400GBASE-LR4 and 400GBASE-LR8 Transmission Reach Maximization Using Bismuth-Doped Fiber Amplifiers

We extend the transmission distance of 400GBASE-LR4 and 400GBASE-LR8 systems by introducing simple and ultrawideband single-stage bismuth-doped fiber amplifiers (BDFAs). The transmission reach of emerging 400GBASE-LR4 and 400GBASE-LR8 transceivers was successfully extended from 10 km to 20 and 90 km, respectively. The transmission links were stable over seven days for both systems. Furthermore, we demonstrate that the transmission reach was maximized up to the chromatic dispersion limit and show the applicability of BDFAs for upgrading the transmission reach of cost-effective transceivers to meet the requirements of 400ZR applications. This offers a reasonable solution for improving the power budget and extending the reach of existing data center interconnections with 400GBASE-LR4/LR8 transceivers.