With the arrival of 40G Ethernet, many enterprise users are starting to fully utilize their current 10G network equipment to upgrade to a 40G network. Specifically, it is about how to pair 40G switches with QSFP+ports with existing 10G devices (switches and servers) with SFP+ports. In this article, SEESUO will share three common solutions and teach you how to interconnect 40G QSFP+ports with 10G SFP+ports on a switch.
 
Cable solution: Use QSFP+branch cables
QSFP+branch cables include QSFP+to 4 * SFP+DAC passive copper cables and QSFP+to 4 * SFP+AOC active optical cables. Both types have one QSFP+module connected to the A end and four SFP+modules connected to the B end. The transmission distance supported by QSFP+to 4 * SFP+DAC passive copper cables is 7m, and the transmission distance supported by QSFP+to 4 * SFP+AOC active optical cables is 70m. In addition to the above two types of cables, there is also a QSFP+to 4 LC duplex AOC cable, with one end being QSFP+and the other end being 4 duplex LC fiber jumpers, which can be used when there are 4 reserved SFP+optical modules, thus achieving the conversion from QSFP+to SFP+.  
SEESUO's QSFP+to 4 * SFP+AOC active fiber optic cable has a built-in 4-channel 850nm VCSEL laser array and PIN photodetector array, with digital diagnostic function (DDM). It can not only predict faults, locate fault locations, shorten fault repair time, reduce losses, but also predict laser life by monitoring the bias current of the laser through comprehensive analysis of detected temperature, voltage, emitted and received optical power, and warning and alarm status of the laser bias current.  
SEESUO's QSFP+to 4 * SFP+DAC passive copper cable has the advantages of anti radiation interference and low power consumption, making it the best low-cost solution for data transmission within 7 meters.
   
In the 10G to 40G network upgrade solution, you can use 40G QSFP+to 4 * SFP+direct connection cables to directly connect to the switch without purchasing additional optical modules, helping you save network costs and simplify the connection process. However, the transmission distance of this connection method is limited, so DAC or AOC direct fiber optic cables are more suitable for connecting switches inside the cabinet or switches between two adjacent cabinets.
 
Jumping scheme: Use MPO to convert 4 duplex LC branch jumpers
MPO to LC branch jumper is a fiber optic jumper that uses an OM3 or OM4 multimode fiber to connect an MPO connector with 8/12 cores on the A end and four duplex LC connectors on the B end. When using the MPO to LC branch jumper scheme, it is necessary to reserve one 40G QSFP+SR4 optical module and four 10G SFP+SR optical modules at both ends of the switch. When in use, simply insert the MPO connector into the 40G QSFP+SR4 optical module interface, and then insert the 4 duplex LC connectors into the 4 10G SFP+SR optical module interfaces.
   
Conversion module scheme: CVR-QSFP-SFP10G conversion module
This solution converts the 40G ports on the switch to 10G ports through the 40G QSFP+to 10G SFP+converter module CVR-QSFP-SFP10G, thereby achieving interconnection between QSFP+ports and 10G SFP+ports. The operation method is to plug the 40G converter CVR-QSFP-SFP10G into the QSFP+port, and then insert the 10G SFP+optical module to replace the 40G port with a 10G port.  
In actual data centers or other high-density cabling applications, network upgrade is a complex process, and sometimes cross connections can also be considered. The specific choice of method also needs to comprehensively consider transmission distance, transmission medium, network density, and cost factors. So, within a transmission distance of 7m, Yitian Optical Communication recommends that everyone choose QSFP+to 4 * SFP+DAC passive copper cable, which has the highest cost-effectiveness in short-range transmission solutions; Within a transmission distance of 70m, it is recommended to use QSFP+to 4 * SFP+AOC active optical cable. Within a transmission distance of 100m, it is recommended to use MPO to 4 duplex LC branch jumpers to connect the 40G SR4 optical module and 10G SR optical module at both ends.
 
As the network develops towards higher speeds, it will eventually become the norm for enterprises and data centers to fully utilize existing network equipment to build high-speed networks. By seeking solutions that can interconnect low-speed devices with high-speed devices, such as converting QSFP+ports to SFP+ports as mentioned in this article, we can fully leverage the performance improvements brought about by hardware upgrades.