An optical fiber sensor for measurement of the refractive index of liq
uids is described. Three parallel fibers and a mirror are used. One fi
ber is used to launch the light to the mirror and the other two captur
e the reflected light. The operation principle is based on the output
light angle change due to the refractive index of the liquid into whic
h the optical fiber probe is dipped. The paper contains the theoretica
l consideration as well as the experimental results. Aqueous solutions
of NaCl and LiBr are used as testing media.