Network elements are identified as being connected to optical nodes by instructing two network elements in a spectrum group of the CMTS to transmit at frequencies f.sub.1 and f.sub.2, respectively. Frequencies f.sub.1 and f.sub.2 are selected such that they produce intermodulation distortions (intermods) in the laser transmitter at f.sub.3 when combined. If intermods are produced which exceed a predetermined threshold, then the two network elements are determined to be on the same node. If the total power of the signal by the laser transmitter exceeds an impact threshold, then the test is stopped and new network elements are selected for testing.