The Cisco GLC-BX40-U-I SFPs operate on a single strand of standard SMF.
The GLC-BX40-U-I SFPs also supports digital optical monitoring (DOM) functions according to the industry-standard SFF-8472 multisource agreement (MSA). This feature gives the end user the ability to monitor real-time parameters of the SFP, such as optical output power, optical input power, temperature, laser bias current, and transceiver supply voltage.