As we know, the most basic 100G interfaces used today are 100G SR4 and 100G LR4 which are defined by IEEE.
However, their reaches are either too short or too long for practical applications in data center. Further more, the 100GBASE-LR4 is often costly.
In fact, for data center operators, a 100G QSFP28 transceiver that is with 2km or 500m max reach is better.
Thus, MSA (Multi-Source Agreement) strategy to bring a mid-reach solutions to the market. And 100G QSFP28 modules with PSM4 and CWDM4 interface are the products in this revolution.
They are much less expensive than the 10km, 100GBASE-LR4 module, and support longer distance than 100GBASE-SR4 QSFP28.
