Experiment results and tentative ideas for improvement of optical design of optical fiber level gauge of remote double light paths

The research of the optical level gauge is to realize its use in oil tank. Its fundamental structure and principle of operation are introduced, especially the technique of double light paths is adopted in order to avoid the influence caused by temperature and the bending resulted from installing and own weight. The experimental set-up and measured data of 40m alignment experiment, the basic experiment using cube corner retroreflector(CCR) and experiment using single wavelength coupler are respectively presented. Some adjustment problems of optical path are analyzed and resolved. It is proved that the selections of single-mode and multimode fibers are suitable through experiments. The right method of optical design is given through experiments and analysis, which effectively reduces the demand for linearity of CCR in moving, that is, to extend the effective diameter of receiving light spot as possible. Finally, the further improvement of optical design-using polarized light and further reducing diameter of CCR are presented in order to easily mount the device on the tank on the basis of the above researches.