32-Channel Tunable and 106Gb/s EAM-Integrated DBR-LD for 6G Mobile Front-Haul Networks

We report on the development of a tunable light source capable of supporting a 106 Gbps optical signal per channel within the CWDM wavelength window at 1290 nm. This device was realized through the monolithic integration of a distributed Bragg reflector laser diode (DBR-LD) with a high-speed electro-absorption modulator (EAM). Precise channel wavelength selection was achieved through both coarse and fine tuning by injecting current into the heater elements formed in the DBR and phase control regions, respectively. Pulse amplitude modulation-level 4 (PAM-4) was performed by applying a voltage signal and bias to the EAM. In static tests, the fabricated LD chips demonstrated an output power exceeding 7 mWand a side mode suppression ratio greater than 40 dB at a gain current of 100 mA within a temperature range of 25–55 °C. Dynamic tests of the LD module revealed clear 106 Gbps PAM-4 eye diagrams for 32 channels at 100 GHz frequency spacing under an operating temperature of 50°C. Based on these results, we conclude that the developed LD is an effective light source for 6G mobile front-haul networks.