Tunable Homodyne Detection of an Incoming QPSK Data Signal Using Two Fixed Pump Lasers

Homodyne detection is of significant interest in optical communications because it detects both the amplitude and phase information of the incoming data channel. One of the challenges in implementing a homodyne receiver is to recover the phase and frequency of the incoming data and to lock these to the local oscillator. We proposed and demonstrated a tunable homodyne detection scheme using two continuous wave pumps to automatically lock a “local” pump laser to an incoming 20-to-40-Gbaud QPSK data signal. Open eyes are obtained for both in-phase and quadrature components of the signal after ∼200-km transmission over single mode fiber (SMF-28) and dispersion compensation fiber without any carrier recovery. The BER performance of the proposed homodyne detection scheme is also performed with and without transmission.