Operative Factors Contributing to the Selection of Fiber-Optic Techniques for Remote Measurement of Strain/Stress

Optical fibers have found exceptional usage in the field of telecommunications, due to their low attenuation, immunity to cross talks, large bandwidth, low cost and robust structure. Some of the factors mentioned here also contribute in the selection of optical fiber as a powerful sensor. The type of sensor that can be designed varies for the type of application it is needed in. This paper shows how optical fiber is used for remote measurement of strain/stress. The quantity measured is the soil pressure, which is identified to be the key factor in determining the possible occurrence of a landslide, a destructive natural disaster which occurs commonly here in South East Asian nations such as Indonesia, Malaysia and Singapore. The optical sensing technique proposed and used in the developed applications in this paper and consequent research is the light intensity modulation and the micro bending technique. Both the techniques are tested under the same conditions and environment and it is found that both techniques have their advantages and disadvantages, where none characteristics can be discarded for this research. An ordinary type laser has been used as the light source in both the sensors. Similarly a light dependent resistor is used for light detection purposes. A suitable microcontroller will be selected for the task of processing a single input from a selected sensor fiber, and displays the output over a LCD, together with soil status displayed via LED. The hardware and the software are then combined together in the prototype hardware to characterize a working model of the system. Cost wise, both the sensors have nearly equal expenditure. Although this complete and ongoing research project covers theoretical, design and testing of the optical fiber sensors as well as the selection, programming and simulation of the selected microcontroller, and the outcome of the completed system, this paper will concentrate on the theoretical selection by elimination and to prove that the light intensity modulation and the micro bending technique are the best fiber optic techniques for stress/strain measurement.