High Sensitive Measurement Sensor for Industrial Hydraulic Cylinder Stroke Based on Fabry-Pérot Optical Interferometer

This paper presents an optical sensing technique based on a Fabry-Pérot interferometer can be used to measure the stroke of an industrial hydraulic cylinder by detecting changes in the distance between the cylinder's piston and the interferometer's mirrors. The proposed cylinder stroke sensor's Faber-Pérot cavity is created by pair or partially transmitted mirrors with reflectivity up to ($\mathrm{R}=0.95$) to make the signal has a high-fineness interference patterns. As the piston moves, it changes the distance between the mirrors, which in turn changes the resonant cavity's length and the wavelength of the light that is amplified or suppressed. By measuring this change in wavelength, the sensor can determine the piston's position and thus the cylinder's stroke. The results demonstrate that the new stroke monitoring sensor has a free spectral range (FSR) up to 0.58GHz with bandwidth equal to ∼28.36MHz with total resolution for the cavity spacing up to 10nm with 33% peak transmission.