Characteristics of potential fibre Bragg grating sensor-based devices at elevated temperatures (original) (raw)
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Applied Optics, 2017
In this work, we have proposed a sensor for strain measurement in high-temperature environments up to 800°C by employing two regenerated fiber Bragg gratings. Two seed gratings (SGs) are inscribed in high Ge-doped and B/Ge-codoped fibers, respectively, which possess different temperature sensitivities. To achieve two gratings with different strain sensitivities, one of the gratings is chemically etched to reduce the fiber diameter for strain sensitivity enhancement. A thermal annealing process is carried out to activate the grating regeneration in the SGs. The temperature and strain calibration experiments indicate that the proposed structure has uncertainty values of 23.42 με and 5.83°C over the ranges of 0-1000 με and 20°C-800°C, respectively.
Bragg grating tuned fiber laser system for measurement of wider range temperature and strain
Optics Communications, 2005
A Bragg grating-tuned fiber laser-based sensor system has been developed to measure over a wide range of temperatures (22-500°C) and strain (0-1200 le) using both a normal grating and a chirped grating as optical feedback elements and Er 3+ -doped fiber as the active gain medium. A high reflectivity normal Bragg grating was written into a specially fabricated high temperature sustaining Sb-Ge co-doped photosensitive fiber and a chirped grating was inscribed into a commercial B-Ge co-doped fiber, due to its higher photosensitivity. The shift in the laser wavelength was monitored in this system when the normal grating was temperature or strain-tuned, with it also forming the active element of the sensor head of the system. The root mean square (RMS) error values of the active sensor system were found to be 2.6°C and 28.3 le over the above measured ranges of temperature and strain, respectively.
In-Fiber Gratings for Simultaneous Monitoring Temperature and Strain in Ultrahigh Temperature
IEEE Photonics Technology Letters, 2015
In this letter, a pair of regenerated gratings with Bragg wavelengths of 1547 and 1304 nm in a single piece of singlemode fiber has been fabricated for simultaneous monitoring of temperature and strain in ultrahigh temperature environment. A 3 × 3 matrix is used to characterize the cross sensitivity of the proposed sensor in which the strain sensitivity varies with temperature change. The proposed structure exhibits the deviation of 28.3 με and 4.1°C at the ranges of 0-1000 με and 25°C− 900°C, respectively. Index Terms-Fiber Bragg gratings, regenerated grating, temperature and strain sensing, ultra-high temperature. I. INTRODUCTION F OR the application of strain and stress monitoring in ultrahigh temperature (UHT) environment such as aerospace engine, high temperature pipelines in oil and gas industry, hydroelectric turbine and high voltage transformers, it is essentially important to acquire multiple physical parameters i.e., strain, temperature, and pressure for comprehensive monitoring of the system. For example, the conventional electric strain gauges are performing well up to 350°C temperature. Beyond that range, the performance of gauges degrades due to the effects of high temperature on gauge bonding, gauge backing durability, electrical properties and the low ability to maintain the actual strain by compensating the thermal apparent strain simultaneously. These reveal the shortcomings of strain gauges employment in UHT environment. In this regard, optical fiber sensors particularly fiber Bragg gratings (FBGs) have emerged as promising substitutions for replacing the conventional sensors in various sensing Manuscript
Optical fibre Bragg gratings for high temperature sensing
20th International Conference on Optical Fibre Sensors, 2009
The development of new techniques for writing and tailoring the properties of Bragg gratings has generated a suite of distinct grating types that are optimised for performance within different temperature windows. These cover gratings produced by recipes such as hypersensitisation, thermal processing and single and multiphoton writing. In this paper, we review four types of high temperature gratings that offer comprehensive coverage of temperature space for most applications of interest. Up to 1200°C novel processing methods allow standard silica-based optical fibres to be used. However, beyond these temperatures, optical fibres made from other materials, such as sapphire, need consideration.
Review of Scientific Instruments, 2004
A simple and effective technique for strain-independent temperature measurement has been demonstrated using the peak wavelengths of both type-I and type-IIA fiber Bragg gratings written without hydrogen loading in the same fiber, this having been specially fabricated with a high concentration of germanium in the core composition. The device is also capable of monitoring strain and temperature simultaneously and can be used to measure temperature over the range of 25-300°C with a strain range of 0-500 , achieving a temperature-dependent sensitivity of 0.53 and 0.31 pm/°C for strain-independent temperature measurement with root mean square errors of 2.4 and 4.1°C at 25 and 300°C, respectively.
Thermal dependence of the strain response of optical fibre Bragg gratings
Measurement Science & Technology, 2004
The temperature dependence of the strain sensitivity of fibre Bragg gratings written into a number of different fibre types was investigated. It was found that the strain response changed on average by 0.21±0.03fm µε -1°C-1 over a range of temperatures between 100-400°C. These results were in agreement with predictions based on material parameters.
Temperature dependence of the stress response of fibre Bragg gratings
Measurement Science and Technology, 2004
Fibre Bragg gratings, used as stress sensing elements, show a temperature dependence of their stress response, which is mainly characterized by Young's modulus of the fibre material. The temperature dependence of the stress response of a fibre Bragg grating over a range from −38 • C to +110 • C has been measured. The stress sensitivity decreases linearly by 1.22 × 10 −4 K −1 over this range which is nearly identical to the increase of Young's modulus of fused silica over this range implying that it is predominantly Young's modulus which defines and characterizes this thermal dependence. Significantly, bare and re-coated fibres show a markedly different behaviour below 0 • C due to the glass transition temperature of the jacket material.
Bragg gratings in standard nonhydrogenated fibers for high-temperature sensing
Applied Optics, 2011
Fiber Bragg gratings engraved in standard telecommunications-grade single-mode fibers without previous hydrogen loading show enhanced thermal stability for high-temperature measurements up to 800°C. The reflectivity decay at that temperature is adequate for industrial applications with a weekly change of sensing heads.