Is Tomlinson-Harashima Precoding Suitable for Fiber-Optic Communication Systems?

Tomlinson-Harashima precoding (THP) is a pre-compensation method, which is exactly fitted to the channel impulse response in order to completely compensate for its linear impairments, and it is in-fact a generalization of partial response precoding. THP is very popular in the field of wireless communications, namely in multi-input multi-output (MIMO) scenarios. It offers an alternative to the decision-feedback equalizer (DFE) with the possibility to apply channel coding conjunctively. In this paper, the compatibility of THP with fiber-optic communication systems is investigated. Different configurations of THP are considered and compared with DFE by means of performance and complexity. Results are examined for 4QAM modulation, where the length of the transmission link and the number of equalizer coefficients are varied. In addition, the effect of the receiver filter's bandwidth on the performance of THP is evaluated. In the second step, possible scenarios for using THP in a fiber-optic system, as well as challenges, which result from properties of the system and equalizer, are addressed and discussed.