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Helical Long-Period Gratings Inscribed in Polarization-Maintaining Fibers by CO2-Laser
摘要： We demonstrate fabrication of helical long-period gratings (HLPGs) in a polarization-maintaining fiber using CO2-laser. The maximum polarization dependent loss (PDL) of the grating was measured to be more than 30 dB at the resonance wavelength. The HLPG was found to have a high index sensitivity of -7248.6 nm/RIU when the surrounding refractive index changes in the range of 1.4470-1.4600, temperature sensitivity of 158.8 pm/°C, and strain sensitivity of 3.17 pm/με. The twist sensitivities based on intensity variation were measured to be 5.98 dB/ (rad/m) (co-directional twist) and -5.97 dB/ (rad/m) (contra-directional twist), respectively. The demonstrated grating devices have promising applications as high-sensitivity fiber sensors, PDL compensator etc.
关键词： optical fiber sensors,Fiber gratings,polarization-maintaining fibers,helical long-period gratings
更新于2025-11-28 14:24:03
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Discerning Localized Thermal Heating from Mechanical Strain Using an Embedded Distributed Optical Fiber Sensor Network
摘要： Prior research has demonstrated that distributed optical fiber sensors (DOFS) based on Rayleigh scattering can be embedded in carbon fiber/epoxy composite structures to rapidly detect temperature changes approaching 1000°C, such as would be experienced during a high energy laser strike. However, composite structures often experience mechanical strains that are also detected during DOFS interrogation. Hence, the combined temperature and strain response in the composite can interfere with rapid detection and measurement of a localized thermal impulse. In this research, initial testing has demonstrated the simultaneous response of the DOFS to both temperature and strain. An embedded DOFS network was designed and used to isolate and measure a localized thermal response of a carbon fiber/epoxy composite to a low energy laser strike under cyclic bending strain. The sensor interrogation scheme uses a simple signal processing technique to enhance the thermal response, while mitigating the strain response due to bending. While our ultimate goal is rapid detection of directed energy on the surface of the composite, the technique could be generalized to structural health monitoring of temperature sensitive components or smart structures.
关键词： smart structures,distributed optical fiber sensors,temperature sensors,structural health monitoring,high energy radiation,polymer matrix composites,strain sensors,strain compensation
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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Femtosecond laser direct written off-axis fiber Bragg gratings for sensing applications
摘要： First order off-axis fiber Bragg gratings (FBGs) were fabricated in a standard single mode fiber (SMF-28e) through femtosecond laser direct writing. A minimum offset distance between the grating and core center of 2.5 μm was found to create a multimode section, which supports two separate fiber modes (LP0,1 and LP1,1), each split into two degenerate polarization modes. The resulting structure breaks the cylindrical symmetry of the fiber, introducing birefringence (≈10?4) resulting in a polarization dependent Bragg wavelength for each mode. Based on the modal and birefringence behavior, three off-axis FBGs were fabricated with 3.0, 4.5 and 6.0 μm offsets from the core center, and then characterized in strain, temperature, and curvature. The tested off-axis FBGs exhibited a similar strain sensitivity of ~1.14 pm/μ? and a temperature sensitivity of ~12 pm/C. The curvature and orientation angle were simultaneously monitored by analyzing the intensity fluctuation and the wavelength shift of the LP1,1 Bragg resonance. A maximum curvature sensitivity of 0.53 dB/m?1 was obtained for the off-axis FBG with a 3.0 μm offset.
关键词： optical fiber sensors,femtosecond laser direct writing,single mode fiber,off-axis fiber Bragg gratings,Birefringence
更新于2025-09-23 15:19:57
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Optical Fiber Refractometer Based Metal Ion Sensors
摘要： Research into optical fiber refractometers yielded remarkable results over the past decade. Numerous sensing schemes were proposed and demonstrated, which possessed different advantages while facing unique limitations. On top of their obvious applications in measuring refractive index changes of the ambient environment, several studies reported advanced applications of such sensors in heavy metal ion detection by means of surface coating of the refractometers with heavy metal ion sensitive materials. This paper surveys the effort these optical fiber metal ion sensors based on surface coated optical fiber refractometer, discusses different technologies and methods involved, and highlights recent notable advancements.
关键词： optical fiber technology,heavy metal detection,optical fiber sensors,chemical sensing
更新于2025-09-23 15:19:57
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Lab-on-Fiber: Plasmonic Nano-arrays for Sensing
摘要： For sensors based on electromagnetic resonance whether surface plasmon resonance (SPR) or localized surface plasmon resonance (LSPR), enhancing the light-matter interactions is the most critical and important way to improve the performance of sensors. Plasmonic nano-arrays is a kind of periodic metal or dielectric nanostructure formed by nanofabrication technology and it can effectively enhance the light-matter interactions by tuning structural parameters to excite different optical effects due to its ultra-high degree of freedom. At the same time, a plug-and-play, remote micro sensor suitable for limited environments (such as in vivo) may be realized due to the rise of lab-on-fiber technology and the progress of nanofabrication technology for unconventional substrates (such as optical fiber tip). In this paper, the advantages and disadvantages of different nanofabrication technologies are briefly introduced and compared firstly, and then the applications of optical fiber sensors (OFS) based on different plasmonic nano-arrays are reviewed. Plasmonic nano-arrays OFS are divided into two categories: one is the refractive index sensor based on the sensitivity of the array to the surrounding environment; the other is the surface enhanced Raman scattering (SERS) sensor based on the enhancement ability of the local electric field around the array. In this review, the present sensors are compared and analyzed from aspects of the geometry, material and dimension of plasmonic nano-arrays and the main research directions and progress are summarized. Finally, the future development trend is proposed.
