Costas Loop Experiments for a 10.6 µm Communications Receiver

We have transferred the principle of the Costas-type nonlinear phase-locked loop to the
\lambda = 10.6 \mu
m wavelength of CO
2
lasers. The ability of the optical Costas loop to regenerate the carrier of a binary phase-shift-keyed input signal and to perform coherent demodulation was demonstrated at a data rate of 20 Mbits/s.