Patent ID: 8483575

Claim:
An apparatus comprising: a coupler; an I/Q modulator; and a wavelength notch filter that has at least one narrow wavelength blocking band; wherein a first input of the coupler is configured to receive at least a first input optical carrier having a first frequency, and wherein a second input of the coupler is configured to receive a set of frequency-shifted carriers from the filter; wherein the I/Q modulator is configured to shift the frequency of a first output of the coupler; wherein the filter is configured to filter shifted output from the I/Q modulator to limit the optical bandwidth of the set of frequency-shifted carriers; wherein a second output of the coupler is configured to provide a plurality of frequency-locked carriers containing the first input carrier and the set of frequency-shifted carriers, and wherein a 3-dB bandwidth of the at least one narrow wavelength blocking band is about equal to the spacing between the frequency-shifted carriers.