A liquid-level sensor developed by Jonathan D. Weiss at Sandia National Laboratories in Albuquerque, N.M., eliminates the hazards of monitoring fluids in explosive environments such as fuel tanks. The sensor, which is an outgrowth of his fiber optic shock-wave position sensor, eliminates the need for electrical and optoelectronic conversion components in or near the tank. Weiss doped a methyl styrene slab with an organic dye that absorbs blue light and fluoresces in the green. In tests that he reported in the August 2000 issue of Optical Engineering, the researcher used 476-, 488- and 496-nm lines from an argon-ion laser and a 471-nm LED as the excitation source. Because the fluorescence escapes only at the interface of the slab and the fluid, a user can determine the level of the liquid from the intensity of the signal. Weiss calculated that the absorption of the 23-mW optical signal in kerosene, which is similar to jet fuel, would create no risk of explosion.