GIGALIGHT 100G QSFP28 ER4 optical transceiver module is used for long-distance transmission in the field of data communication or telecom, which is compliant with 100G Ethernet transmission protocol and compatible with OTN OTU4 transmission protocol. It has a built-in pair of 4-channel LWDM MUX and DEMUX with center wavelengths of 1295.56nm, 1300.05nm, 1304.58nm and 1309.14nm, respectively, and uses a pair of single-mode fibers for transmission over distances up to 30km (without FEC) or 40km (with FEC).