OTN supports Transparent Transport of Client Signals:What does it really mean?

Thus the transport of such client signals in the OTN is bit-transparent (i.e. the integrity of the whole client signal is maintained).

OTN is also timing transparent. The asynchronous mapping mode transfers the input timing (asynchronous mapping client) to the far end (asynchronous de-mapping client).

OTN is also delay transparent. For example if 4 STM-16 signals are mapped into ODU1’s and then multiplexed into an ODU2, their timing relationship is preserved until they are de-mapped back to ODU1’s.