Patent ID: 7945160

Claim:
A method for monitoring a data transmission link, especially an optical, bidirectional data transmission link, received at a remote end of a transmission link, the method comprising: (a) receiving, at the remote end, a first digital transmit signal sent on a first transmission path from a local end of the data transmission link; (b) receiving, at the remote end on a second transmission path, a second digital control signal representing a portion of the power of the transmit signal, sent at the local end delayed by a predetermined non-zero delay time (T D ); (c) checking the transmit signal received at the remote end and the control signal received at the remote end for the presence of one or more events of a certain type; and (d) determining a conclusion on the quality of the data transmission link as a function of a time correlation and a frequency of the one or more event's appearance in the received transmit signal and in the received control signal.