The proposed system was proven to measure methane concentration at multiple points by means of only one optical fiber of an optical cable by using multiple passive remote sensors. The system was laboratory tested in a six-day long experiment using known optical cells with fixed concentrations of 5% and 10% methane, respectively. The system was also tested in a controlled setup with a methane leak flux varying from 0.15 to 5 liter/min at sensor distances from the leakage source between 4 to 28 cm, showing the expected dependence on distance between the sensor installation and the leak point. Finally the system was installed in a real pipeline system, namely a compression station, in which two leak points were previously identified by portable equipment. Results of the field tests have shown that the system is capable of detecting the leaks. The best results were achieved by using compact sensors located very close to the leak points. Thus a novel package of the passive sensors must be developed in order to mitigate the action of the wind dispersion that would allow methane to flow to the atmosphere undetected. A comparison of concentration values measured by the system and by portable equipment was shown to be in good agreement.
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