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Turbulent environment can highly affect the performance of free space optical (FSO) communication links. Therefore, how to obtain the turbulence intensity is a very important issue. The paper has shown the detailed analysis to calculate the log irradiance variance (σ2R) along with the experimental verification under an indoor laboratory controlled turbulence condition. This paper verifies the consistency...
In this paper, a fiber-optic sensing system for simultaneous measurement of temperature and transversal loading based on a fiber-ring microwave photonic filter (MPF) has been proposed and experimentally demonstrated. The temperature variation will induce the central frequency shift of the MPF's passband, while the micro-bend loss induced by transversal loading will cause the change of extinction ratio...
A temperature demodulation method by using compensation of fiber attenuation and dispersion for distributed temperature sensors (DTS) is proposed and demonstrated in order to improve the DTS measuring speed and accuracy. Firstly, the attenuation coefficients difference between anti-Stokes and Stokes backscattering is modified, which avoids the calibration processing on the entire sensing optical fiber...
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...
We demonstrated an optical fiber sensor with high sensitivity of temperature and refractive index, we can use it to measure temperature and refractive index simultaneously. The sensing head consists of a section of multimode fiber (MMF) and a section of multi-core fiber (MCF), which is connected between two segments of single-mode fibers to form a Mach-Zehnder interferometer (MZI). A short section...
Characteristic of two cascaded Mach-Zehnder interferometers based on spherical-shape structures is investigated. When the light in the fiber core is excited into high-order cladding mode, part of the light can propagate along the fiber cladding for a long distance. By cascading two identical interferometers formed by dual spherical-shape structures, it proves that the high-order cladding modes are...
A simple and compact all-fiber sensor based on a sandwich fiber structure for simultaneous measurement of refractive index and temperature is proposed and demonstrated. The sensing element was made by cascading two core-offset attenuators with a fiber Bragg grating (FBG) in between. The two core-offset attenuators make up a Mach-Zehnder interferometer. The transmission spectrum would shift with the...
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...
The applications of specklegram analysis techniques have been developed recently. In this paper, we represent a fiber-optic method to measure the temperature through the analysis of output specklegrams. The proposed all-fiber device excites higher-order modes through splicing a multimode fiber (MMF) to a single-mode fiber (SMF) with a core offset. The basic principle of the sensor is based on determining...
An optical fiber sensor based on concave cone and long period fiber grating (LPG) is proposed, and the experimental curve and temperature are experimentally demonstrated. The sensor head consists of a combination of concave cone and long-period fiber grating. The experimental results show that the interference peaks of the resonant wavelengths of the concave cone and the long-period fiber grating...
We report our recent studies on the use of Neural Networks to process the measured Brillouin gain spectrum (BGS) from Brillouin Optical Time Domain Analyzer (BOTDA) and extract temperature information along fiber under test (FUT). Artificial Neural Network (ANN) is trained with ideal Lorentizian BGS before it is used for temperature extraction. Its performance is evaluated by comparison to conventional...
A thin-core fiber based Mach-Zehnder interferometer (MZI) for simultaneous measurement of temperature and refractive index is demonstrated. It is formed by sandwiching a short section of highly germanium-doped fiber between two single-mode fibers and writing a fiber Bragg grating (FBG) on the germanium-doped fiber. Simultaneous measurement is achieved based on the different responses of the interferometer...
We present an ultra-compact, reflective optical sensor probe based on silicon-on-insulator (SOI) microring resonator and Y-junction structure, which is capable of simultaneously achieving high sensitivity and fine resolution optical sensing. The reflective configuration of the probe enables remote measurements at locations which are otherwise hard to be assessed by transmission based sensors. As an...
This paper presents a temperature measurement system based on fluorescence intensity ratio of erbium-doped fiber. A novel compact system architecture consisted of 980nm pumping laser, 980/1550nm wavelength division multiplexer (WDM), one way Erbium doped fiber was developed. The system performance was verified by the relationship between temperature and the fluorescence intensity ratio(FIR)of 1450nm...
A temperature sensor with two cascaded fiber Fabry-Perot interferometers (FPIs) is constructed and demonstrated, which works on envelope-based demodulation and exhibits a high temperature sensitivity. The sensor is fabricated by splicing a short segment of large mode area (LMA) fiber to a short segment of capillary tube fused with a section of single-mode fiber to form a cascaded FPI structure. Experimental...
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