A system for measuring liquid level in multiple tanks using optical fiber technology has been developed. Oil field service industry or any sector requiring liquid level measurements in inflammable atmospheres can be benefited from this intrinsically safe technology. Three different models considering various effects have been derived and tested on two prototypes. The first model use punctual emitters and divergence, the second model use finite emitters with paraxial approach, and the third model use a constant power rays distribution in the emitters using with each one of the rays the Snell's law, to take in count the optical aberrations. A Monte-Carlo method is used to fit the experimental data and obtain the models parameters. The simplest model is demonstrated to be accurate enough for a proper correlation between the experimental data and the fitted curve in a range of 2 m.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.