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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 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...
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...
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...
We developed a new technique for constructing humidity sensor comprised of two cascaded peanut-shape structure which were coated with polyvinyl alcohol (PVA) and in between was also coated with PVA. The coating changes with the humidity which resulting in the change of the effective refractive index, and lead to the change of the interference wavelength. Experiments show that, with the humidity changes...
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 multiwavelength Er-doped fibre ring laser system using all fibre Lyot filter and highly nonlinear fibre was experimentally demonstrated, with degree of polarization up to 99.9% and 50 channels output.
The fabrication and experiment of a high temperature FBG strain sensor is presented in this paper. Firstly, the high temperature resistant FBG has been fabricated and tested in high temperature environment. Secondly, a novel alloy rhombus packaging structure is designed for packaging the FBG sensor suitable in high temperature strain detection. The fabrication process and strain sensing mechanism...
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...
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,...
The effect of gamma radiation with a maximum dose of 180 kGy at a dose rate of 10.15 kGy/hour on both standard Ge-doped fiber Bragg Gratings (Ge-FBG) and femtosecond-laser-inscribed pure-silica-core fiber Bragg Gratings (FL-PS-FBG) have been investigated. In the case of Ge-FBGs, a maximum Bragg wavelength shifts (BWS) of 140 pm and a decrease of the reflection peak power of 16 dB has been observed...
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...
A sensitivity-enhanced temperature sensor based on Vernier-effect was demonstrated. Vernier-effect is achieved by a cascaded configuration with a fiber Sagnac interferometer (FSI) and a Fabry-Perot interferometer (FPI). FSI, which consists of a certain length of polarization maintaining fiber, is for temperature sensing, while. FPI acts as a filter due the temperature insensitivity. Experimental results...
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...
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...
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