A wavelength meter, an associated method, and system are generally described. In one example, an apparatus includes a photodiode to receive an optical signal and to generate a photocurrent upon receiving the optical signal, the photodiode having an absorption edge that is substantially aligned with a band of wavelengths, wherein the absorption edge shifts toward longer wavelengths when a reverse bias is applied to the photodiode, and control electronics coupled with the photodiode to apply at least a first reverse bias and a second reverse bias to the photodiode, wherein a ratio of a first measurement of the photocurrent at the first reverse bias and a second measurement of the photocurrent at the second reverse bias provides information about the wavelength of the optical signal.