PAM4符号対応CTLEの補償量設計法の検討

抄録

The 400GbE standard has been established to treat the increasing Internet traffic because of IoT devices and teleworking. In the 400GbE, PAM4 codes are adopted in addition to conventional NRZ codes. For a high-speed, long-haul, and complex modulated communication, a waveform signal is degraded by an optical dispersion on a fiber. The receiver utilizes electrical dispersion compensators (EDCs) to compensate for waveforms degraded by transmission lines. Continuous-time linear equalizers (CTLEs) are widely used in EDCs because of their small circuit size. EDCs with CTLEs are studied actively for PAM4 optical communication systems. We propose a CTLE design methodology based on a step response analysis. Appropriate compensation ranges for PAM4 signals are derived by the transfer function of degradation and CTLE mathematical models. From the verification results of circuit simulations with CTLEs designed by the proposed methodology, we have clarified the appropriate CTLE compensation strength for degraded waveform signals. It is possible to design a suitable CTLE for PAM4 signals using the proposed methodology.