The QSFP28-100G-ZR4 optical transceiver is a high-performance module that delivers reliable data transfer across extended distances, with exceptional signal quality and reliability. FS offers a growing portfolio of 100G QSFP28 modules. This guide explains the fundamentals of this essential optical technology, breaks down how it functions, and. Marcus examined the six QSFP28 LR4 modules arranged on his workbench. He had processed $12,000 worth of RMA'd optics in just two weeks. His 100G spine links kept dropping with CRC errors, and the system showed a frustrating mix of interface flapping and unexplained downtime. Pay attention to the FEC status of the peer interface.