Investigation on the use of standard single mode fiber as a displacement sensor using 1050 nm LED light source

Abstract

The use of standard single mode fiber using 1050 nm LED as displacement sensor was studied by examining the bending loss of the fiber. Three standard single mode fibers: jacketed and unjacketed patchcords, 2 m long each; and a 140 m length Fujikura fiber were used in this experiment. To simulate the displacement process, a fiber loop was clamped between the jaws of a vernier caliper to form a loop. Then, one of the movable jaw was shifted gradually every 0.5 mm resulting in the change of the diameter of the fiber and also the fiber output power. The value of the bending loss was measured as the output power at each position of the vernier caliper when varied from 50 to 10 mm. Investigation of bending loss values for all the fibers resulted in measurement range of 40 mm and resolution of 0.65–1.2 mm, depended on the material coating and the physical diameter of the fiber. Furthermore, the whispering gallery modes effect was unnoticeable and the relationship between output (bending loss, dB) and input (displacement, mm) at wavelength 1050 nm was almost linear which makes this system more practical for displacement sensor.