A Transponder is a device which “transponds” or converts a client signal wavelength into another wavelength while keeping the circuit as transparent. A transponder is used at P-P end points connecting L2/L3 devices that either connect directly to the Patch Panel between locations or to a local WDM / CWDM / DWDM or ROADM network.

A muxponder is a device used to “aggregate” multiple lower rate circuits into a single high bandwidth trunk/line for transport over a single pair of fibers or individual wavelength through a new or existing WDM / CWDM / DWDM / ROADM network.