The Xelic 100G Optical Transport Network (OTN) Transponder provides the flexible transport of signals through a configurable highly integrated subsystem. Client signals supported include 100GE and OTU4 rates with line side ODU4/OTU4 signals configurable through internal register control. The subsystem contains independent 100G OTN Framer, OTL4.10, 100GE, and GFEC core processors with configurable options and a comprehensive programmable feature set. Independent interfaces are provided for framer GMP payload insertion/extraction control and external overhead port insertion/extraction. Optional loopbacks bypass modes, counters, and programmable consequential actions are available for debug and system integration purposes. A flexible 640-bit architecture is implemented with a data valid scheme and a high speed system clock operating at a rate up to 185MHz. The 100G Optical Transport Network (OTN) Transponder subsystem is targeted for both ASIC and FPGA applications.