Highly Efficient Full-Duplex Coherent Optical System Enabled by Combined Use of Optical Injection Locking and Frequency Comb

We propose a novel point-to-point (P2P) coherent optical link based on optical frequency comb and injection-locking optical process, featuring single wavelength and wavelength division multiplexing (WDM) full-duplex coherent transmission over a fiber link up to 100-km distance. With light sources and local oscillators that are injection locked to an optical frequency comb, simultaneous down-stream and up-stream operations at the same wavelength using full-duplex coherent optical transceivers have been experimentally demonstrated. 32-GBd dual-polarization quadrature phase shift keying (DP-QPSK) and dual-polarization 16 quadrature amplitude (DP-16QAM) modulation formats have been investigated in the setup. When using QPSK, full-duplex operation up to 100 km has been achieved, which introduces 2.2 dB penalty at the hard-decision forward-error-correction (HD-FEC) and 1.3 dB penalty at the soft-decision forward-error-correction (SD-FEC) threshold. When using 16QAM, full-duplex operation up to 80 km has been successfully achieved and as large as 2 dB penalty is observed at the HD-FEC threshold, and 1 dB penalty at the SD-FEC threshold. The penalty mainly comes from continuous and discrete reflection impairments.