Homodyne receiver for ASK signals to 10-µm wavelength

The principle of coherent amplitude demodulation can be transferred to the optical regime. If phase shift keying demodulation of the transmitter carrier is not available, the coherent amplitude shift keying (ASK) system presented offers an attractive alternative. The homodyne concept for ASK signals requires the use of two detectors, of which one acts as a phase detector for the phase-locked loop.