D8PSK/OOK bidirectional transmission over a TDM-PON

Transmission of a 7.5 Gb/s Differential 8 Phase-Shift Keying (D8PSK) signal, capable of encoding three bits per symbol per polarization, has been demonstrated over an amplified Time-Division Multiplexed Passive Optical Network (TDM-PON) for the first time. The incoherent multilevel receiver is laser-free and utilizes DSP to reduce complexity in the optical domain. A Directly Modulated Laser (DML) operating at 2.5 Gb/s provided a low-cost upstream channel. The performance of both channels after transmission over 25 km of fiber has been evaluated and the effect of bidirectional propagation over the common fiber has been investigated. Experimental results show satisfactory receiver sensitivity, indicating the format's suitability as an enabler for very high bit rates in future TDM-PONs.