ZTE claimed a new record for long-haul 400 Gbit/s single-carrier optical transmission utilising patented compensation algorithms that enable transmission of 84 Gbaud WDM for PDM-8QAM signals over a distance of up to 2,125 km on standard single-mode fibre.

ZTE noted that in 2015 it partnered with OFS to deliver transmission of 128.8 Gbaud WDM QPSK signals over 10,130 km and 6,078 km of terrestrial fibre at different spectrum efficiency, while in 2016 it demonstrated single-carrier 800 Gbit/s transmission with 120 Gbaud WDM 16QAM signals over 1,200 km terrestrial fibre links.
http://www.zte.com.cn/global/about/press-center/news/201703ma/0323ma4