Design and Modeling of fiber-optic displacement sensor with sub-nanometer resolution and long range

All industrial tasks including deep submicron and nanotechnologies such as micro and nano electromechanical systems need high performance and resolution measurements. For this purpose in this paper, we describe an optical displacement sensor with sub-nanometric resolution and operating in long range. High resolution optical displacement sensors have small operating range. To overcome this problem, in the proposed sensor triangular grating is used to extend the range of the measurements. It is shown that the resolution of the sensor depends on the grating angle. We also observed that the best precision situation in the proposed structure corresponds to maximum angle of the grating which is hard from implementation point of view. In fact, there is a trade-off between achievable resolution of the proposed sensor and complexity of realization. The proposed sensor has near 24 pm resolution over the length of grating.