| 摘要 |
PROBLEM TO BE SOLVED: To provide a light reflection measuring circuit, in which the measurement can be made on a long optical fiber even in case of a low interference light source or a light source having a large interval of optical frequency, and the measurement can be made with high accuracy by eliminating the effect of response lag of the light source. SOLUTION: A reflectometry (OCDR) utilizing synthesis of light wave coherence function is employed. A laser 11 is a light source outputting a light pulse having widthΔy at an intervalΔT wherein the i-th light pulse has an optical frequency fi. At the tome of switching the optical frequency, a measuring light is outputted after the laser output is settled through control with an optical switch and the transient part in the light frequency modulation of the laser 11 is masked. An outgoing light from the laser 11 is branched through a photocoupler 4 into a reference light and a measuring light. The measuring light is introduced to an object, i.e., a component 3 to be measured, and the reflected light is taken out through the photocoupler 4. A beat signal of the reflected light and a reference light outputted from the photocoupler 4 is received by a light receiver 2.
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