Towards 50G/100G Passive Optical Networks with Digital Equalisation and Coherent Detection

Abstract

Increasing bandwidth demand in residential, business, and Wi-Fi/cellular backhaul applications means that passive optical networks (PONs) with dense wavelength division multiplexing and bit rates per wavelength channel of 50 or 100 Gb/s will soon be required [1] . However, PON technologies need to be low cost, particularly the optical network units (ONUs). Additionally, the high optical losses arising from the optical splitters used at remote nodes to distribute the signals to and from multiple ONUs, lead to the requirement for high receiver sensitivity. Coherent receivers, since they surpass the sensitivity limitations of the intensity-modulated direct-detection (IMDD) systems currently used, are an attractive solution [2] – [4] . Besides its sensitivity, coherent detection provides other advantages. The local oscillator achieves good wavelength selectivity, avoiding the need for narrow optical bandpass filters. The use of digital signal processing (DSP) enables spectrally efficient signalling and digital equalization of optical transmission impairments.