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Nonlinearity-compensation-free optical frequency domain reflectometry based on electrically-controlled optical frequency sweep
摘要： A nonlinearity-compensation-free optical frequency domain reflectometry (OFDR) scheme is proposed and experimentally demonstrated based on the electrically-controlled optical frequency sweep. In the proposed scheme, the linear frequency sweep light is generated by propagating an ultra-narrow-linewidth continuous-wave light through an electro-optic frequency shifter which consists of a dual-parallel Mach-Zehnder modulator and an electronic 90° hybrid, where the electro-optic frequency shifter is driven by a linear frequency modulated signal generated by a direct digital synthesizer. Experimental results show that the spatial resolution and signal-to-noise ratio (SNR) of the proposed OFDR scheme without the nonlinear phase compensation are comparable to those of the OFDR employing a commercial tunable light source (TLS), an auxiliary interferometer and a software-based nonlinear phase compensation method. The proposed OFDR scheme is helpful to reduce the complexity of optical structure and eliminate the difficulty of developing nonlinear phase compensation algorithm.
关键词： optical frequency domain reflectometry (OFDR),electro-optic frequency shifter,Dual-parallel Mach-Zehnder modulator,optical fiber sensor
更新于2025-09-23 15:19:57
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Enhanced sensitivity of distributed-temperature sensor with Al-coated fiber based on OFDR
摘要： In this paper, we present a distributed-optical fiber temperature sensor with enhanced sensitivity with Al coating using the Rayleigh backscattering (RBS) spectrum shift measured via optical frequency-domain reflectometry (OFDR). The Al-coated sensing fiber having a larger thermal expansion coefficient than that of silica produces a strain-coupled shift in the RBS under an increase in temperature. This effect leads to an enhanced temperature sensitivity of the distributed measurement scheme. In order to analyze the principle of temperature sensitivity enhancement, a simple analysis was performed by considering the fiber directional strain and force equilibrium between the optical fiber and Al-coated layer. Our results revealed that the temperature sensitivity achieved with the Al-coated fiber in OFDR was ～56% higher relative to that of a single-mode fiber.
关键词： Al-coated fiber,Distributed sensor,Thermal expansion,Optical frequency-domain reflectometry,Temperature sensitivity
更新于2025-09-19 17:15:36
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Distributed optical fiber sensing: Review and perspective
摘要： Over the past few decades, optical fibers have been widely deployed to implement various applications in high-speed long-distance telecommunication, optical imaging, ultrafast lasers, and optical sensors. Distributed optical fiber sensors characterized by spatially resolved measurements along a single continuous strand of optical fiber have undergone significant improvements in underlying technologies and application scenarios, representing the highest state of the art in optical sensing. This work is focused on a review of three types of distributed optical fiber sensors which are based on Rayleigh, Brillouin, and Raman scattering, and use various demodulation schemes, including optical time-domain reflectometry, optical frequency-domain reflectometry, and related schemes. Recent developments of various distributed optical fiber sensors to provide simultaneous measurements of multiple parameters are analyzed based on their sensing performance, revealing an inherent trade-off between performance parameters such as sensing range, spatial resolution, and sensing resolution. This review highlights the latest progress in distributed optical fiber sensors with an emphasis on energy applications such as energy infrastructure monitoring, power generation system monitoring, oil and gas pipeline monitoring, and geothermal process monitoring. This review aims to clarify challenges and limitations of distributed optical fiber sensors with the goal of providing a pathway to push the limits in distributed optical fiber sensing for practical applications.
关键词： energy applications,Brillouin scattering,Rayleigh scattering,Raman scattering,optical time-domain reflectometry,distributed optical fiber sensing,optical frequency-domain reflectometry
更新于2025-09-16 10:30:52
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Distributed Fiberoptic Sensor for Simultaneous Humidity and Temperature Monitoring Based on Polyimide-Coated Optical Fibers
摘要： Along temperature, humidity is one of the principal environmental factors that plays an important role in various application areas. Presented work investigates possibility of distributed fiberoptic humidity monitoring based on humidity-induced strain measurement in polyimide (PI)-coated optical fibers. Characterization of relative humidity (RH) and temperature response of four different commercial PI- and one acrylate-coated fiber was performed using optical backscattering reflectometry (OBR). The study addresses issues of temperature-humidity cross-sensitivity, fiber response stability, repeatability, and the influence of annealing. Acrylate-coated fiber exhibited rather unfavorable nonlinear RH response with strong temperature dependence, which makes it unsuitable for humidity sensing applications. On the other hand, humidity response of PI-coated fibers showed good linearity with fiber sensitivity slightly decreasing at rising temperatures. In the tested range, temperature sensitivity of the fibers remained humidity independent. Thermal annealing was shown to considerably improve and stabilize fiber RH response. Based on performed analysis, a 20 m sensor using the optimal PI-coated fibers was proposed and constructed. The sensor uses dual sensing fiber configuration for mutual decoupling and simultaneous measurement of temperature and RH variations. Using OBR, distributed dual temperature-RH monitoring with cm spatial resolution was demonstrated for the first time.
