US Patent 7653318 Photonic phase locked loop detector/discriminator

Disclosed is a Photonic Phase Locked Loop (PPLL) detector/discriminator, which makes possible a system for optically transmitting electromagnetic signals through a transmission medium (such as optical fiber, optical waveguide, underwater, in biological tissue, or in free space) with high sensitivity and extremely high dynamic range exceeding what is possible with present optical intensity modulated (AM) systems. Information is encoded on an optical carrier through the use of phase modulation (PM) or frequency modulation (FM). This information is subsequently demodulated into an accessible form through the use of the PPLL.