Fiber Bragg grating (FBG)-based high-temperature sensor with enhanced-temperature range and stability has been developed and tested. The sensor consists of an FBG and a mechanical transducer, which furnishes a linear temperature-dependent tensile strain on FBG by means of differential linear thermal expansion of two different ceramic materials. The designed sensor is tested over a range: 20°C to 1160°C and is expected to measure up to 1500°C.
A high-temperature sensor using fiber Bragg grating (FBG) integrated with a transducer has been designed, developed, and tested. The transducing element furnishes temperature-dependent tensile strain on FBG by means of differential linear thermal expansion of two different materials—mild steel and stainless steel. The designed sensor is compact, cost effective, and measures temperatures between 20°C and 1000°C. The electrical means output of the sensor against applied temperature is found to be fitted with a second-degree polynomial. The achieved resolution at room temperature is 2°C and is found to be better when moving toward higher temperatures. However, by optimizing the materials and physical dimensions of the transducer, it is possible to improve the temperature range and performance of the sensor.
A low-cost and high-resolution interrogation scheme for a long-period fiber grating (LPG) temperature sensor with adjustable temperature range has been designed, developed and tested. In general LPGs are widely used as optical sensors and can be used as optical edge filters to interrogate the wavelength encoded signal from sensors such as fiber Bragg grating (FBG) by converting it into intensity modulated signal. But the interrogation of LPG sensors using FBG is a bit novel and it is to be studied experimentally. The sensor works based on measurement of shift in attenuation band of LPG corresponding to the applied temperature. The wavelength shift of LPG attenuation band is monitored using an optical spectrum analyser (OSA). Further the bulk and expensive OSA is replaced with a low-cost interrogation system that employ an FBG, photodiode and a transimpedance amplifier (TIA). The designed interrogation scheme makes the system low-cost, fast in response, and also enhances its resolution up to 0.1°C. The measurable temperature range using the proposed scheme is limited to 120 °C. However this range can be shifted within 15-450 °C by means of adjusting the Bragg wavelength of FBG.
This paper reports a simple technique for hydraulic pressure measurement with enhanced resolution using a fiber Bragg grating (FBG) and a metal spring which acts as transducer. The sensor works by means of measuring the Bragg wavelength shift of FBG caused by the longitudinal elongation of optical fiber due to applied pressure. Experimental results show that the sensor possesses good linearity and repeatability in pressure measurement ranging over 0 to 55 bar, with a sensitivity of 57.7 pm/bar. A wavelength-intensity interrogation scheme using single-multiple-single-mode fiber structure is designed for FBG sensor, which enabled the system to be compact, lightweight, inexpensive, and high resolution.
A novel sensor for high-temperature measurement using Fiber Bragg grating (FBG) has been designed and simulated. The sensor works based on measurement of the shift in Bragg wavelength that corresponds to the temperature induced strain by making use of a mechanical transducer. The transducing element provides temperature dependent strain on FBG by means of differential linear thermal expansion of two different ceramic materials: Alumina and Silicon Carbide. The designed sensor can measure the temperatures from 20°C to 1500°C.
A fiber Bragg grating (FBG)–based high-temperature sensor accompanied by a low-cost interrogation scheme with liquid-crystal display (LCD) has been designed, developed, and tested. The sensor probe is configured by encapsulating a femtosecond laser drawn FBG with an aluminum nitride capillary tube, and is used to measure the temperature from 20°C to 650°C. The interrogation system consists of a long period fiber grating, two photodiodes, a 2-channel transimpedance amplifier, and a field-programmable gate array with an LCD. It displays the temperature directly in °C with a resolution of 1°C. The sensor output is found to be linear with coefficient of 0.999, and independent of source power fluctuations. The results showed that the sensor has good accuracy with a negligible error bar of ±1.23%.
A novel sensor for high-temperature measurement using Fiber Bragg grating (FBG) along with its low-cost interrogation system has been designed and tested. The sensor works based on measurement of the shift in Bragg wavelength that corresponds to the temperature induced strain by making use of a mechanical transducer. The transducing element provides temperature dependent strain on FBG by means of differential linear thermal expansion of two different materials, stainless steel and mild steel. The shift in Bragg wavelength of FBG due to this temperature induced strain is measured by using optical spectrum analyser (OSA). Further the bulk and expensive OSA is replaced by a low cost interrogation system that employed an LPG, a photodiode, a transimpedance amplifier, and a digital multimeter. The LPG converts wavelength information of FBG into its equivalent intensity modulated signal which is captured by a simple photodiode and then converted into voltage signal using the transimpedance amplifier. The designed sensor measures the temperature from 20°C to 1000°C with a resolution of 2°C.
This article demonstrates use of a fiber Bragg grating (FBG) sensor for in situ monitoring of vacuum process with high sensitivity. The sensor head consists of a commercial syringe barrel with plunger, metal spring, pressure chamber, FBG and safeguarding outer tube. The sensor is configured by firmly fixing the FBG between the plunger and the rigid support provided to the safeguarding tube. Under vacuum process the metal spring facilitates the FBG to get strained in axial direction which results in shift of Bragg wavelength of FBG. The Bragg wavelength shift of FBG is found to be linear with respect to vacuum pressure with a linear coefficient of 0.9988. Pressure sensitivity of the sensor is found to be 27 pm/cm Hg. The sensor design is simple, low-cost and has the advantage of all fiber optic sensors.
A method is proposed to minimize the effect of temperature on a long-period fiber grating (LPG), enabling its effective use for the interrogation of wavelength-modulated fiber Bragg grating (FBG) sensors. The temperature dependence of LPG is compensated by means of creating the opposite effect from the temperature-induced strain, attributed by appropriately encapsulating in a specially designed Teflon tube. The encapsulated LPG has achieved six times stabilization over the bare LPG response for the temperature range of 20°C to 50°C. Application of the athermalized LPG for interrogation of an FBG-based temperature sensor is experimentally demonstrated.
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