The team of researchers from UCL and the University of Cambridge led by Dr Tianhua Xu and Nikita Shevchenko (both UCL), have developed a new channel model, which accounts for both first-order signal-noise interactions as well as mixing between the signal and first-order signal-noise interactions. This new model will give rise to further investigations of achievable information rates in coded transmission systems.
In addition, this model also enables potential advantages in the analyses of submarine transmission and improved detection schemes.
The development of a series of new technologies including wavelength-division multiplexing (WDM), advanced modulation formats, optical amplifiers and fibres, coherent detection, as well as signal processing enables a dramatic increase of data rates in optical communications. However, achievable information rates of optical communication systems are currently limited by the nonlinear distortions inherent to transmission using optical fibres. When nonlinearity compensation is ideally applied, complete suppression of signal-signal interactions can be achieved, whilst the random signal-noise interactions are left uncompensated. In the range of powers, which are of interest for nonlinearity compensated systems, first-order perturbation analysis is no longer sufficient for an accurate characterisation of system performance, and second-order nonlinear effects need to be taken into account, by considering the additional nonlinear mixing process between signal and residual first-order signal-noise interactions.
In this work, a new channel model considering modulation dependent nonlinear effects and second-order interactions between signal and optical amplifier noise is developed to investigate the performance of nonlinear regimes in wavelength-division multiplexing multi-channel optical communication systems. Our results show that, in the case of full-field nonlinearity compensation, accounting for second-order interactions becomes essential in order to predict system performance of both single-channel and multi-channel systems. Compared to previous research, this developed channel model allows an accurate prediction of system performance at optimum power and beyond.
This research is published in Optics Letters “Modelling of nonlinearity-compensated optical communication systems considering second-order signal-noise interactions”, DOI: 10.1364/OL.42.003351