Signal processing of a high resolution and long-range displacement sensor

This paper describes a signal processing method of a miniature fiber optic displacement sensor and determines the displacement of the mobile part online. The measurement system is based on two Fiber Optic Probes (FOPs) placed in front of a micro fabricated gold coated silicon grating. Two voltage signals are obtained from the probes and a continuous switching between the two signals has been assured in order to achieve millimetric range with nanometric resolution. Different parameters of the FOPs are taken into account such as sensitivity, data acquisition frequency and measurement velocity in order to find the optimal position relative to the silicon grating at which the switching between the two probes has been carried out. The signal processing provides a robust approach in order to work even in the presence of noise.