Distributed temperature measurements using optical fibre technology in an underground mine environment Saiied M. Aminossadati * , Nayeemuddin M. Mohammed, Javad Shemshad The University of Queensland, School of Mechanical and Mining Engineering, CRCMining, QLD 4072, Australia article info Article history: Received 5 January 2009 Received in revised form 21 July 2009 Accepted 17 November 2009 Available online 16 December 2009 Keywords: Underground mine Optical fibre DTS Temperature Heat abstract This article experimentally examines the applicability of a temperature measuring and monitoring sys- tem using distributed temperature sensing by means of an optical fibre in an underground mine environ- ment. The temperature distribution along an optical fibre can be detected by measuring the Raman backscattering of the stokes and anti-stokes lines. The distributed temperature sensing system provided valuable information for the mine safety control and the mine ventilation system. In addition, it proved to be capable of measuring air temperature in the entire mine with an accuracy of 1 °C and within the dis- tance resolution of 1 m. The heating and cooling processes could be detected and the rate of heat gener- ation at any location of the mine could be accurately determined from the temperature measurements. This technology has the potential to be linked to other measuring devices of an underground mine envi- ronment in order to develop a safer ventilation control system. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Over the past few years, many new measurement devices such as digital, laser and ultrasonic sensors have become available for monitoring underground coal mine ventilation. However, the cur- rent monitoring systems suffer from the lack of an active and real- time system. The temperature variation in an underground mine environment is of critical importance to the health and safety of underground miners. In recent years, most of the fatal accidents that have occurred in underground mines around the world could have been prevented if the mine had been equipped with a dynamic and accurate temper- ature monitoring system. Most of the major safety issues in under- ground mines are due to the temperature rise, which is the result of various physical and chemical sources such as blasting, strata, thermal oxidation and human metabolism. It is evident that the lack of reliable and effective monitoring of mine ventilation param- eters such as air temperature leads to serious mine disasters. In fact, early detection and localisation of the temperature variation is considered as one of the initial indicators of hazardous situa- tions. A fast and reliable temperature measurement can assist to control escape routes and to minimise the possible damage caused by various hazards such as fire, methane explosion, spontaneous combustion and coal dust explosion. The temperature profile ob- tained from a real-time and accurate monitoring system helps the mine ventilation operator examine and plan alterations to the mine ventilation conditions and precisely examine the current ventilation conditions. A Distributed Temperature Sensing (DTS) system using optical fibre technology is an intrinsically safe method which can be ap- plied in an underground mine environment to continuously mea- sure and monitor the temperature variation within the mine. The DTS system is based on Optical Time Domain Reflectometry (OTDR). In this configuration, the location of the temperature event can be determined based on the generation of a narrow laser pulse and the travel time of the backscattered light to return to the detection unit. OTDR offers a number of technical benefits for Distributed Temperature Sensing compared to other systems of Optical Fre- quency Domain Reflectometry (OFDR). Temperature changes down to 0.01 °C can be detected along sensing cables of distances greater than 30 km and are less affected by potential anomalies within the fibre such as bends and connectors. The DTS system is a blend of optical, mechanical, electrical and computer integration. The photon flux of anti-stokes Raman back- scattering of the optical fibre is modulated by the spatial tempera- ture field. The optical electronic signals carrying the temperature information can be acquired by demodulating the signals. In the DTS system, the optical fibre is used as both a sensing and trans- mission medium. The main advantages of using the optical fibre as a sensor probe are no need for electricity, explosion-proof, fire-proof, safe in hazardous environments, potentially resistant to ionizing radiation, immune to high voltage and strong electro- magnetic fields, immune to Radio Frequency Interference (RFI) and Electro-Magnetic Interference (EMI), solid-state reliability, se- cure data transmission, self-inspection and self-calibration. The 0886-7798/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.tust.2009.11.006 * Corresponding author. Tel.: +61 7 33653676; fax: +61 7 33653888. E-mail address: uqsamino@uq.edu.au (S.M. Aminossadati). Tunnelling and Underground Space Technology 25 (2010) 220–229 Contents lists available at ScienceDirect Tunnelling and Underground Space Technology journal homepage: www.elsevier.com/locate/tust