Abstract: A method for auto-tuning an optical transponder that is coupled to an optical terminal comprises: cycling through wavelengths in sequence by, for each wavelength: modulating the wavelength to convey a wavelength identifier of the wavelength, to produce a modulated wavelength that conveys the wavelength identifier; transmitting the modulated wavelength from the optical terminal through an optical demultiplexer that is configured to pass wavelengths to output ports of the optical demultiplexer; waiting to detect a response wavelength, transmitted by the optical transponder, which matches the wavelength; and determining, based on whether the response wavelength is detected, whether to repeat cycling using a next wavelength because the optical transponder is not tuned or to stop cycling because the optical transponder is tuned.