Patent ID: 8238745

Claim:
A method of collecting data from an optical channel monitor for monitoring the power of a wavelength-division multiplexed light signal at each wavelength, the method comprising: monitoring a power level of each signal light which enters the optical channel monitor and which is being swept, and when fluctuation in the power levels above a predetermined threshold is detected, discarding the power level at each wavelength and a total power level currently collected from said optical channel monitor and maintaining the data that are collected immediately before, wherein monitoring power levels includes: analog-to-digital conversion of the power; comparing the result of the conversion with a predetermined reference light power; and determining whether or not the difference between the result of the conversion and the predetermined reference light power exceeds the predetermined threshold, and wherein the method further comprises holding the result of the analog-to-digital conversion which is first performed during each data collection period, as the predetermined reference light power.