A new technique for measuring the attenuation of light in clad fibers is discussed. The basic approach is to measure the temperature rise produced in the fiber by the absorption of the light. Calculations indicate that the theoretical limit of sensitivity, which should be approachable with a relatively simple experimental configuration, is a loss of about 2.5 × 10-7/cm with 1 mW of light power and a 1-cm long sample. The theoretical sensitivity limit should improve with the square root of the sample length. A variation of the basic approach, which may make it possible to monitor attenuation in fibers as they are being drawn, is also discussed.
R. L. Cohen, "Loss Measurements in Optical Fibers. 1: Sensitivity Limit of Bolometric Techniques," Appl. Opt. 13, 2518-2521 (1974)