A composite phosphorescent temperature measurement film based on rare earth phosphorescent powder and polymer derived ceramics (PDC) was proposed in this letter. The film was made on nickel-based alloy substrate with yttrium oxide doped europium (Y2O3:Eu3+) and polysilazane (PSN2) precursor ceramic as temperature sensing substances and high-temperature bonding layer respectively. We tested the thermal properties of the film, and built a high-temperature test system based on a calibration furnace. The phosphorescence emission spectrum and 611nm/587nm phosphor intensity ratio were measured with the 407nm excitation laser. The results showed that the film can survive for more than 3 hours at 1000℃, and the adhesion strength could reach up to 30 MPa. In the temperature range of 300~947°C, there is a linear relationship between temperature and phosphorescence intensity ratio. The temperature coefficient of phosphorescence intensity ratio is 0.0149/°C, and the temperature measurement error is less than 2.3%. The influence of high temperature thermal radiation on phosphorescence temperature measurement was studied, and the calibration curve of the sensor was corrected using the thermal radiation correction method based on the theory of incoherent light. The results show that the phosphorescence intensity changes from exponential function to linear relationship with temperature, and the upper limit of temperature measurement of the sensor increases from 947℃ to 1000℃.
Accurate measurement of the surface temperature of the hot-end components of aero-engines is of great importance for health monitoring and design of the engine. As a non-contact temperature measurement technology, the phosphorescence temperature sensing technology based on thermal quenching effect developed rapidly in recent years. It obtains real-time temperature information by measuring the decay time or intensity ratio of the phosphor on the surface of the high-temperature component. Aiming at the problem of the high temperature failure and shedding of the phosphorescent film, polymer derived ceramics (PDC) is used as the adhesion layer, whose thermal and mechanical properties can be easily controlled by doping, to improve the high-temperature oxidation resistance and adhesion of the phosphorescent film. The phosphor temperature sensing film with Y2O3:Eu3+ phosphor and perhydropolysilazane (PHPS) precursor ceramics as temperature sensing substances and high-temperature bonding layer respectively is made on alumina and nickel-based alloy substrates. The phosphorescence emission spectrum and 611nm/620nm phosphor intensity ratio were measured with the 407nm excitation laser. The results show that the phosphor film on the aluminum oxide insulating substrate has higher phosphorescence intensity and temperature sensitivity than phosphor film on the nickel-based alloy metal substrate, the phosphorescence intensity decreases with the increase of sintering temperature, and the phosphor film using PDC as the bonding layer has the characteristics of high temperature oxidation resistance and strong adhesion.
KEYWORDS: Optical fibers, Fluorescence spectroscopy, Luminescence, Near field optics, Microfluidics, Sensors, Polymethylmethacrylate, Signal detection, Integrated optics, Near field
A simple fabrication method of helical micro optical fibers (HMOFs) with controllable diameters and pitches based on micro-Weissenberg effect is proposed in this Letter. Single fibers with minimum diameter and pitch of 5 μm and 15 μm were directly written by near-field electrospinning of molten poly(methyl methacrylate) (PMMA). The morphology and transmission characteristics of single PMMA HMOFs were experimentally measured. The results showed that HMOFs have periodic modulation effect on transmitted light and show its potential as a micro-displacement sensor. Then a fluorescence detection structure based on HMOF is proposed, where HMOF was used to incoming the excitation light and collecting fluorescence. Experimental results show that for the fluorescence sensing of R6G aqueous solution, the fluorescence collection efficiency of HMOF was 4 times that of the micro optical fibers of the same diameter.
We study a novel fabrication method of micro/nano optical fiber by mechano-electrospinning (MES) direct-written technology. MES process is able to precisely manipulate the position and diameter of the electro-spun micro/nano fiber by adjusting the mechanical drawing force, which through changing the speed of motion stage (substrate). By adjusting the substrate speed, the nozzle-to-substrate distance and the applied voltage, the poly(methyl methacrylate) (PMMA) micro/nano optical fibers (MNOF) with controlled diameter are obtained and the tapered MNOF are fabricated by continuously changing the substrate speed. The transmission characteristics of PMMA micro/nano fiber is experimentally demonstrated, and a PMMA micro/nano fiber based refractive index sensor is designed. Our works shows the new fabrication method of MNOF by MES has the potential in the field of light mode conversion, optical waveguide coupling, refractive index detection and new micro/nano optical fiber components.
A novel method to auto-correct the fluctuation of calibration in Raman distributed temperature sensor is proposed in this paper. The proposed scheme combines a fiber coil configuration with a Pt-resistance in the front section to cancel out the impact of fluctuation generated by perturbations of the laser and APD, instability of power supply and environment temperature changes. The sensor performance is significantly improved by exploiting the fiber coil and Pt-resistance to correct the temperature calibration. Our theoretical analysis shows that with the calibration of temperature autocorrection method the sensing system is more suitable for various environments and provides low uncertainty in long term operation, and it has the potential to accurate temperature calibration with simple equipment and to reduce costs of the system.
KEYWORDS: Sensing systems, Error analysis, Signal detection, Signal to noise ratio, Backscatter, Data acquisition, Interferometry, Interference (communication), Interferometers, Polarization
A positioning algorithm for two-wavelength dual Mach-Zehnder interferometry (TDMZI) vibration sensing system is proposed. We employ the reciprocal of the interval between neighboring zero-crossing (NZC) points to represent the frequency distribution of the interference signal in time domain. Meanwhile, these reciprocal points are used to fit a curve and we use cross correlation to estimate the time delay of the two fitted curves. Finally we analysis the positioning error caused by the proposed positioning algorithm and experimentally demonstrate that the algorithm can be used to locating with positioning error of ±50m. This algorithm has a promising potential in long distance two-wavelength vibration sensing system.
KEYWORDS: Correlation function, Super resolution, Sensors, Interferometry, Signal to noise ratio, Fourier transforms, Data acquisition, Zoom lenses, Signal detection, Optoelectronics
A novel positioning algorithm based on super-resolution time delay estimation in dual Mach-Zehnder interferometry disturbance sensor is employed. We first compute the twice correlation function of the two output signal of DMZI by using modified chirp z-transform. Then fine interpolation of correlation peak is adopted to compute waveform of the main correlation peak only using the main segment of the cross power spectrum to improve the resolution of the twice correlation function. At last, in order to enhance the capacity of peak detection, we calculate the difference between the correlation function and its Hilbert transform to sharpen the peak of the correlation function. We have experimentally demonstrated that the proposed positioning algorithm can improve the positioning resolution and accuracy, and it has the potential to accurate positioning in low sampling rate and reduce costs of the system.
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