DAC-less and DSP-free 20 Gb/s PAM-4 transmission based on a dual modulation scheme using DML and external modulation

Abstract

The generation of DAC-less 20 Gb/s PAM-4 using a DML and an external modulator is demonstrated. This dual modulation scheme has been transmitted up to 75-km SSMF with similar performance to PAM-4 DAC transmitter.

PON-FTTX Architecture and Bandwidth Analysis for Future Broadband Communications

“…Multi-level intensity modulations (PAM-4 and PAM-8) require electrical DAC for signal encoding which introduces an extra cost to implement. One simple alternative to solve this problem is using optical-domain-based-DAC [25][26][27]. optical-domain-based-DAC multiplexes two or more binary signals with different amplitudes in the optical domain through either hybrid modulation [25,28], dual drive MZM approach with power divider [26], or a polarization multiplexed 2-external modulator cascaded in parallel [27].…”

“…One simple alternative to solve this problem is using optical-domain-based-DAC [25][26][27]. optical-domain-based-DAC multiplexes two or more binary signals with different amplitudes in the optical domain through either hybrid modulation [25,28], dual drive MZM approach with power divider [26], or a polarization multiplexed 2-external modulator cascaded in parallel [27]. Optical-domain-based-DAC approaches are not only possible for intensity modulation or binary signal multiplexing but researchers in [29,30] also demonstrated the possibility of multiplexing two or more PAM-4 into an array of nPAM-4 using cascaded MZM.…”