Performance Analysis of Optical Nyquist WDM Superchannel systems using Hybrid Modulation Techniques

Abstract

In modern times, internet traffic is increasing by leaps and bounds to fulfil the demand of different services such as multimedia, over the top platforms, cloud services, online gaming etc. This all has resulted in network congestion and to cope up with these demands, high capacity optical transmission systems with efficient use of channel spacing are required. There are a lot of challenges in both short-reach and long-haul optical access networks when the system capacities are upgraded. The earlier capacity growth has been achieved by improving the intensity modulation rate and using the DWDM techniques. However, due to electronics devices limitations and their failure to compensate channel impairments, it has been very tough to increase the data rate beyond 100 Gb/s for each channel. With the development of DWDM in association with digital coherent techniques, the capacity of the system has been increased up to 100 Gb/s for each channel. But Coherent techniques require a hybrid receiver structure to retrieve the phase of the electrical signal. With the help of phase information, distortions like polarization mode dispersion (PMD) and chromatic dispersion (CD) can be compensated. Therefore, more advanced modulation formats and polarization division multiplexing become feasible, enabling a channel speed to 100Gb/s and beyond. Going beyond and to the 100Gb/s per WDM channel requires the use of multiple carriers to make up a single WDM interface. The resulting multiplex, called a super-channel (or superchannel), and creates a multi-wavelength signal in which each wavelength will operate at the maximum data rate. In this, multiple carriers are transmitted over a signal channel. To utilize the channel spacing between these subcarriers, the Nyquist WDM superchannel technique is used which can provide terabit signal transmission for each channel.