A Polarization Multiplexed Carrier based Coherent Link with Adaptive Polarization Control
Transmitting polarization multiplexed carrier makes the receiver of a coherent system local oscillator-less and frequency offset-free. A polarization multiplexed carrier based self-homodyne (PMC-SH) system with an adaptive polarization control (PC) can replace pulse amplitude modulation (PAM- 4) data center interconnects. An adaptive PC technique is practically implemented by using an electrically controlled PC along-with control circuitry for PMC-SH systems. The de-multiplexing of the carrier and the modulated signal by using this technique is validated through simulations for a 50 Gbaud PMC-SH quadrature phase shift keying (QPSK) system with 20km standard single mode fiber (SSMF). We successfully demonstrate 16 Gbaud PMC-SH systems with adaptive PC for 10km SSMF channel. A bit error rate (BER) of 5.9 x 10^(-5) is achieved with 32 Gb/s PMC-SHQPSK system without any signal processing while a BER of 8.7 x 10^(-3) is achieved with a 64 Gb/s PMC-SH quadrature amplitude modulation (16QAM) system after equalization.