Youopto 100G QSFP28 ER4 Optical Transceiver is designed for 40km optical communication applications. 

Optical transceiver integrates the transmit and receive path onto one module. 

On the transmit side, four lanes of serial data streams are recovered, retimed and passed on to four laser drivers, which control four electric-absorption modulated lasers (Lan-WDM) with1296, 1300, 1305, and1309nm center wavelengths. 

The optical signals are then multiplexed into a single-mode fiber through an industry-standard LC connector. 

On the receive side, four lanes of optical data streams are optically DE multiplexed by an integrated optical DE multiplexer. And passed on to an output driver, the receiver adopts APD. 

This module features a hot-pluggable electrical interface, low  power consumption, and 2-wire serial interface.