An efficient adaptive equalization architecture for high-speed coherent PON systems

Abstract

Algorithmic and architectural options and tradeoffs between performance and complexity/power dissipation are imperative to be considered in the transfer of coherent technology from long-haul transmission to passive optical network (PON) application. In this work, a novel low-complexity equalization architecture cascaded two frequency domain equalizers (FDEQs) and one 1-tap 2 × 2 butterfly equalizer is proposed targeting PON applications. FDEQ is designed to handle link chromatic dispersion (CD) and the imperfection of transceiver frequency response. The 1-tap 2 × 2 butterfly equalizer is introduced to realize polarization demultiplexing. A simplified FDEQ tap coefficient calculation method is designed. The performance of the proposed equalization architecture is experimentally verified by a 32-GBaud dual-polarization (DP) Nyquist-QPSK system over 20-km standard single-mode fiber (SSMF) transmission. With the proposed method, the number of hardened multipliers for field-programmable gate array (FPGA) realization is reduced by ∼90% compared with conventional 2 × 2 butterfly equalizer, at the expense of 0.5 dB receiver sensitivity.