Patent ID: 8571419

Claim:
A system comprising: a coherent optical receiver configured to determine a frequency offset between a first frequency of a first optical carrier wave and a second frequency of a second optical carrier wave, wherein the first optical carrier wave is modulated with first information to form a first optical signal and the coherent optical receiver is configured to demodulate the first information associated with the first optical signal; a tunable optical transmitter comprising a tunable laser configured to generate the second optical carrier wave at the second frequency and coupled to the coherent optical receiver such that the coherent optical receiver receives the second optical carrier wave from the tunable laser; a control unit coupled to the coherent optical receiver and the tunable optical transmitter and configured to receive the frequency offset from the coherent optical receiver and adjust the second frequency of the tunable laser according to the frequency offset; and a signal combiner circuit coupled to the tunable optical transmitter and configured to combine the first optical signal with a second optical signal generated by the tunable optical transmitter by modulating second information on the second optical carrier wave.