Fiber optic sensing of displacement and pressure

The use of single- and double-fiber sensors for measuring displacement and gas pressure are presented. In a single-fiber approach it is possible to use either a He-Ne laser or a LED as light source. The double-fiber sensor is operating with a He-Ne laser and shows a higher capability. The LED single-fiber sensor has a sensitivity of about 0.6 mV/mu m, a resolution of 1.25 mu m for displacement. For the nitrogen gas pressure measurement, it shows a sensitivity of 0.7 mV/Torr with a dynamic range of about 100 Torr. The sensitivity of the double-fiber sensor is about 1.8 mV/mu m with a. dynamic range of about 300 mu m for the displacement measurements. The LED single-fiber sensor offers the advantage of simplicity, light weight, and a wide dynamic range at a lower cost. The double-fiber approach provides a higher sensitivity and can be used for the more precise applications. The results obtained from the both sensor systems are satisfactory and show a promise in order to be used in the real field applications.