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A novel fiber optical reflectometry is proposed for long distance measurements and sensing applications. The reflectrometric information is included in the phase difference of two interfering light beams reflected at the same scattering point on the fiber under test (FUT). The reflection position and local information can be determined by modulating the frequency difference and analyzing the reflecting...
Tunable diode laser spectroscopy (TDLS) is one of the most successful techniques for trace-gas environmental monitoring. By modulating the light source at high frequency for suppressing the noise, frequency modulation or wavelength modulation TDLS can measure optical absorption in atomic or molecular samples with high resolution and sensitivity. Apart from these absorptive techniques, there exists...
An FBG sensing system for coal mine security monitoring is proposed in this paper. It works over a spatial-division-multiplexing/coherence-multiplexing network to realize quasi-distributed sensing. Methane concentration, strain, and temperature are measured in the experiment.
Gas inside packed food is monitored by a technique named GASMAS, GAs in Scattering Media Absorption Spectroscopy. The sharp gas absorption line in contrast to the broadband bulk absorption enables gas detection in situ.
LIDAR techniques are used to measure gases in solid scattering media remotely, by analyzing the differential absorption observed in the multiple scattering light. The gas exchange (O2/N2) in polystyrene foam is monitored.
In this paper, we propose a simple fiber-optic sensing system to measure the concentration of the methane based on a special catalyst and fiber Bragg gratings (FBGs). The temperature around the catalyst rises rapidly as the concentration of methane increases, and hence can be detected by an FBG-type sensor through monitoring the wavelength shift of the reflection spectrum. By employing a well-matched...
We propose an optical low-coherent interrogation scheme for multiplexed sensors based on in-fiber Michelson interferometers. In the interferometer, a long period fiber grating (LPG) works as a wavelength-dependant coupler and the fiber core and cladding of a section of the fiber (with a highly-reflective mirror at the end) work as two arms of the interferometer. The optical path difference (OPD) induced...
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