4-level direct-detection polarization shift-keying (DD-PolSK) system with phase modulators

We propose and demonstrate a novel 4-level DD-PolSK system with LiNbO/sub 3/-based phase modulator and alternative allocation of constellations, which lead to a greatly simplified transceiver architecture. A 5 Gb/s (2.5 GS/s) testbed has been build to demonstrate the feasibility of the 4-PolSK transceiver.