pressure principle and adopts differential sensitive architecture composed of a bellows, an equal-strength beam and two fiber Bragg gratings(FBG). Furthermore, an algorithm is introduced for temperature compensation. Through these methods the cross sensitivity of temperature is effectively eliminated. The relation between...
Most sensors have the tradeoff dilemma of high sensitivity and large dynamic range. We demonstrate here an all-fiber refractive index sensor based on a composite intrinsic Fabry-Perot interferometer (FPI), which possesses the co-existence advantages of high sensitivity and large dynamic range. Experimental trends are in good agreement with the theoretical predictions. The co-existence of high sensitivity...
A helical long-period grating (HLPG) was written in a polarization maintaining fiber (PMF) with CO2 laser. The twist characteristics of individual and cascaded PMF-HLPG were investigated experimentally. It was found that PMF-HLPG behaved differently with a different light input. When a polarized light was launched into the cascaded PMF-HLPGs with opposite helical direction, a high twist sensitivity...
The yarn break detection system of ring spinning based on tunnel magnetoresistance effect is proposed in the paper. The TMR element is used to detect the anomaly signal caused by rotating traveler. The signal reflects the rotation speed of traveler and the yarn break is monitored by speed measurement. The yarn break sensor, section detection module, machine monitoring module are designed and implemented...
We demonstrate a novel polyvinyl chloride (PVC) diaphragm-based fiber-tip Fabry-Perot interferometer for gas pressure measurements with ultra-high sensitivity. The PVC diaphragm has been coated to the end facet of a well-cut standard single-mode fiber by use of a plastic welder. Ultrahigh pressure sensitivity of ∼66.07 nm/MPa at 1565 nm and a low temperature cross-sensitivity of —5.5 KPa/°C have been...
A methylcellulose (MC) coated humidity sensor by using photonic crystal fiber (PCF) based Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated. It is fabricated by sandwiching a PCF between two standard single mode fibers (SMFs) with the air holes of the PCF in the fusion splicing region being fully collapsed. Experimental results show that this structure can not only carry...
A novel humidity sensor, which is based on Michelson interferometer (MI) with thin core fiber (TCF) coated with chitosanis proposed and experimentally demonstrated. Its principle is that the light in the single-mode fiber (SMF) core is excited into the cladding of the TCF, and the light transmitted from the end face of the TCF is reflected back to the SMF core. When the chitosan is coated on the end...
We propose and demonstrate a cascaded-cavities Fabry-Perot interferometer (FPI) for simultaneous measurement of pressure and temperature based on photonic crystal fiber. The sensor is composed of cascaded air-cavity and silica-cavity. The air-cavity and silica-cavity are both sensitive to temperature and pressure because of the thermo-optic coefficient and Young's modulus. We can obtain the pressure...
A tadpole-shape fiber sensor, with S-bend fiber cascading spherical shape, has been proposed and experimentally realized in this work. In our experiments, the output spectrum of the proposed sensor was found to be shifted with the changing of the refractive index and the temperature. Experiments results showed that the highest sensitivity of the refractive index was up to −114.845nm/RIU with a wide...
We propose a refractive index (RI) sensor based on a liquid-filled defect hollow core Bragg fiber (DHCBF) for high index sensing, in which a resonant wavelength resulted from the transverse resonant coupling effect between core modes and defect modes is utilized as the characteristic wavelength. The linearity and sensitivity strongly depend on structural parameters of defect layer. Accordingly, we...
A volatile organic compounds (VOCs) sensor based on intrinsic Fabry-Perot interferometer (IFPI) coated with polypyrrole thin film was proposed and experimentally demonstrated. The IFPI consists a section of hollow-core fiber (HCF) sandwiched between two single mode fiber. The polypyrrole is formed chemically via interfacial polymerization technique and coated directly onto the fiber. As the isopropanol...
High-reproducible chiral long-period gratings (CLPGs) are achieved, which are fabricated from normal single mode fibers. To explore torsion sensing application, we investigate the response trend of transmission spectrum versus mechanical twist rate in CLPGs. High torsion sensitivity is achieved, a perfect linear relationship between the resonance wavelength shift and the mechanical twist rate is displayed.
This letter puts forward weak FBGs Fabry-Perot (FP) structures with copper coating for quasi-distributed temperature measurement. The weak FBGs (−33dB) are fabricated by on-line draw tower. The sensors system exhibits the superiorities of high signal to noise ratio (SNR). At the same time, wavelength/frequency/time multiplexing immensely increases the capacity of the sensing system. In the experiment,...
We present and numerically characterize a single liquid-core photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor. The two gold coated liquid analyte channels as big as core are placed near the core for easy excitation of free electrons to produce surface plasmon waves (SPWs). A sufficiently strong SPR is achieved by adjusting the size of the air holes between the core and the...
Optical waveguide sensing has developed rapidly in recent years. In this paper, we review our previous work about the high-sensitivity optical waveguide sensors based on Vernier effect. Experimental results show these optical waveguide sensors have the great potential applications in biological research and environment monitoring.
In this paper, we fabricate a microfiber coupler (MFC) functionalized with Teflon thin film. Since Teflon has a negative thermo-optic coefficient, it can compensate for the thermal effects of silica. The temperature dependence of the MFC depends on the radius of microfiber which controls the thermal effect contributions of silica and polymer. The device we fabricate has the temperature sensitivity...
Comparing with uncoated LPFGs, ZnO coated LPFG shows obvious improvement of RI sensitivity between the RI range of 1.4 and 1.62. The proposed structure exhibits a very high sensitivity of 5175 nm/RIU in the RI range from 1.444 to 1.448, and the sensitivity could be further improved by optimizing the thickness of the ZnO thin film.
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