Surface Enhanced Raman Scattering (SERS) is typically observed with the substrate in a liquid medium and it has been proposed as a promising technique for detecting low levels of pollutants in liquids. The design and fabrication of an optical fibre SERS sensor based on Au nanoparticles (Au-NPs), which is self-assembly immobilized onto the end surface of an optical fibre is described. Two toxic materials, Rhodamine 6G (R6G) and crystal violet were analysed using this optical fibre SERS sensor combined with portable Raman spectrometer. Our proposed fabrication and analytical method offers a rapid, cheap and disposable trace detection capability for toxic materials in the field.
Surface enhanced Raman spectroscopy (SERS) is a fast, convenient and highly sensitive detection technique, and preparing the good effect and repeatable substrate is the key to realize the trace amount and quantitative detection in the field of food safety detection. In this paper, a surface enhanced Raman substrate based on submicrometer silver particles structure was prepared by chemical deposition method, and characterized its structure and optical properties.
Accurate measurement of energy is a technical difficulty that various microseismic monitoring systems are facing. In this article, we applied the groundbreaking fiber optics microseismic monitoring system to mine rock burst monitoring for the first time around the world. We suggest to calculate microseismic energy via the duration of vibration. Precise picking of P wave first arrival and end point is essential to microseismic energy calculation. According to the huge energy difference before and after the arrival of the seismic wave, we use the sliding time-window energy ratio method to pick the first arrival and end point, and put forward the quantitative relationship between the sliding time-window width TWL and the sampling frequency as well as the signal dominant frequency for the first time. The results of P wave automatically picking are almost the same as those manually picked. However the end point may need to be corrected if wave distortion occurred.
The FBG strain sensors were applied to the Dongtan Mine to monitor the stress variation of the lined wall in the gateway retained along goaf of No. 3203 coal mining face on line. The results showed that the FBG strain sensor with high measuring range could measure the stress variation accurately during the support process of the gateway retained along goaf and could provide the basis to further optimize the support structure and to determine the support plan of the gateway retained along the goaf. The FBG micro-seismic sensors were used in Xinglong Mine to detect micro-seismic signal. The signals are well received and analyzed to determine the earthquake source and do warming. The FBG sensors and detecting system show great prospect in micro-seismic detection, and geological disasters detecting.
Microseismic monitoring is essential for rock burst predication in coal mines. However, the existing monitoring instruments based on electric geophone have inherent limitations and hardly progress further. This paper presents the design and implementation of a novel microseismic monitoring system using fiber optic sensing and distributed data acquisition techniques. The technical details including seismic sensor, interrogation system, and seismic substation are introduced. The results show that the system achieves a bandwidth of 0.5-400 Hz and a dynamic range of 80 dB. The location accuracy reaches 10 m by reasonable configuration of sensors, and so it is particularly suitable for precision mine microseismic monitoring.
A high sensitive fiber Bragg grating (FBG) acceleration sensor based on filtering demodulation is analyzed on
sensitivity, resolution and temperature experiment. Sensitivity and resolution of FBG sensor lies on the structure of the
sensor shell and the shape of the reflectivity spectrum of FBG. The temperature experiments of the FBG sensor show the
work and storing temperature range of the sensor based on different preparing stress and packaging glue. Experiments on
the detecting system's frequency character have been done. Results show that this acceleration sensor can detect the
smallest acceleration of 1mm/s2 with a flat response from 5Hz to 40Hz.
A high sensitive fiber Bragg grating (FBG) geophone detecting system based on narrow line width distributed
feedback (DFB) laser is realized by using filtering demodulation. Sensitivity of FBG geophone lies on the structure of
the sensor shell and the shape of the reflectivity spectrum of FBG. Experiments on the detecting system's frequency
character have been done. Results show that this geophone can detect the smallest acceleration of 1mm/s2 with a flat
response from 5Hz to 40Hz.. The experiments on coal mine exhibit that the geophone can be used to measure microseismic
signals. The detecting system shows great prospect in micro-seismic detection, and geological disasters
A temperature adaptive fiber Bragg grating (FBG) vibration sensor system of low frequency based on narrow line
width distributed feedback (DFB) laser is investigated. By automatic controlling the temperature of the DFB laser, the
wavelength of the DFB laser can be locked in -3dB reflectivity spectrum of FBG. So the system can realise the self
adaptation of the temperature changes. Using the reference channel, the measurement precision of the system was
improved by wiping off the power noise of the DFB laser. Experiments show that this sensor has the smallest
acceleration of 1mm/s2 and the sensitivity of 6.2V/m/s2.