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  • Marcus Coleman thinks this is interesting:

As data center designs evolve from 1G to 10G at the access layer, access to aggregation and spine-leaf design at the spine layer will move to 40G. The 40G adoption is slow today because of multiple barriers; the first is the cost barrier of the 40G port itself. Second, when you migrate from 10G to 40G, you must replace the cabling. 10G operates on what is referred to as two strands of fiber; however, 40G operates on eight strands of fiber. Bi-Di optics are standard based, and they enable customers to take the current 10G cabling plant and use it for 40G connectivity without replacing the cabling. Figure 1-16 shows the difference between the QSFP SR and the QSFP Bi-Di

From

Cover of CCNA Data Center DCICN 200-150 Official Cert Guide

Note

QSFP BI-DI Technology for 40 gig