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Fiber optic distributed temperature sensing systems (DTS) are based on the principle of reflectometer and allow us to measure the temperature along the optical fiber. Optical fiber in these systems is used as a temperature sensor which can measure up to thousands of points simultaneously. DTS sensors use nonlinear phenomenon known as Raman scattering for temperature measurement. The advantages of this system include immunity to electromagnetic radiation, low cost of optical fiber, the possibility of measurement to a distance of 10 km and safe use in flammable or corrosive environments. The small size of optical fiber allows using in applications where the dimensions of the other sensors were problematic. A typical example of the DTS application is the fire detection in tunnels and buildings at risk, detection of water leaks on dikes and dams or monitoring of temperature in mine shafts. This article deals with the measurement of temperature transmission over various insulation layers using the DTS system. One of the problems of temperature transmission is that most of the sensors cannot measure the entire temperature profile but only allows a point measurement. This problem is solved by DTS systems with optical fibers. Optical fiber, due to its small size, can be applied among various insulation layers that were formed by rock wool. Three sensory layers formed by rings of multimode optical tightbuffered fiber with 50/125 micron core/cladding dimension were applied. The layers were linked together allowing a direct comparison of measured temperature. Rows of rings were placed on the margins and one was in the middle. Individual rings were linked together into the horizontal lines. Thus we were able to cover the whole surface of the insulation layers. Measurement was carried out in a closed air-conditioned room for 37 hours. Graphs with the progress of temperature at time and place were compiled from the measured data.
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