40-Gb/s Time-Division-Multiplexed Passive Optical Networks Using Downstream OOK and Upstream OFDM Modulations

In this investigation, we first propose and investigate a 40-Gb/s time-division-multiplexed passive optical network (TDM-PON) using four wavelength-multiplexed signals in both downstream and upstream traffic. Here, each downstream signal uses 10-Gb/s on-off keying (OOK) format encoded by a Mach-Zehnder modulator (MZM) in 1.5-¿m band. And each upstream channel utilizes the highly spectral efficient 10-Gb/s orthogonal frequency-division-multiplexing quadrature amplitude modulation (OFDM-QAM) generated by directly modulating a 1.3-¿m laser. Based on the proposed scheme, 40-Gb/s data traffic in a TDM-PON can be obtained easily by using four wavelength-multiplexed channels. In addition, the performance of the proposed PON architecture has also been discussed.