  High-speed long-range quantum communication requires combining frequency
multiplexed photonic channels with quantum memories. We experimentally
demonstrate an integrated quantum frequency conversion protocol that can
convert between wavelength division multiplexing channels in the telecom range
with an efficiency of $55\pm 8\%$ and a noise subtracted HOM dip visibility of
84.5%. This protocol is based on a cascaded second order nonlinear interaction
and can be used to interface a broad spectrum of frequencies with narrowband
quantum memories, or alternatively as a quantum optical transponder,
efficiently interfacing different regions of a frequency-multiplexed spectrum.
