42.7 Gb/s Cost-effective Duobinary Optical Transmitter Using A Commercial 10 Gb/s Mach-Zehnder Modulator with Optical Filtering

Optical duobinary transmission at 42.7 Gb/s is demonstrated using a commercially available 10-Gb/s LiNbO3 modulator. The intrinsic response of the 10-Gb/s electro-optic Mach-Zehnder modulator (MZM) is used to create a low-pass-filtered (LPF) duobinary signal. As compared to non-return-to-zero (NRZ) signals the MZM-LPF duobinary signal shows a minimum OSNR requirement penalty of ~4 dB to ~6 dB. However, when the MZM-LPF duobinary technique is used in conjunction with a 50-GHz 3-dB-bandwidth first-order Gaussian filter directly before the receiver a significant improvement in required OSNR is seen. In contrast, similar optical filtering of NRZ data creates a significant OSNR penalty such that the NRZ and MZM-LPF duobinary data streams have nearly identical OSNR requirements. These results indicate that the MZM-LPF duobinary technique may be a cost-effective approach to high-spectral-efficiency transmission at 42.7 Gb/s.