What is meant by SDH Modernization?

Hi,

Services such as data center (DC) interconnection and 4K video have emerged, and
time division multiplexing (TDM) private line services pose new challenges on transport
network security, latency, and bandwidth. In this ever-changing environment the bearer
technology is best suited for future transport networks.
Synchronous digital hierarchy (SDH), which has been deployed on a large portion of
telecommunications networks around the world for some time.

For further details, please refer to the listed white paper of SDH Modernization.

https://www-file.huawei.com/~/media/CORPORATE/PDF/white paper/White_Paper_on_SDH_Modernization.pdf