For more about their differences, please see the following table What’s more, in the data center fiber infrastructure, the patch panel has to be changed to accommodate MTP cables. This would cost more than LC connectors and regular single mode fiber cables. Besides, it’s not easy to clean MTP connectors. So coarse wavelength division multiplexing is more profitable and popular for 40GBASE-LR4 QSFP+ link.
For 40GBASE-LR4 QSFP+ transceivers, both coarse wavelength division multiplexing link and parallel single mode link can reach the transmission distance of 10 km. 40GBASE-LR4 CWDM QSFP+ transceivers use a duplex LC connector via 2 optical sm fibers. And 40GBASE-LR4 parallel single mode QSFP+ transceivers use an MTP/MPO fiber ribbon connector via 8 optical sm fibers.