Architectural Trade-Offs for High-Speed Real-Time Chromatic Dispersion Compensation FIR Filters With Time-Multiplexed Streaming FFTs

Fiber-optic communication faces challenges to address impairment such as chromatic dispersion, which distorts signals, necessitating efficient chromatic dispersion compensation (CDC) solutions. In this work, architectural trade-offs when implementing finite-length impulse response (FIR) filters in the frequency-domain for high-speed CDC is presented. Most earlier works have considered a fully parallel FFT. However, as shown in this work, it is possible to reduce the power consumption by increasing the FFTs size, leading to time-multiplexed streaming FFT architectures. The results, implemented for a tentative 400 G 16-QAM system, illustrates that traditionally used complexity measures, such as number of multiplications per sample, are not suitable when determining the best FFT size. It is also shown that this size is not necessarily a power of two. Instead, a ratio between the block length and the filter length of between one and two provides the best results in this case, lower than the commonly used multiplications per sample estimate. The results highlights the impact of the data shuffling, required for time-multiplexed FFTs, on the power consumption, but also the possibilities to lower the power consumption by not restricting to power-of-two FFTs.