Mutual information in weak-coherent-state detection using a homodyne optical costas loop with different phase errors
Résumé
A free-space experimental set-up for measuring the quadrature components of weak-coherent-state laser signals, based on a homodyne Costas loop configuration is presented. Loop parameters are optimized as a trade-off between quantum and phase noises. Using binary phase-shift-keying modulation, measurements on the mutual information are presented for different photon numbers and phase errors.