Absorption Measurement of Optical Fiber by Photoacoustic Method

Abstract

Optical fibers are good materials for photo-acoustic investigation. First, their very low absorption limits optical measurements and second the Rayleigh diffused light, often greater than absorbed light, appears as a background. In optical communication range (0.8, 1-3 μm) it is well known that pure absorption is very low and even unmeasurable; nevertheless at other wavelengths such studies by photoacoustic methods are interesting to know the concentration of ions like OH-. On another point of view, if other optical ranges are considered (UV for example) absorption is not negligeable and must be known. But in this case the diffused Rayleigh light is very important (Power varies as λ−4).