Polarisation pulling in Brillouin optical time-domain analysers

The impact of Brillouin scattering on the polarisation of pump and probe in a Brillouin optical-time domain analyser is investigated. Experimental results indicate that the Brillouin interaction integrated along the entire sensing fibre produces a polarisation pulling force that changes the pump polarisation. Although this force can be compensated to first order by dual-sideband probes, the Brillouin gain/loss experienced by probe bands induce a net pulling that leads to uncompensated polarisation fading and reduced signal-to-noise ratio. While the use of two simultaneous orthogonally-polarised probes alleviates fading issues, spectral distortions originate from the coupling between Brillouin gain and polarisation pulling

Distributed Temperature Measurement in a Self-Burning Coal Waste Pile through a GIS Open Source Desktop Application

Geographical Information Systems (GIS) are often used to assess and monitor the environmental impacts caused by mining activities. The aim of this work was to develop a new application to produce dynamic maps for monitoring the temperature variations in a self-burning coal waste pile, under a GIS open source environment—GIS-ECOAL (freely available). The performance of the application was evaluated with distributed temperature measurements gathered in the S. Pedro da Cova (Portugal) coal waste pile. In order to obtain the temperature data, an optical fiber cable was disposed over the affected area of the pile, with 42 location stakes acting as precisely-located control points for the temperature measurement. A monthly data set from July (15 min of interval) was fed into the application and a video composed by several layouts with temperature measurements was created allowing for recognizing two main areas with higher temperatures. The field observations also allow the identification of these zones; however, the identification of an area with higher temperatures in the top of the studied area was only possible through the visualization of the images created by this application. The generated videos make possible the dynamic and continuous visualization of the combustion process in the monitored area

ECOAL Project—Delivering Solutions for Integrated Monitoring of Coal-Related Fires Supported on Optical Fiber Sensing Technology

International audienceThe combustion of coal wastes resulting from mining is of particular environmental concern, and the importance of proper management involving real-time assessment of their status and identification of probable evolution scenarios is recognized. Continuous monitoring of the combustion temperature and emission levels of certain gases allows for the possibility of planning corrective actions to minimize their negative impact on the surroundings. Optical fiber technology is well suited to this purpose and here we describe the main attributes and results obtained from a fiber optic sensing system projected to gather data on distributed temperature and gas emissions in these harsh environments

Fiber optic sensing system for monitoring of coal waste piles in combustion

International audienceThe combustion of coal wastes resulting from mining is of particular environmental concern and therefore the importance of the proper management involving real-time assessment of their status and identification of probable evolution scenarios is recognized. Continuous monitoring of combustion temperature and emission levels of certain gases opens the possibility to plan corrective actions to minimize their negative impact in the surroundings. Optical fiber technology is well-suited to this purpose and in this work it is described the main attributes of a fiber optic sensing system projected to gather data on distributed temperature and gas emission in these harsh environments