Patent ID: 8879919

Claim:
A communications device comprising: a transmitter device comprising first and second optical sources configured to generate respective first and second optical carrier signals at first and second optical carrier frequencies, and a modulator coupled to said first and second optical sources and configured to modulate the first and second optical carrier signals with an input signal; an optical waveguide coupled to said transmitter device; and a receiver device coupled to said optical waveguide and comprising a frequency modulation-phase modulation (FM-PM) discriminator having a single integrated transfer function with a positive slope portion and a negative slope portion so that the first optical carrier frequency is positioned on the positive slope portion and the second optical carrier frequency is positioned on the negative slope portion, a first waveguide path coupled to said FM-PM discriminator, a second waveguide path coupled to said FM-PM discriminator, and an optical-to-electrical converter coupled to said first and second waveguide paths and configured to generate an output signal; said transmitter device comprising a controller configured to compensate for thermal drift in said FM-PM discriminator by adjusting the first and second optical carrier frequencies.