Patent ID: 8050564

Claim:
An optical communications system receiving an input optical signal and producing an output optical signal, said optical communications system comprising: a combining means for receiving the input optical signal and an add optical signal, said combining means combining the input optical signal and add optical signal such that the input optical signal and the add optical signal coherently interfere to form the output optical signal; wherein the light source of the add optical signal is not the light source for the input optical signal, and the optical spectrum of the add optical signal has substantial magnitude at those frequencies where the optical spectrum of the input optical signal has substantial magnitude; at least one laser; at least one modulation subsystem; at least one digital to analog (D/A) converter; and a digital signal processor; and wherein: the input optical signal contains at least one input wavelength division multiplexed channel, the output optical signal having at least one output wavelength division multiplexed channel; and light from said lasers is modulated by said modulation subsystems; said combining means combines the modulated light from said modulation subsystems with one another and with the input optical signal; each of said modulation subsystems is adjusted by at least one analog voltage, said analog voltage being produced by one of said D/A converters; said D/A converters are controlled by said digital signal processor; and the optical phase of light from said lasers with respect to one another is known by said digital signal processor and the optical phase of said input wavelength division multiplexed channels compared to light from said lasers is known by said digital signal processor; and the combining means sending the output optical signal; whereby said output optical signal contains information.