The S-SFP-GE-LH40-SM1550 is an SFP (Small Form Factor Pluggable) Transceiver operating over double fiber single-mode fiber optical cable. It supports a data rate of 1.25 Gbps (Gigabit Ethernet) with transmission distance up to 40 kilometers at 1550 nm wavelength over single-mode fiber. It supports DDM/DOM optical diagnostics, which provide diagnostic information about the present operating conditions.