关键词： surface plasmon resonance,localized surface plasmon resonance,optical fiber sensors,nanofabrication technologies,Plasmonic nano-arrays,lab-on-fiber
更新于2025-09-23 15:19:57
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An air-core photonic crystal fiber based plasmonic sensor for high refractive index sensing
摘要： Most surface plasmon resonance (SPR) based photonic crystal fiber (PCF) sensors have been designed to detect the analyte refractive index (RI) ranging from 1.33?1.41. In this paper, we propose a new approach to extend the detection range of the sensor, and it can be fabricated with the existing fabrication techniques. Contrary to the existing PCF based sensors, our designed sensor is based on an air-core PCF where analyte is placed to the core of the PCF through a vertical side opening channel and is able to detect RI of the analyte higher than that of the PCF background. We use a chemically stable plasmonic material (i.e., gold), where the plasmonic material and analyte are placed in such a way that there is no direct contact between them, thus reducing the interference effect. According to our simulation, we show that the spectral sensitivity and resolution are achieved as 11,700 nm/RIU and 8.55×10–6 RIU, respectively, for the analyte RI of 1.42. We believe that our proposed sensor can be used to detect highly active chemical and biological liquid samples.
关键词： optical fiber sensors,Photonic crystal fiber,surface plasmon resonance
更新于2025-09-23 15:19:57
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[Lecture Notes in Electrical Engineering] Sensors and Microsystems Volume 629 (Proceedings of the 20th AISEM 2019 National Conference) || Relative Humidity Sensor Based on Tip of Multimode Optical Fiber Integrated with Photonic Crystal of Hydrogel Coated Polystyrene Nanoparticles
摘要： A relative humidity (RH) sensing device based on photonic crystal colloids auto-assembled directly on the tip of a multi-mode optical fiber is here described. The core-shell nanospheres are obtained by Polystyrene (PS) nanoporous structures (core) incorporated into a poly(N-isopropylacrylamide) (PNIPAM) hydrogel (shell) and are subsequently deposited via a vertical dip-coating technique on a multimode optical fiber tip. The sensing capability is due to the hydrogel shell that swells depending on the relative humidity that induce wavelength shift and amplitude changes in the photonic bandgap peak. Spectral characterization and sensing analysis are performed, and the obtained results show that spectral characteristics are highly non-linear and strongly manufacturing dependent. A resolution of 1% RH is measured at 30% RH that significantly decreases at higher RH. Hereby, numerical simulations based on the finite element method (FEM) have been performed in order to investigate the sensing mechanism.
关键词： Structural health monitoring,Deflection monitoring,Optical fiber sensors,Strain measurement
更新于2025-09-23 15:19:57
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Monitoring of Strain and Temperature in an Open Pit Using Brillouin Distributed Optical Fiber Sensors
摘要： Marble quarries are quite dangerous environments in which rock falls may occur. As many workers operate in these sites, it is necessary to deal with the matter of safety at work, checking and monitoring the stability conditions of the rock mass. In this paper, some results of an innovative analysis method are shown. It is based on the combination of Distributed Optical Fiber Sensors (DOFS), digital photogrammetry through Unmanned Aerial Vehicle (UAV), topographic, and geotechnical monitoring systems. Although DOFS are currently widely used for studying infrastructures, buildings and landslides, their use in rock marble quarries represents an element of peculiarity. The complex morphologies and the intense temperature range that characterize this environment make this application original. The selected test site is the Lorano open pit which is located in the Apuan Alps (Italy); here, a monitoring system consisting of extensometers, crackmeters, clinometers and a Robotic Total Station has been operating since 2012. From DOFS measurements, strain and temperature values were obtained and validated with displacement data from topographic and geotechnical instruments. These results may provide useful fundamental indications about the rock mass stability for the safety at work and the long-term planning of mining activities.
关键词： temperature,brillouin shift frequency,geotechnical monitoring system,strain,robotic total station,marble quarry,distributed optical fiber sensors,unmanned aerial vehicle
更新于2025-09-23 15:19:57
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Fiber Bragg Grating-Based Oil-Film Pressure Measurement in Journal Bearings
摘要： The on-line measurement of oil-film pressure inside a journal bearing based on an optical fiber Bragg grating (FBG) is proposed and described for the first time. Two methods are described, one includes inserting the packaged FBG into the bearing using rubber and the other is involved the packaged FBG being directly embedded on the bearing surface. The inserted method has a higher sensitivity than the embedded version, while the embedded method incurs less damage to the bearing being small in size. Experiments to verify the feasibility of both methods are described with parameters being measured over the full motor operating range. Experimental results of the oil film pressure measured by these two methods agree well with simulated values, demonstrating excellent prospects for using the sensing schemes described in this paper as the basis for real industrial measurement systems. Furthermore, due to its small size and high sensitivity, coupled with excellent immunity to external electromagnetic interference the FBG sensor is an ideal candidate for measurement in which a strong electromagnetic field exists, e.g., in the case of electrical motors and generators.
关键词： temperature compensation,optical fiber sensors,oil film,pressure measurement,Fiber Bragg gratings (FBGs)
更新于2025-09-19 17:15:36