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Waveguide optimization and its evaluation of a doped polymer optical ???ber designed for visual detection of stress
摘要： A fiber-optic strain sensor using a fluorophore-doped polymer optical fiber (POF) was fabricated at various waveguiding conditions. The effects attributed to each structural feature of the sensor were characterized by observing the sensor?s response. Two fluorophores, Coumarin 540A and Rhodamine 6G, were used to dope the core and the cladding of a poly(methyl methacrylate)-based POF, respectively. Using doped POFs with different numerical apertures (NAs), the changes in the fluorophore peaks upon the application of stress were analyzed by applying macrobending (s) to the fiber. Although the sensor response did not show linearity with respect to the NA, it was found that the shape of the Coumarin 540A-attributed peak was a factor that represented the sensor?s sensitivity. As a result, the double-cladding structure demonstrated its effectiveness in improving the stress sensitivity.
关键词： double-cladding structure,fluorophore-doped,polymer optical fiber,numerical aperture,fiber-optic strain sensor,stress sensitivity
更新于2025-09-23 15:21:01
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Fiber temperature and humidity sensor based on photonic crystal fiber coated with graphene oxide
摘要： A temperature and humidity sensor based on photonic crystal fiber(PCF) coated with graphene oxide (GO) cascaded with two spherical structures is presented and demonstrated. The principle of this sensor is based on Mach–Zehnder interferometer (MZI), and the interference spectrum is sensitive to the change of temperature and humidity. Because of the hydrophilic property of GO, refractive index (RI) of the fiber surface changes significantly with the variation of humidity. Therefore, the GO film deposited on the PCF surface can improve the humidity sensitivity of the sensor. Experimental results show that the temperature sensitivities are 0.063 nm/?C and 0.086 nm/?C from 10?C to 70?C. The humidity sensitivities are 0.128 nm/%RH and 0.159 nm/%RH from 30% to 70%. Moreover, it also contains the following advantages: low cost, simple construction, and high sensitivity.
关键词： Photonic crystal fiber (PCF),Graphene Oxide (GO),Optical fiber sensor,Humidity,Temperature
更新于2025-09-23 15:21:01
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Slit beam shaping technique for femtosecond laser inscription of enhanced plane-by-plane FBGs
摘要： In this work, the development of plane-by-plane (Pl-b-Pl) fiber Bragg gratings (FBGs) by using a single pulse is reported. A slit oriented along the longitudinal axis of the fiber is employed for this. The purpose is to shape the beam so that the focal volume is spatially wider in the transverse direction of the fiber. In this way, it is possible to make 2-D modifications of the refractive index whose width and height depends on the slit width and the pulse energy, respectively. Through an analytical mathematical modelling, the relationship between the diameter of the Gaussian laser beam (Dx) and the slit width (s = Dy) is determined in order to obtain a circular cross-section. In the experimental results carried out, it can be observed that Dx/Dy=3 ratio cause positive and uniform refractive index changes, compared to the negative and inhomogeneous refractive index changes corresponding to point-by-point (PbP) FBGs. Likewise, Pl-b-Pl FBGs, presenting a broader modification of the core cross-section, show significantly lower losses in transmission (0.3 dB), as well as better reflectivity and FWHM. It is observed that these three parameters (losses, reflectivity and FWHM) have a monotonous tendency according to the slit width. Polarization-dependence is also evaluated.
关键词： Optical Fiber Sensor,Slit beam technique,Femtosecond laser,Plane-by-Plane,Fiber Bragg grating
更新于2025-09-23 15:21:01
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A new type of structure of optical fiber pressure sensor based on polarization modulation
摘要： In this study, a new type of structure of optical fiber pressure sensor (OFPS) based on polarization modulation is proposed, which selects a high-birefringence fiber (HBF) as the sensing unit to measure the pressure in the fluid medium. The PM-1550-01 fiber produced by NTK Photonics Inc. is evaluated as the sample in our subject. Firstly, the regularities of birefringence variation on the PM-1550-01 followed by the external pressure load and the ambient temperature are analyzed by the finite element method (FEM). The results show that the pressure sensitivity is 2.05 × 10 ? 6 RIU/MPa in the pressure range of 0–100 MPa, and the temperature sensitivity is 7.27 × 10 ? 10 RIU/°C in the temperature range of 0–100 °C. Thus, the pressure-temperature cross-sensitivity is only 0.355 kPa/°C in theory. Secondly, the expression of the output light intensity of the introduced OFPS is deduced based on the principles of polarization interference and phase modulation. Combined with simulation results, the measurement ranges of the sensor can be set and adjusted by the length of the sensing unit. Finally, the proposed OFPS is fabricated and external pressure tests within the range of 0–50 MPa are completed. The results show that the pressure sensitivity is approximately 0.145 dB/MPa in the pressure range of 0–44 MPa. There is a fine consistency between the experimental data and simulation results. In addition, the proposed OFPS has many other advantages, such as small size, simple fabrication process and large measurement range, which make it appropriate to be applied in high-pressure measurement in hostile conditions, e.g., downhole and ocean-bottom.
