100-Gb/s/λ PAM-4 EAM-Integrated DBR-LD Supporting Multiple Sub-Channels Within 1.29 μm Window

We present a distributed Bragg reflector-laser diode (DBR-LD) monolithically integrated with an electroabsorption modulator (EAM) offering a 100-Gb/s pulse amplitude modulation 4-level (PAM-4) signal per sub-channel under a CWDM window of 1.29 μm. For the integrated structure, the DBR-LD and EAM were implemented using a trenched waveguide in the tuning sections for achieving energy-efficient wavelength-tuning and a deep ridge waveguide with an optimized structure for a 100-Gb/s PAM-4 operation, respectively. The fabricated chip shows a threshold current of approximately 12 mA and a tuning range of greater than 13 nm, which corresponds to a wavelength band capable of supporting 16 channels with a 150-GHz grid, while maintaining a side mode suppression ratio of greater than 40 dB. In dynamic tests, the results show clear 100-Gb/s PAM-4 eye openings with an outer extinction ratio of more than 4 dB and a transmitter dispersion eye closure quaternary of less than 1.5 dB for all measured channels.