Recommendation ITU-T G.709.5 specifies 100G, 200G, 400G and 800G flexible optical transport network (FlexO) short-reach interfaces. This Recommendation specifies the structure using forward error correction (FEC) code with a coding gain suitable for short-reach applications, and references common elements from Recommendation ITU-T G.709.1. Amendment 1 to Recommendation ITU‑T G.709.5 adds a new FOIC1.2-RS optical short reach interface. Corrigendum 1 makes the following changes: • Clause 13.5.2. Corrects a typographical error in the Note. • Clause 14.5.2. Aligns the lane skew tolerance requirement with the IEEE 802.3df value. • Figure 13-5. Corrects a typographical error in the text label beside the FEC encode #1. Amendment 2 to Recommendation ITU‑T G.709.5 aligns to latest terminology and frame representation from G.709.1 Edition 4.0. It also introduces new 800G optical short reach interfaces..