Most 200G-SR4 transceivers designed for hyperscale data centers mate with APC MPO8 connectors, and 400G-SR4 (IEEE 802.3db) will use the same. Optical transceivers compliant to 400G-SR8 have an APC MPO16 interface. In standards, and in the operations of the largest data center operators in the world, APC multimode connectivity is featuring more in the plan for 400G and beyond. And multimode fiber links do not use fiber amplifiers or have unterminated connectors that may be present in some single mode fiber links. Usually, there are fewer connections in a multimode fiber link than a single mode fiber link due to the reduced reach and therefore, fewer sources of multipath interference.
The lasers used to transmit signals over multimode fiber are more resilient to back reflections than those used in single mode fiber links. Traditionally, only UPC connectors have been used with multimode fiber cables for several reasons.
