METHOD FOR MEASURING TRANSMISSION LOSS OF OPTICAL FIBER

摘要

PURPOSE:To perform accurate measurement, by a method wherein an optical fiber to be measured is immersed in liquid helium to form a thermal equilibrium state and light is allowed to be incident on said optical fiber from one end thereof and absorbed thereby while the transmission loss thereof is calculated from the quantity per hour of helium vaporized by the heat energy due to light absorption. CONSTITUTION:A loss measuring optical fiber 1 is immersed in liquid helium held in a cryostat to be brought to a thermal equilibrium state and light is allowed to be incident on said optical fiber 1 from one end thereof and absorbed thereby. On the other hand, the other end of said optical fiber 1 is immersed in matching oil having a refractive index equal to that of said optical fiber 1 to prevent the evaporation of liquid helium at the end surface thereof. In this case, the quantity of helium vaporized per an elapsed time by heat energy due to the light absorption of the optical fiber is calculated as the difference of first helium quantity and the second one before and after the incidence of light and transmission loss is calculated from said difference. By this method, the transmission loss of the optical fiber 1 having a short length and low in loss can be accurately measured with high accuracy.