40G-QSFP-2.1 is Multi-Vendor MSA Compatible QSFP (Quad Small Form-factor Pluggable) Transceiver, operating over pair of singlemode or multi-mode optical fiber with four independent optical communication lanes seperated from each other using WDM technology. Module has minimum guaranteed optical budget of 4.5 dB if used on SMF and 2.5 dB if used on MMF, which in most cases is enough to reach 2 km distance using single-mode cable and 150m distance using OM4 multi-mode cable, or 100m distance using OM3 multi-mode cable. However, distance is just 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. 40G-QSFP-2.1 uses 4 x DFB transmitting lasers and 4 x PIN receivers, operating each lane with speeds of 11.2 Gbps, giving an aggregated maximum bandwidth of 44.8 Gbps. Module supports DDM/DOM optical diagnostics, which provide diagnostic information about the present operating conditions. 40G-QSFP-2.1 operates in Standard 0°-70°C temperature range and has double LC connector. QSFP+ support 39.81 – 44.8 Gbps data rate and such applications as 40G Ethernet (41.25 Gbps), STM256 (39.81 Gbps), OTU3 (43.108 Gbps) and OTU3e2 (44.58 Gbps). 40G-QSFP-2.1 optical transceiver is multi-purpose module used in number of different places of today’s networking. Consequently, most popular applications are Internet Service Provider (ISP) Fiber To The Home aggregation and backbone, Mobile operator core and back-haul 40G applications, Data Center networking site interconnections and other optical links.