A single mode SFP (Small Form-factor Pluggable) is a type of transceiver used for long-distance, high-bandwidth optical fiber communication. It uses a small-diameter core (9 microns) and lasers at specific wavelengths, typically 1310nm or 1550nm, to transmit a single light path over distances up to 80km or more. Single mode SFPs are ideal for networks like internet backbones, telecommunications, and wide-area networks where extended reach and low signal loss are crucial.