关键词： Low temperature cross-sensitivity,Polarization modulation,High-birefringence fiber,Optical fiber pressure sensor
更新于2025-09-23 15:21:01
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Towards Smart Selective Sensors exploiting a novel approach to connect Optical Fiber Biosensors in Internet
摘要： The selective detection of pollutants in water in a laboratory scenario has been presented by authors exploiting low-cost optical biosensors based on plastic optical fibers (POFs) and biological or bio-mimetic receptors. For instance, the detection in water of naphthalene, perfluoroalkyl and polyfluoroalkyl substances (PFAs) have been investigated with interesting detection limits when compared to those obtained by using different expensive traditional approaches (e.g. liquid chromatography-mass spectrometry with high performances). In this work, we have developed and tested a novel approach used in a smart measuring system to use POF sensors in situ for the remote measures of pollutants in water for smart cities applications. More specifically, we have used different water-glycerin solutions to test the novel sensor system based on a Raspberry PI connected to the Internet and to a spectrometer, a light source, a POF sensor, and two computers connected to Internet used as client and server.
关键词： optical fiber sensors,water quality,pollutants,software,biosensors,Plastic optical fibers (POFs),Internet of Things (IoT)
更新于2025-09-23 15:21:01
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[IEEE 2019 XXIX International Scientific Symposium "Metrology and Metrology Assurance" (MMA) - Sozopol, Bulgaria (2019.9.6-2019.9.9)] 2019 XXIX International Scientific Symposium "Metrology and Metrology Assurance" (MMA) - The metod of reducing measurement error of the propagation delays in optical elements and optical fibers
摘要： The paper presents a method of reducing the measurement error propagation delays of signals in optical elements and optical fibers, based on the approximation of the recorded form of optical pulses and determining the time intervals between pulses, using the values of the parameters of the approximating functions. The scheme of the installation implementing the proposed method is presented, as well as the results of experimental approbation of the method.
关键词： optical element,optical fiber,signal propagation delay,approximation
更新于2025-09-23 15:21:01
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Drying-induced soil shrinkage and desiccation cracking monitoring with distributed optical fiber sensing technique
摘要： Monitoring of drying-induced volume shrinkage and desiccation cracking in clayey soils is of great importance in geological and geotechnical engineering. Compared with conventional strain monitoring methods providing discrete measurements, the Brilliouin optical time domain reflectometer (BOTDR) technique enables continuous measurement of the distributed strain generated along optical fibers. In this study, a physical model test is conducted to investigate the feasibility of monitoring drying-induced soil shrinkage and desiccation cracking using BOTDR. Three optical fibers with different surface protections (thermoplastic polyester elastomer (TPEE) jacket, nylon jacket, and acrylate coating) are tested and compared. Experimental results validate that BOTDR is applicable for the direct strain monitoring of desiccation cracking soils. Monitored strain values are strongly influenced by water content, soil cracking, and fiber types. The strain measured by the optical fiber reaches only several micro strains when the soil is over-saturated, gradually increases with the decreasing water content and the increasing soil-fiber interfacial shear stresses, and drops rapidly after the occurrence of decoupling between fiber and soil resulting from the mature development of desiccation cracks. The optical fiber with acrylate coating is not suitable because of its fragility and the poor interfacial coupling with the soil. Optical fibers covered with TPEE jacket or nylon jacket are both applicable for soil strain monitoring, with the former one more sensitive to water content variations. The study is the first attempt to apply the BOTDR technique for the direct and continuous monitoring of drying-induced soil shrinkage and desiccation cracking process. It is expected bring new insights into the fundamental understanding of volumetric shrinkage and desiccation cracking in clayey soils.
