Recommendation ITU-T G.709.3 specifies 100G, 200G and 400G FlexO Beyond 100G (B100G) long-reach interfaces. The Recommendation specifies the structure using forward error correction codes with a higher coding gain suitable for longer reach applications and references common elements from Recommendation ITU-T G.709.1 and FEC structures from Recommendation ITU-T G.709.2. Edition 3.1 contains the following extensions to Edition 3.0: Add FlexO skew to scope of clause 10 Changes to 802.3 references