The GLC-LH-SM is a long haul or long wavelength SFP module (1310 nm nominal), for use in 1000BASE-LX links. Use only the SFP modules with your Modular Fast Ethernet line card. Each SFP module contains an internal serial EEPROM that is security-programmed by the SFP manufacturer with information that provides a way for Cisco (through the Cisco IOS software) to identify and validate the SFP module as a module type that was tested and qualified by Cisco to operate properly with Cisco Modular Fast Ethernet line cards.