 Various categories of OXCs include electronic ("opaque"), optical ("transparent"), and wavelength selective devices.Cisco's Enhanced WDM system combines 1 Gb Coarse Wave Division Multiplexing (CWDM) connections using SFPs and GBICs with 10 Gb Dense Wave Division Multiplexing (DWDM) connections using XENPAK, X2 or XFP DWDM modules.These DWDM connections can either be passive or boosted to allow a longer range for the connection.