Techniques for multiplexing and demultiplexing signals for optical transport networks are presented. A network component comprises a multiplexer component that multiplexes a plurality of signals having a first signal format to produce a multiplexed signal in accordance with a second signal format, while maintaining error correction code (ECC) of such signals and without decoding such signals and associated ECC. The multiplexer component interleaves the plurality of signals with stuffing and adds overhead without generating new ECC. A second network component receives the multiplexed signal as part of a frame in accordance with the second signal format. A demultiplexer component of the second network component demultiplexes the multiplexed signal using the original ECC associated with the plurality of signals, wherein the second network element removes and filters the stuffing from the multiplexed signal and produces a plurality of demultiplexed signals as an output, in accordance with the first signal format.