Apparatus and method for monitoring the transmission characteristics

PROBLEM TO BE SOLVED: To provide an apparatus and a method for accurately monitoring transmission characteristics of an optical transmission path.SOLUTION: A transmission characteristics monitoring apparatus monitoring transmission characteristics of an optical transmission path between nodes, the apparatus comprises: a detection section for detecting an average of receiving powers of a frequency modulation optical signal and a tendency of transmission characteristics; a function generation section for generating a tendency function indicating the tendency of transmission characteristics between a first frequency and a second frequency; a correction section for adding an integral of the tendency function into a first power value detected from the first frequency so as to generate a correction power value; a determination section for determining whether a difference between a second power value detected from the second frequency and the correction power value is bigger than a prescribed threshold or not; and a calculation section for calculating the transmission characteristics in the second frequency based on a second power measurement value when the difference is the threshold or less, and for calculating the transmission characteristics in the second frequency based on the correction power value when the difference is bigger than the threshold.SELECTED DRAWING: Figure 7