What is the difference between ODUk and ODU flex?

Dear friend!
There are limited types of ODUk channels, which face the challenge of insufficient bandwidth utilization. Ethernet services (10GE), SAN storage services (FC400), and video and other services (3G-SDI) are mapped to ODUk services. (On the TDC board, they must be mapped to ODU4.)
When the ODU4 medium payload is 2 Gbit/s, the bandwidth utilization is only 2%.
The FC400 rate is 4.25 Gbit/s, and the bandwidth utilization is only 5%.
The 3G-SDI rate is 2.97 Gbit/s, and the bandwidth utilization is only 3.75%.

Huawei proposed the idea of ODUflex transmission pipes in 2007. In 2011, it became an ITU-T standard, that is, the G.HAO protocol, which is called the Hitless Adjustment of ODUflex. Note that ODUflex has no adaptive capability for client-side signals. It is only a granularity that carries client-side signals. The difference between ODUflex and ODUk granularity is that the granularity can be customized based on the client-side signal rate.

The ODUflex is mapped to the higher-order ODUk channel and occupies the timeslots that match the size of the higher-order ODUk channel. Other higher-order ODUk timeslots can be used to carry other services, thereby ensuring 100% bandwidth utilization.

The minimum granularity of ODUflex is 1.25 Gbit/s. ODU4 (100 Gbit/s) can accommodate up to 80 ODUflex. Therefore, 2XODU4 can accommodate up to 160 ODUflex.
Thank you!