关键词： Brilliouin optical time domain reflectometer (BOTDR),Desiccation crack,Volumetric shrinkage,Strain monitoring,Optical fiber sensing
更新于2025-09-23 15:21:01
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Tests under irradiation of optical fibers and cables devoted to corium monitoring in case of severe accident in a Nuclear Power Plant
摘要： The DISCOMS project, which stands for “DIstributed Sensing for COrium Monitoring and Safety”, considers the potential of distributed sensing technologies, based on remote instrumentations and Optical Fiber Sensing cables embedded into the concrete floor under the reactor vessel, to monitor the status of this third barrier of confinement. This paper focuses on the selection and testing of singlemode (SM) optical fibers with limited RIA (Radiation Induced Attenuation) to be compliant with remote distributed instruments optical budgets, the ionizing radiation doses to sustain, and their reduction provided by the concrete basemat shielding. The tests aimed at exposing these fibers and the corresponding sensitive optical cables, to the irradiation doses expected during the normal operation of the reactor (up to 60 years for the European Pressurized Reactor), followed by a severe accident. Several gamma and mixed (neutron-gamma) irradiations were performed at CEA Saclay facilities: POSé?DON irradiator and ISIS reactor, up to a gamma cumulated dose of about 2 MGy and fast neutron fluence (E > 1 MeV) of 6 x 1015 n/cm2. The first gamma test permitted to assess the RIA at various optical wavelengths, and to select three radiation tolerant singlemode fibers (RIA < 5 dB/100 m, at 1550 nm operating wavelength). The second one was performed on voluminous strands of sensitive cables encapsulating selected optical fibers, up to approximately the same accumulated dose, at two temperatures: 30°C and 80°C. A significant increase of the RIA, without any saturation tendency, appeared for fibers inserted into cables, correlated with the increase of the hydroxyl attenuation peak at 1380 nm. Molecular hydrogen generated by the radiolysis of compounds of the cable is at the origin of this phenomenon. A third gamma irradiation run permitted to measure the radiolytic hydrogen production yield of some compounds of a dedicated temperature cable sample. The efficiency of a carbon coating layer over the silica cladding, acting as a barrier against hydrogen diffusion, was also successfully confirmed. Finally, the efficiency of this carbon coating layer has also been tested under neutron irradiation, then qualified as a protection barrier against hydrogen diffusion in the optical fiber cores.
关键词： carbon coating layer,radiation effects,optical fibers,hydrogen diffusion,gamma,radiolysis,rad-hard optical fiber,neutron,distributed measurement
更新于2025-09-23 15:21:01
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Transmission of Higher Order Solitons created by Optical Multiplexing
摘要： The nonlinear Fourier transform (NFT) is a promising tool to linearize the inherently nonlinear optical fiber channel. The NFT transforms a time domain signal into the continuous and the discrete spectrum. The discrete spectrum is composed of an arbitrary number of complex valued discrete eigenvalues and their associated amplitudes. These discrete eigenvalues relate to solitons, which maintain their shape or return to it in an oscillating manner, while passing through the optical channel. Higher order solitons consisting of multiple eigenvalues are complex pulses, which are created and demodulated by sophisticated digital signal processing (DSP) leading to demanding hardware requirements. This paper shows a way to work with higher order solitons in a WDM like fashion by using optical-electrical signal processing and presents boundaries of this method. Optical-electrical signal processing decreases the required electrical and electro-optical hardware specifications substantially and enables to use a simplified DSP. The proposed creation method is subsequently employed to transmit higher order solitons consisting of five QPSK modulated eigenvalues. Furthermore, the optical-electrical processing is benchmarked against the Darboux transformation, which creates higher order solitons purely numerically. The results show that for a 5th order soliton transmission the proposed method can significantly reduce the hardware requirements and DSP complexity.
关键词： solitons,nonlinear Fourier transform,optical signal processing,nonlinear optics,optical fiber communication,Darboux transform
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE CHILEAN Conference on Electrical, Electronics Engineering, Information and Communication Technologies (CHILECON) - Valparaiso, Chile (2019.11.13-2019.11.27)] 2019 IEEE CHILEAN Conference on Electrical, Electronics Engineering, Information and Communication Technologies (CHILECON) - Explosive detection system based on Leddar sensor and Self-Organizing Maps in controled environments
摘要： Mobile fronthaul is an important network segment that bridges wireless baseband units and remote radio units to support cloud radio access network. We review recent progresses on the use of frequency-division multiplexing to achieve highly bandwidth-efficient mobile fronthaul with low latency. We present digital signal processing (DSP) techniques for channel aggregation and deaggregation, frequency-domain windowing, adjacent channel leak age ratio reduction, and synchronous transmission of both the I/Q waveforms of wireless signals and the control words (CWs) used for control and management purposes. In a proof-of-concept experiment, we demonstrate the transmission of 48 20-MHz LTE signals with a common public radio interface (CPRI) equivalent data rate of 59 Gb/s, achieving a low round-trip DSP latency of <2 μs and a low mean error-vector magnitude (EVM) of ～2.5% after fiber transmission. In a follow-up experiment, we further demonstrate the transmission of 32 20-MHz LTE signals together with CPRI-compliant CWs, corresponding to a CPRI-equivalent data rate of 39.32 Gb/s, in single optical wavelength channel that requires an RF bandwidth of only ～1.6 GHz. After transmission over 5-km standard single-mode fiber, the CWs are recovered without error, while the LTE signals are recovered with an EVM of lower than 3%. Applying this technique to future 5G wireless networks with massive multiple-input multiple-output is also discussed. This efficient mobile fronthaul technique may find promising applications in future integrated fiber/wireless access networks to provide ultrabroadband access services.
关键词： fifth-generation (5G),frequency-division multiplexing (FDM),common public radio interface (CPRI),Cloud radio access network (C-RAN),optical fiber transmission,mobile fronthaul
更新于2025-09-23 15:21:01