Method and apparatus for creating a clone relationship between two or more optical-frequency comb sources (OFCSs). In one embodiment, the invention is an apparatus having (i) first and second OFCSs, each adapted to generate a respective frequency comb, and (ii) means for locking the phases of two comb lines of the first OFCS and the phases of the respective two comb lines of the second OFCS to create a full or partial clone relationship between these two OFCSs. In one system configuration, the locking of the phases of the first and second OFCSs is achieved by locking the phases of two selected comb lines generated by each of these OFCSs to the phases of the respective comb lines generated by the same (third, reference) OFCS. In an alternative system configuration, the locking of the phases of the first and second OFCSs is achieved by locking the phases of two selected comb lines generated by the first OFCS to the phases of the respective comb lines generated by the third OFCS, and locking the phases of two selected comb lines generated by the second OFCS to the phases of the respective comb lines generated by the first OFCS.