hi,
I would like to share these information with you ,
I think the real achievment of the high speed using fiber optic is when used on DWDM not in short distance , because that means increase in Core networks .
and the maximum speed using DWDM practically is 72Tb/s . when each channel carry 800G .
please refer to huawei using 800G in following article.
https://www.huawei.com/en/news/2021/2/telefonica-600g-800g-osn9800-madrid?fbclid=IwAR0_yqaevptRIrJlQqFrHadMC0V-qz8e_5XGZ-J6mr3OzJ2yrypT4C_9Lz4