2x100G-QDD-2.1 is Multi-Vendor MSA Compatible 2x100G CWDM4 QSFP28-DD (Quad Small Form-Factor Pluggable Double Density) Transceiver designed for operation over single-mode optical fiber. 2x100G CWDM4 has a QSFP-DD form factor which supports eight electrical interface lanes which can operate in 25G NRZ encoding mode resulting in 200G (8x25G) data rate. Technically 2x100GBASE-CWDM4 QSFP28-DD modules consists of two 100G transceivers in one housing which can provide great flexibility for operators in their migration path towards QSFP-DD gear and 400G PAM4 infrastructure and help to make necessary interconnections with high density legacy 100GBASE-SR4 QSFP28 interfaces which use NRZ encoding. Module has a minimum guaranteed optical budget of 5 dB, which in most cases is enough to reach 2 km over OS2 single mode optical fiber. However, distance is just an indicative parameter calculated for comfort of identification. Eventually we calculate distance taking in account minimal optical budget and average attenuation of optical cabling in industry. 2x100G CWDM4 uses 8x25Gb/s Uncooled DFB (1271/1291/1311/1331nm) laser transmitters and 8x25Gb/s PIN Photo Detectors. 2x100GBASE-CWDM4 QSFP28-DD module supports DDM/DOM optical diagnostics, which provide diagnostic information about the present operating conditions. 2x100G-QDD-2.1 operates in standard 0°-70°C temperature range and has a double duplex CS connector. CS connectors have been standardized by CS Consortium and require special CS patch cables. 2x100GBASE-CWDM4 QSFP-DD supports 2×103.125 Gbps data rate and such applications as 2x100G Ethernet (206.25 Gbps). 2x100G-QDD-2.1 optical transceiver is a multi-purpose module which can be used in various scenarios in today’s networking environment. Most popular applications are Telecom Metro, Telecom Core, Wireless Backhaul and Data Center Interconnect (DCI).