Callite-C4 is 400G SOC solution to transpond 4x100GE or 400GE client onto Optical Transport Network (OTN). In 4x100GE mode, each lane can be configured independently and clocking and timing are also independent. In 400GE/OTUC4 mode, the Callite-C4 processes the OTUC4 OH bytes in multiplexed fashion. In OTUC4 mode, the GFEC per 100G slice can be disabled or removed if external coherence module or high-gain FEC is used.