An optical source (100, 200), comprising: a set of light sources (110-1, 110-2,..., 110-N) configured to output optical signals having a set of wavelengths with a substantially fixed spacing, wherein a given light source is configured to output a given optical signal having a given wavelength in the set of wavelengths, and wherein the set of wavelengths constitutes a wavelength comb; an optical combiner, optically coupled to the set of light sources, configured to combine the optical signals; an optical device, optically coupled to the optical combiner, that includes a diffraction grating on a curved surface, wherein the optical device is configured to image and diffract the optical signals using a reflective geometry and to output the optical signals at corresponding diffraction angles of the diffraction grating, thereby maintaining the wavelength comb; optical detectors (128-1, 128-2) optically coupled to the optical device, configured to determine optical metrics associated with the optical signals output at the diffraction angles, wherein the optical detectors include power monitors and a given optical detector is configured to determine a given optical metric associated with the given optical signal; and control logic, coupled to the optical detectors and the set of light sources, configured to provide control signals to the set of light sources based on the optical metrics, wherein the control signals adjust at least one of gains, phases and emitting wavelengths of the set of light sources, thereby maintaining a substantially fixed spacing between adjacent wavelengths in the set of wavelengths. a set of light sources (110-1, 110-2,..., 110-N) configured to output optical signals having a set of wavelengths with a substantially fixed spacing, wherein a given light source is configured to output a given optical signal having a given wavelength in the set of wavelengths, and wherein the set of wavelengths constitutes a wavelength comb; an optical combiner, optically coupled to the set of light sources, configured to combine the optical signals; an optical device, optically coupled to the optical combiner, that includes a diffraction grating on a curved surface, wherein the optical device is configured to image and diffract the optical signals using a reflective geometry and to output the optical signals at corresponding diffraction angles of the diffraction grating, thereby maintaining the wavelength comb; optical detectors (128-1, 128-2) optically coupled to the optical device, configured to determine optical metrics associated with the optical signals output at the diffraction angles, wherein the optical detectors include power monitors and a given optical detector is configured to determine a given optical metric associated with the given optical signal; and control logic, coupled to the optical detectors and the set of light sources, configured to provide control signals to the set of light sources based on the optical metrics, wherein the control signals adjust at least one of gains, phases and emitting wavelengths of the set of light sources, thereby maintaining a substantially fixed spacing between adjacent wavelengths in the set of wavelengths.