OPTICAL FIBER COATED WITH CARBON

摘要

PROBLEM TO BE SOLVED: To provide a carbon-coated optical fiber having excellent hydrogen- resistant characteristics. SOLUTION: This optical fiber coated with carbon is obtained by disposing a carbon film on the surface of an optical fiber. Therein, dielectric loss with microwaves is >=1.4%. The carbon-coated optical fiber can be produced by the application of a monitor device. The monitor device has a branched bridge circuit comprising a microwave three-dimensional circuit and used for dividing microwaves in two directions, a microwave-introducing means for introducing the microwave into the branched bridge circuit, and a detection means for detecting the imbalance output of the branched bridge circuit. At least one direction of the branched bridge circuit is formed so that a circuit constant can be changed, and the carbon-coated optical fiber is introduced into the branched bridge circuit.