A signal processing system includes an input for receiving an input signal, a light source for generating an optical carrier signal having a pre-determined wavelength, a modulator for receiving the input signal and the optical carrier signal and modulating the optical carrier signal based upon the input signal, and an optical filter having a plurality of signal channels, wherein at least one of the signal channels is locked by a reinsertion of the optical carrier signal to pass signals having a wavelength substantially the same as the wavelength of the optical carrier signal.