The Cisco GLC-ZX-SM / GLC-ZX-SMD is a 1G SFP (Small Form-Factor Pluggable) transceiver for long-distance single-mode fiber (SMF) links, supporting 1000BASE-ZX Gigabit Ethernet up to 80km, using a 1550nm wavelength, and featuring an LC connector, with the 'D' in SMD indicating Digital Diagnostics Monitoring (DDM/DOM) for real-time monitoring, providing cost-effective, high-performance optical connectivity for service providers and data centers.