Wavelength Conversion for Enhanced Fiber Optic Ultraviolet Sensing

A fluorescent coating (phosphor) applied to the tip of an optical fiber converts incident radiation to longer wavelengths, and can considerably improve fiber-based UV spectrometry. Longer wavelengths are more readily transmitted by the fiber, are less apt to cause UV-induced damage in the fiber, and are more easily detected. Alignment of the fiber is much less critical for fluorescent-tipped fibers and the use of inorganic phosphors which have “peaked” excitation curves can help increase wavelength selectivity. This paper presents a method for evaluating the effectiveness of different combinations of fiber, phosphor, source collimation state, and detector, and describes two different methods for applying durable phosphor coatings to optical fibers.