Methods and systems for superchannel subcarrier monitoring using frequency modulated (FM) tones includes frequency modulating an optical subcarrier of a superchannel with a first frequency that is unique to the optical subcarrier and is chosen to be smaller than an optical transmission frequency for carrier data modulated onto the optical subcarrier. Then, downstream detection and monitoring of the optical subcarrier may be performed based on demodulation of the first frequency. Each optical subcarrier in the superchannel may be modulated using a respectively unique FM tone.