Cisco Small Form-Factor Pluggable transceiver modules (SFP) are hot-swappable input/output (I/O) devices that plug into 100BASE and 1000BASE ports, which connects the module port with the fiber-optic or copper network.GLC-BX-D= is a 1000BASE-BX10 SFP module for single-strand SMF, 1490-nm TX/1310-nm RX wavelength.