Self-homodyne coherent system based on polarization-multiplexed pilot-carrier

This paper proposes an original self-homodyne coherent system based on the copropagating pilot carrier, which does not require the SOP tracking at the receiver. The system allows to double the whole transported capacity with respect to the standard on-off keying (OOK) modulation thanks to a tailored modulation scheme combined with a specific transmitter (TX) based on the direct modulation of a single laser to achieve both the carrier and the signal, and a RX architecture based on direct detection. By means of suitable simulations, the performance of the proposed system is compared with respect to the employment of 4-level pulse-amplitude modulation (4PAM), which is a very effective modulation format able to double the capacity exploiting direct detection suitable for short-reach applications. Moreover, also polarization shift keying (POLSK) modulation is taken into account in the comparison. Finally, experimental measures confirm the feasibility of the proposed system.