First Realtime Synchronous 16-QAM Transmission with Coherent Digital Receiver

This letter presents for the first time 1.25 Gb/s synchronous coherent 16-point Quadrature Amplitude Modulation (16-QAM) transmitted and received data in a real-time homodyne setup with external cavity laser (ECL). For powers larger than ?20dBm, the average bit error rate (BER) is below forward-error correction (FEC) limit.