1000BASE-X modules for 10G ports
1000BASE-SX SFP for multimode fiber only
The SFP-1G-SX module operates in 10G, 10/25G dual rate and 10/25/50G tri-rate ports of Cisco switches and routers, but provides 1G connectivity. The SFP-1G-SX interoperates with 1000BASE-SX modules.
The SFP-1G-SX module will only operate in 10G capable ports and will not operate in 1G only ports.
1000BASE-LX/LH SFP for singlemode fiber and multimode fiber
THE SFP-1G-LH module operates in 10G, 10/25G dual rate and 10/25/50G tri-rate ports of Cisco switches and routers, but provides 1G connectivity. The SFP-1G-LH interoperates with 1000BASE-LX/LH modules.
The SFP-1G-LH module will only operate in 10G capable ports and will not operate in 1G only ports.