Patent ID: 8811815

Claim:
A method, comprising: generating an amplified stimulated emissions (ASE) test signal; modulating the ASE test signal; transmitting the test signal on an optical path, the optical path including a plurality of add-drop multiplexer devices and a plurality of amplifiers, wherein the plurality of amplifiers generate continuous wave (CW) ASE; receiving the modulated test signal at a destination device; converting the received test signal into an electrical signal, wherein the electrical signal includes an alternating current (AC) portion corresponding to the modulated test signal and a direct current (DC) portion corresponding to the CW ASE; measuring the AC portion of the electrical signal and not the DC portion, wherein the measured AC portion of the electric signal corresponds to a portion of the modulated test signal that passed through each of the plurality of add-drop multiplexers, and does not include CW ASE generated by the plurality of amplifiers; generating, based on the measured AC portion of the electrical signal and not the DC portion, an output graph representing a pass-band associated with the optical path, wherein the generating the output graph comprises: identifying a frequency in the measured AC portion of the electrical signal having a highest amplitude, setting the frequency having the highest amplitude as a center frequency, and generating values relative to the highest amplitude for measured AC portions of the electrical signal other than the center frequency; and determining, based on the output graph, a pass-band characteristic of the optical path.