关键词： fiberoptic sensors,distributed humidity sensing,polyimide-coated optical fibers,optical frequency-domain reflectometry,dual sensing
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Integrated Optical Fibre — Investigating the Vibrational Response using Optical Frequency Domain Reflectometry
摘要： Integrated Optical Fibre (IOF) is a new technology in integrated optics using flame hydrolysis deposition to permanently attach an optical fibre onto a silicon substrate. This approach combines the low losses of optical fibre with the mechanical integrity of an integrated planar platform. By attaching the fibre with high quality optical glass we create devices that transform the packaging of fibres for sensing applications removing any use of glues, epoxies, adhesives and making it suitable for harsh environments such as aerospace. The binding medium itself can also be used for its optical properties. Aerospace environments are demanding, both for temperature range (-50 to +120 °C), but also for vibration and shock. In this work we are investigating a technique for monitoring the vibration sensitivity and damage points of the IOF under typical structural vibration conditions. In particular, here we report the use of Optical Frequency Domain Reflectometry (OFDR), which can reveal spectral and spatial information of features within a fibre such as Fibre Bragg Gratings (FBGs). This is of particular interest when applied to structural health monitoring, distributed strain and temperature sensing.
关键词： Optical Frequency Domain Reflectometry,vibration sensitivity,structural health monitoring,Integrated Optical Fibre,Fibre Bragg Gratings
更新于2025-09-12 10:27:22
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Magnetic Optical FBG Sensors Using Optical Frequency-Domain Reflectometry
摘要： The optical frequency-domain reflectometry (OFDR) sensing system and signal processing method, which is based on the short-time Fourier transform, enable us to interrogate reflected wavelengths of fiber Bragg gratings (FBGs) and their relative position along the optical fiber with high spatial resolution. An FBG is an optical fiber with an appropriately inscribed periodic refractive index modulation. When a broadband optical signal is launched into the FBG, narrow wavelength bandwidth is reflected. Due to an attached transducer, such as Terfenol-D, the reflected wavelength changes with the applied magnetic field. The proposed magnetic FBG sensor consists of a small rod of magnetostrictive alloy TbDyFe, also known as Terfenol-D, which has large magnetostriction. The FBG is attached to the Terfenol-D rod with UV glue. Consequently, the external magnetic field is applied to the sensor and as a result, the Terfenol-D rod length increases. The reflected wavelength shift is observed and measured by the OFDR sensing system. Therefore, we determine the external magnetic field along the optical fiber from the reflected Bragg wavelength shift. The measurement results show that the proposed magnetic field sensors based on Terfenol-D using OFDR can be successfully used for measurement of the external magnetic field along an optical fiber.
关键词： Terfenol-D,optical frequency-domain reflectometry (OFDR),magnetic field sensor,Fiber Bragg gratings (FBGs)
更新于2025-09-09 09:28:46
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[Advances in Chemical Engineering] Spatially Resolved Operando Measurements in Heterogeneous Catalytic Reactors Volume 50 || Spatio-Temporal Phenomena in Monolithic Reactors Measured by Combined Spatially-Resolved Mass Spectrometry and Optical Frequency Domain Reflectometry
摘要： Measuring the spatiotemporal temperature and reacting species concentrations of a reacting system under realistic conditions is essential to optimize the reactor design and operation. Conventional measurements of the inlet and outlet values provide only a partial picture of the reactor behavior. We describe the novel method coherent optical frequency domain reflectometry (c-OFDR) which provides unparalleled information about the spatiotemporal temperature in a catalytic reactor. c-OFDR launches a laser beam through an optical fiber positioned inside a reactor. The spatial dependence of temperature is determined through the measured spectral shift of reflected scattering light frequency. The advantages of c-OFDR include high spatial and temporal resolution (3 mm and 0.9 Hz), broad operating range (up to 800°C), noninvasive measurement (125 μm OD), stationary, and chemically resistant (gold-coated) sensor. In addition to describing the theory and standard operation of c-OFDR, we demonstrate c-OFDR for several applications involving reaction in a catalytic monolith during both steady-state and transient operation. The combination of c-OFDR with spatially resolved capillary inlet mass spectrometry (SpaciMS) provides detailed characterization of a catalytic reactor under periodic operation. Combined SpaciMS and c-OFDR successfully follow the cyclic lean/rich behavior during temperature programmed oxidation experiments. SpaciMS invasiveness is assessed through systematic measurement of the temperature by c-OFDR and concentration by SpaciMS. In an ideal adiabatic reactor, the temperature peak and complete reactant conversion should occur at the same position. Our experiments enabled generation of a map of operating conditions under which this did not occur which helps identify when the SpaciMS method is invasive.
关键词： reactor design,SpaciMS,catalytic reactor,spatiotemporal temperature,coherent optical frequency domain reflectometry
更新于2025-09-04 15:30:14