Method and Circuit for Determing the Optical Signal to Noise Ratio for Optical Transmission

摘要

The invention relates to the determination of the carrier-to-noise ratio for optical transmissions when a noise-affected optical signal containing a message signal is transmitted along an optical signal transmission path, whereby the optical signal together with the optical noise transmitted therewith is fed to an optical filter (OF). The optical output signal from the above is converted into a corresponding electrical signal in a detector device (Det) and either the mid-frequency of the optical filter (OF), or the detector device (Det) is periodically modulated with a modulation signal (Um). The received total light power (Pges) is determined from a direct current component of the electrical signal and the signal power (Pse) of said message signal is determined from a time-dependent modulation component. The carrier-to-noise ratio is determined from the above parameters.