Optimization of fiber radius and sensor probe-reflector distance of trifurcated fiber optic angular displacement sensor

Abstract

Intensity modulated fiber optic sensor probes having various configurations of transmitting and receiving fibers are demonstrated by many researchers for angular displacement measurement. These sensors have a limited range of angular displacement measurement. The sensitivity and measurement range of these sensors depends on the spacing between fibers and sensor-probe reflector distance. This paper presents an asymmetric trifurcated fiber optic angular displacement sensor having one transmitting (TR) and two receiving fibers (RFA and RFB) placed on the same side of transmitting fiber. The output of the sensor is the ratio of light powers collected by the receiving fibers. For optimization of sensitivity and measurement range transmitting fiber with core radius ‘re’ and receiving fibers RFA and RFB in a ratio of 0.5 re, 1 re, 1.5 re and 2 re is selected. The distance (D) between sensor-probe-reflector is varied between 2 to 4 mm of front slope region displacement characteristics of the sensor probe. Simulation results indicate that sensor probe configuration with transmitter fiber having core radius re = 0.5 mm and receiver fibers RFA and RFB with core radii 0.5 re and 2 re ratios gives larger sensitivity of 6.09/° for D= 2mm. The sensitivity gets improved further to 39.07/° with the increase in sensor probe–reflector distance from 2 to 4 mm. The range of measurement is improved from 18 to 32° for transmitting and receiving fibers are having same radii.